Lead-Zinc Deposits of 

Cordillera Blanca and 

Northern Cordillera 

Huayhuash, Peru

Prepared in cooperation with the 

Ministerio de Fomento, Instituto 

Geologico del Peru, under the auspices 

of the Interdepartmental Committee on 

Scientific and Cultural Cooperation "' 

with the American Republics 

Department of State

GEOLOGIC INVESTIGATIONS IN THE AMERICAN

REPUBLICS

LEAD-ZING DEPOSITS OF CORDILLERA BLANCA AND 

NORTHERN CORDILLERA HUAYHUASH, PERU

By ALFRED J. BODENLOS and GEORGE E. ERICKSEN

ABSTRACT

Base metal deposits in the central and southern Cordillera Blanca and the 

northern Cordillera Huayhuash comprise 6 mineral districts, 5 in the Departamento cle Ancash and 1 in the neighboring Departamento de Huanuco. Although 

many of the deposits were prospected and some mined on a small scale during 

the Spanish Colonial period, most activity has taken place in the last hundred 

years. Concentrates were produced in 194S and 1949 at the rate of about 1,000 

tons annually, and the rate of production during ceveral previous years was 

evidently about the same. Silver-bearing galena concentrate is the chief product. Sphalerite either is not mined or is discarded because its value lias been too 

low to cover costs of production and transportation.

The sedimentary rock units of the region are Jurassic (?) marine quartzites 

and phyllites, Lower Neocomian iluviatile and brackish-water sandstones, shales, 

and coals, Barremian marine and nonmarine limestones, marls, shales, and 

tuffs, and Middle Cretaceous marine limestones. During a period of orogeny beginning at the end of the Cretaceous the sedimentary sequence was compressed, 

commonly forming upright folds, but also some recumbent folds, many small bedding-plane faults, and some large reverse faults. At or near the end of deformation the sedimentary rocks were intruded by a batholith of granodiorite. The 

sedimentary rocks are slightly metamorphosed on a regional scale as a result 

of folding and locally are more highly metamorphosed in zones bordering igneous 

bodies. During subsequent uplift of the Andean block the sedimentary rocks 

were dislocated along normal faults and intruded by igneous stocks, dikes, and 

sills. Deposition of base metals is thought to have accompanied or immediately followed this stage of igneous activity.

The most common sulflde minerals in the deposits are galena, sphalerite, and 

pyrite; chalcopyrite, tetrahedrite-teunantite, arsenopyrite, and stibuite may 

also be present. Silver occurs in galena, in the copper sulfides, or as free sulfides. 

The sulflde minerals are oxidized to shallow depths, and the upper parts of many 

veins have been secondarily enriched in silver. Common non-metallic gangue 

minerals in most deposits are quartz and carbonates; fluorite and barite are 

found in some deposits, and silicate minerals are found in contact deposits in 

calcareous rocks. Most deposits are fissure filling veins along small fault or 

shear zones, but a number are replacements of wall rock along small faults, certain sedimentary beds, or contact zones. The fissure filling veins occur in any 

type of country rock, sedimentary, metaseclimentary, or igneous. Most replacement deposits are in calcareous rocks, but a few are in other rock types. Min1
2 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

eralogy and textures of the deposits indicate that nearly all are within the range 

of inesotherrual-epithermal origin.

Mineralized faults and shear zones are from several hundred meters to more 

than a kilometer long and have vertical extents of at most a few hundred meters; 

they are generally from 0.0 to 1 meter wide. Ore shoots containing argentiferous galena occupy only a fraction of such structures, have sporadic distribution, and in most deposits are small and lenticular, with galena ranging in tenor 

from 5 to SO percent. Replacement deposits have a wide range in size and are 

characterized by a low tenor of galena.

At most mines ore is mined selectively, crushed, and concentrated by hand. 

For this reason fissure-filling veins containing ore shoots with high tenor of 

galena are preferred by miners. Small concentrators in the Quebrada HondaVesuvio and the Pachapaqui districts treat ore from only a few deposits. The 

size of ore bodies in most deposits precludes larger scale mining or mechanizations of operations, and it is concluded that only minor expansion of production 

is possible under existing conditions.

The greatest deterrent to increased production is the high cost of transportation of concentrates by pack animals to roadheads. It is recommended that access roads be constructed to, or at least part way to, four of the mineral districts. With reduced transportation costs, miners could extract lower grade ore. 

Construction of small mills in other districts would also permit mining of lower 

grade ore.

Replacement deposits of lead-zinc sulfides in the Pacllon-Llamac and Pachapaqui districts and copper sulfldes in the Antamina-Contonga district contain 

large reserves of possibly minable material. However, development of these 

deposits would require large investments in roads, concentrating plants, and 

mining machinery.

INTRODUCTION

The Andean mineral province, a major metallogenic area of the 

world, comprising thousands of ore deposits, covers an area including 

Peru, Bolivia, and northern Chile and Argentina. Metals present in 

quantity are copper, lead, zinc, silver, tin, and iron; those present in 

smaller but appreciable amounts include vanadium, tungsten, gold, 

antimony, arsenic, bismuth, and cadmium. In addition, a few deposits yield small amounts of manganese, cobalt, molybdenum, and 

mercury.

In Peru zinc, lead, copper, and silver are the principal metals extracted from many base metal sulfide deposits. Nearly all such deposits contain lead and zinc. Copper is not so widespread but provides 

the bulk of ore minerals in major deposits such as Toquepala and 

Quellaveco in southern Peru. Silver occurs in primary sulfide deposits associated with lead or copper minerals or in oxidized zones 

where primary sulfides of lead and copper have been leached. The 

deposits of the Departamento de Ancash are similar to many elsewhere 

in Peru, and although the emphasis in this report is on lead and zinc 

resources, silver occurs with lead in all deposits, and copper minerals 

are present in most.
INTRODUCTION 6

Inasmuch as a great number of deposits throughout the Andean 

Cordillera in Peru consist mainly of lead and zinc ores, the government of that country suggested that such occurrences be studied 

systematically and sought assistance from the United States government in planning and executing this nation.Avi.de appraisal. A cooperatiA*e program Avas developed in 1946 betAveen the Institute Geologico 

del Peru, Ministerio de Fomento y Obras Publicas, and the Geological 

Survey, United States Department of the Interior. The contribution 

of the United States Avas sponsored by the Interdepartmental Committee on Scientific and Cultural Cooperation Avith the American 

Republics, United States Department of State.

The first area selected for comprehensive investigation Avas the 

Departamento de Ancash, the State north of the. Departamento de 

Lima and Avest of the Departamento de Huanuco. In 1947 the deposits 

in the Cordillera Negra, the Avesternmost range in Ancash, Avere 

studied, and in 1948 and 1949 the Avork Avas extended to the central and 

southern Cordillera Blanca and northern Cordillera Huayhuash. 

This report summarizes information obtained from the 1948-49 

investigations.

Mineral production from the Cordillera Blanca and northern 

Cordillera Huayhuash never has been large, and we conclude from 

our studies that only minor expansion is possible under existing conditions. Modest increases will be possible in several districts if access 

roads are built either partAvay to or directly to these mineralized areas. 

Construction of small mills or improvement of'existing mill facilities 

also Avould stimulate production.

GEOGRAPHY OF THE REGION AND LOCATION OP DEPOSITS

GEOGRAPHY

The Departamento de Ancash extends from the Pacific Ocean eastAvard to its boundary Avith the Departamento de Huanuco; the boundary betAveen these States folloAvs the Cordillera Huayhuash in the 

south and the Rio Maranon in the north. Huanuco in turn extends 

eastAvard to the Amazon Basin. All but one of the mineral districts 

described in this report are in the southeastern part of Ancash 

(fig. 1). One district in Huanuco lies along the southeast border of 

Ancash.

Most of Ancash and Avestern Huanuco are in the Andean Cordillera, 

and are characterized by very rugged terrain. The only comparatively 

level areas are in the coastal regions, at a feAv places along the crest of 

the Cordillera Negra, and in narroAv valley floors. ElseAvhere slopes 

are steep and highly dissected and provide some of the most spectacular scenery in Pern. Peaks reach altitudes from 4,500 to 6,700 meters*

1 AH measurements in this report are expressed in the metric system. A table of conversion factors between the English and metric systems is appended (p. 162).
LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUATHUASH

EXPLANATION

3

Number refers to list below

LIST OF MINING DISTRICTS 

1 Ouebrada Honda-Vesuvio

O.MABAMBA

 VVMonte

HUARAS

A /

 . * 3 VHuollanca

M 7 / 

o Pachapaqui I

t y

78° 77°

FIGURE 1. Index map of the Departamento de Ancash, showing location of mining

districts.

and include some of the highest in South America. Those in the 

Cordillera Blanca and Cordillera Huayhuash extending above 5,000 

meters are covered with active mountain glaciers.

The three major mountain ranges of Ancash are the Cordillera 

Negra, which borders the Pacific Ocean, the Cordillera Blanca, which
INTRODUCTION 5

follows the medial part of the Departamento, and the Cordillera Huayliuash, which marks the southeastern border of the Departamento and 

extends southward along the boundary between the Departamentos de 

Lima and Pasco. The south end of the Cordillera Blanca and the 

north end of the Cordillera Huayhuash overlap by about 35 kilometers; 

the southern part of the Cordillera Blanca lies about 20 kilometers 

west of the Cordillera Huayhuash. Except for the offset and overlap 

the two ranges form a continuous mountain chain more than 300 kilometers long. The crest of the chain is 100 to 125 kilometers distant from 

the coast and is the continental divide in this part of Peru. The three 

ranges all trend about N. 30° W., more or lebS parallel to the coast.

All streams east of the continental divide in Ancash floAV eastward 

into the Rio Maraiion, a major tributary of the Amazon River. West 

of the continental divide streams are comparatively short and flow directly into the Pacific Ocean. The more important of the westwarddraining rivers are the Rios Pativilca, Fortaleza, and Santa. The 

streams within the offset region between the Cordilleras Blanca and 

Huayhuash flow southward and form the Rio Pativilca, or as it is 

known locally in its upper reaches, the Rio Chiquian; this drainage 

system empties into the Pacific near the town of Pativilca. The Rio 

Fortaleza heads in the southern part of the Cordillera Negra and flows 

southwest, reaching the Pacific just north of the mouth of the Rio 

Pativilca.

The headwaters of the Rio Santa are in the southern end of the 

Cordillera Blanca, between the watersheds of the Rio Pativilca and 

the Rio Fortaleza. The Rio Santa flows northwest more than 150 

kilometers, parallel to the coast and between the Cordilleras Blanca 

and Negra, then cuts westward through the Cordillera Negra and 

reaches the Pacific just north of Chimbote. Of the westward-flowing 

streams only the Rio Santa carries appreciable amounts of water to 

the ocean.

Most population centers in Ancash are in the agricultural areas 

which follow the major river systems and lie at altitudes ranging from 

about 2,000 to 3,500 meters. A number of towns are on alluvial fans 

of rivers along the Pacific coast. In the mountains the largest agricultural area is along the middle reaches of the Rio Santa and is known 

as the Callejon de Huaylas (Huaylas Corridor). Huaras, the capital 

of Ancash, is near the upper end of the Callejon de Huaylas at an 

altitude of about 3,000 meters; its population is about 20,000. Other 

principal towns of the Callejon de Huaylas, having populations of 

from 1,000 to 5,000, are Marcara, Carhuas, Yungay, Caras, and 

Huaylas north of Huaras, and Recuay and Ticapampa south of 

Huaras. At the upper end of the Santa Valley, just east of a pass in 

the Cordillera Negra, is the village of Conococha, a way-stop on the 

main highway. Below the agricultural belt and at the mouth of the
6 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

Cainon del Pato, where the Rio Santa turns west towards the Pacific, 

are the towns of Huallanca and Hidroelectra. Huallanca is at the 

junction of the railroad from Chimbote and the road leading up the 

Santa Valley, and Hidroelectra, a comparatively new town about 2 

kilometers to the south, is headquarters for the large hydroelectric 

development of the Corporacion Peru ana del Santa.

East of the Cordillera Blunca all towns and villages are small. The 

more important are Chiquian and Aquia in southeastern Ancash and 

Chavin, San Marcos, Huari, and Chacas in central Ancash. On the 

east slope of the Cordillera Huayhuash, in the Departamento de Huanuco, the only town of any size is Huallanca. Except for a few small 

towns on the west slope of the Cordillera Negra, the only concentrations of population in the coastal part of Ancash are at Chimbote, 

Casma, and Huarmey.

LOCATION AND ACCESSIBILITY OF MINING DISTRICTS

The six mining districts described in this report are in the higher 

parts of the Cordilleras Blanca and Huayhuash on both sides of the 

continental divide. They lie in an area about 60 kilometers wide and 

about 125 kilometers long, between latitudes 9° 10' S. and 10°20' S. 

and longitudes 76°55' W. and 77°25' W. From north to south the 

districts are:

District Departamento Province

1. Quebrada Honda-Vesuvio----------- Ancash_____.____ Huari

2. Antamina-Contonga________________ Ancash__________ Huari

3. Huallanca_________________________ Huanuco________ Dos de Mayo

4. Pachapaqui.-_____________________ Ancash__________ Bolognesi

5. Tuco-Chira________________________ Ancash__________ Bolognesi

6. Pacllon-Llamac___________________. Ancash__________ Bolognesi

The mines and prospects of the Quebrada Honda-Vesuvio district 

are in the central Cordillera Blanca, from 16 to 25 kilometers airline 

distance east and northeast of Chancos (fig. 2). Deposits in the Quebrada 2 Honda are west of the continental divide, and those in valleys 

to the north are east of the continental divide. The mines extend over 

a belt trending west of north for about 25 kilometers and range in altitude from 4,100 to 4,800 meters. From the roadhead above Chancos a 

trail leads up the Quebrada Honda to the deposits in the upper part 

of the valley, and a branch crossing the north wall of the valley leads 

via circuitous routes to mines and prospects east of the continental 

divide. Trail distances from Chancos are from more than 20 to nearly 

50 kilometers.

The Antamina-Contonga district is in a northern ramification of 

the Cordillera Huayhuash about 10 kilometers east of San Marcos. 

The district has two centers of mineralization, the larger in the upper

2 Quebrada, defined by the dictionary as a ravine or gorge, is applied in Peru to all but 

the very largest valleys.
INTRODUCTION

-A

-4
8 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

part of the Quebrada Antamina and the smaller, about 5 kilometers to 

the north, at the head of Quebrada Pajush. Deposits range from about 

4,200 to 4,700 meters in altitude. One branch of the trail from San 

Marcos goes directly up the Quebrada Pajush to Contonga, and the 

other goes southeast before ascending the Quebrada Antamina. Both 

areas are about 15 kilometers by trail from San Marcos (fig. 3).

Four districts form a group in southeastern Ancash and Huanuco. 

The Huallanca district is near the north end of the Cordillera Huayhuash and on its eastern slope. Most deposits occur in an area 12

Reverse fault, showing direction 

of dip, approximately located

10 Kilometers

Deposit containing disseminated 

copper minerals

Syncline, showing trace 

of axial plane

Geology by A. J. Bodenlos and G. E. Ericksen, September 1948 

Base from topographic map of the Cordillera Blanca (Kinzl, 1939a)

FIGURE 3. Geologic sketch map of the San Marcos area.
INTRODUCTION 9

kilometers east-west by 11 kilometers north-south to the west of Huallanca (fig. 4). Mines of the Pachapaqui district are west of the continental divide east and north of Pachapaqui, a small town about 20 

kilometers southwest of Huallanca. The main group of deposits is 

from 4 to 7 kilometers east of the town and extends along the slope of 

the Cordillera for about 6 kilometers. A smaller group of deposits is 

found 6.to 9 kilometers north of the town (fig. 5).

>>, «... *" - , v^' J& ^t^' ... ,,?/**4 A

^^sf^*****// n % M^^)

NEVAOO RUCA6AOAAV'*-' /^ « t^« ^^^^gf^V,

FIGURE 4. Index map of the Huallanca mining district, showing location of mines and

prospects.

The Pacllon-Llamac district, also west of the crest of the Cordillera 

Huayhuash, is about 35 kilometers south of Pachapaqui. The deposits are in an area about 2 by 3 kilometers and lie from 8 to 10 kilometers east of the village of Llamac (fig. 6).

The Tuco-Chira district is at the southern end of the Cordillera 

Blanca about 12 kilometers west of Pachapaqui. All deposits but one 

are on the west slope of the Cordillera:' The deposits are in an area 

about 5 by 6 kilometers, and tlie southernmost is 14 kilometers northeast of the village of Conococha^and 16 kilometers northwest of the 

town of Chiquian (fig. 7). Most of the deposits in these southern districts are between the altitudes of 4,000 and 5,000 meters.

321628 55 2
10 LEAD-ZINC DEPOSITS. CORDILLERAS BLANCA AND HUAYHUASH

2 Espe

3 Otito

4 Otito

5 Vetllla

6 Abandonada

7 Arabia

8 Santa Elena I

9 Santa Elena II

10 Santa Benita

11 Dos Compadres 

12Sinchi Roca

13 Primavera

14 Riqueza

15 Rascacielo

16 Socorro

18 Prospect I

19 Santa Clara

20 San Miguel II

21 San Miguel I

22 Paclencia

23 Luls Adolfo

24 Fortuna

25 Gaby I

26 Gaby II

27 Exito

BURRO ^''-^NEVADO BURRO

Base of area north of Pachapaqui adapted from map of the 

Cordillera BlencatKinzl, 1939a). Area east of Pachapaqui 

(Quebrada Cara and tributary valleys) mapped by plane 

table triangulatlon by G. E. Erlckson and A. J. Indacochea, 

July 1940

FIGURE 5. Index map of the Pachapaqui mining district, showing location of mines and

prospects.

The trail from the roadhead at Chiquian to Pachapaqui extends 

northward along the Rio Pativilca, a trail distance of about 35 kilometers. Two other trails continue northeastward through Paso Burro 

(Burro Pass) and Paso Yanashallash across the Cordillera Huayhuash to Huallanca, an additional distance of about 30 kilometers. 

The Pacllon-Llamac district is accessible from Chiquian by a 30 to 35 

kilometer trail extending southeastward along the Rio Pativilca and 

then eastward in Quebrada Llamac to Hacienda Palca near the north 

side of the district. A narrow mountain road about 18 kilometers long
INTRODUCTION 11

°Llomoc

-X CCORIDEUA

XSUSANA 

\

LA ESPERANZA-X.K*sAN SAMUEL

ROSITA "

LAGUNA 

SOLTERANCACOCHA

^NEVADO RONDOY "'"""" fj El. 5789

NEVADO 

JIRISHJANCA

ff

n

NEVADO YERUPAJA 

El. 6634 A

Base compiled from map ol the CordillBra 

de Huayhuash by Kinzl, end aerial photographs 

by the Serviclo Aerofotogr<fico Naclonal del Peru

FIGUIIE 6. Index map of the Pncll6n-Llamac mining district, showing location of mines and

prospects.

connects the Tuco-Chira district to the Conococha-Chiquian road at 

Hacienda Mojon, about 12 kilometers by road east of Conococha.

CLIMATE AND VEGETATION

Although the entire region lies within 10° 20' of the Equator, the 

high altitudes influence the climate to such an extent that in many 

respects it is more typical of a cold temperate zone than of the tropics. 

During the winter months of June to October there is very little precipitation; the days are warm, but the temperatures at night drop to 

near freezing or a few degrees below freezing. The summer months 

of December to April are characterized by a tropical type of rainy 

season with rainstorms in afternoon and evening at the lower altitudes and snowstorms at altitudes above 4,000 meters. Night time 

temperatures during the rainy season are generally higher than during the dry season.

Above 4,000 meters the temperature drops to the freezing point or 

below at night, and only the hardiest of grasses, shrubs, and trees can 

survive. In such areas a coarse pampa grass thrives in marshy land 

on hillslopes and in valleys, and a type of bunch grass called by the
12 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

El.5487 mj*^Z> NE^AD Q//xTLi9°

*2"" ^ C1 C /I -7 Q M. '*. ^.

* .>< i = ^vJ \ X ' ' ^ 

El.4930 ftf A>NK ^ =' 

f$S/B£ffM <$jlXMERC£pES

EXPLANATION

Approximate crestline of ridge

^

Mine or prospect

77°15' 77°10'

Base compiled from map of the Cordillera Blanca by Kinzl, and aerial 

photographs by the Servicio Aerofotografico Nacionai del P=.-»

FIGURE 7. Index map of the Tuco-Chira milling district, showing location of mines and

prospects.

Quechua name ichu grows on drier ground. Protected hillslopes 

along narrow valleys commonly support growths of crooked broadleaf evergreen trees (quinual), which grow to a maximum height of 

about 5 meters. In nonglacial areas above 5,000 meters vegetation consists largely of sparse growths of mosses and scattered bunches of ichu. 

Areas between altitudes of 4,000 and 5,000 meters are sparsely 

settled by Indians Avhose main source of livelihood is the raising of 

sheep and cattle or small-scale mining. The main agricultural products exported are wool, hides, cheese, and meat. The Indian women 

are adept at spinning raw wool into yarn and weaving cloth for their 

families' clothing. Indian huts are constructed of adobe bricks,
INTRODUCTION 13

chunks of sod, or large rocks haphazardly chinked with mud, and 

have thatched roofs of bunch grass.

Indians living in areas below 4,000 meters are generally more prosperous because here land can be cultivated and crops of grain, corn, 

potatoes, and alfalfa can be grown during the rainy season. In some 

localities fields are irrigated, and certain crops can be grown all year. 

From 2,500 to 4,000 meters eucalyptus is planted to supply timber for 

construction and fuel. In addition, the areas of lower altitudes support a wide variety of natural shrubs, grasses, cacti, and trees, which 

become progressively more tropical toward sea level.

WATER SUPPLY AND TIMBER

Most ores are mined and sorted by hand, and therefore not much 

water is needed other than for camp use and for hand jigs. An adequate supply of water is available near most mines should mechanization be considered. The major streams in all the districts have moderately large volumes of water the year around, and, in addition, the 

many lakes form catchment and storage basins. Water for beneficiation plants is insufficient at a number of mines, especially at those near 

ridge crests and on higher peaks. Even in such areas, streams or lakes 

are within a few kilometers of the deposits. In the Vesuvio area, for 

example, a 2-kilometer aerial tram was built from one mine to a mill 

in the valley below.

A minimum of timbering is required in underground workings 

because most deposits are either veins or replacements following narrow and comparatively steep zones and because wall rock alteration is 

either limited or not intense. Stulls are used here and there in open 

stopes, short stretches of drift may be timbered and lagged, and some 

man-ways and ore chutes are cribbed. Local quinual trees generally 

furnish adequate mine timber, but at times eucalyptus is hauled in 

from the nearest agricultural area for permanent timber installations.

TRANSPORTATION ROUTES

Central Ancash may be reached over two roads and a railroad, all 

of which branch from the Pan-American Highway, the major coastal 

road of Peru. The more important of the two roads branches at 

Paramonga, just north of Pativilca, 190 kilometers from Lima. It 

follows the valley of the Rio Fortaleza, crosses the Cordillera Negra 

126 kilometers from Pativilca, and then continues 184 kilometers along 

the valley of the Rio Santa to Huallanca. The second road leaves 

the coastal highway at Casma, a small town 150 kilometers north of 

Pativilca, crosses the Cordillera Negra, and joins the Santa Valley 

road at Huaras. This road, 135 kilometers long, is in poor condition 

a-nd follows an extremely tortuous route.
14 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

From the port of Chimbote, 420 kilometers north of Lima, the railroad extends up the lower part of the valley of the Rio Santa to 

Huallanca, a distance of 133 kilometers. At Huallanca the railhead 

meets the northern termination of the Santa Valley road.

Roads branching eastward from the Santa Valley road lead to towns 

or inns whence trails continue to the various mining districts. The 

southernmost extends from Conococha to Chiquian, a distance of 31 

kilometers; from Chiquian trails lead to 3 and a road to 1 of the 4 

southern districts. From Recuay a road'leads 126 kilometers northeast to Huari. At San Marcos, 87 kilometers northeast of Recuay, trails 

branch eastward to the Antamina-Contonga district. A 5-kilometer 

branch road extends between Marcara and Chancos; trails continue beyond the roadhead just above Chancos to the Quebrada Honda-Vesuvio 

district as well as to the towns of Chacas and Huari. The accompanying table lists road and railroad distances from shipping points to the 

towns and ports along the coast. Distances to Huaras are included, 

as some ore is sent to dealers there before being shipped to the coast.

Distances, in kilometers, from shipping points in Departamento de Ancash to

junctions and ports

Town

Route

Rio Santa Rfo Fortalcza road

Pativilca

158 

127 

271 

184 

235 

210

Supc

174 

143 

288 

201 

251 

226

Lima

347 

316 

460 

374 

425 

400

Chimbote

390 

359 

503 

416 

467 

442

Rfo Santa road railroad

Huaras

114 

83 

111 

24

25

Huallanca

224 

193 

221 

134 

85 

110

Chimbote

357 

326 

354 

267 

218 

243

Because of the long truck haul along the coast, little ore is sent to 

Lima for export from the port of Callao, although modern facilities 

there permit dockside loading. Most ore shipped to the south is sent 

to the shallow-water port of Supe, 16 kilometers south of the Pativilca 

turnoff, where it is transferred to lighters for loading. Ore sent to 

Chimbote is trucked out either via Pativilca and then north along the 

coast, or north along the Santa Valley road to Huallanca, where it is 

transferred to the railroad. Chimbote, one of the best ports in Peru, 

has a moderately well protected harbor and new dockside loading

facilities.

PREVIOUS GEOLOGIC WORK

Previous geologic reports present only reconnaissance studies of the 

regional geology, mineral deposits, physiography, and glaciology. No 

reports cover completely any of the mining districts herein described, 

although a large number of deposits are mentioned in comparatively 

old papers. Recent but unpublished descriptions of many mines and 

prospects are in mining company files.
INTRODUCTION 15

One of the earliest reports, by Raimondi (1873), describes the general geology, mineralogy, and mining activity of several areas in the 

Cordillera Blanca. A comprehensive report by Steinmann. (1930) on 

the geology of Peru includes discussions of the structural geology, 

stratigraphy, and mineral deposits of several regions in southern 

Ancash.3 Velarde (1908) and Miller and Singewald (1919) briefly 

described mines and mineral production in the Vesuvio and Antamina areas and in the Huallanca district. The only detailed mine 

report is that of Duenas (1904) which covers the deposits of the Vesuvio area. A few short papers deal with minerals and mines in southeastern Ancash and southwestern Huanuco: Comstock (1879) reported on tetrahedrite from Huallanca; Dunstan (1909) briefly summarized the mining industry in the province of Bolognesi; and Garbin 

(1904) gave descriptions of some minerals of the Huallanca district.

Among papers discussing the glaciology of the area are those of 

Borchers (1935), Kinzl (1942), Heim (1947), and Szepessy Schaurek 

(1949). Topographic and glaciologic maps of the Cordillera Blanca 

and northern Cordillera Huayhuash (scale 1:100,000) were published 

by Borchers (1935a, 1935b) and by Kinzl (1939a, 1939b). A mudflow at Chavin was described by Indacochea and Iberico (1947), and 

its origin was discussed by Spann (1947).

FIELD WORK AND ACKNOWLEDGMENTS

This report is based on the reconnaissance examination of more than 

100 lead, zinc, silver, copper, and antimony mines and prospects in 

central and southern Ancash and in southwestern Huanuco. The 

districts in the central Cordillera Blanca were studied by Bodenlos 

and Ericksen in August and September 1948, and those in the southern 

Cordillera Blanca and Cordillera Huayhuash by Ericksen from July 

to October 1949. Brief descriptions of several deposits in the Huallanca district, examined by F. S. Simons in 1952, are also included. 

Dr. Angel Indacochea and Sr. Ulrich Petersen, geologists of the Institute Geologico del Peru, ably assisted the Geological Survey personnel 

during both 1948 and 1949.

Most of the deposits are one to two clays journey by trail from the 

nearest roadhead, so that it was necessary to transport men and equipment by pack mules and saddle horses. In those districts having a 

large number of deposits the parties worked from centrally located 

base camps.

In the central Cordillera Blanca, regional geology was mapped on 

air photos and on the base maps of Borchers (1935a) and Kinzl 

(1939a). District geology in various areas was mapped with plane 

table and telescopic alidade on scales ranging from 1:10,000 to

3 Steinrnann's book on the geology of Peru originally was written in German and published in 1929. The Spanish translation was published in the following year; all page 

references in this paper are to the Spanish edition.
16 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

1:25,000. Deposits were mapped with plane table or compass and 

tape on scales 1:1,000,1: 2,000, or 1: 5,000 and underground workings 

with compass and tape on scale 1: 500 or 1:1,000. The underground 

maps included in this report show geology as mapped or projected to 

floor level. Only principal workings are shown; stopes are omitted. 

Bases for the underground maps of several mines were graciously 

furnished by mining companies as follows: the Atlanta mine, Empresa 

Minera Vesuvio; the Huamaiia mine, Empresa Minera Pompei; and 

the Huanzala mine, Compafiia Minera Santa Barbara. The Compafiia 

Minera Santa Barbara also furnished a topographic map of part of the 

Huallanca district, and the Northern Peru Mining and Smelting Company gave general information about the Pacllon-Llamac district. 

Officials of Mauricio Hochschild y ia. permitted study of company 

reports on the central Cordillera Blamca region and the Pachapaqui 

and Tuco-Chira districts. '?

All bearings are given relative to true north, using an assumed magnetic declination of 6° 30' east of north. Altitudes of most mines were 

established by airplane-type altimeters and generally can be considered correct only to the nearest 150 meters; these altitude measurements have been rounded to the nearest 10 meters. Altitude measurements to the nearest meter were taken from published maps or from 

company surveys or were established by mapping in relation to a single 

aneroid station. The relative reliability of altitude measurements in 

given areas is indicated in district descriptions.

The field investigations were made possible only through the assistance and cooperation of many governmental and mining company officials and technologists as well as private mine owners, local miners, 

ranchers, merchants, camp hands, and guides. Grateful acknowledgment is made to all those listed below as well as to those whose names 

are not included. Their information and suggestions were invaluable 

and permitted acquisition of maximum data in the shortest possible 

time. We also wish to express our gratitude for the courteous hospitality tendered us by many residents of the region.

The foremost among those to whom heartfelt thanks are given is 

Ing. Jorge A. Broggi, Director of the Institute Nacional de Investigacion y Fomento Mineros and of the Institute Geologico del Peru. 

Not only was the cooperative work between the Institute Geologico 

del Peru and the Geological Survey first suggested by him, but he also 

worked tirelessly to assure the success of the cooperative program. 

From the smallest detail to major planning Ing. Broggi's energy and 

wisdom Avere indispensable to us, and through him all facilities of the 

Institute Geologico were put at our disposal.

In addition to the field assistance of Dr. Indacochea and Sr. Petersen, special credit is given to the following members of the Institute 

Geologico del Peru: Sr. Petersen for assistance in compiling the
GEOLOGY 17

bibliography and in mineralogic studies, Srta. Rosalvina Eivera for 

paleontologic compilations, and Sr. Dante Brambilla for assistance in 

compilation of index maps.

In Lima all officials of the Direction de Minas and the Ministerio de 

Fomento y Obras Ptiblicas were most cooperative, as were the Prefects 

and Sub Prefects in the Departamento de Ancash. In Huaras the 

Secretary to the Prefect, Sr. Eudoro Holguin, capably handled our 

official transactions.

Also of inestimable help to us was Mr. Carrel B. Larson, Minerals 

Attache of the United States Embassy in Lima. In addition to expediting our official business, Mr. Larson provided us with abundant 

background data on Andean mineralization and mining, gleaned 

from his extensive travels and research in Peru.

In addition to acknowledgments to mining companies for technical 

information as listed above, thanks are given to Mauricio Hochschild 

y Cia. for the use as field headquarters of the staff house at their hydroelectric plant near Huaras. Sr. Alberto Lopez, manager of the 

Hochschild ore buying depot at Huaras, Sr. William Brameld, manager of the Empresa Minera Pompei, Ing. Francisco Gadivia and Ing. 

Giovanni Rosson, managers of the Empresa Minera Vesuvio, and Ing. 

Eugenio DeEoet, manager of the Compania Minera Santa Barbara, 

all extended every courtesy to us.

The stratigraphy in this paper has been revised according to more 

recent work by V. E. Benavides, who in 1951 and 1952 studied the 

Cretaceous rocks of central and northern Peru. Mr. Benavides has 

most graciously permitted our use of his revision in age and correlation of stratigraphic units in Ancash, prior to publication of his results (Ph. D. thesis, manuscript in preparation, Columbia University, 

New York).

Our camp staff in both years, Srs. Policarpo Caballero, Ambrosio 

Resales, and Manuel Perez, efficiently handled our packing and also 

served as rodmen when needed.

GEOLOGY

Rock units in the area herein described are mainly marine strata of 

late Mesozoic age and batholithic rocks. Smaller intrusive masses, 

including stocks, sills, and dikes, thought to be younger than the 

batholithic rocks, are common in most mineralized areas. The sedimentary rocks have been intensely folded and to a lesser extent faulted. 

Sedimentary rocks were unaffected or only slightly metamorphosed 

during folding, but some thermal metamorphism occurred in their 

contact zones with igneous bodies. Un con soli dated till and outwash 

deposits of Pleistocene and Recent giaciation partly mantle all older 

rocks. In several localities travertine is being deposited from active 

hot springs. Tertiary volcanic rocks do not crop out within any of
18 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

the six mining districts but are present along the route leading from 

the Santa Valley to the southern mineralized areas.

STRATIGRAPHY

The complexity of structure and scarcity of fossils made it impossible to work out fully the stratigraphic relations between mineral districts in the brief time available for field studies, but it is probable that 

all sedimentary rocks in the region are of Late Jurassic and Early 

and Middle Cretaceous ages. The correlations made here are based 

on general lithologic similarities to a few sections described by Steinmann and others as well as unpublished revisions by V. E. Benavides, 

and on several fossil identifications by R. W. Imlay of the Geological 

Survey.

For a general description of the paleogeography of Peru during the 

Jurassic and Cretaceous, the reader is referred to the papers by 

Weaver (1940),Kummel (1948), and Huff (1949).

JTJBASSIC(?) ROCKS

The oldest sedimentary rocks in. the region crop out east of the batholithic core of the Cordillera Blanca in the Quebrada Honda-Vesuvio 

mining district (fig. 8). These rocks include a thick sequence of 

quartzites, shales, low-grade phyllites, and andalusite- and zoisitebearing hornfels. Massive-bedded dark-gray quartzites, dark-gray 

and blue-gray shales, and gray phyllites compose the bulk of the rocks; 

cream and white quartzites occur in places. Zoisite- and andalusitebearing hornfels are not as abundant and occur for the most part close 

to the contact with the batholith. (See p. 39.) Foliation planes in 

phyllites are commonly macaceous. In the area we studied there is 

little development of secondary foliation, so it is thought that metamorphism was induced primarily by contact rather than by dynamic 

effects. Weathered surfaces of these rocks are dark, and areas underlain by them have a marked somber appearance. Many craggy peaks 

in this part of the Cordillera Blanca consist of quartzitic parts of the 

sequence.

Raimondi (1873, p. 283) and Duenas (1904, p. 37) stated that shales 

and quartzites are bleached near the contact with the batholith, a 

phenomenon which we did not see. Raimondi also commented on the 

bleaching and alteration of country rock near hydrothermal veins, a 

feature common to many veins that we examined. These authors and 

also Boit (1926, p. 53) noted the development of andalusite-bearing 

rocks near the contact with the main intrusive mass.

The strata in the Quebrada Honda-Vesuvio district are isoclinally 

folded, so that considerable detailed mapping would be necessary to 

determine the thickness of the sequence. These rocks underlie a belt
GEOLOGY 19

Geology mapped by A. J. Bodenlos and G. E. Erli 

lordillera Blanca (Borclwi 1935: Kinzl.1939a)

FJGUKB S. Geologic sketch map of the Quebrada Honda.-Vesuvio mining district

about 5 kilometers wide in the upper Quebracla Honda and can be 

traced from the southeast end of the district northward about 25 kilometers to the Laurion and Apasli mines. According to Kaimondi and 

Dueilas, comparable strata are exposed in the Cajavilca district about 

7 kilometers north of the Laurion mine, and farther north Boit found 

similar rocks east of the divide at Quebrada Llanganuco.

These rocks were assigned to the Tithonian (Portlandian) stage of 

the Jurassic by Steinmann (1930, p. 83-84) and are so shown on the 

Geologic Map of South America (1950). Steinmann wrote (p. 84) :

The first occurrence described is at Huayanca (Huallanca, Departamento de 

Huanuco) where ammonites appear together with some lamellibranchs. From 

here the Tithonian can be followed to the Cordillera Blanca and its northern 

continuation to the valley of the Rfo Chicama (in northern Peru). In the vicinity of the granite masses of the Cordillera Blanca the sendiments are altered by
20 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

contact rnetamorphisni and converted to andalusite schists . . . (translation by 

the present authors).

At Huallanca these rocks seem to be present only in the area north of 

town and do not crop out in the mining district to the southwest.

The general geographic location of the Quebrada Honda-Vesuvio 

district suggests that these rocks could correspond to strata of Tithonian age cropping out both to the north and to the south. Furthermore, at least part of the sequence contrasts in color with overlying 

Lower Cretaceous elastics; Raimondi and Duenas well before Steinmann noted this lithologic difference. We found no fossils in the district, presumably because they have been destroyed by metamorphism, 

and therefore we consider the Jurassic age of the sequence questionable.

Review of the literature indicates why Ave hesitate to assign all 

these rocks to Jurassic. Although abundant fossils of Tithonian age 

have been found, especially in northeastern Ancash (Welter, 1913; 

Boit, 1926, p. 62; Knechtel, Richards, and Rathbun, 1947), there is 

no record that the strata actually have been walked out from fossiliferous areas to metamorphosed areas. Secondly, although Steinmann 

and, more recently, Huff (1949, p. 9) considered the Tithonian in 

northern Peru to be of marine origin, Steinmann noted that coals may 

occur in association with green and red shales in the Tithonian sequence. In northern Ancash Singewald (in Knechtel, Richards, and 

Rathbun, 1947, p. 24-25) found thin coal beds in Tithonian strata. 

As the overlying rocks of earliest Cretaceous age in that area are of 

fluviatile and brackish-water origin and contain coal beds, the boundary between the rocks of the two periods might be difficult to 

establish even by detailed stratigraphic work.

Boit (1926, p. 62) stated,

In the shale formation fossils of the Portlanclian have been seen, comprising 

in its upper part Valanginian species.

Singewald found blue-black shales, not only of Tithonian age but 

also as young as middle Albian, in the Aco-Cabaiia area of northeastern Ancash (Knechtel, Richards, and Rathbun, 1947, p. 15, 23). In 

our investigation of the Tuco-Chira district we found strata of Cretaceous age converted to hornfels rather similar in appearance to the 

metasedimentary rocks in the Quebrada Honda-Vesuvio district.

We therefore conclude that rocks of comparable lithology occur in 

both the uppermost part of the Jurassic and the lowermost part of 

the Cretaceous. Although most of the darker strata of marine origin 

seem to be of Jurassic age, the Jurassic system may include rocks of 

fiuviatile and brackish-water origin, and the Cretaceous in places may 

include rocks that resemble the marine Jurassic strata. Apparently 

Boit and Steinmann have taken the boundary of metamorphism as the 

dividing line where paleontologic evidence is not available. We iise
GEOLOGY 21

the same division in this report but reserve judgment on the definite 

age of the metamorphosed rocks.

CRETACEOUS SYSTEM

Other than the quartzites, shales, and metasediments of possible 

Jurassic age, all sedimentary rocks in the Cordillera Blanca and 

northern Cordillera Huayhuash are of Cretaceous age. Inasmuch as 

the nomenclature of Cretaceous rocks in Peru is that used in Europe, 

the following table, with equivalents used in the United States, is

given for reference:

Divisions of the Cretaceous Period

In Peru '

In the United States 2

Western interior Gulf coast

C

Upp

Middle Cretaceous

0

Danian 3

Maestrichtian

Campanian

Santonian

Coniaciau

C

Turonian

Cenomanian

Albian

Aptian

Barremian

Hauterivian

C

Valanginian

Berriasian 4

Fox Hills ss.

Pierre 

shale

Niobrara 

chalk

Benton shale

Dakota ss.

Purgatoire fin.

No deposits

Coman- he serie

Navarro group

Taylor group

Austin chalk

Eagle Ford shale

Woodbine formation

Washita group

Freeridcksburg group

Trinity group

(base concealed)

1 After Stelnmann, (1930).

2 Simplifled from C. 0. Dunbar and others (1942).

s The Danian Is not included In the Cretaceous by Dunbar.

< The Berriasian is not included in the Cretaceous by Steinmann.
22 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

The threefold division of the Cretaceous system used by Steinmann 

is followed in this report. Fossils collected during our study are representative of his lower and middle parts of the system.

The broad outlines of stratigraphy in central and northern Peru 

have been established, but sections of the Cretaceous rocks differ in 

these two regions. The area described in this report lies between them, 

and although it had the benefit of some study by Steinmann (1930), 

the work lacks sufficient detail to permit ready correlation of his units 

with those found in central Peru. More recently V. E. Benavides 

(Ph. D. thesis, manuscript in preparation, Columbia University, New 

York) correlated the Cretaceous strata of northern Peru with those 

of central Peru. This work included correction of Steinmami's correlations in An cash, which Benavides graciously has permitted us to use. 

In the following description the nomenclature of the rock units is 

that of Steinmann and of previously published geological literature 

on central Peru, but units are reclassifted with regards to age on the 

basis of determinations by Benavides.

Three main rock units comprise the bulk of the Cretaceous system of 

central Peru: The Goyllarisquisga formation, the Machay limestone, 

and the Jnmasha limestone. The equivalents of these formations continue northward from central Peru into Ancash, but in the latter area 

overlie a sequence of sandstone, shale, and coal, as well as a younger 

sequence of limestone and shale.

The Goyllarisquisga formation (Jenks, 1951, p. 211), formerly 

known as the Goyllarisquisga-Jatunhuasi sandstone (McLaughlin, 

1924, p. 605-607) and described by Harrison (1943, p. 9) as the Lower 

Cretaceous sandstone series, was named after the coal district northwest of Cerro de Pasco. McLaughlin noted that the formation is TOO 

to 900 meters thick and consists principally of quartz sandstone, in 

part somewhat conglomeratic, and that it also includes thick sequences of black and red shale as well as lesser coal beds. He further 

stated that similar strata occur at Oyon in northern Departamento de 

Lima, whence they can be traced northward into the Departamento de 

Ancash.

Throughout most of the western ranges in central Peru, a sequence 

of limestones from 600 to 700 meters thick forms a prominent unit in 

the Cretaceous rocks. This sequence was given formational status by 

McLaughlin (1924, p. 608-609), who named it the Machay limestone 

from a locality near Goyllarisquisga. McLaughlin divided the formation into two members: the Chulec, a thin-bedded light-gray limestone, 

which he considered to be of Aptian age; and the Pariatambo, a 

darker and partly bituminous limestone, which he considered to be of 

Albian age.

Overlying the Machay is the Jumasha limestone, described by McLaughlin (p. 609) as a uniform light-gray limestone which generally
GEOLOGY 23

is more massive-bedded than the Machay. The Jumasha limestone 

was determined by McLaughlin to be possibly of Senonian age.

Limestones overlying the Goyllarisquisga \vere not subdivided by 

Harrison (1943, p. 9-11) who referred to them only as the Middle 

Cretaceous limestone series. He did note that the base consists of 

yellow-brown and rust-colored limestones overlain by an alternating 

sequence of partly bituminous limestone, marl, and shale. The oldest 

fossils collected by Harrison are of Albian age, the youngest of Cenomanian age, so evidently his series includes beds younger than the 

Machay.

Steinmann's column for Ancash and northwestern Huanuco includes 

lower Neocomian sandstone, shale, and coal; a Barremian sequence of 

three units consisting of a lower limestone, a middle heterogeneous 

group of sandstone, shale, limestone, marl, and tuff, and an upper 

limestone; and limestones of Aptian and Albian age. He correlated 

the lower Neocomian clastic sequence with the Goyllarisquisga formation, the limestones of Aptian and Albian age with the Machay limestone, and placed the Barremian sequence between them.

Recent work by Benavides in Ancash has resulted in substantial 

revision of age determinations of the various units as well as revision 

of several of Steinmann's correlations. The lower Neocomian sandstone, shale, and coal sequence is restricted by Benavides to the inf raValanginian, and the lower limestone unit of the Barremian sequence 

of Steinmann is established as upper Valanginian in age; neither of 

these units occurs in central Peru. The middle heterogeneous unit of 

Steinmann's Barremian is determined by Benavides to range in age 

from uppermost Valanginian through the Aptian and is correlated 

with the Goyllarisquisga formation of central Peru. The upper limestone unit of Steinmann's Barremian is placed in the lower Albian. 

Benavides confirms Steinmann's correlation of the Aptian and Albian 

limestones with the two members of the Machay of McLaughlin, but 

both are dated as middle Albian as the result of this recent work. The 

Jumasha limestone, traced into Ancash by Benavides, is considered as 

ranging in age from upper Albian through the Turonian, or older than 

the previous age determination by McLaughlin.

THE LOWER NEOCOMIAN SEQUENCE OF STEINMANN

Steinmann (1930, p. 98, 112-114) shows sections of the lower Neocomian sandstones, shales, and coal beds in the valley of the Rio Santa 

near Marcara and in the Departamento de Huanuco near Huallanca. 

Yanez Leon (in Steinmann, p. 98) reported the sequence to be as much 

as 760 meters thick in the valley of the Rio Santa. Steinmann described two profile sections of the Cretaceous rocks in the valley of the 

Rio Torres west of Huallanca in which strata of the lower Neocomian
24 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

sequence are shown as carbonaceous sandstone containing intercalations of shale.

We found that the sandstone in the valley of the Rio Torres crops 

out throughout the Huallanca district, and a similar sandstone is exposed in the Pachapaqui and Pacllon-Llamac districts. At most places 

it appears to be several hundred meters thick and is medium to thick 

bedded and light gray. Certain zones contain bituminous shale and 

in most of the mining districts the sequence contains one or more beds 

of coal. The sandstone consists of firmly cemented, uniform-size, irregular to angular quartz grains, many of which have been secondarily 

enlarged. In places it contains small amounts of sericite, pyrite, and 

augite.

In the Quebrada Honda-Vesuvio district, a sequence probably corresponding to the lower Neocomian crops out east of the Jurassic (?) 

strata. In the Quebrada Illauro (Quebrada Juitush on older maps) 

the bulk of the rock is sandstone, but shales and included coal beds 

crop out several kilometers farther east (Duenas, 1904, p. 77-96). It 

is possible that some rocks in this area represent the middle unit of 

the Barremian sequence, but the intervening lower limestone unit of 

the Barremian was not seen.

A light-gray thick-bedded sandstone cropping out west of the main 

fault at the mouth of Quebrada Antamina (fig. 3) is correlated with 

the lower Neocomian on the basis of lithologic similarity.

In summary, the lower Neocomiaii of Steinmann has widespread 

distribution in Ancash and northwestern Huanuco. The only district 

in which we did not see it is the Tuco-Chira. It is best exposed in the 

Huallanca and Pacllon-Llamac districts.

THE BARREMIAN SEQUENCE OF STEINMANN

The sequence of calcareous rocks with associated shales, sandstones, 

and tuffs immediately overlying the lower Neocomian was said by 

Steinmann (1930, p. 111-116, 121) to be of Barremian age. On 

the basis of Steinmann's section Weaver (1940, p. 171) referred to it 

as the Huaras formation. As noted above, important changes have 

been suggested by Benavides, one in the age of the sequence and another in his correlation of the middle unit with the Goyllarisquisga 

formation.

Steinmann reported that the Barremian sequence crops out in the 

valley of the Rio Santa from Monterrey northward, in the vicinity of 

Paso Yanashallash east of Recuay, and in the valley of the Rio Torres 

in the Cordillera Huayhuash. The general descriptions by Steinmann 

of sections in four localities in the valley of the Rio Santa between 

Quebrada de Banos and Carhuas indicate that the sequence consists 

of three units. The basal unit is a limestone, described only as being
GEOLOGY 25

relatively thin and barren of fossils. AboA^e lies a unit as much as 

300 meters thick consisting of a heterogeneous group including marls, 

dark limestones, impure limestones, tuffaceous marls, tuffs, light sandstones, and dark shales; the calcareous strata contain fossils, some of 

Avhich are of marine and some of which are of brackish- and of freshwater origin. The uppermost unit is dominantly calcareous and as 

much as 100 meters thick; near Marcara its loAvest part is well-bedded 

blue-gray .limestone, the middle is poorly bedded limestone, and the 

upper part is marl. Near Paso Yanashallash, according to Steininann, the middle unit consists of marl and volcanic tuff overlain by 

sandstone, and the upper unit is limestone. In the valley of Rio 

Torres (fig. 4) the lowest unit is blue-gray fossiliferous limestone 

about 100 meters thick, the middle unit consists principally of marls 

and sandstone, and the upper unit is fossil-bearing massive limestone 

at least 80 meters thick.

Although all units of Steinmann's Barremian are not seen in every 

district, the sequence is sufficiently A\ddespread to indicate its extent 

throughout central and southeastern Ancash. The entire section is 

best exposed in the Pacllon-Llamac mining district and, despite complex structure, most of it also may be discerned in the Pachapaqui and 

Huallanca districts. Good exposures of the sandstones and shales of 

the middle unit are seen east of the crest of the Cordillera Blanca 

along the Recuay-Huari road.

The loAver unit is thin- to medium-bedded, dark-gray, fine-grained 

to lithographic limestone containing shale layers and partings. We 

definitely established its presence only in the Huallanca and PacllonLlamac mining districts, Avhere it is 100 to 200 meters thick. The 

middle unit, seen in all four southern districts, consists of interbedded 

shales, shaly sandstones, and impure limestones. It varies Avidely in 

lithology from place to place and is several hundred meters thick. 

The upper limestone unit is directly overlain by younger limestones of 

similar lithology and in the absence of fossils is difficult to recognize as a distinct stratigraphic unit, especially in reconnaissance 

examination.

Along the Recuay-Huari road, the sandstones and shales of the 

middle unit are closely folded and underlie a belt from 15 to 20 kilometers Avide. The sandstones include thin- to massiA7e-bedded rocks 

of gray, yelloAvish, and brown colors. The shales are broAvn, reddish, 

and dark gray. Several thin coal beds also are found in these rocks. 

Neither the underlying nor the overlying limestone units Avere seen in 

this area. The thickness of these elastics seems to be considerably 

greater than the 300 meters measured for the middle unit of the Barremian by Steinmann in the Santa Valley.

321628 55 3
26 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH 

MACHAY AND JUMASHA LIMESTONE

Near Marcara, Steinmann (1930, p. 112-113, 120-121) found units 

equivalent to the lower and upper members of the Machay limestone. 

The lower unit consists of marly limestone and yellowish marls, and 

the upper unit of bituminous black shales with interbedded light and 

dark limestone. He stated that similar limestones rest on the upper 

limestone unit of the Barremian sequence in the valley of the Rio 

Torres west of Huallanca. Benavides traced the OA7 erlying Jumasha 

limestone from central Peru into central Ancash, where it had not 

been previously identified by Steinmann.

The Machay and probably the Jumasha limestones crop out in the 

four southern mining districts and are best exposed in the Huallanca 

district. The Jumasha limestone underlies a broad area in the Antamina-Contonga district.

West of Huallanca, we found that the limestone above the upper 

unit of the Barremian Avas several hundred meters thick and consisted 

of an impure fossiliferous limestone and interbedded soft bituminous 

shale. Fossils collected above that part of the section described by 

Steinmann Avere studied by R. W.-Imlay of the Geological Survey, 

Avho identified the ammonite MoTtonioeras (Pervinguieria) sp. and 

the pelecypod Inoceramus sp. Imlay stated that the ammonite is of 

upper Albian age and is common in the TVashita group of Texas. The 

upper limestones of the Huallanca area thus are roughly equivalent 

to the Machay and the loAver part of the Jumasha.

In the Pachapaqui district thick-bedded fine-grained dark-gray 

limestone predominates. Comparable limestones in the PacllonLlamac district contain minor amounts of shale. Limestones overlying the middle unit of Steinmann's Barremian in the Tuco-Chira district are seA^eral hundred meters thick. They may be equivalent to the 

upper unit of Steinmann's Barremian sequence, the Machay, and part 

of the Jumasha.

About 5 kilometers east of San Marcos a folded limestone sequence 

at least 700 meters thick is in fault contact with the loAver Neocomian 

sequence of Steinmann. In the Antamina-Contonga district the formation is principally limestone, but includes several dolomite beds. 

The strata are thin to massive bedded, and various shades of gray, and 

range from extremely fine grained to moderately coarse grained in 

texture (fig. 9). Above Lake Antamina on the east side of the cirque 

several massive beds contain concentric structures that may be of algal 

origin. Fossils are scarce and poorly preserved. Collections made 

from talus beloAv a steep bluff near the Pallares prospect include specimens of Lopha, Pecten, and Arctica, Avhich according to R, W. Imlay 

indicate only that the strata are of Cretaceous age.

The lithology of the limestone of the area corresponds to that of the 

Jumasha. On aerial photographs the limestone can be traced south-
GEOLOGY 27

FIGURE 9. Jumasha limestone in the Autamiiia. area. View to the southwest i'rom near 

the Cantonga area ; Quebracla Antamina is beyond the crest line extending from the 

high peak to the shoulder on the left.

ward to a point west of Huallauca. A'. E. Benavides (personal communication) found both the Maehay and the Jumasha in the Quebrada Puchca, 15 kilometers north of San Marcos.

TERTIARY SYSTEM

Folded volcanic flows and agglomerates, cropping out in the Santa 

Valley between Huaras and Recuay, are said by Steinmann to have 

been deposited during the orogeny occurring from the end of the Cretaceous to early in the Tertiary. They possibly are equivalent to 

similar folded volcanic rocks found in the valley of the Rio Eimac 

east of Lima (Steinmann, 1930, p. 191, and McLaughlin, 1924, p. 622).

Volcanic rocks of Tertiary age, deposited after the last period of 

major folding before and during epeirogenic uplift of the Andean 

block, lie along the crest of the Cordillera Xegra and along the upper 

parts of the valleys of the Rio Fortaleza and the Rio Santa. For the 

most part the rocks are found only in areas west of the Rio Santa, but 

at the south end of the Santa Valley outcrops extend eastward nearly 

to Chiquian. The volcanic rocks here appear to be andesite flows 

and rhyolite tuft's which in most outcrops are deeply weathered or 

have been altered by hydrothermal solutions. The outcrops near 

Chiquian seem to be the most easterly extent of the volcanic rocks in 

Ancash, as they appear to be absent throughout the rest of the region 

described in this report.

PLEISTOCENE AND RECENT SERIES

As a result of glaciation during the Pleistocene and Recent epochs, 

areas formerly covered by ice are now partly mantled with till, and
28 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

pro-glacial areas are blanketed with outwash deposits. In higher 

regions active glaciers are still depositing morainal material, and runoff water charged with rock debris is filling in newly formed glacial 

lakes. These unconsolidated glacial deposits are described more fully 

in the section on glaciation (p. 41-46).

During Recent time hot springs have been depositing traA^ertine and 

calcareous sinter. In the Santa Valley a spring at Chancos is depositing a travertine of comparatively pure calcium carbonate, and another spring at Monterrey is depositing both ocherous and calcareous 

material (Duenas, 1904, p. 30). In the southern part of the region 

one thermal spring in Quebrada Azulmina (fig. 4) near the Pachapaqui-Huallanca trail is depositing small amounts of travertine, and 

another spring, no longer flowing, has built up a small travertine deposit on the north side of Quebrada Tuco (fig. 7). None of the four 

deposits is large.

INTRUSIVE BOCKS

Intrusive rocks in the region include the batholith in the Cordillera 

Blanca, several stocks, and many dikes and sills. The batholith and 

several stocks are composed of granodiorite; other stocks are of rhyolites or diorite. Sills and dikes consist of rhyolite, granodiorite, granite, aplite, granite pegmatite, andesite, and diabase. The batholith in 

the Cordillera Blanca is at least 120 kilometers long by 10 kilometers 

wide. Stocks are from less than 1 to about 5 kilometers in diameter; 

dikes and sills range from less than a meter to 20 meters in thickness 

and are traceable over distances ranging from 50 meters to several 

kilometers.

The intrusive mass in the Cordillera Blanca is one of the largest 

in Peru. Although on the Geologic Map of South America (Stose 

and others, 1950) this intrusive mass is shown as being more than 250 

kilometers long, its southern limit is incorrectly indicated; the southern margin is between the pass on the Recuay-Huari road and Huarapasca Pass 20 kilometers to the south. The western limit of the batholith in the vicinity of Huaras, as shown on the geologic map, also 

seems to be too far Avest, because sedimentary and volcanic rocks crop 

out along the Rio Santa both north and south of the city (p. 24-27).

Above Marcara the western margin of the batholith is comparatiA^ely 

regular and forms the steep front of the Cordillera Blanca facing the 

Santa Valley; here the contact Avith sedimentary rocks is faulted, but 

the magnitude of the movement is not knoAvn (p. 38). In the Quebrada Honda-Vesuvio district the eastern margin of the mass is less 

regular; to the east of the border are stocks that evidently are cupolas 

of the main body. The stock in the upper part of the Quebrada Honda 

is 5 kilometers in diameter, and the one just southeast of Pompei is 

smaller. Outcrops are massiA^e and OAving to recent glaciation are
GEOLOGY 29

comparatively fresh and light in color. Granodiorite forms most of 

the higher peaks in the range.

Most of the rock has granitic texture, although in places it is somewhat porphyritic. At a few places, especially near contacts, the rock 

is foliated. Such, structure can be seen near the power plant in the 

Cafion del Pato and has been described by Boit (1926, p. 52) as occurring in Quebrada Llanganuco north of Nevado Huascaran.

As far as can be determined from the microscopic study of a few 

specimens, the batholith consists mainly of metalum.in.ous granodiorite, 

but in a few places is an albite granite or a soda tonalite. The more 

calcic A^ariety contains more andesine and dark minerals and less 

quartz than the average type. In granocliorite medium-sized plagioclase feldspar grains form from 40 to 50 percent of the rock. The 

composition of the plagioclase ranges from An1G to An50 , but most is 

between An20 and An30 . Zoning is common and is both oscillatory and 

normal; where zoning is normal, cores may be andesine and mantles, 

ol igoclase. Orthoclase or inicrocllne, occurring as finer grains interstitial to plagioclase, forms from 10 to 15 percent of the rock. Finegrained quartz, also interstitial to plagioclase, forms from 15 to 25 

percent of the rock. One highly altered specimen from the Huamana 

area contains 40 percent of quartz, but some may be secondary. Biotite and hornblende form medium-sized grains and make up from 5 

to 30 percent of the rock. Apparently biotite is present in all specimens, but hornblende is not. Hornblende may be poikilitic, enclosing 

flakes of biotite. Accessory minerals are apatite, zircon, and epidote. 

Very small amounts of muscovite and microperthite were seen in several specimens.

Biotite and hornblende, together with the accessory minerals, 

crystallized first. Following, plagioclase feldspars formed and then 

orthoclase and quartz. Microcline may have crystallized either before 

or after the quartz. Orthoclase corrodes plagioclase and biotite, and 

quartz seems to have replaced some plagioclase.

Feldspars are sericitized and dark minerals chloritized to some degree in all rocks, and in the most intensely altered rock, part of the 

orthoclase is epidotized. Slight alteration is attributed to the action 

of deuteric solutions, but more intense alteration, generally found in 

the vicinity of sul.fi.de veins, evidently has been caused by hydrothermal 

solutions.

The stock in the upper part of the Quebrada Honda, particularly 

in the vicinity of the Arequipa and Chaco mines (fig. 2), contains 

bleblike inclusions of darker material several centimeters in diameter. 

.Microscopic examination shows that the inclusions have gradation al 

contacts with the host rock and that they contain the same minerals. 

However, biotite, hornblende, and muscovite are present in larger and 

orthoclase in smaller percentages than in the normal granodiorite, and
30 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

the texture is finer grained. A dark-colored dioritic rock along the 

north edge of the stock, exposed most extensively in the vicinity of 

the Rataquenua deposit, shows a more marked divergence from the 

predominant rock type. This dioritic rock occurs in a belt at least 

100 meters wide and has highly irregular contacts with the graiiodiorite. Minerals comprising the diorite include plagioclase, orthoclase. and hornblende as well as accessory apatite and sphene. About 

50 percent of the rock is zoned plagioclase averaging An40 in composition. Locally this plagioclase is partly replaced by orthoclase. 

Hornblende, which originally formed about 30 percent of the rock, 

is largely altered to chlorite; some grains have pyroxene outlines, indicating transformation during crystallization.

The batholith is cut by aplite and pegmatite dikes, and the stock 

in the upper Quebrada Honda contains diabase dikes. The aplites 

have sugary texture and are made up of equal-sized grains of quartz 

and orthoclase and a slightly smaller amount of plagioclase. The 

dikes are light tan or light gray, and most are unaltered. Diabase 

dikes in the vicinity of the Arequipa and Chaco mines in the upper 

Quebrada Honda are gray green, have equigranular texture, and consist of plagioclase (An,is ), pyroxene (pigeonite), and biotite. The 

pigeonite is partly changed to amphibole and the biotite partly altered 

to chlorite.

Stocks are found in 4 of the other 5 mineral districts. Those consisting of granodiorite are in the Tuco-Chira, Pachapaqui, and Huallanca districts. Stocks with granitic composition occur in the TucoChira and Pachapaqui districts, and the stock in the northern part of 

the Antamina-Contonga district is rhyolite. A poorly exposed intrusive of dioritic composition in the Huallanca district may be a stock. 

Most of these bodies have associated sills and dikes with lithology 

comparable to the parent mass. Neither these nor other small igneous 

bodies have prominent lineation of minerals.

The largest of these stocks, in the Tuco-Chira district, crops out in 

the vicinity of the Mercedes, Siberia, Rusia, and Chira deposits 

(fig. 7). It consists of granodiorite similar to that of the batholith. 

The texture is granitic with mineral grains from 2 to 3 millimeters in 

diameter. The rock consists principally of oligoclase, quartz, orthoclase, and biotite as well as the accessory minerals apatite, sphene, zircon, and magnetite. In specimens studied oligoclase about An2 o in 

composition makes up 50 percent or more of the rock; grains of this 

mineral are zoned. Orthoclase constitutes from 5 to 10 percent of the 

rock, quartz from 10 to 20 percent, and biotite about 10 percent.

Smaller stocks of granodiorite porphyry crop out in the Pachapaqui 

district and at the Sirena Encantadora deposit in the Huallanca district (fig. 4). This granodiorite contains phenocrysts of quartz and 

oligoclase in a fine-grained matrix predominantly of quartz and feld-
GEOLOGY 31

spar with minor amounts of biotite, augite, hornblende, apatite, and 

sphene. Most of these rocks are altered and contain sericite, chlorite, 

epidote, and calcite.

In the Tuco-Chira and Pachapaqui districts small irregular bodies 

which may be either stocks or sills are composed of porphyritic granite. The rock consists predominantly of orthoclase and quartz; northeast of the Cascajal deposit in the Tuco-Chira district it contains 

Carlsbad twins of orthoclase as much as 5 centimeters long. > At the 

Perla deposit in the Huallanca district several outcrops of diorite in 

an area of poor exposures may be part of a stock. The rock has granular texture and consists largely of anclesine, oligoclase, and orthoclase, 

with small amounts of ferromagnesian minerals, partly altered to 

chlorite, and minor amounts of apatite. The stock in the Contonga 

area of the Antamina-Contonga district is rhyolite containing phenocrysts of quartz, feldspar, and dark minerals. The marginal part of 

this body is noticeably finer grained than its interior.

Dikes and sills not related to larger igneous masses are composed 

of rhyolite, granodiorite, granite, and andesite. Those consisting of 

grandiorite and granite are comparable petrographically to the porphyritic stocks of similar composition described above.

The most common rock type in dikes and sills is a rhyolite consisting of phenocrysts of anclesine, oligoclase, orthoclase, and quartz, set 

in a macrocrystalline or cryptocrystalline groundmass of quartz and 

feldspar with minor amounts of biotite, hornblende, apatite, zircon, 

and magnetite. On the basis of phenocrysts some material may be 

classed as rliyod.aci.te or quartz latite, but owing to the difficulty of 

identifying the feldspars and quartz in the groundmass by means of 

microscopic examination, the classifications used here can be only 

general.

The rhyolite intrusives are altered, some only slightly but others to 

such an extent that of the original rock only a few grains of quartz 

remain. Biotite is altered to chlorite or is bleached and grains of 

hematite and pyrite formed along cleavage planes. Feldspars are 

altered to sericite and calcite. In a few intensely altered rhyelites 

outlines of feldspar phenocrysts are preserved, but the interiors consist of felted masses of sericite crystals set in groundmasses of finegrained sericite and quartz. Phenocrysts of quartz commonly are corroded and rounded, and borders have a thin layer of radiating quartz 

prisms. In some specimens feldspar phenocrysts have been, dissolved, 

and their former presence is indicated only by Avispy fragments at the 

edges of cavities.

In the AntaiTiiiia area, sills and dikes contain, phenocrysts either of 

oligoclase or of andesine (An33 ), rounded quartz grains, biotite, and in 

places the pyroxene pigeonite set in a groundmass of quartz, orthoclase, biotite, and chlorite. Feldspars are sericitized and dark min-
32 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

erals chloritized; epidote occurs in specimens containing oligoclase but 

not in those containing andesine. Quartz phenocrysts are more numerous in rock from the western part of the area, and chlorite representing altered dark minerals is more abundant in rock from the eastern 

part of the area; thus it would appear that the rock is rhyolite in the 

west and rhyodacite in the east.

Andesite dikes consist of plagioclase feldspar ranging in composition from oligoclase to labradorite; hornblende or biotite; and minor 

amounts of orthoclase. Textures range from granular to porphyritic. 

In the south, andesite dikes were seen only at the Misericordia deposit 

in the Pacllon-Llamac district (fig. 6) and the Venus and Cosmos 

deposits in the Tuco-Chira district. In the north an andesite dike 

occurs at the Apash deposit at the north end of the Quebrada HondaVesuvio district (fig. 2) ; in addition to the usual minerals the rock 

here contains pyroxene and some quartz.

The batholith is similar in lithology to the coastal batholith, and 

they may be genetically related and contemporaneous. Both McLaughlin (1924) and Harrison (1943, p. 33) considered the coastal 

batholith in central Peru to have been intruded at or near the end of 

the second major orogeny (the Incaic orogeny of Steinmann). The 

two orogenies as yet have not been differentiated in Ancash, so in the 

absence of further evidence nothing can be added to these prior opinions of McLaughlin and Harrison.

The smaller granodiorite stocks and sills possibly may be contemporaneous with the batholith in the Cordillera Blanca, but the age of 

stocks of different composition cannot be fixed other than that they 

are younger than the period during which folding took place. Some 

sills, such as those of andesitic composition in the Tuco-Chira district, 

may have been intruded before folding, but most tabular bodies definitely were emplaced subsequently. Because these bodies are fractured, brecciated, and faulted in places, they probably antedate at 

least part of the series of uplifts which raised the Andean block to its 

present elevation.

STRTJCTUEE

The Andean Cordillera was formed during orogenesis which began 

in either Late Cretaceous or early Tertiary time and has continued to 

the present. Deformation and uplift occurred in three principal stages. 

The first two, the more important, were periods of compression, or 

erogenic movement; the third was predominantly a period of uplift, 

or epeirogenic movement. During-the erogenic stages, folds; small, 

reverse faults along bedding planes; and larger, reverse or thrust 

faults were formed. Folds are the most prominent structural features 

in southern Ancash. They are accompanied by many bedding faults, 

but large-scale reverse faults were seen in only one district. During
GEOLOGY 33

the epeirogenic stage, open flexures and many normal faults were 

produced.

Sedimentary rocks of central Ancash have been compressed into 

long, relatively narrow, alined folds striking about N". 30° W., parallel 

to the regional trend of the Andean Cordillera and to the coastline.

O

Major folds in most places are upright or only slightly overturned; 

many are closed or isoclinal, having sharp crests and steeply dipping 

limbs (figs. 10,11).

In certain areas folds are noticeably overturned and in the Quebrada 

Tuco are nearly recumbent; in the latter area the axial plane of one 

major fold is nearly horizontal (fig. 12). Competent beds, such as 

those of limestone or sandstone, forming the broad outline of folds are 

bent into simple curves, but at places these beds may be complexly 

folded (fig. 13). Associated incompetent beds, principally of shaly 

sediments, are, in general, much more complexly folded. Shaly sediments are predominant in areas which show isoclinal folding.

Other than crumpling and minor flowage of incompetent strata in 

the folds, most movement during folding apparently has taken place 

along bedding faults. At most places the competent strata are only 

slightly thinned on limbs and thickened on crests, so the folding seems 

to be predominantly of the parallel type (fig. 14). HoAvever, in a few 

of the more complexly folded areas even competent strata show considerable flowage, and folds tend to be of the similar type. The 

quartzites and phyllites of Jurassic(?) age on the east side of the 

batholith in the Queclrada Honda-Vesuvio district and some of the 

Cretaceous limestones in the Tuco-Chira district seem to have developed flowage to some extent. Throughout the region, however, few 

folds can. be classed as either ideally parallel or purely similar. Bedding faults contemporaneous with folding are characterized bj reverse 

movement and consist of gouge and breccia zones with slickensided 

walls. These faults are limited to bedding planes or are closely 

parallel to them and obviously are restricted to one limb of any fold. 

Although movement along most is comparatively small, a few appear 

to have cut several tens of meters of beds.

Large-scale reverse faulting was recognized only east of San Marcos. 

Several hundred meters east of the contact between the lower Neocomian sandstone and the Jumasha limestone a reverse fault completely within limestone dips 60° SW. The bedding in the western 

block parallels the fault plane, but the bedding in the eastern block is 

truncated by the fault (pi. 1, sec. A-A'). At the contact between the 

lower Neocomian sandstone and the Jumasha limestone, stratigraphic 

and structural evidence indicates that the lower Neocomian is upthrown more than 1,000 meters along another fault.

Normal faults, considered to have formed during the stage of 

epeirogenic movement, have displacements ranging from a few meters
co

FIGUEE 10. Isocllnally folded sedimentary rocks of the middle unit of the Barremian sequence, looking south just east of pass, Recuay-Himrl 

road. Apophysis of batholith extends from right to right center of photograph. Axial planes of folds are nearly vertical.

o

N

o 

aOano a aa >

CO

t-1oO

W

M

I

M
GEOLOGY 35

FIGURE 11. Isoclinal folding of Cretaceous sedimentary recks on north-west side 

of Nevado Yerupaja (peak obscured by clouds). Axial planes of folds are nearly 

vertical. Isoclinal anticline is visible to right and syncline to left of glacia^ 

valley. Lake in valley is dammed behind recessional moraine.

FIGURE 12. West side of Quebrada Tuco, showing nose of overturned syncline. White 

streaks extending downward from axis of structure near nose are dumps of the Cascajnl 

mine.
36 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUATHUASH

 H " '4
o

K 

O

FIGURE 14. Crest of parallel fold in south wall of Quebrada Antamina. The anticline is flanked by two sharply folded synclines ; strata 

along ridge crest above are unfolded and dip eastward at low angles. In lower part of photograph, material devoid of bedding is 

silicated limestone containing disseminated copper sulftdes.
38 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHTJASH

to several hundred meters. In the southern districts many valleys 

have been eroded along large fault zones, as is indicated by different 

structures and rock types on opposite valley walls. Some folds in the 

medial parts of the southern, ranges appear to be broken by normal 

faults having displacements of several hundred meters. Smaller 

faults, common throughout the region, are traceable for only a few 

hundred meters; their short horizontal extent indicates that their 

vertical displacements are correspondingly small.

Normal faulting is taking place at the present time; in 1946 an 

earthquake in northeastern Ancash resulted from movement on a fault 

which produced a scarp as much as 2 meters high (ITeim, 1949). 

Fault scarps, between 5 and 10 meters high, cut glaciofluvial fans and 

extend for kilometers along the western front of the Cordillera Blanca 

east of Eecuay, east of Huaras, and in the vicinity of the Quebrada 

Honda east of Marcara. These scarps provide clear evidence that the 

range has been raised relative to the Santa Valley block comparatively 

recently.

The sedimentary rocks of the region are intensely fractured and 

jointed. At most places the fractures and joints form very complex 

patterns, but in the southern districts limestone at several localities 

is broken by joints into large, nearly equal-sized rhombic blocks. At 

several other localities intersecting joints and bedding planes separate the rock into rectangular blocks.

Joints, fractures, and faults with small displacements also cut all 

igneous rocks. Joints in massive rocks do not form well-oriented 

systems in most places, but some prominent sets are seen here and 

there. At the mouth of Quebrada Honda strong sheeting near the 

west contact of the batholith dips about 45° SW. The joints steepen 

to the east and then fade in prominence several hundred meters from 

the contact. Faults in massive rocks also seem to be alined in a few 

areas. The stock in the upper Quebrada Honda is cut by small 

faults generally trending north to northwest. At the Huamana mine 

in the Vesuvio area intersecting faults strike north to northwest; 

one set dips about 15° and a second set about TO 0 westward. 

Faults of small displacement are common along contacts between 

sedimentary and igneous rock. Along the large intrusive bodies 

these faults may branch into either rock type; examples are the 

Cruzada vein in the Atlante mine and the veins around the stock in 

the Contonga area (pi. 2). Contact faults may swing completely 

across tabular igneous bodies and follow opposite contacts, as shown 

by a number of structures followed by veins in the Antamina area. 

Other faults Avith small displacements transect contacts at large 

angles.

Few generalizations can be made regarding differences of magnitude of faulting in one rock type as compared Avith another. Mine
GEOLOGY 39

maps of the Quebrada Honda-Vesuvio district shoAv that some faults 

are strong in igneous rock and fade in sedimentary rock a short distance from the contact, whereas the opposite is true along other 

faults.

Small faults with either normal or reverse mo'vement are economically important because many are loci of mineral deposits. Most 

are narrow shear zones ranging from about one-half to several meters 

in width. Details of their configurations, internal structure, and 

associated fractures are given later in the descriptions of mineral 

districts and deposits.

METAMOBPHISM

Sedimentary rocks have been regionally metamorphosed throughout extensive areas and locally metamorphosed along contacts of the 

more acidic intrusive rocks. Shales, shaly limestones, and shaly 

sandstones seem to have been the rock's most susceptible to regional 

metamorphism. Shales and shaly limestones are changed to IOAVgrade phyllites and, in a feAv isolated places, to slate and schist. The 

purer sandstones are quartzitic in some areas, but, in general, are not 

regionally metamorphosed. Shaly sandstones are changed to argillaceous quartzite. Most limestones are not metamorphosed but in places 

contain scattered crystals of wollastonite; elsewhere beds have been 

silicified or serpentinized. Such alteration of limestone over wide 

areas may have resulted in part from regional metamorphism. of impure limestones and in part from introduction of new minerals by 

hydrothermal solutions.

In contact zones, especially near granodiorite and rhyolite intrusives, limestone and shaly limestone are silicated, and shaly sandstone is metamorphosed to tough gray or green hornfels. Horn f els, 

silicic or argillaceous rock recrystallized by heat of intrusion, occurs 

with Jurassic(?) quartzites and phyllites in the Quebrada HondaVesuvio district. One specimen collected at several hundred meters 

distance from the.contact with the batholith consists of 40-45 percent quartz, occurring as angular grains, and 50-55 percent zoisite, 

as well as accessory zircon; this rock originally may have been an 

arkose. Thirty meters from the batholith at the Huamana mine the 

rock consists of 15 percent quartz, 50 percent andalusite, 30 percent 

biotite, and 5 percent muscovite; its unmetamorphosed equivalent 

could have been an argillaceous sandstone.

Silicated limestone was formed either by reaction with or replacement of limestone by silica and other lesser constituents introduced in 

magmatic solutions or by recrystallization of impure limestone by heat 

of intrusion. The first process seems to have been predominant because in most silicated zones highly altered limestones contain patches 

of limestone which have been only bleached and recrystallized to either 

fine- or coarse-grained marble, an indication that the original rock
40 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

was comparatively pure. Minerals in silicated limestones include 

garnet, idocrase, epidote, diopside, wollastonite, serpentine, and 

quartz.

Most silicated limestones in the southern districts consist of quartz 

and grossularite garnet or epidote. In addition to these constituents, 

felted or radiating masses of acicular to bladed crystals of white 

wollastonite may be present. The rocks range in color from gray to 

pale green and bright green. Vugs and fractures commonly are lined 

with well-formed crystals of green garnet, which range from less than 

a millimeter to about 2 centimeters in diameter. A few contact zones 

contain minor quantities of brown garnet. Additional petrographic 

details on silicated limestone are given below (p. 56-57).

A substantial mass of silicated limestone occurs along a large rhyolite sill (?) in the middle of the Antamina area. The highest degree 

of alteration produced an assemblage identified by R. V. Lewis of 

the Geological Survey as diopside, grossularite garnet, wollastonite, 

and idocrase. Less profound alteration produced garnet-serpentine 

and garnet-diopside rocks.

GLACIATION

Glaciation during Pleistocene and Recent time has produced Alpine 

sculpture in most of the higher ranges of the Andean Cordillera and 

has resulted in deposition of great amounts of till and drift (Stein 

mann, 1930, p. 267-76). Although ice still covers some ranges, glaciers have been receding at a rapid rate throughout the country during the past 25 to 50 years (Broggi, 1943).

In the Cordillera Blanca and in the northern Cordillera Huayhuash 

the present snowline lies at an altitude of 5,100 meters or above. The 

lower limit of most glaciers is several hundred meters below this altitude, and some valley glaciers extend as low as 4,300 meters. On the 

north side of Nevado Huandoy, one glacier reaches the exceptionally 

low altitude of 4,100 meters. During a period of greater glacial activity in. the past ice extended even lower; Steinmann (1930, p. 270) 

reported a terminal moraine above Huaras at an altitude of 3,300 

meters. The lowest glacial deposit seen during our investigations is 

the lateral moraine just below the mouth of Quebrada Honda. This 

moraine lies at an altitude of 3,400 meters, 950 meters below the lowest ice now present in the upper part of the quebrada. Evidence of 

rapid recession of ice is provided by the uncovering of one mineral 

deposit in the Huallanca district within the past 15 years. At the 

Atlante mine in the Yesuvio area a fairly large lake has formed behind a small recessional moraine that marked the ice front in 1932, 

and the ice has retreated from the portal of level 3 since this working 

was first cut. One valley glacier has stagnated to such an extent that
GEOLOGY 41

its lower extremity is completely separated from the main body of 

ice (fig. 15), and ice caps on shoulders of peaks are wasting irregularly

(fig. 16).

Most of the erosional features commonly resulting from mountain 

glaciation, including horns, aretes, cirques, faceted spurs, U-shaped 

Aralleys, hanging tributary valleys, stoss and lee topography in valley 

floors, and striated outcrops (figs. 11, 17, 18, and 19), may be seen in 

these ranges. Floors of many valleys are divided into steplike treads 

a few hundred meters to several kilometers long, covered with marshes 

and drier pasture land. Interspersed are steeper sections in which 

outcrops are polished and striated or quarried on the down slope side. 

The relief between main valley floors and ridge crests is commonly 

more than 1,000 meters.

Glacial deposits include many forms of till and stratified (or 

washed) drift. From the mouths of U-shaped valleys upward, most 

deposits are till which forms lateral, terminal, and ground moraines 

(figs. 15, 16, and 20). Stratified drift occurs only locally, in basins 

behind rock dams or where lakes were temporarily impounded behind 

terminal moraines and at the bases of oversteepened and hanging 

valleys where fans were deposited over either moraine or lake-filling 

material.

Below the mouths of U-shaped valleys glaciofluvial deposits predominate. In the valley of the Rio Santa tremendous deposits are 

found in the area between Lake Conococha on the south and the Canon 

del Pato on the north. In most places they form large fans which may 

coalesce to form aprons extending for many kilometers along the base 

of the steep front of the Cordillera Blanca. Most of the glaciofluvial 

material is only rudely sorted and stratified, probably because streams 

fed by glaciers were heavily loaded and had steep gradients. Steinmann (p. 276) stated that north of Caras much outwash material was 

deposited as the filling of a now-extinct lake. Present glacial lakes, 

especially those newly formed below receding glaciers, are being filled 

slowly with glacial debris, and broad, flat valley floors, such as those 

on the step-like treads in the upper reaches of Quebradas Honda and 

Llamac, are suggestive of filled-in lakes.4 Banded clays exposed at 

Chancos are definitely of lacustrine origin and are considered by 

Heim (1947, p. 114) to be varved.

At the south end of the Santa Valley the glaciofluvial deposits have 

been dissected only slightly during the present cycle of erosion, but 

from Huaras northward they have been strongly dissected. BetAveen 

Caras and the Canon del Pato at least four terrace levels are visible 

above the present river channel. The Rio Santa still is cutting down-

* Flat marsh- or grass-covered areas at the bottoms of glaciated valleys are locally 

culled pampas and are referred to as such throughout this report.

321628 55 4
42 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

FIGURE 15. Wastage of ice and lateral moraine, Quebrada Cancahua. View to the west, 

showing tongue of ice in bottcm of valley completely separated by wastage from main 

valley glacier above. Well-developed lateral moraine is shown at base of hill at right. 

Spur on left and hill on right are inetasedimentary rocks of Jurassic( ?) age ; granodiorite 

underlies peaks in background. Esr.arta mine is at foot of shoulder above lower glacial 

remnant.

FIGURE 16. Wastage of ice and recess'onal moraine, Quebrada Cancahua. View to the 

south from upper Quebrada Honda, showing irregular wastage of ice caps on peaks. The 

quebrada is a hanging valley ; recessional moraine occurs at its foot, and lacustrine sediments cover its floor. Eight shoulder of main peak is underlain by inetasedimentary 

rocks of Jurassic (?) age; other rock in photograph is granodiorite. Arequipa and 

Chaco mines are just below the ice line, right center of photograph.
GEOLOGY 43
44 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

FIGUEE 18. U-shaped glaciated valley, the lower Quebrada Honda, view 

to the west; flat floor in the middle foreground is result of lake 

filling.

FIGUBE 19. U-shaped glaciated valley, the (juebrada l,lnmac, view to 

the west; pampa in foreground is at Hacienda Palca.
GEOLOGT 45

IfiuuuE 20. Lateral moraine and post-glacial sediments, upper Quebrada Honda,. View 

to the west, showing lateral moraine, which on the right wall of the valley extends to 

above the height of the observer. The flat valley floor, the Vinoyapampa, contains 

lacustrine sediments deposited in a lake dammed by rock barrier. Ice-covered peaks 

on right are underlain by metasedimentary rocks of Jurassic (?) age and in center and 

right center by grandodiorite.

ward, but in a few places between Huaras and Caras it is cutting laterally and is forming small and separated flood plains.

As is common elsewhere in glaciated regions, erosion and deposition 

resulting from ice action have blocked and disrupted normal drainage. 

During the present cycle of glacial recession many lakes have formed 

in front of receding glaciers in basins which before had been occupied 

by ice. The waters are dammed either by the dowiislope rims of rock 

basins or by recessional moraines. Steinmann (p. 275) reported that 

Lake Llanganuco in the quebrada north of Nevado Huascaran is 

dammed solely by a landslide. Lake Parron, the largest lake in the 

Cordillera Blanca, in the quebrada on the north side of Nevado 

Huandoy, is dammed partly by a glacier from a tributary valley and 

partly by a terminal moraine. Lake Conococha, at the head of the Rio 

Santa, apparently formed by the disruption of drainage by large 

coalescing fans emanating from quebradas at the southern end of the 

Cordillera Blanca.

Morainal dams of glacial lakes are subject to failure, and resultant 

"aluviones," or mud flows, have transported and deposited large quantities of material. Since 1941 three morainal dams in the Cordillera 

Blanca have broken, and aluviones have devastated the valleys below.

The most destructive aluvion from the standpoint of loss of life and 

property occurred in December 1941 when a lake at the head of Que-
46 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

brada Cohiip broke through its morainal dam. Water, mud, rocks, 

and huge boulders swept for a distance of 23 kilometers down the 

quebrada and through the center of Huaras, burying one-fourth of the 

city to a depth of about 20 meters and causing a great loss in lives, 

estimated as between four and six thousand (fig. 21). The power of 

this aluvion is shown by the fact that it carried into Huaras a block 

of granodiorite, the visible part of which was estimated to weigh at

FIGURE 21. View ut' tin luvinn Ilial dev;isl;i In! Ilnnras 

from the Cordillera Xo^ra.

least 700 tons. Along the Rio Santa farms downstream were washed 

out or buried, and those a short distance upstream were flooded when 

the river backed up against the mudflow barrier. Two days later the 

river breached the mudflow, and the resulting flood caused further 

damage downstream.

In January 1945 a similar aluvion swept down the Quebrada Huachesca, the mouth of which is at the town of Chavin, 7 kilometers south 

of San Marcos. The lesser amount of material carried by this aluvion 

combined with sparse population of the area, resulted in comparatively small loss of life (Indacochea and Iberico, 1947; Spann, 1947). 

In 1950, during the course of draining a lake above the Caiion del 

Pato in an attempt to forestall similar destruction in the lower Santa 

Valley, the moraine broke prematurely. Hydroelectric installations 

downstream were damaged, and the access bridge to the power plant 

as well as railroad bridges below Huallanca were washed out.
GEOLOGY 47

There is no reason to suppose that aluviones occur more frequently 

now than in the earlier stages of ice recession, and it is probable that 

in the aggregate they have been important geologic agencies. Inasmuch as Flint (1947) does not mention this type of pro-glacial feature, 

it is either not too common or has not been recognized to any extent in 

North America or Europe.

GEOLOGIC HISTORY

The rocks of the Andean Cordillera include both marine and continental sedimentary rocks, and volcanic and intrusive rocks, of preCambrian through Tertiary age, as well as local poorly indurated glacial, fluvial, and lacustrine deposits of the Pleistocene and of Recent 

age. In the Paleozoic and Mesozoic eras the site of the Peruvian Andes 

was occupied by a major geosyncline in which as much as an estimated 15,000 meters of sedimentary and volcanic rocks were deposited. 

During the first of two major orogenies, in Late Cretaceous and Early 

Tertiary time, the rocks were folded and to a lesser extent faulted, 

and marine deposition in the Andean area came to a close. Deposition 

of continental elastics and volcanics in intermontaine basins followed, 

and then in a second major orogeny, definitely during the Tertiary, the 

rocks were again uplifted and folded. Large batholiths were intruded, 

probably at or near the end of the second orogeny. Thereafter, many 

stocks and related bodies were emplaced, and abundant volcanic material was extruded, Yolcanism continued into Recent time in parts 

of Peru. Epeirogenic movement later in. the Tertiary again raised the 

Andean region several thousand meters and also caused block faulting and flexing of the rocks. The present physiography results from 

fluvial and glacial erosion of the uplifted Andean block during the 

Pleistocene and Recent epochs (Steinmann, 1930, p. 294-302; Harrison, 1943, p. 30-33; Yates and others, 1951, p. 5; and Jenks, 1951, p. 

216-218).

Our studies can contribute little to the geologic history of Peru as 

given above. In the region under discussion in this report sedimentation took place from the Late Jurassic to the Albian stage in Middle 

Cretaceous time. During this interval seas occupied the region in the 

Portlandian stage of the Jurassic and during Early and Middle Cretaceous. Yolcanism occurred during the late Neocomian, and some tabular bodies may have been intruded into rocks of comparable age before 

their folding. The absence of younger strata prevents close dating of 

the subsequent stages of diastrophism and large-scale igneous intrusion. 

Most Tertiary volcanic rocks probably were emplaced after major folding and subsequent planation and either before or during epeirogenic 

uplift. The region attained nearly its maximum elevation by Pleistocene time, but small vertical movements are continuing even to the
48 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

present. Glaciatioii which began during the Pleistocene is continuing, 

although glaciers now are receding at a comparatively rapid rate.

Deposits of metallic sulfide minerals were formed at some time in 

the Tertiary after the igneous masses solidified and fractured. In the 

batholith underlying the Cordillera Blanca these deposits are younger 

than diabase dikes which intruded the hardened and fractured mass.

MINERAL DEPOSITS

LITHOLOGIC AND STRUCTURAL ENVIRONMENT

Metallic sulfide and associated gangue minerals were deposited in all 

types of rock. The size or number of deposits does not seem to be 

related to lithology of the wall rock, although deposits are not as common in argillaceous or partly argillaceous rock as in other rock types. 

Lithology therefore does not exert clear-cut control on mineral deposition. The absence of lithologic control perhaps is best illustrated in 

the Quebrada Honda-Vesuvio district where good ore bodies occur in 

igneous rocks and in metasedimentary quartzites and phyllites. Even 

where veins cross contacts, as at the Atlante mine, large ore bodies are 

apt to be found in rocks of both types. The comparatively small incidence of deposits in rocks either partly or entirely argillaceous in composition is attributed to their relatively low competence and, hence, low 

permeability.

Most deposits occupy fissures or faults which clearly were channelways for mineralizing solutions. These fractures were formed during 

different stages of the structural development of the region. The oldest planes of weakness originated along or nearly parallel to bedding 

planes during folding. Later some planes of weakness apparently 

formed at contacts during intrusion of igneous masses. During epeirogenic uplift of the Andean mass other faults and fissures were produced, not necessarily alined with older structures. It is reasonable to 

suppose that earlier bedding-plane and contact faults were reopened 

and made more permeable during this uplift. Movements along all 

these structures continued during the period of mineralization, as 

shown by brecciation of mineral masses, slickensiding of mineralized 

walls, and successive reopenings of fissures during deposition. All 

such movement, as well as nearly all occurring after mineralization, 

was along the plane of the veins. Only a few ore-bearing structures 

are cross faulted, and these are displaced only a few meters.

Ores were deposited by fissure-filling and by replacement. The two 

types are gradational to different degrees, but in most deposits one 

process has dominated over the other, and the deposits may be classified on the basis of mode of emplacement. The few contact deposits 

that are not associated with obvious fissure channelways logically form 

a subdivision of the replacement class.
MINERAL DEPOSITS 49

The large replacement deposits of disseminated copper sulfide minerals in silicated limestone in the Quebrada Antamina are not included 

in this section of general description. These were studied only briefly, 

and therefore only a brief summary of their characteristics is given in 

the section on the Antamina area (p. 99-100).

FISSURE-FILLING DEPOSITS

Fissure-filling deposits consist for the most part of minerals deposited in open spaces in fault and shear zones.5 With few exceptions 

the structures have limited horizontal and vertical extent and small 

displacement. Ores consist principally of sphalerite and argentiferous galena, with smaller amounts of copper sulfides. Ore minerals 

occur with gangue throughout the veins, but mi nab] e material in most 

deposits is confined to high-grade shoots of comparatively limited 

extent.

Fissure-filling deposits show crustified banding or layering of the 

minerals. In some deposits crustification is very faint, whereas in 

others it is so prominent that the material appears to be made up of 

distinct layers of individual minerals. Nearly all veins contain lenticular- to irregular-shaped cavities and pores, most of which are 

lined or filled with crystals. Some cavities are lined with the same 

minerals as in the adjacent vein, suggesting merely incomplete filling, 

Avhereas others are lined with different minerals, suggesting a second 

stage of mineralization. Most of the minerals are in medium to large, 

Avell-formed crystals.

Minerals that replace country rock along fissure veins are principally pyrite, quartz, and silicates. These occur as disseminated 

grains, irregular pods, or massive bodies and generally are confined 

to zones less than 1 meter to either side of the vein; along some veins 

replacement zones extend outward for several meters. Ore minerals 

deposited as replacement of wall rock may either be massive or be disseminated and tend to be restricted to narrow zones generally only a 

few centimeters thick around the ore bodies. Breccia and shear fragments in many ore bodies are partly replaced by vein minerals.

At most deposits only one fault or shear zone forms the locus of deposition, but branches or splits from the vein may also be mineralized. 

In the larger deposits, where several fault or shear zones carry ore, 

most veins are parallel or nearly parallel, but in some deposits veins 

intersect at fairly high angles. Most mineralized fault or shear zones 

are comparatively straight or slightly undulating, but a few are quite 

irregular. Dips of most are steep, but may change with depth. One 

vein at the Atlante mine dips as much as 65° in the upper part and

5 Fault zones, us used in this report, clearly show displacement of the country rock or 

contain well-developed breccia, whereas shear zones show no obvious displacement and 

contain sheared wall rock with little or no breccia.
50 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

flattens to as little as 20° in the loAvest part of the mine workings. 

Ore occurs predominantly in breccia, at intersections of branching 

fault or shear zones or shear planes within an individual vein, or at 

places where the vein changes in strike and dip.

The larger parts of most veins are from 0.5 to 1.0 meter wide, although in even comparatively small veins the maximum width may 

be greater over short segments of the mineralized structure. In horizontal and vertical dimensions one of the largest single veins in the 

region is the Animus in the Huamana mine, exposed in mine workings 

400 meters horizontally and 160 meters vertically (see pi. 8). Fault 

or shear zones are traceable for greater distances in both dimensions, 

but it is rare to find mineralization along the entire length of these 

larger structures.

Most silver is intimately mixed with galena, but some occurs as 

veinlets of proustite, and some is with copper minerals, principally 

tetrahedrite. The silver content of galena ore may be less than 100 

grams and as much as 4 kilograms per ton. In every mine and 

prospect in this region the silver content of ore is of utmost importance to profitable operation, as lead, zinc, and copper veins IOAV 

in silver commonly cannot be exploited. Sphalerite with uniformly 

low silver content is either left unmined or is discarded before shipment. Very few deposits contain enough copper to warrant mining 

for that metal alone.

Ore bodies have wide ranges both in tenor and in dimensions. Some 

of the highest grade ore bodies, containing 75 percent or more combined galena and sphalerite, Avere seen in the Huamana mine and in 

several mines of the Antamina area. One sphalerite lens in the Hnamana mine was 20 meters long and as much as 40 centimeters thick, 

and galena lenses in the Antamina area were as much as 10 meters 

long and had a maximum width of 30 centimeters. Lower grade ore 

shoots are larger, not uncommonly 90 meters long and as much as a 

meter wide in the Huamana and Atlante mines. The over-all grade 

of ore from all operating deposits is generally low and requires some 

form of concentration to obtain shipping-grade material.

REPLACEMENT DEPOSITS

Replacement deposits, in contrast to fissure-filling deposits, result 

from replacement of pre-existing rocks. However, most replacement 

deposits also contain vein minerals deposited in fractures, fissures, and 

cavities Avhich served as channelways for mineralizing solutions. In 

the region herein discussed these deposits typically consist of disseminated grains or a granular mixture of sulfide minerals cut by 

lets, pods, and lenticular masses of more solid and crystalline 

material Avhich Avas deposited in cavities. The deposits are restricted 

Jargely to limestone, but occur also in calcareous shales, either along
MINERAL DEPOSITS 51

fault or shear zones or along contacts with intrusive bodies. In a few 

contact deposits minerals replaced intrusive rock as well as sedimentary rock, but always to a .lesser extent.

Replacement of limestone by sul.fi.de minerals along steeply dipping 

fault or shear zones is common. Some of the zones are parallel to bedding planes, and others cut across bedding at an angle. The richest 

ore shoots occur where the country rock is most strongly brecciated 

and sheared. Apparently these areas were more permeable to mineralizing solutions. The association of breccia and ore is well shown at the 

Patria mine in the Pachapaqui district, Avhere the highest grade ore and 

most complete replacement occur where the rock is most strongly 

brecciated. At the San Antonio prospect minerals replaced limestone 

along en echelon gash fractures of an extensive shear zone. Vein 

minerals also replace limestone along bedding planes at Patria and 

several other mines.

In contact zones, especially along granitic or rhyolitic intrusives, 

minerals replaced the country rock along fractures and bedding planes 

in the sedimentary rock, fractures in the intrusive rock, or along the 

contact. Whereas much of the contact zone may contain disseminated 

grains of minerals, most of the ore is concentrated in isolated lenticular or podlike bodies. Contacts between these bodies and the surrounding rock may be gradational, indicating incipient replacement, 

or may be comparatively sharp. Many of these ore bodies occur along 

some contacts, but all are small.

The principal, ore minerals in order of their abundance are sphalerite or marmatite, galena, and ch.alcopyr.ite, and the principal gangue 

minerals are pyrite, quartz, calcite, rhodochrosite, and rhodonite. 

Some of the deposits also contain minor amounts of arsenopyrite, 

barite, fluorite, stibnite, and tetraheclrite. Two or three small bodies at 

the Susana mine contain magnetite and pyrrhotite. The silver content 

of most replacement deposits is lower than that of most fissure-filling 

deposits. HoAvever, small ore bodies of nearly solid galena at the 

Sirena Encantadora mine in the Huallanca district contain as much 

as 4 kilograms of silver per ton, the highest of any operating mine in 

the region.

As most of the ore minerals are intimately mixed Avith the Avail 

rock, structures such as crustification or banding are faint or absent. 

Minerals tend to be fine grained and poorly crystallized, and vugs or 

cavities are rare. In a feAv deposits faint banding is discernible Avhere 

replacement has taken place parallel to bedding or closely-spaced 

parallel shear planes. In each deposit the richer ore shoots tend to 

have a preponderance of one ore mineral A\7 hich may be coarse grained 

but seldom has well-formed crystals.

Country rock in and near replacement deposits tends to be more 

intensely altered than along fissure-filling deposits. Sedimentary
52 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

rocks generally are altered by introduction of quartz, garnet, epidote, 

and serpentine; intrusive rocks are altered by introduction of quartz 

and by conversion of feldspars to sericite clay, and by ferromagnesian 

minerals to chlorite. In many deposits it is evident that the alteration 

took place before deposition of the sul.fi.de minerals. Alteration of 

wall rock will be discussed in more detail below.

Replacement deposits show great variation in size, ranging from 

small irregular bodies less than a meter long to large tabular bodies 

several kilometers long. The largest deposits in the region, at Patria, 

Esperanza, and Otito, are replacements of brecciated and sheared 

limestone on two limbs of a complex anticline. These are at least 4 

kilometers long and range from 10 to 50 meters in width. Contact 

deposits may be several meters wide and several hundred meters long, 

but most of the snlfi.de minerals are in small bodies a few meters long 

and less than a meter wide.

MINERALOGY

Information on mineralogy is based on macroscopic field and laboratory study of hand specimens, supplemented by blowpipe determinations and microscopic study of thin and polished sections. The only 

minerals listed in this section are the sulfides and their alteration 

products, and gangue minerals.

Data on chemical composition and physical properties of the sulfide 

and oxide minerals were taken from Dana (1932 and 1944) and data 

on the other minerals from Winchell (1933).

PRIMARY MINERALS

Argentite, Ag2S. Vei.nlets and disseminated grains of argentite 

were seen at two or three mines, and minute quantities of argentite 

may be associated with most of the argentiferous galena of the region. 

The argentite is fine grained, lead gray, and very sectile.

Arsenopyrite, FeAsS. Massive and crystalline arsenopyrite occurs 

in only a few of the deposits.

Barite, BaS04 . White, crystalline barite occurs in small caAdties 

or as veinlets in a few veins, associated with galena and sphalerite or 

as a webbing in. limonite.

Bornite, Cu5FeS4 . Small grains of bornite are associated with chalcopyrite in the large replacement body at Antamina. Duenas (1904, 

p. 53) reported that he found this mineral at the At]ante mine.

Bournonite, 2PbS.Cu2 S.Sb2 S3 . Duenas (1904, p. 53) reported that 

bournonite occurred in the Atlante mine. Although we did not identify it in this mine or in other mines of southern Ancash, possibly it 

occurs in small amounts, associated with a few lead ores.

Calcite, CaC03 , is one of the common gangue minerals. In a few 

veins it forms pyramidal (dog-tooth) white to transparent crystals,
MINERAL DEPOSITS 53

but in most veins it forms compact masses of white to gray rhombs 

showing only cleavage faces. Rhombs range in size from less than a 

millimeter to several centimeters in diameter. The most coarsely 

crystalline calcite is associated with low-grade fissure-filling deposits 

in limestone.

Chalcopyrite, CuFeS2 . Chalcopyrite is massive and occurs as small 

blebs disseminated in other vein minerals. Replacement deposits in 

the Antamina area contain disseminated grains of Chalcopyrite in silicated limestone.

Dolomite, CaC03 .MgCo3 . White crystalline dolomite occurs in 

small quantities in most of the veins in the Quebrada Honda-Vesuvio 

district, but is comparatively rare in the other districts.

Fluorite, CaF2 . Small amounts of white or pur-pie fl.uor.ite are found 

in a few veins in the southern districts and in most veins in the Antamina area. It appears to fill cavities between earlier minerals.

Galena, PbS. Three distinct varieties of galena can be recognized: 

cubic, plumose or bladed, and A^ery fine-grained or massive. Cubic 

galena, occurring in nearly all the veins, forms compact masses which 

show cleavage faces and crystal faces in pores or cavities. Mine owners report that this type of galena contains only a few grams of silver 

per ton. Plumose or bladed galena is less common. The blades are 

flattened and elongated cubes which retain cubic cleavage and are commonly oriented so that the long axis is parallel to the vein walls. This 

type of galena is reported to have a high silver content. Fine-grained 

galena, also high in silver, occurs in minor quantities in many of the 

veins.

Magnetite, FeFe2O4 . A small body of fine-grained magnetite \vas 

found in one of the Susan a veins of the Pacllon-Llamac district. It 

was not observed elsewhere.

Polybasite, 9Ag2S.Sb2 S3 and Stephanite, 5Ag2 S.Sb2 S3 , were reported by Dueilas (1904, p. 47) as occurring in the enrichment zones 

of veins at the Atlante mine in the Quebrada Honda-Vesuvio district. 

We did not see these minerals, but it is possible that they occur in 

ores of some veins.

Proustite, Ag3AsS3 . Veinlets of the light-ruby silver mineral proustite were recognized in a few specimens on the dumps of one silver 

mine in. the Huallanca district. The proustite is finely crystalline, 

soft, and vermilion in color.

Pyrargyrite, 3Ag2 S.Sb2 S3 . The dark-ruby si.Vver mineral pyrargyrite was seen at one mine in the Antamina district.

Pyrite, FeS2 . Pyrite is by far the most common sul.fi.de mineral 

and ranks with quartz as a major gangue mineral. Pyrite ranges in 

texture from massive or finely crystalline to coarsely crystalline; in 

the crystalline variety cubes and pyritohedrons are as much as three 

centimeters in diameter. Striated cubes appear to be much more
54 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

common than pyritoliedrons. Practically all the veins and nearby 

wall rock contain disseminated pyrite. Most pyrite is hard and solid, 

but in a few replacement veins pyrite and wall rock form a granular 

mixture that is soft in the vein and disintegrates rapidly on the dump. 

This unstable variety probably is marcasite.

Pyrrhotite, Fei._xS (where x varies from 0 to 0.2). Small quantities of pyrrhotite occur in a f CAV A^eins of the Pacllon-Llamac district 

and at one mine in the Quebrada Honda area. It is fine grained, 

bronze yelloAv to broAvn gray, and moderately magnetic.

Realgar, AsS. Yeinlets of realgar Avere observed only at the 

Danubio mine in the Pachapaqui district. The material is soft, 

bright red, and fills narroAv fractures which cut through the other 

sulfide minerals.

Quartz, SiO2 - Quartz, the most common gangue mineral of the 

region, ranges in texture from massiA^e to crystalline and is Avhite to 

clear. White massiA^e quartz is the predominant type. Crystals 

seldom exceed a centimeter in length.

Rhodochrosite, MnCO3 , and rhodonite, (MjST,CaFe) SiO3 , are 

major gangue minerals in many replacement deposits and are so intimately mixed that they can,be differentiated only by close examination ; they also are found in some fissure A^eins. Rhodochrosite occurs 

in irregular grains 1 to 2 millimeters in diameter, Avhereas rhodonite 

is massive. Fresh surfaces of these minerals are rose red to yelloAvish gray but Aveather readily to black.

Siderite, FeCO3 , and ankerite, 2CaCO3 .MgCO3 .FeCO3 . Gray to 

tan manganiferous carbonates occurring in a feAv veins Avere tentatively identified as siderite or ankerite.

Sphalerite, ZnS. Most sphalerite contains iron, and a more accurate chemical formula is (Zn,Fe)S. Ordinary sphalerite contains 

less than 10 percent iron and is white to light broAvn; marmatite, a 

variety, contains more than 10 percent iron; and christophite, another variety, contains the theoretical maximum of 26 percent iron 

(Dana, 1944, p. 212). In most veins of this region sphalerite is the 

most abundant ore mineral. Massive sphalerite veins are made up of 

irregular grains Avhich shoAv only cleavage faces, Avhereas in cavities 

and porous parts of fissure A^eins sphalerite grains exhibit welldeveloped crystal faces. Specimens of sphalerite from a feAv veins 

are triboluminescent, i. e., give off sparks Avhen scratched Avith a 

harder material.

Much of the sphalerite is dark brown to black and probably is the 

variety marmatite. Chemical analysis of marmatite from the Susana 

mine of the Pacllon-Llamac mining district showed 13.65 percent 

iron.
A1INERAL DEPOSITS 55

Stibnite Sb2 S3 . Stibnite was found in one or two lead-zinc veins 

and in several quartz-calcite veins. It forms slender, striated, prismatic crystals either in radiating masses or in open meshworks.

Tetrahedrite, (Cu,Fe) 12SbdS13 , and tennantite, (Cu,Fe)i2As4Si.v 

Small blebs and crystals of argentiferous tetrahedrite or tennantite 

occur in many veins of the region. The material is steel gray to black, 

very brittle, and hard. Massive tetrahedrite-tennantite ore is mined 

only from a fissure vein at the Carmen del Macizo mine in the 

Huallanca district.

SECONDARY MINERALS

Azurite, Cu(OH) 2 .2CuCO3 , and malachite, Cu(OH) 2 .CuC03 . 

Crystals and crusts of malachite with minor amounts of azurite occur 

in cavities in the oxidized zones of copper-bearing veins. Crystals 

are few in number and are seldom more than 1 to 2 millimeters long. 

Malachite stain and thin crusts are common in many old drifts and 

pits. Water from a few adits has deposited malachite on outcrops 

and boulders of limestone.

Cerussite, PbC03 . A few white prismatic crystals of cerussite 1 to 

2 millimeters long were found in cavities in oxidized zones at the 

Huan.za.Ui mine in the Huallanca district. Small cavities in many 

oxidized veins in the same area are coated with a white powdery material which may be in part cerussite. It is also probable that oxidized portions of many other deposits throughout the region contain 

minor quantities of lead carbonate.

Chalcanthite, CuS04 .5H2 0. Protected walls of old surface pits 

and drifts in some places exhibit coatings several centimeters thick 

of bright-blue crystalline ch.alcanthi.te.

Chalcedony (chalcedonite) and opal, SiO2 or SiO2 ,nH2 O. A few 

veins contain small masses or coatings of white to tan, cryptocrystalline or non-crystalline Si02 , which appear to have been deposited by 

surface water. This material is either chalcedony or opal.

Gypsum, CaS(X.2H2 0. Crusts of prismatic to acicular white crystals of gypsum form on walls or floors of some old workings. Some 

gouge contains fine-grained gypsum, and a few iron oxide zones and 

gossans contain veinlets of the mineral. A soft, plastic white material which oozes from fractures in workings at the Cosmos mine in 

the Tuco-Chira district consists largely of fine-grained gypsum.

Epson-rite, MgS04 .7H2 0, and goslarite, ZnSO,.TH2 dT Walls of 

many old mine workings have thin crusts or are coated with hairlike 

crystals of water-soluble, white epsomite and goslarite. Old workings of the Ispac mine in the Huallanca district contain stalactitic 

masses of these minerals.

Limonite cry ptocry stall ine goethite Fe2O3 .H2 0, with adsorbed 

or capillary water; and hematite, Fe2 O3 . The iron oxides are the most
56 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

abundant secondary minerals and can be seen in all the veins. They 

form gossans over many veins, especially those some distance from 

recently glaciated areas. In the field no attempt was made to distinguish between the iron oxide minerals. Although iron oxide in. the 

gossans ranges in color from ocher yellow through red brown to black, 

the color of most is dark red brown. Limonite can be found as pseudomorphs after blebs or crystals of pyrite, sphalerite, or chalcopyrite; 

as crusts on walls of old workings; as thick and extensive gossans; 

as cementing material in fault breccia zones; and as cementing material in alluvium. Gossans are porous to massive, and in most only 

a part of the sulfide minerals has been altered to iron oxide. Welldeveloped boxwork structure is rare.

Smithsonite, ZnCO3 . Crusts as much as 2 millimeters thick of moderately fine-grained (1 to 3 millimeters) light-tan or cream-colored 

smithsonite coat crystal faces of sphalerite in vugs at the Humana 

mine. Surfaces of sphalerite crystals under smithsonite crusts are 

corroded or etched. It is probable that smithsonite also occurs in small 

quantities in the oxidized parts of many veins, but it was not recognized in the field.

WALL ROCK ALTERATION

Alteration of wall rock along the veins is accomplished by heat and 

by the action of hydrothermal solutions and gases. Several processes 

may be involved in the ultimate alteration; but the most important 

probably are reaction between existing minerals to form new minerals 

and reaction between existing minerals and elements introduced by 

solutions or gases. Walls of most veins in limestone and calcareous 

shale have been silicified and those of some veins garnetized, serpentinized, or epidotized. Calcareous and shaly sandstones near a few 

veins have been similarly altered. In most places such alterations 

preceded sulfide mineralization, but during mineralization wall rock 

was further altered by the development of sericite and clay minerals.

During silicification of limestone, quartz replaced calcite along 

fractures and bedding planes and in scattered grains in the groundmass, forming a tough gray to light-gray rock. Microscopically, such 

rock consists of irregular to wispy veinlets or wormlike growths of 

quartz in a granular groundmass of quartz and calcite. Locally the 

calcite has been completely replaced. In some veins the wall rock 

was silicified during sulfide mineralization.

Garnetized limestone, most common in contact metamorphic zones, 

occurs along a few veins away from intrusive bodies. In thin section 

the garnet is colorless, pale yellow, pale yellow brown, or pale green; 

garnet crystals show four- to six-sided outlines and have anomalous 

extinction to first order white. Many crystals consist of irregular 

isotropic centers surrounded by twinned layers parallel to the crystal 

faces. Some crystals with six-sided outlines consist of wedge-shaped
MINERAL DEPOSITS 57

twins; each wedge has a crystal face as a base and apexes at the center of the crystal. Under crossed nicols, opposite wedges become extinct simultaneously. Some garnet crystals contain pyrite grains near 

their centers, or sericite and calcite grains between twin wedges or 

bands. Most of the garnet is probably the variety grossularite.

Silicified Avail rock at many veins has a pale-green color, which may 

result from small amounts of associated epidote or serpentine. Limestone in the walls of a few veins was altered by the introduction of 

both epidote and garnet and at places contains irregular bodies or 

stringers of bright-green material, largely epidote. In thin section 

the epidotized limestone consists of irregular grains or bladelike 

crystals of epidote in a matrix of granular quartz and calcite. The 

most intense epidotization occurred in contact metamorphic zones.

Walls of nearly all veins contain veinlets and disseminated grains 

of pyrite, which fill fractures and cavities as well as replace the host 

rock. Pyrite ranges in texture from massive to crystalline; in crystalline form cubes are more common than pyritohedrons. Microscopically, pyrite appears to have replaced the wall rock along fractures 

and in isolated grains and patches away from fractures. In a few 

specimens pyrite appears to have replaced large calcite crystals along 

cleavage planes.

Sericitization, already mentioned in the discussion of igneous rocks, 

also has affected shaly limestones, shaly sandstones, and sandstones to 

a slight degree. In these rocks minerals along fractures and in the 

more dense groundmass have been altered to fine-grained sericite. 

Sericitization of intrusive bodies is most intense near sulftde deposits, 

and it is possible that this type of alteration was contemporaneous with 

sulfide mineralization.

Limestone of some contact deposits has been partly altered to 

wollastonite or has been bleached and recrystallized. Bladed Avhite 

wollastonite, associated with other silicate minerals in a few deposits, 

occurs as scattered crystals or, more commonly, as radiating crystals 

in pods as much as 50 centimeters in diameter. The largest pods of 

pure wollastonite were seen at the Sirena Encantadora mine in the 

Huallanca district. Lenticular, tabular, or irregular bodies of recrystallized white limestone occurring near ore bodies of many contact 

deposits range in size from a few meters to nearly a kilometer in length 

and from a few centimeters to more than 10 meters in width. One of 

the largest bodies seen at the Susana mine in the Pacllon-Llamac district is nearly a kilometer long and ranges from 2 to 10 meters in 

width. This body is in. a band of silicated limestone parallel to a 

rhyolite sill.

Some of the white and tan clays associated with many veins probably resulted from hydrothermal alteration of wall rock. J. M. Axel321628 55 5
58 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

rod of the Geological Survey carried out X-ray examination of claylike material from 6 of the mines and determined that only 2 specimens 

contained the clay minerals kaolinite, halloysite, and possibly 

endellite. The other specimens consisted of one or more of the following minerals: mica (one unidentified form and another form similar 

to phlogopite), hydromica, quartz, and gypsum.

CLASSIFICATION AND GENESIS OF DEPOSITS

Most veins are porous, vuggy, and banded, and the minerals are 

well crystallized, indicating that deposition was fairly near the surface in an environment of medium to low pressures. The minerals in 

the deposits of this region are known to have a range of deposition 

which includes formation at medium and low temperatures, and some 

minerals in these deposits, such as the silver sulfides, are restricted 

entirely to formation at low temperatures. In view of these conditions the deposits are classified as ranging from mesothermal to epithermal, according to the classification of Lindgren (1933, p. 211). A 

few deposits contain, pyrrhotite, a mineral commonly found in ore deposits believed to have formed at high temperatures. Inasmuch as 

these pyrrhotite-bearing veins also contain minerals deposited at 

lower temperatures and possess textures characteristic of deposition at 

low pressures, they probably are telescoped deposits, deposits in which 

geochemical environment during the period of mineralization changed 

rapidly owing to near-surface penetration of igneous source-rock.

Replacement deposits of the contact type contain silicate gangue 

minerals formed at high temperatures as well as sulfide minerals 

probably deposited at lower temperatures. On the basis of the sulfide 

minerals and structures of ore minerals (p. 51) these deposits are 

classed as mesothermal.

As the result of extensive studies, the geological staff of the Cerro 

de Pasco Corporation (1950) has concluded that all major lead-zinccopper-silver deposits in central Peru were derived from hydrothermal solutions emanating from Tertiary intrusive stocks of intermediate composition. Although many deposits in central and southern 

Ancash are related spatially to intrusive bodies, at most places their 

genetic relationship is not obvious. Contact replacement deposits are 

probably closely related to the intrusions, but there is no positive evidence that other replacement deposits and fissure-filling deposits far 

from visible intrusive bodies were derived from igneous rocks.

METHODS OF MINING AND CONCENTRATING ORE

All active operations visited in 1948 and 1949 were worked by hand. 

Ore was drilled by hand, blasted with small charges, and either back-
ECONOMIC FACTORS AFFECTING MINERAL PRODUCTION 59

packed or hand-trammed to the portal. Atlante was the only mine to 

have any power; a small dynamo run by mine water and glacial melt 

water generated enough current to operate a small inclined hoist and 

pumps.

All veins are worked either by open or by partly filled stopes; stoping is overhand from most drifts but also underhand from pits and 

some drifts. The larger mines, under supervision of engineers, are 

worked by moderately systematic mining methods and are adequately 

timbered and pillared. Smaller mines, worked by prospectors and 

miners, are less systematically developed. In such mines winzes may 

be cut across floors of drifts, stopes left in precarious condition, and 

waste dumped wherever convenient. A number of irregular veins and 

replacement deposits are opened through surface pits which are deepened and become complex as ore bodies are mined. The resulting 

underground workings are almost impossible to describe in conventional mining terms. These workings, as well as any below the lowest 

level opening directly to the surface, flood soon after operations cease, 

leaving no access to areas beyond flooded sections.

The only concentrating plants operated during 1948 and 1949 were 

at the Atlante mine, at Pompei just below the Huamana mine, and at 

Pachapaqui; of these, Pompei closed in 1948. At the Pachapaqui plant 

ores are ground in a ball mill, and a bulk concentrate of lead, copper, 

and silver is produced in flotation cells; comparatively low-grade ores 

from two or three small mines furnished the mill feed in 1949. Both 

the Atlante and Pompei concentrators are small flotation plants concentrating lead, copper, and silver only. The Empresa Minera 

Vesuvio, operators of Atlante, were planning a larger concentrator to 

handle lower grade ore and fill from old stopes. The Empresa Minera 

Pompei handled ores from its own mine, Huamana, and also customtreated ores from other mines to the north.

At all other operating mines ore is broken on flat rocks with sledge 

hammers and fragments of sulfides are sorted out by hand. In 1948 

and 1949 sphalerite was discarded with gangue. At most mines ore is 

further crushed and hand sorted to produce the final concentrate, but 

at a few after the second crushing it is hand-jigged to produce shipping-grade material. The concentrate, consisting of fragments 1 

centimeter or less in diameter, is packed in burlap bags for shipment. 

Lead-silver concentrate is the main product, but copper-silver concentrate was being produced from one deposit in 1949, and several mines 

were producing lead-copper-silver concentrate. Antimony (stibnite) 

concentrate was produced at one mine and lead-antimony concentrate 

at another.

The only smelter in operation in the region is at the main camp of 

the Empresa Minera Vesuvio. It is a comparatively simple unit designed to produce lead-silver bullion. Coal and limestone are obtained
60 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

from the surrounding area, and these, as well as lead concentrate, are 

stockpiled throughout the year for an annual charge. The only ore 

handled at the smelter is that from the Atlante mine.

At larger mines supervised by engineers most laborers work for 

wages which in 1949 were S/o. 5.00 ($0.28) or less per day. 6 Operations at most smaller mines and prospects are carried out by contract 

miners who do all work, development included, at a per-ton of production rate. Hand crushing and sorting generally is done by the families of these miners. In 1949 contracts were S/o. 150.00 ($8.32) and 

higher per ton of lead concentrate. It was not possible to gather precise data on costs, but it is estimated that mining and concentrating ore 

at the various deposits ranged from S/o. 100.00 ($5.55) to S/o. 400.00 

($22.22) per ton of concentrate in 1949.

TRANSPORTATION FACILITIES AND COSTS

All the mines use pack animals for transport of ore from mine to 

roadhead; ore is backpacked short distances to trails at a few deposits 

where terrain is exceptionally rugged. In the Tuco-Chira district 

concentrates are packed by burros and mules only 1 to 2 kilometers 

from the deposits to the road leading to Conococha; from all other 

districts concentrates are packed 15 to 60 kilometers. Roadheads are 

at Chancos for the Quebrada Honda-Vesuvio district, at San Marcos 

for the Antamina-Contonga district, and either' at Conococha or 

Chiquian for the southern districts other than Tuco-Chira. From 

these points ore is trucked to ports (p. 13-14).

The cost of animal transport depends on the trail distance and the 

availability of animals. A fairly representative cost is that of the 

Sirena Encantadora mine in the Huallanca district. Sr. Arnulfo 

Carbajal, owner of the mine, stated that he contracted to have concentrates packed directly to Conococha, a trail distance of about 60 

kilometers for S/o. 120.00 ($6.67) per ton. From Conococha to Lima 

the concentrates were trucked for the same price, so the total cost of 

shipping from the mine to Lima was S/o. 240.00 ($13.35) per ton. 

With transportation costs from the southern districts to Lima ranging from S/o. 200.00 to 300.00 per ton, and mining costs from S/o. 

100.00 to 400.00 per ton, total cost of ore laid down in Lima may be 

between S/o. 300.00 and 700.00 per ton or between $17.00 to $39.00 

per ton.

In 1948 transportation from the Quebrada Honda to Chancos cost 

S/o. 100.00 per ton and from Pompei or Vesuvio to the same roadhead from two to three times this amount. From Chancos most ore 

was shipped to Huaras by truck for about S/o. 15.00 per ton and sold 

there to ore buyers who assumed the cost of shipment to ports.

6 Cost data in dollars are computed at the exchange rate of S/o.18.00: $1.00.
ECONOMIC FACTORS AFFECTING MINERAL PRODUCTION 61 

PRODUCTION AND RESERVES

In 1948 at least 14 lead-zinc mines and prospects were being operated or explored in the two northern districts, and in 1949 11 deposits were producing lead and copper concentrates in the southern 

districts; in addition one mine in the Pacllon-Llamac district produced stibnite concentrates. The production figures listed below are 

based on information furnished by mine owners and operators or estimated by the Avriters. Miners and prospectors generally overestimated 

production and potential production.

The principal product of the region is silver-bearing lead concentrate, but some material contains a little copper as well. All producers 

try to ship concentrate containing 60 percent of lead, but this grade is 

not always attained. The concentrate varies considerably in silver 

content and may contain from less than 100 grams per ton to as much 

as 4 kilograms per ton. As a result profits may be as high as several 

hundred soles per ton, but on the other hand some material shipped 

may not pay mining and shipping costs. In 1948 and 1949 sphalerite 

with low silver content was discarded because prices offered did not 

pay shipping costs.

The one active mine in the Pacllon-Llamac district produced about 

5 tons of stibnite concentrate in 1949, and one mine in the Huallanca 

district produced a few tons of stibnite as well as galena. The total 

stibnite production was probably less than 10 tons for the year. Several mines near San Marcos on the east side of the Cordillera Blanca 

also produced stibnite concentrates, but these mines were not seen during our investigation.

Production of lead-silver and lead-copper-silver concentrates, central and southern 

Cordillera Blanca, and northern Cordillera Huayhuash, Departamento de Ancash 

and Departamento de Hu&nuco

Estimated 

production 

of concentrates (in 

District Number of active mines ' tons')

Quebrada Honda-Vesuvio__-___--__-____-__ 6_________________ 400

Antamina-Contonga._______________________ 7_________-_______ 400

Huallanca 2 ..__---__----___________________ 4.________________ 90

PachapaquL ___-_______-_-___-_--_--_____-_ 5..----------_____ 100

Tuco-Chira_----_-------------_-------_---- 2_________________ 35

1,025

1 Quebrada Honda-Vesuvio and Antamina-Contonga, 1948; Huallanca, Pachapaqui, and Tuco-Chira, 1949.

2 Includes one mine producing both galena and stibnite concentrates and another producing coppersilver concentrates.

The available data on reserves and grade of ore are so scanty that 

we cannot estimate closely the ore reserves of the region. Most 

of the veins are small, and possible reserves range from, a few tons 

to a few hundred tons. A few veins of intermediate size have possible
62 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

reserves of a few thousand to a few tens of thousands of tons. The 

largest mineralized zones of the region, in the Pachapaqui district, 

have possible reserves of several million tons. Many of the small veins 

and a few of the intermediate ones can be worked profitably by small 

scale hand mining, but most are too small to support mechanized operations. The largest deposits of the region are low in grade and 

under present conditions of poor transportation cannot be worked at a 

profit.

FUTURE POSSIBILITIES AND RECOMMENDATIONS

The present rate of mineral production probably can be maintained 

for several years. The 1950 price of base metals and concentration 

facilities at Pachapaqui should bring about a material increase of production in that district.

No great increase in mineral production is possible until adequate 

roads are available. The road from Chiquiaii to Huallanca could be 

constructed at a comparatively low cost. The cheapest and most logical route for this road would be along the Rio Chiquiaii, through 

Pachapaqui, up Quebrada Tunacancha, across the north end of the 

Cordillera Huayhuash, and then down the Rio Torres to Huallanca. 

This route offers the least amount of rock work and an easier grade 

than other routes under consideration, including those through Paso 

Burro between Huallanca and Pachapaqui or through Paso Cuaush 

between Huallanca and Quebrada Llamac. Road transportation in the 

Pachapaqui and Huallanca mining districts should stimulate mineral 

production, and the added tax revenue from this source would 

probably pay for the road in comparatively few years.

Additional roads are not necessary in the Tuco-Chira district. The 

reserves of this district are small, and although small scale mining 

may continue for several years, any great increase in production is 

doubtful. The main veins of the Pacllon-Llamac district have fairly 

large tonnages of marmatite but are low in sulfides of lead, copper, 

and silver. A careful study of the milling qualities of the marmatite should be made before constructing roads and opening mines, 

principally because the comparatively long access road will require 

a major investment.

At both northern districts spur roads built part way to the mining 

districts would greatly reduce the cost of transporting ore. A comparatively inexpensive road from the hotel at Chancos up the Quebrada Honda to the fork in the trail just below the Vinoyapampa, a 

distance of about 20 kilometers, would reduce the haul by 2 days per 

round trip and save about 50 soles per ton of ore. Extensions of the 

road to the upper Quebrada Honda and across the pass to the Vesuvio 

area would be expensive and unwarranted in view of reserves in sight 

at the time of our examination. A similar spur road from San Marcos
DESCRIPTION OF DISTRICTS AND DEPOSITS 63

leading eastward up the Quebrada Yaquish, a distance of about 6 or 7 

kilometers, would save 1 day per round trip for pack animals carrying ore from Quebrada Antamina.

Production of lead ore from the Antamina area would be greatly 

stimulated by the construction of a small mill.

DESCRIPTION OF DISTRICTS AND DEPOSITS

The names of mining districts used in this report are those in local 

usage, and names of individual mines were furnished by mine oAvners 

and guides. These do not necessarily correspond to the listing in the 

Padron General de Minas (issued biannually), the official roster of 

the Direccion de Minas of mining concessions on which taxes have 

been paid. The district names used in this report and the official 

designations (Padron General de Minas, 1949) are:

Quebrada Honda-Vesuvio __ __-- Huari 

Antamina-Contonga______ ____ _ _ _. Huari 

Huallanca _ _ Huallanca 

Pachapaqiui ___________________________ Bolognesi

Pacll6n-Llamac_________________________- Bolognesi 

Tuco-Chira___________________________. (Notlisted)

Less than 50 percent of the mines and prospects herein discussed 

are listed in the Padron General de Minas (second half, 1949), and no 

deposits of the Tuco-Chira district are included. The discrepancies 

are due to lapsing of ownership of old concessions, lag in entering new 

registrations, and differences between local and registered names. 

Owing to the last, some concessions listed in the Padron may correspond to concessions on deposits visited in our investigations, but 

locations as given in the Padron are so brief that it was not possible 

to correlate these with deposits we saw in the field.

In terms of mining activity in the present century, the two most 

important districts are Quebrada Honda-Vesuvio (Vesuvio area) and 

Huallanca. Several good-sized fissure-filling deposits have been the 

mainstays of production in each, but these mines now have comparatively small reserves. Nevertheless, the presence of steadily producing 

mines has been a great stimulant to prospecting and exploration in 

these districts, and sufficient ore is in sight to indicate that production 

will continue on the present scale for several years to come. Of the 

remaining districts, the Pacllon-Llamac contains large reserves of 

low-grade zinc ores; two low-grade veins in the Pachapaqni district 

are the largest in central and southern Ancash, and the AntaminaContonga district includes a number of good fissure-filling deposits 

which have been comparatively little mined as well as large reserves 

of copper ores. With improved transportation these three districts 

would be the main source of future larger scale production.
64 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH 

QUEBBADA HONDA-VESUVIO MINING DISTBICT

The Quebrada Honda-Vesuvio mining district is near the crest of 

the Cordillera Blanca and from 16 to 25 kilometers east and northeast 

of Chancos, in a belt about 25 kilometers long and roughly parallel 

to the trend of the Cordillera. The southern deposits are in the upper 

end of the Quebrada Honda, a valley extending eastward from the 

valley of the Rio Santa, and in tributary valleys of the quebrada. The 

upper Quebrada Honda locally is known as the Quebrada Pomabamba, 

and its flat floor is named the Vinoyapampa. Those tributary valleys 

containing mineral deposits are Quebrada Cancahua and Quebrada 

Pacllash, both south of the main valley. The northern deposits are at 

the heads of valleys draining eastward into the Bio Maranon. The 

southern deposits of the northern group are at the head on the west 

side of Quebrada Checchipampa. This valley joins Quebrada Huichjanca at Vesuvio and drains northeastward through Pompei. Several veins in Quebrada Huichjanca have been worked in past years. 

The northern deposits of the group are north of Pompei in the Quebrada Apash (figs. 2 and 8).

The only means of access to the district is a trail extending from 

Chancos to Huari. From Chancos the trail ascends the Quebrada 

Honda for a distance of about 20 kilometers, crosses the north wall of 

the valley (about 10 kilometers), and descends Quebrada Illauro 

northward to Chacas, an additional 15 kilometers. From Chacas it 

continues via a number of valleys to Huari, 29 kilometers airline distance to the southeast. Spurs leading to deposits branch from the 

main trail. One spur branches from the main trail about 20 kilometers 

beyond Chancos and continues up the Quebrada Honda about 8 kilometers. Another branches about 5 kilometers southwest of Chacas and 

extends about 5 kilometers westward to Pompei.

Trails connect Pompei with Vesuvio and nearby mines. All mineral products from the district move to Chancos and Marcara; none 

are shipped via Huari. The high point of the trail system is the pass 

between the Quebrada Honda and Quebrada Illauro, at an altitude of 

4,822 meters.

The physiography of the district displays the results of strong 

glaciation; most valleys are U-shaped, with flat floors and steep walls, 

and most ridges and peaks are cut into aretes and horns (p. 40-41, 

and figs. 15-21). The floors of quebradas are easily passable except 

where glaciers quarried bedrock or deposited heavy end moraines. 

Where trails ascend valley walls, however, gradients are steep and 

travel is difficult. Ice caps mantle all peaks above 5,000 meters, and 

valley glaciers occupy the upper parts of most quebradas. Ice lies 

above most mines in the Quebrada Honda and above the Atlante mine.

Floors of quebradas have a moderately good cover of pasture 

grasses, and in places quinual trees form comparatively thick growths
QUEBRADA HONDA-VESUVIO MINING DISTRICT 65

*

on floors and walls of valleys. The quinuales in the northern area 

are sufficiently abundant to provide adequate mine timber. Vegetation is sparse along most valley walls and virtually absent just below 

ice sheets.

The major rock units in the district are the granodiorite batholith 

and stocks and the Jurassic(?) metasedimentary rocks. Associated 

with the granodiorite are local masses of diorite and dikes of pegmatite, aplite, and diabase (p. 28-30). The sequence of metasedimentary 

rocks consists mainly of dark-colored quartzites, shales, and phyllites, 

but also includes zoisite- and andalusite-bearing hornfels (p. 18-20, 

39). Lower Neocomian sandstone was seen in Quebrada Illauro but is 

not exposed in the mine areas.

The outcrop of the batholith is from 10 to 14 kilometers wide; its 

west contact follows the steep west front of the Cordillera Blanca. 

From south to north, the east contact runs from just west of the Espar-ta mine in Quebrada Cancahua to the Atlante mine and then 

swings west past the Huamana mine. At most places the contacts are 

vertical or dip steeply. The stock in the upper Quebrada Honda, as 

much as 5 kilometers in diameter, lies 1.5 kilometers east of the batholith in Quebrada Cancahua. Its contacts dip 45° N. in the vicinity 

of the Soledad mine and 65° E. at the Santa Barbara prospect. A 

smaller stock southeast of Pompei occupies part of the north end of 

the ridge between Quebrada Illauro and Huachacpampa (fig. 8).

The metasedimentary rocks are closely folded; axial planes of major folds strike northwest, and beds dip vertically or steeply to the 

east or west. Along the north and northeast wall of the upper Quebrada Honda, an anticline broken along its axis is seen in the vicinity 

of the Rataquenua prospect. Immediately to the northeast is a strong 

syncline. At the Condor mine near the head of the quebrada, beds are 

uniformly steeply dipping and may be isoclinally folded. At the 

Huamana mine beds strike east and dip north from low to high angles, 

a marked divergence from the regional structure elsewhere in the 

district.

The deposits of the district are near the contacts of the batholith 

or stocks and the surrounding metasediments and occur in both rock 

types. Minerals were deposited as fissure-fillings and to a minor extent as replacements along small faults or shear zones. In the upper 

Quebrada Honda area, deposits in metasedimentary rock are in fault 

or shear zones which parallel or almost parallel bedding planes; deposits to the north tend to cut across bedding planes. The attitudes 

of fault or shear zones in igneous rocks are not conspicuously related 

to regional structure.

Most minerals in the veins are primary, but several secondary and 

oxidized minerals are common. Primary metallic minerals found in 

this district are galena, sphalerite, chalcopyrite, tetrahedrite-tennan-
66 LEAD-ZINC DEPOSITS, CO'RDILLERAS BLANCA AND HUAYHUASH

tite, stibnite, bornite, bournonite, silver sulfides, polybasite, stephanite, gold, pyrite, pyrrhotite, and arsenopyrite. Of these, galena, 

sphalerite, and pyrite are present in largest quantities and arsenopyrite occurs in many veins. Minor quantities of copper minerals occur 

in most deposits. Silver is in galena and in copper minerals and also 

was found as polybasite and stephanite in the upper parts of the veins 

of the Atlante mine (Duefias, 1904, p. 47). Pyrrhotite was seen only 

at the Tomelamano mine and stibnite only at Huamana. Gold occurs 

in minor amounts (a few grams per ton) in a number of deposits but 

never is megascopically visible. Duenas (1904, p. 53) stated that 

bornite and bournonite also were found at Atlante.

Nonmetallic primary minerals include quartz, dolomite, rhodochrosite, siderite or ankerite, and rarely calcite. Alteration of ^silicates 

of wall rock produces sericite, chlorite, and minerals of the clay group. 

Secondary and oxidized minerals are silver sulfides, limonite, malachite, manganese oxides, smithsonite, anglesite,' and cerussite. Limonite is the most common, found along outcropa and in the upper 

parts of all veins, and malachite and manganese oxide stains do extend deeper in most mines. Smithsonite coats sphalerite only at 

Huamana, and anglesite and cerussite are reported to have been 

common in the upper parts of the veins at the Atlante mine (Duenas, 

1904, p. 47).

Ore shoots in this district, consisting of galena and silver sulfides, 

may be as short as a few meters and as long as 90 meters. Where silver 

content is high, as little as 10 centimeters width of galena is stoped. 

Such minable shoots, lenticular, tabular, or irregular in shape, are 

found sporadically along veins that for the most part contain insufficient amounts of recoverable sulfides or are barren. In well-exposed 

veins it can be seen that location of shoots is related to configurations 

of vein structure.

Some deposits in the Vesuvio area were prospected or mined on a 

small scale by the Spanish during the Colonial period and in the 

early 19th century, according to Duenas (1904, p. 13, 46, 65, 71), but 

between 1860 and 1885 only mines farther north, in the vicinity of 

Cajavilca and San Luiz, were operated. The Sextri deposit was discovered in 1885, and the company now known, as Empresa Minera 

Vesuvio built concentrating units and the smelter at Vesuvio for 

treating ore from the mine. Operations were financially unstable until 

the Atlante vein was discovered in 1895; this area had no signs of 

previous prospecting. Laurion, mined before on a small scale, was 

rediscovered by the company before 1900. The lead-silver ore at 

Sextri was mined out by 1904, but the Atlante and Laurion mines 

have been producing with moderate regularity since their development. , Only small amounts of high-grade lead-silver ore remain in 

the deposits of the two mines, but they still contain moderate amounts
QUEBRADA HONDA-VESUVIO MINING DISTRICT 67

of low- and medium-grade ore. To recover material Avith lower tenor, 

concentrating units are necessary at both deposits.

Huamana, worked in some earlier period and then forgotten, was rediscovered between 1895 and 1900, and as a result the Empresa Minera 

Pompei was formed. Shortly after, this company built a lixivation 

plant which more recently has been converted to a flotation plant. 

Huamana produced with moderate regularity until 1948 but ceased 

operations in that year owing to depletion of high-grade lead-silver 

ore. This area, Sextri, Atlante, and Laurion have moderate to substantial reserves of sphalerite, and mining for zinc ore could be 

started should transportation costs be reduced or the price of zinc 

increased.

Discovery of the deposits in the upper Quebrada Honda area came 

much later, and the only date we have is that of the opening of the 

Tomelamano deposit in 1928. Tomelamano, Condor, Chaco, and Esparta are the only mines shown on the Kinzl map of the Cordillera 

Blanca, published in 1939 (Kinzl, 1939a). Apparently most other 

known deposits were found after that date. From what we could see 

in 1948, lead-silver ore in developed parts of Condor, Esparta, Anna, 

and Chaco mines had been worked out. The Santa Barbara, Rataquenua, and Damelamano, as well as the prospects in Quebrada Pacllash, are small and seem to offer little promise for development. The 

Tomelamano and possibly the Arequipa mines are the only ones having lead-silver ore reserves; and Soledad, just being opened at the 

time of our examination, may develop some workable shoots. As in 

the northern part of the district, moderate amounts of sphalerite occur 

in workings and on dumps in both active and inactive mines.

In summary, the mines in the Quebrada Honda-Vesuvio district 

having promise of continued production of lead-silver ore are: 

Tomelamano Small high-grade reserve 

Atlante Substantial medium- to low-grade reserve 

Huamana Small medium- to low-grade reserve 

Laurion Moderate medium- to low-grade reserve 

Locations of deposits in the upper Quebrada Honda are referred to 

the falls at the foot of the Vinoyapainpa, and locations of deposits in 

Quebrada Cancahua are referred to the stream flowing along the 

Vinoyapampa. Trails leading to the deposits are clearly visible from 

the Vinoyapampa; travel time from the falls to any of the mines and 

prospects is from 1 to 2^ hours. Altitudes of the Rataquenua, 

Tomelamano, Damelamano, Chaco, Arequipa, and Soledad deposits 

were established by plane table triangulation and are correct to within 

20 meters relative to each other; the datum is interpolated from the 

map of the Cordillera Blanca by Kinzl (1939a). Altitudes of the remaining deposits visited in the upper Quebrada Honda area were 

obtained by aneroid and can be considered correct only to the nearest
68 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

150 meters. Altitudes at the Atlante mine are based on an assumed 

elevation of 4,600 meters at the portal of level 3, interpolated from the 

map of the Cordillera Blanca by Kinzl (1939a). The altitudes at the 

Huamana mine are from a company map, but these seem to be about 

200 meters too high when compared to altitudes of the area shown on 

the map of Kinzl. Altitudes at the Sextri mine are aneroid readings, 

using the elevations of the company survey at Huamana as a datum. 

Altitudes at Laurion were taken from company maps and seem to be 

about 100 meters too low as compared with the map of the Cordillera 

Blanca by Borchers (1935a).

RATAQUENUA PROSPECT

The Rataquenua prospect is on the north side of the upper Quebrada 

Honda 2.25 kilometers northeast of the falls at the foot of Vinoyapampa, in outcrops betAveen scree and lateral moraine below and ice 

above. The camp near the prospect is at an altitude of 4,490 meters.

The country rock is granodiorite and diorite in contact with Juras^ 

sic(?) quartzite. Contacts of diorite both with granodiorite and 

quartzite are exceedingly irregular. The quartzite forms the west limb 

of a closely folded anticline broken by faults along its axial plane.

Fissures and narrow shear zones contain small amounts of galena 

and sphalerite together with pyrite, arsenopyrite, quartz, and kaolin, 

as well as limonite and hematite. Small pits and short tunnels expose 

the veins over an area about 200 meters long which has a vertical 

extent of about 100 meters; the uppermost prospect is just below 

glacial ice.

The lowest vein, in granodiorite, strikes N. 2° W. and dips 45° W. 

It is traceable 20 meters and is from 15- to 20-centimeters wide. 

Sphalerite stringers as much as 5 centimeters in width contain veinlets 

of galena several millimeters wide. The middle veiiij a vertical distance of 25 meters above the lower vein, is also in granodiorite and is 

traceable for 40 meters. It strikes N. 45° W. and dips from 35° SW. 

to horizontal. This vein consists of iron-stained gouge and contains 

a few veinlets of galena and sphalerite. The upper prospect, in quartzite north of the stock, exposes a 20-centimeter wide shear zone striking 

N". 45° W. and dipping 25° SW. Gouge and clay, stained by iron oxide, 

contain veinlets and short lenses of galena, sphalerite, and arsenopyrite 

as much as 5 centimeters wide.

Other than material removed during prospecting, no ore has been 

mined and reserves are small, so it is doubtful that the prospect can 

be developed from the present showings.

. TOMELAMANO MINE

The Tomelamaho. mine, on the north side of the upper Quebrada 

Honda, is. in a small valley cut in.quartzite and underlying granodi-
QUEBRADA HONDA-VESUVIO MINING DISTRICT 69

orite. The outcrops form a comparatively narrow band along the 

valley wall between scree and morainal material below and ice above. 

The main adit is at an altitude of 4,480 meters, about 300 meters above 

the floor of the valley and 4 kilometers east of the falls at the lower end 

of the Vinoyapampa.

The country rock is dark-gray massive-bedded quartzite on the west 

limb of a closely folded syncline. The contact between quartzite and 

the granodiorite stock is from 30 to 40 meters vertically below the main 

adit. West of the main adit the quartzite strikes N. 5° W. and dips 

55° E., but within the mine workings the strike is more westerly. The 

rock has been bleached along parts of the veins.

The main vein, followed by a drift on the main level for about 175 

meters, lies in a bedding-plane fault zone striking N. 25° W. at the 

south and N. 45° W. at the north end of the workings; the vein dips 

from 50° NE. to vertical (fig. 22). Vein walls are slickensided.

The vein contains argentiferous galena, sphalerite, pyrrhotite, 

pyrite, arsenopyrite, and quartz which were deposited for the most 

part as fissure-fillings. In places the vein is banded and contains 

numerous vugs. Part of the pyrrhotite is replaced with galena and 

sphalerite. Graphite, apparently derived from carbonaceous material 

in quartzite, occurs at places, and miners stated that chalcopyrite 

occurs in small quantities.

Most galena consists of grains from 1 to 2 millimeters in diameter; 

along openings grains may be as much as 5 millimeters in diameter. 

The richest ore evidently contains less than 20 percent of galena. 

Miners stated that silver in the concentrates was as much as 180 ounces 

per ton. Ore shoots and minable pockets are comparatively small, 

ranging from 5 to 15 meters in length, as judged by sizes of stopes, 

and from several centimeters to 2 meters in width. Most ore bodies 

occur at intersections of shear planes or at places where the vein 

changes in dip or strike.

The main ore body, locatejd where the adit intersects the vein, has 

been stoped to the surface some 20 meters above as well as below the 

floor of the drift. In 1948 the northwest heading on the main level 

was being advanced, but no ore had been encountered, and a crosscut 

35 meters below had not yet reached the vein.

Four shear zones are cut by the crosscut on the main level but contain only quartz and minor amounts of sulfides. About 200 meters 

northwest of the main adit another shear zone exposed in a trench and 

a crosscut contains only small amounts of sulfides.

Reserves in sight will enable the mine to operate several years at 

the present rate of production, but it is doubted that further exploration will reveal larger ore bodies.
70 LEAD-ZINC DEPOSITS; CORDILLERAS BLANCA AND HUAYHUASH

El:4480m 

Elevation at portal, in meters,

Datum is mean, sea level

Surveyed with compass and tape by A. J. Bodenlos and G. E. Ericksen, 

August 1948. Base elevation interpolated from map of Cordillera Blanca

FIGURE 22. Geologic map of the main adit of Tomelamano mine, Quebrada HondaVesuvlo mining district.
QUEBRADA HONDA-VESUVIO MINING DISTRICT 71 

SANTA BARBARA PROSPECT

The Santa Barbara prospect is at the base of steep cliffs on a spur 

in the northeast wall and near the head of Quebrada Honda, just south 

of the tributary valley Quebrada Yanatsilca. It is about 6 kilometers 

airline distance from the falls and about 2.5 kilometers southeast of 

the Tomelamano mine. The altitude of the lowest workings is 4,500 

meters (barometric).

The country rock is quartzite and phyllite, striking N. 20°-30° W. 

and dipping steeply northeast, on the west limb of the same syncline 

exposed at the Tomelamano mine. The quartzite is dark gray to white, 

and interbedded phyllite is gray. The contact with granodiorite is 

about 50 meters west of the mine.

The prospect is on a vein traceable for 110 meters and from 0.4 to 

1.0 meters wide. Shear-plane walls are continuous, and movement 

along them is indicated by gouge and breccia in the vein. The vein 

strikes a few degrees west of north and dips 70°-80° W. in most underground workings but dips 85° E. near the portal of the north drift.

Minerals, in order of deposition, are quartz, pyrite, carbonate 

(ankerite?), and galena. Galena, occurring only in breccia cavities, 

is in crystals as much as 2 centimeters in diameter.

The north drift is 30 meters long with a winze at its heading. The 

south drift, although partly inaccessible, is at least 20 meters long. 

From what could be seen in accessible workings, a few small ore bodies 

were mined before the prospect was abandoned. There is little hope 

of finding additional ore.

CONDOR MINE

The Condor mine, also known as the Cahuide mine, is in the steep 

north face of a shoulder east of the glacial lake at the head of Quebrada Honda and above a tributary glacier flowing southwest from 

Nevado Copap. The country rock is quartzite and phyllite striking 

N. 5° W. and dipping from 80° NE. to vertically. Several veins 

appear to occupy bedding plane faults. The trail to the mine is 

washed out, and the workings are inaccessible, so we were unable to 

examine the veins.

PROSPECTS IN QUEBRADA PACLLASH

Three prospects occur in Quebrada Pacllash, a tributary valley 

which trends southeast from near the head of Quebrada Honda. The 

prospects are Cusca, Ollanta, and Estrella de Oriente. Local miners 

reported that the Ollanta vein was explored by a 10-meter drift, the 

Estrella de Oriente vein was trenched, and the Cusca vein was covered 

by an ice fall. Another small prospect, Recompensa, is on the shoulder 

overlooking the upper Quebrada Honda between Quebradas Pacllash
72 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

and Cancahua. These prospects had been abandoned prior to 1948 

and were not visited in the course of our examination.

DAMELAMANO PROSPECT

The Damelamano prospect is on the south side of the Vinoyapampa, 

3 kilometers southeast of the falls and at the foot of a steep cliff between Quebradas Pacllash and Cancahua. The lower tunnel, 4.5 

meters long, is about 10 meters above the pampa at an altitude of 

4,150 meters; the upper tunnel, about 10 meters long, is 45 meters S. 

20° E. of the lower. The vertical difference between the two is 7 

meters.

The two workings follow a low-dipping shear zone in granodiorite. 

In.the lower tunnel the zone strikes N". 20° E. and dips 15° NW. In 

the upper tunnel it strikes N". 5° E. and dips 25° W. It ranges from 30 

to 40 centimeters in thickness and consists largely of iron-stained 

gouge and altered granodiorite. In the upper tunnel the zone contains 

veinlets and disseminated grains of galena, sphalerite, pyrite, arsenopyrite, and quartz.

The vein is essentially barren, and it is doubtful that further prospecting is merited.

CHACO MINE

The Chaco mine, on the east wall of Quebrada Cancahua, is 1.5 kilometers south of the stream flowing along the Vinoyapampa. Workings on the principal vein are between the altitudes of 4,755 and 4,775 

meters. A trail from the floor of the quebrada extends to both this 

and the neighboring Arequipa mine.

Granodiorite, the country rock, is cut by steeply dipping diabase 

dikes striking N. 25°-65° E. The principal vein, striking N. 25° E. 

and dipping steeply, is at least 50 meters long. It has been explored 

and mined in two short adits. All ore has been removed from the lowest level to the surface, a maximum vertical extent of about 20 meters. 

Two smaller veins carrying mostly quartz and pyrite are in parallel 

diabase dikes east of the principal vein. These were explored by three 

short adits.

As far as could be ascertained from pillars and from rock on dumps, 

the minerals in the Chaco vein are galena, sphalerite, dolomite, pyrite, 

and quartz; local miners reported that the veins also contained copper sulfides. Little could be determined of the nature of ore shoots 

or their dimensions, but one pillar shows a width of 30 centimeters of 

galena and sphalerite. The mine was closed at the time of our examination in 1948, but it is possible that ore shoots could be found at 

depth.

A number of other veins, essentially barren of sulfide minerals, have 

been prospected in the area between Chaco and the Arequipa mine.
QUEBRADA HONDA-VESUVIO MINING DISTRICT 73

Most of these have the same general orientation, striking a few degrees either east or west of north and dipping steeply.

AREQUIPA MINE

The Arequipa mine is in the southeast wall of Quebrada Cancahua 

2 kilometers south of the main stream at the Vinoyapampa and 800 

meters southwest of the Chaco mine. The lower level of the workings 

is at an altitude of 4,720 meters. The vein crops out between morainal 

material below and a glacier above. The country rock is granodiorite 

cut by diabase dikes below the mine.

The principal vein can be traced for more than 190 meters horizontally and 115 meters vertically. It is slightly sinuous, with an over-all 

strike of N. 27° W. and with dips ranging from 85° SW. to vertical 

to 85° NE. Shear planes along which the minerals were deposited are 

comparatively straight, branch or feather in places, and are slickensided, with striations plunging from 55° to 75° NW. Movement along 

the shear planes evidently was small but caused some brecciation of 

the rock (pi. 3 and fig. 23). The granodiorite is altered along this 

vein as well as along shear zones to the west.

Minerals consist of quartz, pyrite, arsenopyrite, chalcopyrite, 

galena, sphalerite, and dolomite. Chalcopyrite and galena occur as 

coarse-grained crystals or blebs as much as 2 centimeters in diameter 

and as veinlets up to 1 centimeter wide and 10 centimeters long. 

Sphalerite at places forms stringers as much as 20 centimeters thick 

and several meters long.

Little ore was seen at the time of our examination, as the surface 

stopes had been mined out, and the upper and lower drifts apparently 

had not been advanced to the main ore body. In 1948 ore was mined 

from a vein 10 to 20 centimeters wide, of which at least 50 percent was 

gangue.

The main surface stope is about 70 meters long and was mined for 

a vertical extent of more than 20 meters. The upper drift (level 1) 

was being cut about 10 meters below the floor of the stope. In 1948 

ore was not exposed in this drift, although the face was at least 20 

meters beyond the front of the stope above. ;

A smaller surface stope, from which a lens possibly 15 meters long 

and 10 meters high had been mined, is below and north of the main 

ore body. Level 2, a drift below, exposed only minor amounts of ore. 

One short tunnel is said to have been driven on the camp level, about 

10 meters below level 2, but dump material from the latter conceals 

its location.

Further exploration may expose additional ore at depth. Advancement of the upper level was the best possibility of finding ore in 1948:

321628 55 6
74 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

Vein.less than 30 centimeters 

thick, showing dip; dashed 

where approximately located

Surveyed with compass and tape by A. J. Bodenlos and G. E. Ericksen, 

August 1948

FIGURE 23. Composite geologic map of levels 1 and 2, Arequipa mine, Qucbrndti 

Honda-Vesuvio mining district.
QUEBRADA HONDA-VESUVIO MINING DISTRICT 75

if a moderate quantity was thus developed, driving on level 2 certainly is warranted.

SOLEDAD MINE AND CARMEN DEL PELARTE PROSPECT

The Soledad mine and Carmen del Pelarte prospect are on the east 

side of the glacier-capped mountain, Tocllaraju, which here forms 

the south wall of the upper Quebrada Cancahua. The deposits are 

from 2.5 to 2.75 kilometers south of the stream in Vinoyapampa and 

about 850 meters southwest of Arequipa mine. The lowest workings 

of the Soledad mine are at an altitude of 4,830 meters, and those at 

Carmen del Pelarte are at 4,785 meters. Carmen del Pelarte is about 

300 meters N. 25° W. of the Soledad mine. The area is nearly surrounded by ice, and a major glacier terminates at ledges above the 

Soledad mine, making working conditions unsafe owing to constant 

ice falls. A stagnant glacier in Quebrada Cancahua is nearly directly 

below Carmen del Pelarte. The area is accessible by a poorly defined 

trail, passable only on foot.

Metasedimentary rocks form the host for the veins. At the Carmen del Pelarte prospect they strike N. 10° W., and dip 70° NE., 

and about 100 meters to the north they are in irregular contact with 

granodiorite.

A mineralized shear zone at the Soledad mine, striking N. 25° W. 

and dipping 80° NE., is from 15 to 70 centimeters wide and has an 

outcrop length of about 100 meters. Near its north end the zone 

splits, forming an eastern branch striking N. 25° W. and dipping 

55° SW. and a western branch striking N. 35° W. and dipping 

75° NE. The zone consists principally of bleached metasedimentary 

rock and quartz, with lesser amounts of argentiferous galena, 

sphalerite, chalcopyrite, pyrite, and arsenopyrite. At places it contains stringers as much as 15 centimeters wide of nearly solid galena 

with minor amounts of chalcopyrite and sphalerite. At the north 

end the eastern split is 50 centimeters wide and contains a stringer 

12 centimeters wide of galena and sphalerite. The western branch is 

70 centimeters wide and contains veinlets of galena.

The lower prospect pits at Carmen del Pelarte are in a 50-centimeter wide shear zone traceable only 10 meters. The zone strikes 

N. 25° W. and dips 75° SW. and contains short stringers of galena 

as much as 10 centimeters wide. The upper prospect, about 15 meters 

to the southeast and 20 meters higher, exposes a comparable zone 

which strikes N. 30° W. and dips vertically.

The owners stated that the concentrates from the mine were high 

in lead and carried up to 150 ounces of silver per ton. Because of 

the high silver content small ore bodies can be mined profitably, 

but unless larger shoots are found at depth, the mine can have only 

small production for one or two years. Surface showings at Carmen 

del Pelarte prospect are insignificant.
76 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

ESPARTA MINE

The Esparta mine is low on the north wall and near the head of 

Quebrada Cancahua. It is about 2.75 kilometers south of the stream 

in Vifioyapampa and nearly 1.5 kilometers west of the Arequipa mine. 

The veins are in a large precipitous shoulder surrounded by ice and 

glacial debris; the mine camp is on a well-developed lateral moraine 

(fig. 15). Ice from the main lobe of the glacier extends into the 

valley below the mine.

The country rock, quartzite and phyllite striking N. 25° W. and 

dipping steeply northeast, is cut by several veins. The principal 

vein, evidently the only one which carried ore, is traceable on the 

surface for nearly 100 meters horizontally and 70 meters vertically 

and is followed by the principal adit a total length of 105 meters 

(pi. 4). Twenty-five meters to the southwest of the vein a 4-meter 

wide breccia zone exposed by several short adits contains only quartz 

and pyrite. Other narrower zones opened only by prospect pits are 

similarly barren.

The principal vein contains galena, sphalerite, quartz, pyrite, 

arsenopyrite, and dolomite. Most galena and sphalerite occur in 

quartz-pyrite gangue but some is in sheared quartzite.

Two adits have been cut on the principal vein, one 4,730 meters 

in altitude and the other 35 meters higher. The lower adit, now 

flooded, exposes a zone of sheared quartzite 4 meters wide, which contains quartz and pyrite. The upper adit follows the principal vein 

55 meters and a branching vein another 50 meters. At this level the 

principal vein strikes N. 27° W. and dips from 65° to 90° NE., and 

the branch strikes N". 18° W. and dips 70°-85° NE. The vein was 

stoped upward several meters, in part to the surface, and four 

winzes probably connect to the lower adit. In one pillar the sulfidebearing part of the vein is 40 centimeters wide, and certain parts 

contain as much as 80 percent of galena.

One short segment of the branching vein contains galena. In this 

area a raise at least 20 meters long extends to workings above. The 

remainder of the branch contains only quartz, pyrite, and arsenopyrite. 

The principal vein, exposed in two short adits near the upper end of 

the outcrop at altitudes just under 4,800 meters, ranges from 0.7 to 1.5 

meters in width and contains much pyrite and quartz with minor 

amounts of galena and sphalerite.

The mine was not operated in 1948, and it is evident that nearly 

all the ore was mined before the operation was abandoned. As the 

area is thoroughly prospected, it is doubtful that further exploration 

is warranted.
QUEBRADA HONDA-VESUVIO MINING DISTRICT 77 

MERCED MINE

The Merced mine, also known as the Anna, is on the south wall of 

the Quebrada Honda 1.75 kilometers southeast of the falls. The upper 

drift is at an altitude of 4,560 meters.

A slightly curved vein, striking a few degrees west of north and 

dipping steeply southwest to vertically, is in granodiorite; slickensides along vein walls plunge 65° NW. Minerals in the vein are sphalerite, galena, quartz, pyrite, and arsenopyrite. In places arsenopyrite, 

pyrite, and quartz form distinct bands; elsewhere sphalerite-quartz 

bands are prominent. Local miners reported that the vein also contained chalcopyrite and that galena assayed as much as 70 ounces of 

silver per ton.

The upper level consists of a drift 37 meters long with stopes both 

above and below. All galena has been mined, but some sphalerite remains. To judge from the size of stopes, galena ore apparently occurred in shoots averaging 10 meters in both horizontal and vertical 

extents. About 40 meters lower a crosscut 30 meters long exposes only 

quartz and pyrite on the vein.

It is reported that the mine was worked as recently as 1947, but it 

was not working in 1948. No ore is exposed in the workings, and it 

is improbable that additional exploration would reveal ore.

ATLANTE MINE

The Atlante mine is at the head, or south end, of Quebrada Checchipampa 15 kilometers northeast of Chancos and east of the continental divide. From Chancos the trail distance to the mine is about 

55 kilometers via Quebradas Honda, Illauro, and Checchipampa. The 

altitude at the portal of level 3 was interpolated from base maps as 

4.600 meters. Veins in the area extend from the southwest wall of 

Quebrada Checchipampa across a spur to the tributary valley Quebrada Bayacocha, a distance of more than 1 kilometer. Glaciers from 

surrounding peaks extend into the mine area.

Atlante, discovered in 1895, produced 5,000 tons of concentrate by 

1903 (Duenas, 1904, pp. 46-65; Velarde, 1908, pp. 72-73) and since 

has had a comparable production up to 1948. According to data furnished by the Empresa Minera Vesuvio, in 1946 the mine produced 350 

tons of galena concentrate which contained 28 percent lead, 20 percent 

zinc, and 1.9 kilograms of silver and a few grams of gold per ton. 

From the concentrates 100 tons of silver-bearing lead bullion were 

produced at the smelter. Production was somewhat less in 1947 and 

1948.

At the Atlante mine the contact between granodiorite and metasedirnentary rocks, principally quartzites, crosses the vein system, and 

although irregular, it generally trends northwest and dips steeply
78 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

northward to vertically (pi. 5). The metasedimentary rocks for the 

most part strike northeast and dip southeast or northwest but in places 

strike northwest and dip southwest; evidently the rocks are folded, 

but data at hand are insufficient to ascertain the nature of these 

structures.

The three major veins, Atlante, Juno, and Cruzada, and several 

splits or smaller veins, have been explored and mined on six levels. 

Altitudes of the levels are as follows: level 1 4,735 meters, level 2 

4,670 meters, level 3 4,600 meters, level 4 4,560 meters, level 5 

4,540 meters, and level 6 4,532 meters.

Atlante, the most northerly vein, is arcuate, striking N. 10°-45° 

W. and dipping 35°-55° SW. at its southeast end and striking N. 

60°-85° W. to west and dipping 55°-75° SW. at its northwest end. 

The vein is traceable for a total length of 400 meters and has been 

stoped from level 3 to the surface, a vertical distance of 150 meters. 

It extends from an intersection with the Cruzada vein on the east to 

irregular exploratory drifts and stopes in the Urano area on the west. 

In the central part of the workings a short parallel vein or split occurs a few meters north of the Atlante vein from above level 2 to the 

surface. This split extending along much of the western part of the 

vein is well shown on level 2 (pi. 5). All high-grade ore in the 

Atlante vein has been mined; the most productive part was near the 

southeast end of the vein.

About 150 meters southeast of the intersection of Atlante and Cruzada another vein, shown on the mine map as Atlante East, is followed 190 meters by a drift; only a short stope from level 2 to the 

surface was productive. Because this vein has about the same attitude as Atlante, mine operators are of the opinion that Atlante East 

is its extension. However, Atlante definitely is truncated by Cruzada, so the eastern segment is probably an independent fissure. The 

Atlante vein and its splits and most of Atlante East are in metasedimentary rock.

Southwest of the Atlante and Atlante East veins is the slightly 

sinuous Juno vein which strikes N. 35°-50° W. and dips 15°-65° SW.; 

the flatter dips are prevalent at depth. The Juno vein is traceable 

for a length of 400 meters but not for more than 240 meters on any 

one level and has been opened from level 2 to level 6, a vertical distance of 140 meters. On levels 3 and 4 it ends against the Cruzada 

vein, but it cuts across the Cruzada vein on level 5. Juno has been 

most productive from a short distance above level 3 to level 6, but 

near the southeast end of the mine workings a small ore body was encountered on level 2. High-grade ore remains only in the lowest 

levels. The Juno vein is in granodiorite except for the segment extending north of the Cruzada vein on level 5, which is in metasedimentary rock.
QUEBRADA HONDA-VESUVIO MINING DISTRICT 79

The Cruzada vein, extending between the Atlante and Juno veins, 

strikes eastward and dips vertically. The Cruzada is traceable for 

a total distance of 360 meters, with a maximum of 280 meters on a 

given level, and has been opened from levels 2 to 4, a vertical distance 

of about 110 meters. Apparently it fades at depth, and only a short 

east-trending segment is seen on level 5. The vein, now mined out, 

was productive only from half-way between levels 2 and 3 to halfway between levels 3 and 4. The Cruzada vein is more or less parallel 

to the contact between the metasedimentary rock and the granodiorite. 

As can be seen in pi. 5, this contact is very irregular and cuts across 

the vein several times.

Vein structures and mineralization seem to become weaker at depth, 

and ore bodies are progressively shallower northward. The vein 

structures are evidently faults of small displacement, all formed about 

the same time. Vein walls are slickensided, and the vein material 

contains much brecciated wall rock and gouge.

The principal vein minerals are galena, sphalerite, pyrite, quartz, 

and carbonate (probably dolomite). Chalcopyrite, tetrahedrite, and 

stibnite occur in minor amounts. In addition Duenas reported that 

anglesite and cerussite were in the oxidized zone, polybasite and 

stephanite occurred in the upper parts of the mine, and arsenopyrite, 

bornite, and bournonite occurred at greater depths.

Sphalerite, at present the most abundant ore mineral in the veins, 

generally does not occur as discrete grains but forms veinlets, veins, 

or lenses. Galena occurs as crystals, veinlets, and massive lenses, 

either pure or associated with sphalerite. Gangue consists principally of carbonate and brecciated country rock, but at places quartz 

and pyrite are abundant. Minerals were deposited in fissures along 

the faults and in breccia cavities. Much of the ore is vuggy or drusy 

and at places is conspicuously banded.

Silver was concentrated in the upper parts of the veins by secondary enrichment. The first ore mined averaged over 3 kilograms of 

silver per ton of concentrate (Duenas, 1904, p. 46) and was as high 

as 10 kilograms per ton (Velarde, 1908, p. 72). In contrast, some 

ore from the lowest levels of the Juno veins carries less than 100 grams 

of silver per ton.

Lead-silver ore shoots are as much as 90 meters long but more commonly are between 10 and 40 meters long, and their vertical dimensions are of comparable magnitudes. Ore bodies seem to be most frequent along those parts of veins having numerous flexures and comparatively infrequent along straight segments. Much less ore was 

encountered on the comparatively straight Cruzada vein than on 

either the Juno or Atlante veins.

Other than on the lower levels of the Juno vein most high-grade ore 

had been extracted from this deposit by 1948, so the possibilities of
80 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

future mining of virgin ground are considerably limited. A company 

survey in 1939 showed substantial amounts of lower grade ore, either 

unmined or occurring as fill in old stopes. Construction of a larger 

flotation plant should permit extraction of much of the lower grade 

material, and this could result in continuing production at modest 

rates for several years to come.

The Italia mine, not visited during our investigation, was mined 

out by 1900 after producing several hundred tons of lead-silver concentrate. The adit of the main level is about 1 kilometer west of the 

adit of level 2 of the Atlante mine, and its altitude is above 4,750 meters. Between this mine and the Atlante two other small mines, the 

Urano and Judas, were opened before 1895. Subsequent exploration 

showed these to be on the western extension of one of the veins in the 

Atlante deposit. The vein at these two mines was worked out a number of years ago.

HUAMANA MINE

The Huamana mine is high on the north wall of Quebrada Huichjanca, a west tributary valley of Quebrada Checchipampa, 17 kilometers northeast of Chancos and 3.5 kilometers southwest of the company camp and flotation plant at Pompei. The trail distance from 

Chancos is nearly 50 kilometers. The datum used in this report, taken 

from a company survey, is the adit of the Santa Rita tunnel just behind the mine camp; this seems to be several hundred meters high 

when compared to the topographic map of the Cordillera Blanca 

(Borchers, 1935). The Huamana mine includes veins extending over 

an area about 350 meters east-west by 700 meters north-south, between the altitudes of 4,595 meters and 4,835 meters. Other veins just 

to the south, or downslope, are beyond the company concessions but 

form part of the Huamana vein system.

Although several of the veins in this deposit had been worked during the Colonial period, the mine was forgotten and rediscovered 

only shortly before 1900. A lixivation plant, later changed to a flotation plant, was built by the Empresa Minera Pompei to concentrate 

ore from this area. By 1948 most of the silver-bearing galena ore was 

mined out, and the company stopped operations. Records show that 

concentrates produced before 1908 contained from 3.3 to 6.5 kilograms 

of silver per ton (Velarde, 1908, p. 75), and as late as 1946 hand-sorted 

ore ran to as much as 1.9 kilograms of silver per ton. In 1948 ore was 

selectively mined, hand-sorted, and sent by aerial tram to Pompei. 

The tram, 3 kilometers long, carries 60 buckets, each with a capacity of 

150 kilograms. A new cable was installed and the tram renovated in 

1947. The flotation plant has a capacity of 10 tons per day and produced only lead-silver concentrate.

At Huamana the contact between the batholith and the metasedimentary rocks strikes nearly west and dips north at moderate angles
QUEBRADA HONDA-VESUVIO MINING DISTRICT 81

(fig. 8). The dip of the quartzite, phyllite, and andalusite hornfels, 

generally parallels the contact. The veins, for the most part, are confined to granodiorite, but the northwest end of one, the Animus, continues into the metasedimentary rocks (pi. 6).

Minerals in the veins are galena, sphalerite, pyrite, stibnite, quartz, 

and rhodochrosite. Silver occurs with galena, and secondary smithsonite coats some sphalerite. Where the wall rock is granodiorite, it 

is altered; metasedimentary rocks appear to have been unaffected by 

mineralizing solutions. Galena and sphalerite occur as scattered 

grains, veinlets, and small pods or as stringer's or lenses several meters 

long and as much as TO centimeters thick. Most minerals were deposited as fissure fillings.

Galena is fine grained, occurring in massive or laminated aggregates, or is coarsely.crystalline; grains are less than 1 millimeter in 

diameter, and crystals are as much as 5 centimeters in diameter. 

Sphalerite is crystalline and honey colored, and thin cleavage fragments are transparent. Grains forming massive aggregates are from 

0.2 to 10.0 millimeters in diameter, crystals from 0.5 to 10.0 centimeters in diameter. Pyrite, quartz, and rhodochrosite are finely crystalline or massive, and stibnite occurs as interlacing or radiating groups 

of needles.

Ore shoots are lenticular, occurring most frequently along sinuous 

parts of the veins and where veins split or shear planes branch, and 

are very irregular, ranging in thickness from a few centimeters to 

as much as 1.5 meters. Sulfide minerals are banded in places but elsewhere form heterogeneous mixtures. Minerals were deposited in fissures as well as in breccia cavities.

The veins at Huamana occupy three principal shear zone systems. 

The first strikes northwest and dips southwest at moderate to steep 

angles, the second has similar strike but dips southwest at only low 

angles, and the third strikes east and dips south at low to moderate 

angles. Of these, only the first carries major ore bodies. Movement 

along the shear zones evidently was small. The zones consist of comparatively short and branching shear planes along which are fissures, 

gouge, and breccia. Although several shear zones continue into the 

metasedimentary rocks north of the contact, mineralization outside 

the igneous mass is insignificant.

The principal veins are Animus, Ribordonesia, San Jose, Santa Isabel, Prascondu, and San Pedro. Several of these have smaller associated veins, and in addition a number of small unnamed veins occur 

south of Animus and San Pedro (pi. 6 and fig. 24). The Animus 

vein, on the east side of the area, is by far the largest and has furnished the bulk of the ore. It and Santa Isabel in the northwest part 

of the area were the only veins being worked in 1948.
82 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHtJASH

Compiled from map supplied by the Empress Miners Pompei; 

datum established by barometer

FIGURE 24. Principal underground workings of the Huamand mine, Quebrada HondaVesuvio mining district.
QUEBRADA HONDA-VESUVIO MINING DISTRICT 83

Ribordonesia, west of Animus and on the north side of the area, 

and Prascondu, in the southwest corner, are reported to have been 

mined out in the Colonial period, but some workings on them seem 

to be more recent. In our study all workings were visited, but only 

the geology of the surface and the two lower levels of the Animus 

vein were mapped.

The Animus vein is opened on six levels, the Sagrario 1 and 2, the 

Animus 1, 2, and 3, and the Santa Rita, exposing the vein for a length 

of 400 meters between the altitudes of 4,645 and 4,765 meters. Mining 

and exploration were extensive, and small amounts of high-grade 

galena remain only on the Santa Rita and Animus 3 levels. Highgrade sphalerite ore remains in many parts of the vein.

On the Animus 3 level, about 110 meters from the portal, the vein 

is terminated at the southeast by a cross fissure. BeloAv on the Santa 

Rita level the vein turns into the west wall of the drift about 125 

meters from the portal. The intersecting vein is not exposed, but to 

the south the most prominent structures are south-dipping veins which 

undoubtedly cut off the Animus vein (pis. 7 and 8).

The overall strike of the vein is N. 30° W., and it dips 40°-80° SW. 

Two major branches are found on the lower levels (pis. 7 and 8); 

on the Animus 3 level the vein splits to the west about 200 meters from 

the portal and then to the east about 470 meters from the portal. The 

southeastern branch rejoins the main vein about 65 meters to the 

northwest; both junctions plunge steeply south. The junction of the 

northwestern, branch plunges northwest at moderate angles and overlaps the southeastern on Animus 1 level. Additional splits or subparallel veins develop on the two upper levels, totalling four mineralized and two barren shear zones on Sagrario 1 level. Most mineralization occurred on levels Animus 1, 2, and 3; the vein definitely is 

thinner and ore shoots are smaller on the Santa Rita level.

The Santa Isabel vein, the most northwesterly of the area, is traceable on the surface for 150 meters and is opened on two drifts, one at 

4,750 meters and the other at 4,770 meters altitude. It also is exposed 

in the Cerro Cuni adit at 4,715 meters altitude. In the upper drift 

the vein consists of straight segments striking N. 60° W., that are 

connected by more northerly striking simple or branching shear 

planes. In the lower drift the vein strikes about N. 40° W. and dips 

40° SW. Ore shoots, all less than 1 meter thick, were mined out along 

the upper drifts, and probably another shoot was worked from the 

Cerro Cuni level. The upper drift on Santa Isabel was being advanced in August 1948, but the exposed vein contained only minor 

sulfides.

The Ribordonesia vein is at the north side of the mine area between 

the Animus and Santa Isabel veins. Several irregular drifts and im-
84 LEAD-ZINC DEPOSITS,, CORDILLERAS BLANCA AND HUAYHUASH

dercuts follow it for a distance of 125 meters between the altitudes of 

4,765 and 4,800 meters. The vein strikes N. 40°-60° W. and dips 

15°-20° SW. It intersects more steeply dipping fissures in the two 

southwestern adits (pi. 6). Apparently all ore has been mined from 

the workings.

The San Jose vein, east of Santa Isabel and southwest of Ribordonesia, is exposed in two drifts, the longer at 4,730 meters and the 

shorter at 4,745 meters altitude, and also is exposed in the Cerro Cuni 

adit below. The main drift shows an arcuate vein striking N. 40° W. 

which swings to strike due west about 150 meters from the portal; the 

vein dips 20°-50° S. Well within the workings a 40-meter crosscut to 

the north exposes another vein striking N". 50° W. and dipping 50° 

SW. Galena has been mined out of several small stopes, but some 

, sphalerite remains in the upper workings; only gouge was seen on the 

Cerro Cuni level.

The Prascondu vein in the southwest corner of the area is traceable 

220 meters horizontally and 60 meters vertically in an arcuate outcrop 

trending N". 65°-70° E. at the northeast end and N. 80° W. near the 

southwest end of the outcrop. The dip is 10°-30° S. on most of the 

vein but locally is as much as 45°-55° S. Associated with the vein are 

splits, branches, and cross fissures as well as isolated vein segments to 

the north. Drifts are cut on Prascondu at the following altitudes: 

4,700, 4,688, 4,675, 4,661, 4,651, and 4,638 meters, of which only the 

uppermost is shown on fig. 24. The vein as exposed in the drifts is 

very low grade, but the several stopes indicate that a few small ore 

bodies were found.

About 50 meters northwest of the 4,700 meter level adit, a vein striking N. 60°-70° W. and dipping 50° SW., traceable for 50 meters, has 

been stoped from 4,720 to 4,760 meters altitude. Branching north 

from this is a sinuous vein dipping 15°-35° W., Avhich was explored 

by pits.

The San Pedro vein, between Animus and Prascondu, is exposed in 

an adit 120 meters long at 4,665 meters altitude and in a short adit to 

the southeast at an altitude of 4,621 meters. The vein strikes N. 20° W. 

and dips 65° SW. at the portal of the 4,665 meter level but strikes more 

westerly and dips at lower angles within the adit. Ore was mined 

from several small stopes, but the remaining material is barren. No 

ore was found on the lower level.

A number of small veins occur south of the Animus and San Pedro 

veins, several of which are shown on the map of the Santa Rita level 

(pi. 7). The largest veins have been stoped for short distances. 

Southeast of the lower San Pedro tunnel and at 4,595 meters altitude 

(pi. 6) are two shear zones followed by drifts, each about 50 meters 

long. Both zones strike northwest and dip southwest at moderate to 

low angles. The western is barren, but the eastern carries large lenses
QUEBRADA HONDA-VESUVIO MINING DISTRICT 85

of pure sphalerite. About 50 meters to the north, at 4,615 meters altitude, are two tunnels. The western tunnel is short and follows a barren shear zone; the eastern tunnel, about 100 meters long, is on a 

branching shear zone Avith an overall strike of N. 15° E. and a dip of 

45° NW. A feAv lenses of galena and sphalerite are on this zone, one 

of Avhich has been stoped doAvn 5 meters. At the base of the dump 

from the Santa Rita adit, at an altitude of 4,595 meters, a 20-centimeter thick vein striking N". 85° W. and dipping 30° S. is exposed in 

a 75-meter drift. The vein contains minor quantities of galena and 

sphalerite.

BeloAv these and south of the company concessions two veins Avere 

explored by drifts at 4,570 and 4,550 meters altitude. The vein in the 

upper drift, AA'hich is 60 meters long, strikes N. S°-30° W. and dips 

45°-65° SW. It contains small lenses of galena and rhodochrosite. 

The loAver adit, east of the main gully and belovv the vein at the base 

of the Santa Rita dump, exposes a shear zone striking north and 

dipping 25° W. This zone has a maximum Avidth of 20 centimeters 

and contains only minor amounts of galena and sphalerite.

SEXTRI MINE

The Sextri mine, doAvnslope from Huamana and at the base of a 

steep Avail in Quebrada Huichjanca, is about 2 kilometers north Avest 

of Vesuvio. Velarde (1908, p. 75) reported that veins here contained 

high-grade galena and silver ore.

The country rock is granodiorite. TAVO drifts, one at 4,250 meters 

and the other at 4,270 meters altitude, folloAv a slightly sinuous vein 

for about 200 meters. On the loAver level the vein strikes N. 30° W. 

and clips 30° SW. at the portal but trends N. 10° E. and dips 60° NW. 

near the north end of the Avorkings. A barren cross fissure with the 

attitude N. 70° E., 45° SE. intersects the vein about half-Avay between 

the portal and the face. Stopes, most of Avhich are open to the surface, 

have maximum Avidths of about 1 meter. To judge from examination 

of the vein and material on the dumps, mineralization is about the 

same as at Huamana, except that pyrite here is more abundant and 

sphalerite is darker. According to Duenas (1904, p. 71-72) the carbonate is siderite, and he further noted that the galena and sphalerite 

extracted prior to 1900 contained fine-grained argentiferous tetrahedrite.

Above the Sextri Avorkings, at 4,315 meters altitude, a small tunnel 

folloAvs a vein striking N. 5° W. and dipping 60° SW. The Avorking 

is noAv flooded, but Avaste material contains rhodochrosite, quartz, 

pyrite, and minor amounts of galena.

Veins at Sextri appear to be barren or Avorkecl out, and further 

exploration is not warranted.
86 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

LAURI6N MINE

The Laurion mine, about 24 kilometers northeast of Chancos and 7 

kilometers northwest of Chacas, is in a ridge named Cerro Torojirca 

between Quebrada Apash on the east and Quebrada Carhuanca on the 

west. The camp and main workings are near the head of Quebrada 

Apash and are reached by a 10-kilometer trail from Pompei. Altitudes cited for this mine are from company maps and are low as compared with the map of the Cordillera Blanca.

Although the mine was worked either in the Colonial period or 

during the early days of the Republic, it was left dormant for many 

years before being reopened by the Empresa Minera Vesuvio just 

before 190.0 (Duenas, 1904, p. 65-66). The ore in the first decade of 

the present century commonly contained as much as 40 percent lead, 

2 percent copper, and 3.3 kilograms silver per ton (Velarde, 1908, p. 

74), but after 50 years of nearly continuous operations only moderate 

amounts of lower grade ore remain.

Argentiferous galena, sphalerite, pyrite, quartz, and carbonate are 

seen in present workings. Duenas (p. 66) stated that chalcopyrite 

and silver-bearing tetrahedrite also were common in the deposits at 

the turn of the century. All minerals Avere deposited as fissure 

fillings; massive quartz, deposited first, was brecciated prior to deposition of the sulfide minerals.

The country rock, largely quartzite but including some phyllite, is 

cut nearly at right angles to the strike by several veins, of which only 

one, the Laurion vein, carries ore. In Quebrada Apash this vein is 

exposed on 5 levels at altitudes of 4,000, 4,060, 4,165, 4,220, and 4,290 

meters. In Quebrada Carhuanca several other levels on the vein are 

known as the Lepanto workings. The Laurion vein is the largest in 

the district, traceable 750 meters horizontally and 400 meters vertically, but is not ore-bearing over the entire extent. Most of the vein 

has been mined above the 4,060 level. On the 4,060 level which is 

about 350 meters long, the vein consists of long, almost straight, and 

vertical or steeply dipping en echelon segments. The first segment is 

225 meters long and strikes 1ST. 30°-40° E.; the second, offset 15 meters 

to the southeast, strikes N. 60° E. and was followed for 35 meters; and 

the third, striking N. 50° E. was followed for 90 meters. All minerals 

occur as fissure fillings, and on this level, ore shoots range from 0.25 to 

1.0 meter wide. Duenas (1904, p. 66) stated that above level 4,165 

the vein reached a maximum width of 2.5 meters.

In 1948 ore was dropped to level 4,060 through ore chutes and from 

there to the valley floor by aerial tram. It was concentrated in hand 

jigs before shipment to Pompei for flotation. A small flotation unit 

at Laurion would help to utilize the moderate reserve of low-grade ore 

still remaining above 4,060 meters. Little hope is held for finding ore
ANTAMINA-CONTONGA MINING DISTRICT 87

at depth as the loAvest level, at about 4,000 meters altitude, is essentially 

barren of sulfides.

APASH MINE

The Apash mine is northeast of the Laurion mine, on the north 

side of Quebrada Apash. Drifts on the vein are at the altitudes of 

4,000, 4,040, 4,060, 4,080, and 4,130 meters. The country rock and 

minerals are similar to those at Laurion. The vein itself may be a 

continuation of the Laurion vein, but here it strikes N. 20°-40° E. and 

dips about 75° SE. Several adits are walled at the surface, and the 

others are blocked a few meters in from the portal, so little information 

was acquired on size of stopes or extent of reserves. It is inferred that 

a dike follows the vein in the mine because broken rock on the dump 

includes considerable andesite (p. 32).

Dueiias (1904, p. 66) concluded that old workings on the vein date 

from the Colonial period.

CHILE PROSPECT

Several hundred meters northwest of the Apash mine and high on 

the west slope of Quebrada Conchas a vein follows an andesite dike in 

the granodiorite batholith. The dike, as much as 2 meters wide, strikes 

1SL 85° W. at the east end and N. 75° E. at the west end and dips 

70° to 90° N". The vein, traceable about 125 meters horizontally, was 

explored in three prospects.

Only pyritized dike rock is seen in the eastern prospect pit. The 

second prospect 25 meters west and 10 meters higher is a tunnel and 

underhand stope in which quartz and some sulfides are exposed. The 

third prospect, 40 meters west and 10 meters higher, is a 40-meter drift. 

Here the vein follows both sides of the dike; the thin sulfide-bearing 

parts of the vein contain no more than 1 percent galena overall. The 

largest quantity of galena forms a lens only 1 meter long and 5 centimeters wide. Possibilities for mining this vein seem distinctly 

limited.

OTHER DEPOSITS

Duenas (1904, pi. 1) shows several deposits in the upper tributary 

valleys of Quebrada Illauro and one on the west side and about halfway up the quebrada. He also stated (p. 75) that several small deposits are near the head of Quebracla Putaca, which is the valley extending west from Pompei. All apparently are small and are unknown to present inhabitants of the region.

ANTAMINA-CONTONGA MINING DISTRICT

The Antamina-Contonga district, consisting of tAvo centers of mineralization about 5 kilometers apart, is east of San Marcos, a town 87
88 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

kilometers by road northeast of Recuay (fig. 1). The Antamina area 

centers at the head of Quebrada Antamina 10 kilometers S. 80° E. of 

San Marcos, and the Contonga area at the head of Quebrada Pajush is 

about 10 kilometers 1ST. Y0° E. of the town. Both areas are reached via 

a trail extending eastward from San Marcos up Quebrada Pajush. 

Four kilometers from town the trail forks, and one branch continues 

about 10 kilometers up Quebrada Pajush to the Contonga area. The 

other, also about 10 kilometers long, follows Quebrada Yaquirsh 

southeast, crosses a spur, and turns east-northeast into Quebrada 

Antamina (fig. 3).

The terrain is rugged in places and comparatively open elsewhere. 

Major valleys were glaciated and are U-shaped, but many ridges are 

rounded rather than serrate. The heads of Quebrada Antamina, the 

valley immediately to the north, and Quebrada Pajush are cirques. 

Outcrops are extensive only on steep slopes, most of which are walls 

of glaciated valleys and peaks. Moraine covers valley floors, and soil 

and scree mantle the flatter slopes and ridge crests.

Strata of the middle unit of the Barremian sequence and the 

Jumasha limestone (p. 24, 26-2T) are the two major rock units 

of the region, and are separated by a thin band of Lower Neocomian 

sandstone about 5 kilometers east of San Marcos. Sedimentary rocks 

are folded and to a lesser extent faulted. Folds range from closed to 

open structures with vertical or steeply dipping axial planes trending 

in a northwesterly direction. Small gravity faults are common, but 

only two large reverse faults were seen (p. 33 and pi. 1).

The limestone is intruded by numerous sills and dikes in the Antamina area and by a small stock and sills and dikes in the Contonga 

area, all of rhyolitic or rhyodacitic composition (p. 31-32). The 

largest intrusive in the Antamina area is a dike 1,500 meters long and 

as much as 20 meters thick, cutting the south wall of the quebrada. 

A large mass in the cirque north of Quebrada Antamina may be either 

a small stock or, more probably, a thick sill. Other dikes and sills in 

this area are at most several hundred meters long and from 2 to 20 

meters thick. The stock in the Contonga area has a maximum diameter of 350 meters; associated dikes and sills are from 20 to 300 meters 

long and from 0.5 to 15 meters thick (pis. 1 and 2).

Limestone immediately adjacent to all large and some small igneous 

masses is silicated, marbleized, or bleached (p. 39-40). The largest 

metamorphosed block is in the upper Quebrada Antamina, covering an 

area with maximum dimensions of YOO by 1,YOO meters. Here limestone largely is converted to garnet-serpentine and garnet-diopside 

rock and, in places, to diopside-garnet-wollastonite-idocrase rock. 

Smaller patches of silicated rock are several hundred meters southwest of the main mass in the south wall of the quebrada. Elsewhere 

in the Antamina area and also at Contonga most alteration consists
ANTAMINA-CONTONGA MINING DISTRICT 89

of recrystallization and bleaching of limestone, Avith or without 

accompanying silication.

Lead-zinc fissure-filling veins occur in both the Antamina and 

Contonga areas, and in addition large deposits of disseminated copper 

replacements, described separately below, are in the center of the 

Antamina area. Minerals in the lead-zinc veins include galena, 

sphalerite, pyrite, chalcopyrite, tetrahedrite, pyrargyrite, calcite, 

fluorite, quartz, and opal. Minerals of the oxidized parts of the veins 

are limonite and malachite.

In many veins the minerals are coarsely crystalline. For example, 

cleavage cubes of galena 1 to 2 centimeters across are common. Tetrahedrite and chalcopyrite occur as scattered grains or as crystals in 

cavities of many deposits. The material is vuggy. The deposits of 

this district contain less sphalerite and quartz and more calcite and 

fluorite than those in the Quebrada Honda-Vesuvio district.

DEPOSITS IN THE ANTAMINA AREA

The center of mineralization in the Antamina area is the large disseminated copper deposit in the floor of the quebrada, and this is 

flanked by two smaller copper deposits to the southwest and by leaclzinc veins peripherally located in the walls of the quebrada and across 

the ridge crest in adjacent valleys. All these occurrences are associated with intrusive dikes or sills. The lead-zinc veins are most 

common at contacts between igneous bodies and limestone or in either 

rock type near the contacts.

Vein structures consist of comparatively short fissures and shear 

planes, some linked and others isolated. The fissures and shear planes 

tend to parallel dikes but cut sills at high angles. Movement is indicated by the presence of breccia and gouge along the structures. Deposits are from 30 to 300 meters long and from 15 to 200 meters in 

vertical extent. Most ore shoots are small, comparatively pure lenses 

of galena from 2 to 15 meters long and from 10 to 50 centimeters thick, 

but larger shoots as much as 40 meters long and from 0.5 to 1.0 meter 

thick, with lower tenor (5 to 30 percent galena), are found in several 

of the larger veins. Galena concentrates are reported to contain from 

50 to TO percent galena, some of which contains 1 to 2 kilograms of 

silver per ton.

Raimondi (1873, p. 542-47) stated that during his visit to the area 

in 1860 the copper deposits were being explored, and ore from one 

lead-zinc vein was being smelted near San Marcos. He stated that 

replacement copper deposits were mined before the arrival of the 

Spaniards, but because of the low silver content of these deposits, the 

Spanish did little work on them and apparently did not notice the 

lead-zinc veins. Several mining companies explored the copper deposits in the past few years, but as yet none has started mining.

321628 55 7
90 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

Most lead-zinc veins seem to have been developed since the close of 

World War II. All mining in 1948 was either from small pits and 

underhand stopes or from short drifts and small overhand stopes. All 

operations were manual. In 1948 and 1949 production was hampered 

by lack of pack animals to haul supplies and concentrates.

The map of the district (pi. 1) was compiled by plane table triangu^ 

lation. Most topography was sketched in the field and refined somewhat after study of air photographs; those areas shown by dashed contour lines were sketched without ground control from air photographs. 

The datum is the peak on the north side of the quebrada, Cerro 

Yaquirsh, shown on the map of the Cordillera Blanca as 5,017 meters 

in altitude. All altitudes cited in the following deposit descriptions, 

other than those in areas shown by dashed contours, can be considered 

correct to within 20 meters of the datum.

Three deposits in the area probably contain moderate reserves: the 

Fortuna, the Rosita de Oro, and the Casualidad. Others, along small 

dikes or sills, have small reserves or are nearly barren.

FORTUNA MINE

The Fortuna mine is in a saddle on the divide between Quebrada 

Antamina and the cirque to the northwest, between the altitudes 4,680 

and 4,745 meters. The dump of the southernmost working is 1 kilometer N. 23° W. of the outlet of the lake. The mine was the largest 

producer of the area in 1948 and contains moderate reserves.

Limestone striking northwest and dipping gently southwest is cut 

by two large and two small dikes (pi. 9). The major dike with a sinuous outcrop trending N. 15° W., dips 45° SW. and is traceable for 

180 meters. East of this dike are two small dikes, each traceable for 

10 to 20 meters, and northeast is the second large dike, with a sinuous 

liorthtrending outcrop and dipping from 25° to 40° W., traceable for 

nearly 90 meters.

The minerals, commonly occupying openings in fissures and shear 

zones, are galena, sphalerite, pyrite, pyrargyrite, and calcite. Both 

the limestone and dike rocks are pyritized, and the phenocrysts of the 

dike rock are altered.

Mineralized fissures and shear zones are comparatively short, at 

most traceable for 55 meters horizontally. The more important ones 

are parallel or semiparallel to the dikes. Ore shoots consist, for the 

most part, of small high-grade galena lenses but also include larger 

lower grade galena bodies. Most veins are in limestone, although all 

are within 50 meters of dike rock.

The largest vein is east of the major dike and is the southernmost of 

the group. It is sinuous, striking north-northwest and dipping 45°- 

55° W. It has been exposed and mined by pits, drifts, and small stopes 

for a length of 55 meters and a vertical extent of 17 meters. The vein
ANTAMINA-CONTONGA MINING DISTRICT* 91

ranges from 0.6 to 1.5 meters wide; galena lenses worked in 1948 

averaged 20 centimeters wide and several meters long. Overlapping 

and possibly branching from this is an arcuate vein traceable for 40 

meters, striking northward and dipping 45°-70° W. An adit on it 

exposed a stringer of galena 5 to 20 centimeters wide and 7 meters 

long; a lenticular body 3 to 4 meters long and 30 centimeters wide was 

mined from a pit to the north.

North of the overlapping vein are a number of short veins, several 

of which carry small lenses of galena. To the east short nearly barren 

veins parallel the two small dikes.

Northward along the major dike is another group of short veins, 

several of which follow the dike and then branch into limestone. 

Small lenses of galena are present in this vein group, but none seems 

to offer much promise of being minable at depth. Two veins in limestone between the two largest dikes are both essentially barren.

Another vein, traceable for 35 meters, occurs along the northeast 

dike, either at the east contact or just within the dike. The vein was 

opened by a surface stope 5 meters long and 7 meters deep. At the 

bottom of the stope the vein is 20 to 30 centimeters thick and contains 

a minimum of 50 percent sulfides. Twenty meters to the south is a pit 

which exposes a galena lens 2 meters long and 20 centimeters thick. 

The remainder of this vein and two other small veins in the dike contain only minor amounts of sulfides. About 50 meters east of the dike 

a trench exposes a 1-meter wide shear zone consisting of pyritized limestone with veinlets of calcite and galena.

The southernmost veins contains shoots of very high-grade galena, 

but unfortunately all veins are comparatively short. Additional exploration of the veins at depth probably would expose other small 

high-grade ore bodies.

BARR6N PROSPECT

The Barren prospect, in the northwest wall of the quebrada and several hundred meters east of the Fortuna mine, is at the base of a limestone cliff about 1 kilometer N. 10° W. of the lake outlet. The workings are both above and below 4,600 meters altitude.

Veinlets containing galena, sphalerite, pyrite, quartz, and tetrahedrite are exposed by prospect pits along the contact between a dike 

and limestone. The minerals occur in a zone about 30 centimeters wide, 

which can be traced along the contact for 30 meters. Both dike rock 

and limestone are pyritized, limestone at the contact contains talc, and 

veinlets contain minor amounts of malachite and limonite. The contact was explored by three pits and a 3-meter drift. The zone as 

exposed in these workings strikes N. 40°-45° W. and dips 55°-80°

sw.

To judge from exposures, the zone contains little or no minable 

material.
92 LEAD-ZESB3 DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

SANTA ROSA PROSPECT

The Santa Rosa prospect, the lower tunnel of which is at an altitude 

of 4,410 meters, is near the north side of the lake 800 meters N. 17° E. 

of the lake outlet. Small veins occur along a short dike from 2 to 5 

meters wide, which has a sinuous outcrop. Minerals in the deposit are 

galena, sphalerite, chalcopyrite, pyrite, quartz, and fluorite.

The principal vein, striking N. 10°-1$° W. and dipping 60°-75° 

SW., follows the south west, contact of the dike through a vertical distance of 25 meters. The vein is from 0.5 to 1.0 meter wide and contains as much as 20 percent sulfides. Along this vein are several 

parallel veinlets; near its north end several branching veins strike 

N. 50° W. and dip 60°-85° NE.

The veins were explored through several adits, one as much as 

10 meters long, and by pits. The veins are small and low grade, so 

it is doubtful that they can be worked at a profit.

SAN FRANCISCO MINE

The San Francisco mine, in the north wall of the cirque, is 1,300 

meters N. 10° E. of the lake outlet; the veins extend from about 

4,560 to 4,610 meters altitude. The deposit was opened in 1947 and 

was being mined and explored on a small scale in 1948. In contrast 

to operations at most other deposits in the Antamina area, where ore 

is removed by underhand stoping from surface cuts, mining at the 

San Francisco deposit is carried out by drifting and overhand stoping.

Limestone dipping southward at low angles is cut by a large sill 

or dike. The intrusive is at least 20 meters thick and is traceable 

600 meters; its north end splits into three tongues. Overlying limeStone has been stripped by erosion. In the mine area the basal contact is irregular but is nearly parallel to bedding.

Galena, calcite, and some pyrite were deposited in fissures, and the 

intrusive rock and limestone are pyritized in places. Galena bodies 

are exceptionally pure, being contaminated only by the two associated 

minerals or by wall rock where the veins contain breccia. Although 

shoots are small, ore is easily hand-sorted to a high-grade concentrate. Argentiferous galena is fine grained with laminated texture 

or is coarse grained.

The mine area centers near the east side toward the north end of 

the intrusive. Several short steeply dipping veins, mostly confined 

to the intrusive and striking northwest, crop out over an area 70 

by 20 meters (fig. 25). The southernmost working is an adit 21 meters 

long. At the portal it cuts the contact between limestone and overlying intrusive rock, but owing to the low southeast dip of the contact, most of the adit is in limestone. The working follows a vein 

striking N". 20° W. and dipping vertically, which contains only minor 

galena and calcite. About 20 meters north of this adit is the south-
ANTAMINA-CONTONGA MINING DISTRICT 93

Surveyed with compass and tape by A. J. Bodenlos 

and G. E. Ericksen, September 1948

FIGURE 25. Geologic sketch map '.and sections of the San Francisco mine, AntaminaContonga mining district.

east end of the largest known vein of the deposit, traceable about 50 

meters on the surface and in workings. This vein strikes N. 25° W. 

and dips from 80° to 90° SW. Ten meters above the limestone-intrusive contact are a surface cut and a drift which follow the vein for 30 

meters. One short stope extends from the drift to the surface, and a 

prospect pit is cut on the northwest end of the vein outcrop. Parts 

of the vein contain short lenses of solid galena as much as 10 centimeters thick, but other parts contain much pyrite and calcite and 

lesser amounts of galena,

Between this vein and the south vein a pit exposes a 15-centimeter 

wide vertical vein striking N. 35° W., which contains about 50 percent galena mixed with brecciated intrusive rock. A few meters 

northeast of the main vein another pit exposes a small vein carrying 

some galena. Northward from the southern adit other pits along 

the contact expose a few veinlets of galena. Other small veins have 

been explored by pits to the north and west of the mapped area, but 

all are small and essentially barren of ore minerals.

Although reserves are small, the ore is sufficiently high in grade to 

permit mining of the comparatively small veins. Mining may continue to be profitable for a few years.
94 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

RECOMPENSA MINE

The Recompensa mine at the head of the valley north of Quebrada 

Antamina is just across the divide from the San Francisco mine and 

1,600 meters N. 13° E. of the lake outlet. Workings extend along veins 

for a distance of 150 meters and are between the altitudes of 4,550 

and 4,595 meters. The mine was being operated on a small scale in 

1948. At that time pits and small surface stopes were the principal 

workings, although one adit, now caved, and one open adit 14 meters 

long also have been driven.

Limestone in this vicinity is cut by several dikes, the largest of 

which trends northwest and is traceable 450 meters from the ridge 

at the north end of Quebrada Antamina to the north of the deposit. 

It is paralleled by two shorter dikes. These three intrusive bodies 

dip 65°-85° SW. A fourth dike, near the divide, has a more westerly 

strike and dips 25°-35° SW.

The vein minerals, galena, sphalerite, pyrite, and calcite, were deposited along fissures in fractures or shear zones in and near the 

dike. Most intrusive rock is hydrothermally altered, and the limestone near the veins is pyritized.

The deposit consists of four veins (fig. 26). The southeastern vein 

follows the northeast or footwall contact of the dike 40 meters, branching at the northwest end. Ore shoots are few but consist of high-grade 

lenses of galena as much as 4 meters long and 20 centimeters wide. 

The vein to the north is at the hanging wall of the dike. It is 35 meters long and as much as 40 centimeters wide and contains veinlets 

and lenses of galena from 1 to 10 centimeters thick. The northernmost veins, both east of the dike, are in limestone, the north end of 

each impinging against the footwall of the dike. These veins contain 

short stringers of solid galena, 1 to 10 centimeters thick. Just west of 

the divide, prospect pits and a 6-meter adit expose sulfide veinlets, 

none of which contains minable material.

Small stringers of galena in the veins might yield a few tons of highgrade concentrate, but elsewhere the veins are almost barren. It is improbable that further exploration will reveal sulfide bodies larger 

than those exposed in the workings.

PODEROSA PROSPECT

The Poderosa prospect, low in the northeast wall at the head of 

Quebrada Antamina, is 1,150 meters N". 37° E. of the lake outlet. A 

number of short drifts and pits were cut on the veins, but the deposit 

was not being worked in 1948.

In the vicinity of the deposit limestone, dipping at low angles, is 

partly serpentinized and is intruded by a rhyolite dike dipping steeply 

to the southwest. A second and smaller intrusive to the west may be a 

split of the larger mass. These bodies seem to be on the continuation
ANTAMINA-CONTONGA MINING DISTRICT 95

Mapped with compass and tape by A. J. Bodenlos and 

G. E. Ericksen; base elevation established with altimeter

FIGURE 26. Geologic sketch map of the Recompensa mine, Antamina-Contongn

mining district.
96 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

of the large dike at the Casualidad mine. The dike contains several 

veins, the largest of which has an outcrop length of about 60 meters. 

This vein strikes N. 25°^tO° W. and dips 40°-TO° SW. Smaller veins, 

most of which strike more northerly and dip more steeply, are along 

the contacts of the larger dike and also in the smaller dike.

The veins consist principally of quartz and pyrite with minor 

amounts of galena, sphalerite, chalcopyrite, opal, and fluorite. The 

largest vein averages between 0.25 and 0.5 meter in width but is 1.5 

meters wide in one prospect; the smaller veins are from 5 to 50 centimeters wide.

The exposed veins are small and low grade. However, additional 

exploration of the largest vein might expose small ore bodies which 

could be mined at a profit.

CASUALIDAD MINE

The Casualidad mine in the northeast Avail of Quebrada Antamina 

is southeast of the Poderosa prospect and extends from near the floor 

of the cirque to the ridge crest, between the altitudes of 4,480 and 

4,680 meters. The veins, among the most extensive lead-zinc occurrences in the district, were being actively developed in 1948 by drifts 

and pits.

A. dike at Casualidad, which can be traced 200 meters horizontally 

and about 175 meters vertically, strikes N. 40°-55° W. It dips about 

40° SW. at the northwestern end and 80° .SW. near its southeastern or 

upper end. Near the valley floor the dike is 20 meters thick, but it 

pinches to 5 meters at 4,570 meters, the altitude of the main drifi;, and 

to 1 or 2 meters above. The intrusive is cut by branching, crosscutting 

fractures and shear zones below the main drift and by comparatively 

regular parallel fractures above. The most persistent vein in the area 

is in the southeast part of the dike, and from the main drift it extends 

southeastward about 170 meters.

Mineralization is similar to that at the Poderosa prospect. Prospect pits in the lower part of the dike expose stringers of solid galena 

as much as 2 meters long and from 5 to 10 centimeters thick. Vein 

material near the stringers averages 30 centimeters in width and contains 10 to 30 percent of galena. The main drift exposes a shear zone 

about 2 meters wide, which contains stringers of sulfides, 10 to 30 centimeters wide. The vein in this drift was worked during 1948, and we 

estimated that the ore contained from 5 to 15 percent galena.

During 1948 short, narrow stringers of galena in the drift were 

mined, but as these are few in number, it is questionable that the production paid mining and shipping costs. However, as the main vein 

is more persistent than most other veins of the district, further exploration might prove moderate reserves of ore.
ANTAMINA-CONTONGA MINING DISTRICT 97 

JULIA ELOISA PROSPECT

The Julia Eloisa prospect near the ridge crest on the east wall of 

the cirque is 1,100 meters N. 87° E. of the lake outlet. A 3-meter 

drift and several pits expose small northwest-striking veins through 

a length of 100 meters. Minerals in the veins are galena, sphalerite, 

chalcopyrite, pyrite, quartz, calcite, limonite, and malachite.

The veins seem to be in a northern extension of the mineralized 

area at Eosita de Oro (pi. 10). The southwestern vein is in the footwall of a south-dipping dike which crosses the ridge, and the other 

two veins, dipping to the southwest, crop out within 50 meters to the 

northwest. The sulfide-bearing segments of veins, at most 20 centimeters thick and 6 meters long, carry only minor amounts of galena 

and sphalerite. No ore is in sight, and it is doubted that further exploration would expose minable material.

ROSITA DE ORO MINE

The Kosita de Oro mine extends from near the ridge crest of the 

cirque down the slope of the valley just east of Quebrada Antamina. 

The deposit is from 1,100 to 1,200 meters east-southeast of the lake 

outlet, and mineralization occurs between 4,485 and 4,635 meters altitude. It is one of the largest deposits of the area and in 1948 was 

one of the largest producers.

Limestone in this vicinity strikes from west to northwest and dips 

south at low angles. It is cut by a ramified and branching dike system. The largest of the intrusives is the eastern continuation of the 

large dike in Quebrada Antamina, which crosses the ridge crest near 

the north end of the deposit. Several branching dikes can be seen 

near the ridge crest. To the east is another large dike which crosses 

the ridge crest in the Julia Eloisa area. These dikes generally trend 

north and dip west from 45° to 60°. In addition, a number of small 

dikes crop out both east and west of the main intrusive bodies.

The largest dike is traceable for a distance of nearly 600 meters 

southward from the ridge crest. At the ridge crest its outcrop width 

is more than 60 meters, but elsewhere it ranges from 10 to 20 meters 

in width. The eastern dike can be traced about 350 meters southward 

from the ridge crest and has an outcrop width of from 3 to 10 meters. 

Limestone along parts of the dikes is silicified.

Minerals were deposited in fissures and shear zones largely confined 

to dike rock or at contacts between dike rock and limestone; only in 

two places do veins extend short distances into limestone (pi. 10). 

Minerals include galena, sphalerite, tetrahedrite, pyrite, quartz, and 

fluorite. The feldspars in the dike are altered, and oxidation of pyrite and copper-bearing sulfides has produced limonite and malachite. 

Gouge is found along some shear planes.

The sulfides occur as isolated crystals, veinlets, and lenses in aggregates of quartz, fluorite, altered feldspar, and gouge. Ore shoots gen-
98 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

erally contain from 10 to 30 percent sulfides, although several carry 

as much as 50 percent sulfides. It is estimated that ore shoots contain from 5 to 20 percent galena.

The veins are along simple to branching and alined fissures and 

shear planes. In the principal dike these structures are short and 

simple at the north and long and branching at the south end of the 

main mineralized area. They range from 15 to 105 meters in length, 

have a vertical extent of as much as 25 meters, and generally are 

from 20 to 40 centimeters wide, although in places they are as much 

as 1 meter wide. They strike roughly parallel to the dike and dip 

westward from 20° to 60°. On the eastern dike veins range from 5 

to 45 meters in length and average 25 centimeters in width, with a 

maximum of 60 centimeters. They dip from 15° to 70° westward.

Only the veins in the central part of the principal dike have been 

mined to any extent, although the veins in all parts of the area have 

been prospected by pits and trenches. Most ore has been mined from 

surface stopes as much as 15 meters long and 10 meters deep and from 

small pits. A 37-meter adit near the south end of the principal dike 

did not expose ore, but another 20 meters long near the north end of 

the main mineralized area exposed a small but rich ore body.

The main mineralized area on the principal dike should provide 

ore for small but steady production for a number of years. The 

showings in the rest of the deposit are small and probably cannot 

be mined at a profit.

PUTAPUOUIO PROSPECT

The Putapuquio prospect, in the valley east of the Quebrada Antamina, is about 450 meters southwest of the Rosita de Oro mine. The 

lowest working is at an altitude of 4,450 meters. A short adit and 

five pits expose mineralized shear and breccia zones along a sill for 

a horizontal distance of 40 meters and a vertical distance of less than 

20 meters. The prospect was inactive in 1948.

The limestone in the vicinity strikes N. 10° W. and dips 25° NE. 

It is intruded by a fine-grained sill with an outcrop length of about 

60 meters and a thickness of from 2 to 5 meters. Several outcrops 

of intrusive rock also occur about 100 meters southeast of the sill. The 

sill is pyritized in places and is cut by steeply dipping irregular, mineralized shear and breccia zones, en echelon gash veins, and isolated 

veinlets which contain minor amounts of galena, sphalerite, tetrahedrite, pyrite, quartz, fluorspar, limonite, and malachite. Limestone 

above and below the sill is barren. No ore is exposed at the prospect, 

and it is doubted that further exploration would reveal ore.

PALLARES PROSPECT

The Pallares prospect is in a precipitous spur on the south side of 

the lower part of Quebrada Antamina, 1,600 meters S. 35° W. of the
ANTAMINA-CONTONGA MINING DISTRICT 99

lake outlet. A narrow mineralized area was explored by prospect pits 

through a length of about 120 meters between altitudes of 4,525 and 

4,595 meters. The prospect was being explored in 1948, but as far as 

is known, no shipping-grade ore was produced.

Limestone in the vicinity of the deposit, striking N. 35°-70° W. and 

dipping 40°-70° SW., is in part dolomitized, serpentinized, and silicified. It is cut by several dikes, which in places contain feldspar 

phenocrysts as much as 4 centimeters long and quartz crystals 2 centimeters long. The largest dike, as much as 2 meters wide, has an outcrop length of about 125 meters. It strikes N. 40°-65° W. and dips 

70°-85° SW. In places the dike is brecciated, and fragments as much 

as 10 centimeters long are common. Near the wTest end of this dike 

another dike, exposed in a small outcrop, strikes N. 45° W. and dips 

40° SW.

Vein minerals were deposited along shear planes at rhyolite-limestone contacts, in rhyolite breccia cavities, and to a lesser extent in 

fissures in limestone. Galena and pyrite are most abundant; sphalerite, tetrahedrite, chalcopyrite, quartz, and calcite occur in minor 

quantities. Most veins are thin, short, and low grade. None of the 

veins seen in 1948 merited development.

PROSPECTS IN THE CIRQUE NORTHWEST OF QUEBRADA ANTAMINA

A number of small mineral deposits are in the cirque just northwest of Quebrada Antamina (pi. 1). All are along small dikes, except 

two which are in the large mass of igneous rock on the southeast side 

of the lake. In addition to those shown, several unmapped veins and 

dikes are in the low knoll on the northwest side of the lake. Two 

prospectors working in this area stated that they had recovered only 

5 tons of galena concentrate during the previous year.

Northwest of the cirque in a steep valley wall above a large swamp 

a short tunnel exposes a brecciated and silicified zone in limestone. 

Breccia cavities contain small amounts of galena. In a narrow valley 

between the lake and the Fortuna mine, prospect pits along a dike 

expose a narrow shear zone which contains veinlets of sulfide 

minerals.

None of these prospects seemed worthy of development.

DISSEMINATED COPPER DEPOSITS

Limestone in Quebrada Antamina has been bleached, recrystallized, 

silicated, and mineralized over a large area nearly surrounding the 

lake at the head of the quebrada and extending about 900 meters southwest of the lake outlet. Two small areas of mineralized silicated limestone also occur in the southeast wall of the quebrada 1,300 and 1,600 

meters southwest of the lake outlet (pi. 1). Minerals replacing limestone in the altered zone include diopside, garnet, wollastonite, ido-
100 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

erase, serpentirie, dolomite, and chert (p. 40). The limestone is irregularly altered at most places, but on the northwest fringe of the main 

body it can be seen that silicates and quartz were introduced along 

fractures and joints. The largest altered mass is cut by the main dike 

of the area as well as by smaller dikes, and the two small southwestern masses likewise are cut by dikes.

Minerals introduced into the altered limestone are chalcopyrite, 

bornite, tetrahedrite, sphalerite, galena, pyrite, and calcite. Raimondi 

(1873, p. 543^46) stated that small amounts of* native copper and 

molybdenite were found,, and analyses published by him show a low 

percentage of silver in the copper. The sulfides, of which only pyrite . 

and chalcopyrite occur in substantial amounts, were deposited principally as disseminated grains replacing altered limestone and to a lesser 

extent as filling of small fractures and cavities. Calcite is found only 

with fissure-filling material. The overall grade of copper is judged 

to be very low.

The sulfides have been oxidized at the surface, producing a gossan 

consisting of yellow, red, and black iron oxide with minor amounts of 

malachite and azurite.

Sulfide minerals can be found throughout most of the largest mass 

extending over an area 1,700 meters along the axis of the quebrada 

and from 400 to 1,000 meters across the valley, with a maximum vertical range of 350 meters. However, the highest degree of sulfide mineralization is near the center of the valley at the south side of the lake; 

areas on either side of the lake are only sparsely mineralized. The 

depth of the deposit is not known. The southeast contact of the deposit dips steeply to the northwest, and part of the northwest contact 

dips southeast at low angles (pi. 1, sections B-B', C-G'). The southwestern deposits are at most 100 by 200 meters in horizontal 

dimensions.

The southwest part of the largest deposit and the smaller deposits to 

the southwest were prospected by pitting, tunneling, and the sinking 

of shafts, some of which are said to have been opened prior to the 

Spanish conquest. However, most of the work was done in the second 

half of the 19th century in an attempt to find high-grade copper-silver 

ore. The deposits have also been examined by several mining companies during recent years, but as yet have not been developed. The 

metal reserve in these replacement bodies is very large (these and 

large replacement bodies in the Pachapaqui district represent the two 

largest mineralized areas described in this report), and at some future 

time exploitation may be profitable.

DEPOSITS IN THE CONTONGA AREA

In the Contonga area the Jumasha limestone has been folded, forming a broad anticline to the east and a sharp syncline to the west. In
ANTAMINA-CONTONGA MINING DISTRICT 101

the mine area bedding on the common limb of the two folds strikes 

northwest and dips 55°-SO° SW. The limestone was intruded by 

stocks, dikes, and sills of porphyritic rhyolite. The largest intrusive 

is a stock measuring 300 by 350 meters, and around it are dikes and 

sills ranging from 20 to 300 meters in length and from 0.5 to 15 meters 

in thickness (pi. 2). At contacts rhyolite is noticeably finer grained, 

and limestone is partly bleached and recrystallized. Near veins the 

rhyolite is hydrothermally altered.

The principal lead-zinc veins are near the contact between the stock 

and the limestone, and the rest are along dikes and sills extending from 

the stock or along silicified zones in limestone. Another group of 

veins, northeast of the ridge crest, is in slightly silicified and pyritized 

fault or shear zones nearly parallel to the bedding of the country rock.

Except for the absence of tetrahedrite and pyrargyrite, the minerals 

found in the veins at Contonga are the same as those in the lead-zinc 

veins at Antamina. For the most part they were deposited as fissure 

fillings, but some pyrite and quartz were deposited as replacements of 

both rhyolite and limestone. In one vein, sulfides form concentric and 

banded spheres up to 15 centimeters in diameter; these are considered 

to be of replacement origin.

Structures forming the loci of mineralization are fault and shear 

zones which range from a few meters to 175 meters in length, and 

mostly from less than 1 meter to 3 meters in width. However, along 

the northwest contact of the stock one shear zone is as much as 15 

meters wide. Quartz and pyrite are the most common vein minerals; 

galena, sphalerite, and chalcopyrite occur in irregular small veinlets, 

pods, and lenses which comprise only a fraction of the lengths and 

widths of the veins. Argentiferous galena, the only mineral being recovered in 1948, occurs in comparatively small shoots and is low grade.

Most of the workings are old, but in 1948 the area was being actively 

prospected and mined on a small scale from pits and two small adits, 

of which one is on a vein at the northwest side of the stock and the 

other on veins northeast of the divide. Production was less than 5 

tons of lead concentrate per month.

In view of the low tenor and small size of ore shoots, the area is considered to have only limited reserves. Three veins on the north, west, 

and south sides of the stock may merit further exploration at depth.

The area- was mapped by plane table traverses, using a barometric 

datum.

DEPOSITS IN THE VICINITY OF THE STOCK

In a knoll just south of the pond on the west edge of the map area 

(pi. 2) small rhyolite dikes are bordered by bleached and silicified 

limestone zones with maximum widths of about 20 centimeters. The 

silicified limestone contains a few small veinlets of pyrite, galena, and 

sphalerite. About 75 meters to the south a bedding-plane fault zone,
102 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

exposed in trenches for a length of 50 meters, is from 0.5 to 1.0 meter 

wide and contains up to 5 percent combined galena and sphalerite. A 

split of the zone is 2 meters wide but contains only thin, short lenses of 

sulfide minerals. To the east, at the west contact of the stock, the limestone has been bleached, partly silicified, and mineralized for a distance of 75 meters and through a width of from 1 to 2 meters. This 

zone was explored by five prospect pits, and sulfide minerals make up 

5 to 20 percent of the zone.

Along the south edge of the stock four pits extending over a distance of 75 meters expose a mineralized zone 0.7 to 2 meters wide, 

which, crosses the contact between the intrusive and limestone at a 

narrow angle. In the intrusive the zone contains minor amounts of 

pyrite and galena with abundant calcite; at the contact it contains 

pyrite and some galena in quartz; and in the limestone it contains 

minor amounts of pyrite and galena associated with much gouge.

In a valley southeast of the stock and in bluffs northeast of the valley 

several short veins occur in limestone. These carry small scattered 

veinlets of pyrite, galena, and sphalerite, but in no place is mineralization sufficiently great to form an ore body.

Along the east side of the stock a mineralized zone about 120 meters 

long and as much as 3 meters wide has been explored in several prospect pits. The zone contains only limonite with scattered small veinlets and pods of pyrite, galena, and sphalerite, none of which forms a 

minable shoot. At the northeast side of the stock two sills are bordered by silicified limestone for distances of 120 and 150 meters. The 

silicified zone north of the south sill contains veinlets of pyrite and 

galena and in places sphalerite. Near the east end of the north sill the 

silicified zone contains pyrite, galena, and minor amounts of chalcopyrite. The zones contain a maximum of 5 percent galena and 

sphalerite.

Some 60 meters north of the west end of the sills are several northeast-striking veins in silicified limestone, the longest of which can be 

traced for 80 meters. The width of the silicified zones generally is 

about 1 meter but reaches 8 meters toward the northeast end of the 

longest vein. The sulfides occur as scattered veinlets, precluding the 

possibility of profitable extraction.

A number of discontinuous shear zones extend for a length of 180 

meters along the north and northwest contacts of the stock. The 

easternmost, exposed in a shallow pit, consists of thin, irregular veinlets of sulfides in a zone 1.5 meters wide. About 50 meters to the west 

a prominent shear zone 65 meters long cuts across the contact. It is 

15 meters wide at the west end but only 3 meters wide at the contact. 

At the west end the zone contains veinlets of calcite and sulfides, and 

at the contact it contains much quartz and pyrite and minor amounts
ANTAMINA-CONTONGA MINING DISTRICT 103

of galena and sphalerite. Mineralization fades out on the zone in 

the stock.

On the northwest side of the stock are five northwest-striking and 

steeply dipping veins, all close to the contact. Each is short, between 

1 and 2 meters wide, and contains veinlets and disseminated grains 

of galena and sphalerite together with larger amounts of pyrite.

A 20-meter adit and pits near the northwest contact of the stock expose a 1- to 3-meter wide breccia zone in bleached limestone. The zone 

as exposed in the adit and prospect pits consists of altered limestone 

with minor amounts of quartz, pyrite, galena, sphalerite, calcite, and 

fluorite. Minerals occur in veinlets and breccia cavities.

From 50 to 75 meters north of the northwest part of the stock a 

silicified zone as much as 5 meters wide parallels the bedding of limestone for a distance of 175 meters. Small veinlets and vugs, and in 

places breccia cavities, contain small percentages of pyrite and galena.

Within the stock two small veins carry quartz and disseminated 

grains of pyrite and galena. Elsewhere in the stock patches of igneous 

rock are heavily stained with limonite, but no primary sulfides were 

seen.

A few of the mineralized zones around the stock may be worthy of 

additional exploration, and it is possible that small ore bodies may thus 

be found. However, judging from the exposed veins, it is doubtful 

that exploration would reveal large ore bodies.

DEPOSITS NORTHEAST OF THE DIVIDE

Northeast of the divide scattered veins and veinlets in shear zones 

extend over an area 250 meters long by as much as 200 meters wide. 

Shear zones can be traced for a length of as much as 50 meters, and 

most are less than 1 meter wide, but one short zone is as much as 3 

meters in width. The shear zones contain minor amounts of ore and 

gangue minerals. At no place do ore minerals occur in minable 

quantities.

OTHER DEPOSITS

A number of other small deposits are known in the San Marcos area 

but were not visited during our investigation. Among these is the 

Victoria, said to be a few kilometers from San Marcos and near Cerro 

Hueglla-Caga; it is a lead-zinc vein on which drifts have been cut 

over a vertical extent of 140 meters. Another is the Socorro, several 

kilometers southwest of Chavin. This is in Cerro Huecho and consists of a vein carrying galena and stibnite. In addition, several small 

stibnite veins Avest of San Marcos have been producing a few tons of 

antimony concentrate during recent years.
104 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH 

HUALLANCA MINING DISTBICT

The Huallanca mining district is west of the town of Huallanca and 

east of the crest of the Cordillera Huayhuash, in the province of Dos 

de Mayo, Departamento de Huanuco (fig. 4). Huallanca is nearly 

80 kilometers airline distance due west of Huanuco, the capital of the 

departamento, and about 35 kilometers northeast of Chiquian. The 

district is accessible by a 60 to TO kilometer trail from Chiquian, the 

nearest roadhead. It is also accessible by trails from Huanuco and 

from Conococha and Recuay in the Santa Valley.

Nearly all valleys of the region have been glaciated, and peaks along 

the crest, of the Cordillera Huayhuash are still partly covered with 

glaciers. However, the area is near the north end of the range where 

peaks are not so high nor so heavily glaciated as they are farther to 

the south. The two major streams of the region, Rio Torres and 

Rio Viscarra, join at Huallanca to form the Rio Huallanca which 

flows northeastward to the Rio Maranon.

The regional structures here, as elsewhere in the Cordillera Huayhuash, consist of folds having a regional strike of N. 20°-30° W. in 

sedimentary rocks. These sedimentary rocks consist of lower Neocomian sandstones; Barremian shales, sandstones, and limestones; and 

Machay and Jumasha limestone and have an aggregate thickness of 

more than 1,000 meters. The lower Neocomian sandstone contains 

several seams of coal. The only igneous rocks are dikes, sills, and 

small irregularly shaped stocks.

Historically the district is well known for its silver production 

during the early part of the present century. Velarcle (1908, p. 85) 

reported that the veins were discovered in 1721 and had been worked 

intermittently since that time. Prior to 1925,.when most of the silver 

mines were shut down, at least three concentration plants and one 

smelting or roasting furnace were operated. The machinery of these 

old plants has been removed, and most of the buildings are now in 

ruins.

Since 1925 small mines have been worked for copper, lead, and 

antimony. A concentration plant and smelter was built in Huallanca 

and operated until 1940. The Compania Minera Santa Barbara, the 

only major company still operating in the district, owns most of the 

old silver mines, some of the copper and lead mines, and the mill. 

This company is working a silver-copper mine on a small scale, but 

its main operation is a stibnite placer to the east of Huallanca.

Several coal seams are mined for local use. Some coals, stockpiled 

in Huallanca, are blocky high-grade bituminous or anthracite. Other 

coals, such as those from seams near the west end of Quebrada Torres, 

tire intermixed with shale and burn very poorly.

The ore minerals of the district are largely chalcopyrite, galena, 

marmatite, and tetrahedrite. Several veins can be worked profitably
HUALLANCA MINING DISTRICT 105

on a small scale, and one or two might be developed into moderatesized mines if the district were accessible by road. A few mines are 

being worked by hand on a small scale. 

The most promising mines of the district are:

Carmen del Macizo: high-grade copper-silver ore, several years'

reserves for a small operation. 

San Jose de Huanzala: medium to low-grade lead-zinc-copper

ore, potentially a moderately large mine. 

Sirena Encantadora: high-grade lead ore, many short veins,

exploration may prove substantial ore reserves. 

Perla prospect: low-grade zinc-lead ore, warrants further

prospecting. 

Ispac: low-grade zinc-lead ore, many veins in rather large

mineralized zone, possibly may be a moderately large mine. 

Danubio-Diamante mine moderate grade lead-zinc-coppersilver ore, reserves may support a small scale operation for 

several years.

HUALLANCA MILL AND SMELTER

The Huallanca mill and smelter is at the east edge of the town of 

Huallanca at the junction of the Viscarra and Torres rivers and at 

an altitude of about 3,420 meters.

The mill was in operation until 1940, when it was shut down because of difficulties in ore transportation and concentrate shipment. 

Eugenio Da Roet, General Manager of the Compaiiia Minera Santa . 

Barbara in Huallanca, stated that the plant produced about five tons 

of copper and silver concentrates per day. The furnace was experimental and produced only a minor amount of metal.

The following equipment or facilities are either ready for operation or could be put into operation within a few months: machine 

shop, woodworking shop, ball mill, flotation cells, ore roasters, leaching-tanks, brick kilns, electrical power plant, and hospital.

CARMEN DEL MACIZO MINE

The Carmen del Macizo mine is at the head of Quebrada Copacog 

4.5 kilometers airline west of Huallanca. The portal of the main adit 

is at an altitude of 4,160 meters. A good trail. 7 to 8 kilometers long 

connects the mine with Huallanca. The mine is owned and operated 

by Compania Minera Santa Barbara.

The country rock is coarse-grained light-gray sandstone in beds 10 

centimeters to a meter thick, striking N. 35° W. and dipping TO0 NE. 

The major vein consists of small isolated lenses and pods of tetrahedrite in solution cavities or fissures along a shear or fracture zone 

striking N. 35° E. and dipping 50°-70° SE. Most lenses are 2 to 4 

meters long and have a maximum thickness of 50 centimeters; the

321628 55 8
106 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHTJASH

pods, although irregular in shape, range from a few centimeters to 

as much as 50 centimeters in diameter. The ore bodies are several 

meters apart, and connecting fractures are tight and barren except in 

a few places where they contain crystals and veinlets of tetrahedrite. 

The lenses form an ore shoot which plunges 75°-85° NE. and has a 

horizontal range of about 25 meters and a vertical range of more than 

100 meters. Slickensided walls, breccia, and gouge seem to be absent.

The individual ore bodies are either solid lenses and pods or cavities 

partly filled with tetrahedrite and quartz crystals. Many small splits 

from the main fissure carry veinlets of tetrahedrite which range from 

a few centimeters to as much as 3 meters in length. Most ore consists 

of massive and crystalline tetrahedrite with minor amounts of pyrite 

and quartz. Cavities in a few ore bodies are filled with a white plastic 

clay. Much of the ore appears to contain more than 75 percent tetrahedrite.

The vein has been explored by an adit 150 meters long, but ore was 

encountered only in the one shoot which has been stoped upwards for 

50 to 75 meters. Two or three men produce less than one ton of handsorted concentrate per month.

Most of the ore has been mined above the level of the main adit, but 

the same ore shoot was cut in a second exploratory adit about 10 meters 

lower. The reserves are probably large enough to sustain small scale 

mining for several years.

A few other mineralized zones in Quebrada Copacog have been explored, but the workings were not accessible in 1949. We examined 

the surface areas and mine dumps of one or two of these zones but 

saw only iron oxide and pyrite.

MERCED, PURfSlMA, SANTA ROSA, AND SAN FRANCISCO MINES

The Merced, Purisima, Santa Rosa, and San Francisco mines are 

at the west end of Quebrada Tucapac about 5 kilometers west of 

Huallanca and 1 kilometer north of the Carmen del Macizo mine. A 

mineralized zone containing many veins trends northwest about 500 

meters and is 100 to 200 meters wide. It is perforated by many adits, 

prospect pits, and shafts. Most underground workings were inaccessible in 1949, and much of the surface area was covered with waste 

material, so we were not able to make complete examinations.

All four properties are owned by the Compania Minera Santa Barbara. The mines were worked until 1925 and then were shut down 

either because of lack of ore or because of transportation difficulties. 

According to reports from local people, these four mines, and the San 

Jose del Banco mine, produced most of the copper and silver of the 

Huallanca district.

The country rock is light-gray coarse-grained sandstone overlain by 

dark-gray metamorphosed shale, with a regional strike of N. 20°-35°
HUALLANCA MINING DISTRICT 107

W. and a dip of 65° NE. to vertical. Movement along the contact 

between the shale and sandstone formed breccia and gouge, and at 

one place blocks of sandstone as much as a meter in diameter were 

broken out and mixed into a gouge zone in the overlying shale. A sill 

of altered rhyolite 2 to 3 meters thick crops out east of the mine area, 

striking about N. 35° W. and dipping 75° NE. to vertically.

The veins apparently occupy faults parallel or nearly parallel to 

bedding. They strike N. 20°-35° W., dip 45° NE. to vertically, and 

consist of shattered wall rock and gouge webbed with veinlets and 

irregular pods of finely crystalline pyrite. The few veins seen were 

barren. Careful examination of the many dumps revealed only a few 

specimens with crystals or veinlets of tetrahedrite and galena. It is 

possible that rich pockets of tetrahedrite similar to those at Carmen 

del Macizo were exploited and that the mines were abandoned after 

the pockets had been mined out.

The mines have been inactive since 1925; mill machinery has been 

removed, and most of the buildings are in ruins. Company maps on 

file in Huallanca show drifts and crosscuts totalling more than a kilometer in length.

Steinmann (1930, p. 342) stated that some of the veins contained 

1.5 to 2.5 kilograms of silver per ton and 1.5 to 2 percent of copper 

but that others contained as much as 15 to 20 kilograms of silver per 

ton and 14 to 17 percent of copper.

As a thorough examination of the area was not made, it is impossible to evaluate the property. Inhabitants of Huallanca who are 

familiar with the mines mentioned that large rich ore bodies still remain in the now inaccessible workings, but the veins in the accessible 

workings are singularly barren.

SAN JOSE DEL BANCO MINE

The San Jose del Banco mine, owned by the Compania Minera Santa 

Barbara, is 1.5 to 2 kilometers northwest of the Santa Rosa mine in a 

small valley on the south side of Quebrada Torres near Lake Cotaicoccha. The explored area is nearly 500 meters long and lies between 

the altitudes of 3,700 and 3,900 meters.

The mineralized zone is near the same sandstone-shale contact exposed at the mines of Merced, Purisima, etc. However, most of the 

veins are in shattered and crumpled black carbonaceous shale which 

strikes N. 20°-40° W. and dips 60°-70° NE. The veins appear to be 

associated with breccia and gouge zones in the shale, and most are 

nearly parallel to the regional strike and dip of the strata. Several 

veins were worked from adits, shafts, pits, and surface stopes. A typical major vein of the area is 1 to 3 meters wide and more than 50 meters 

long, striking about N. 35° W. and dipping 80° NE. This vein consists of black, shattered shale webbed with veinlets of pyrite and
108 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

quartz. The veinlets range from 0.5 to 5 centimeters wide and a few 

centimeters to a meter long.

The mine has not been worked since 1925. Mine buildings and the 

old mill have been completely destroyed, and most of the underground 

workings are inaccessible.

A careful examination of accessible workings and dumps revealed 

only a few crystals of sphalerite, galena, tetrahedrite, and chalcopyrite. Local inhabitants stated that the mine-produced a large quantity 

of silver.

SAN JOS£ DE HUANZALA MINE

The San Jose de Huanzala mine is on the south side of Cerro 

Huanzala north of Quebrada Torres and about 2 kilometers west of 

the San Jose del Banco mine. The altitude at the portal of the main 

adit is about 3,960 meters. Airline distance from Huallanca is 8 

kilometers, and the trail distance along the Rio Torres is about 12 

kilometers. Like most of the other large mines in the district, the 

Huanzala mine has not been worked since 1925.

Most of the veins are exposed over an area about 50 meters wide 

and 150 to 200 meters long and appear to be replacements of gouge and 

breccia zones in fine-grained pyritized and silicified, light-gray limestone and sandy limestone. The area is on the western, overturned 

limb of an anticline whose beds strike N. 20°-40° W. and dip 40°-70° 

NE.; the crest of the anticline is 200 to 300 meters to the east. An 

overturned sequence of coarse-grained light-gray sandstone, apparently the same as that exposed at San Jose del Banco and other mines 

to the east, crops out on the east side of the mine area. Most of the 

veins are in limestone near the contacts of two andesite sills which 

range in width from 5 to 10 meters and lie about 40 meters apart. The 

western sill is the more prominent and can be traced northwestward 

for more than three kilometers; isolated veins and irregular replacement zones of copper, lead, zinc, and iron sulfides are exposed along 

the entire outcrop. Three kilometers northwest of the Huanzala 

mine is exposed a replacement body of nearly pure pyrite, about 10 

meters long and 3 to 4 meters wide. Many of these mineralized zones 

have been explored by pits and short adits.

The main vein area is perforated by shafts and adits, most of which 

are now caved and inaccessible. The best view of vein structures and 

the nature of mineralization is afforded in the accessible portion of 

the principal adit. Within this adit, shown in fig. 27, are exposures 

of at least five veins which seem to contain a moderate percentage of 

lead and zinc as well as several low-grade veins which are largely 

pyrite and quartz. In addition, a zone of rubbly material about 12 

meters thick, consisting of fragments of limestone mixed with iron 

oxide and clay, may be low-grade ore. The veins tend to be parallel 

to bedding planes of the limestone. Four of the richest veins occur
HUALLANCA MINING DISTRICT 109

within a 10-meter wide alteration zone at the west side of a sill (fig. 

27), and it is possible that the altered limestone between these veins 

contains enough ore minerals to warrant mining the entire zone.

Geology mapped with compass and tape by G. E. Erlcksen and A. J. tndacochea, 

August 1949 on plan supplied by Companfa Mlnera Santa Barbara

FIGOKB 27. Geologic map of the principal adit, San Jos<5 de Huanzala mine, 

Huallanca mining district.
110 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

The higher grade veins consist of fine-grained galena, marmatite, 

pyrite, and minor chalcopyrite in a matrix of altered wall rock, clay, 

and quartz. Minerals are somewhat oxidized, and part of the ore 

contains crystalline cerussite. The major veins range from 30 centimeters to a meter in width and probably from 10 to 50 meters in 

length. The lower grade veins range from 20 centimeters to 2 meters 

in width and consist largely of pyrite, quartz, clay, and iron oxide 

with minor amounts of lead, zinc, and copper sulfides. Many cavities in these veins and walls of the adit along the veins are coated with 

copper sulf ate and carbonate.

The number, size, and grade of the veins indicate that the San Jose 

de Huanzala mine is one of the more valuable mines of the district. 

It seems probable that ore reserves are large enough to supply a small 

concentration plant for a number of years.

SIRENA ENCANTADORA MINE

The Sirena Encantadora mine is at Lake Tancancocha, a small lake 

at the head of Quebrada Chuspi near the crest of the Cordillera Huayhuash, 12.5 kilometers airline west of Huallanca. The trail distance 

to Huallanca via Quebrada Chuspi and Quebrada Torres is about 25 

kilometers. The main mine area lies between the altitudes of 4,550 

and 4,610 meters. (See fig. 28.)

Cerro Tancancocha to the south of the mine is covered by glacial 

ice, and one of the lobes extends down into the mine area. According to local reports, the area was covered with ice until about 1935.

Several veins crop out in a granodiorite porphyry stock and in altered limestone between the stock and a 7-meter wide dike to the west. 

The stock, although irregular in shape, seems to be 200 to 300 meters 

wide and extends southward from the mine area more than 500 meters 

along the axis of a sharp chevron anticline in unaltered fine-grained 

dark-gray limestone. The axial plane of the anticline strikes N. 

20°-30° W. and dips vertically, and beds on the limbs dip steeply.

Limestone in the vein area has been recrystallized and bleached, 

partly silicified, and partly replaced by garnet, epidote, and white 

bladed wollastonite. At one place the dike was broken into sharp 

angular fragments a few centimeters to a meter across, and between 

these fragments spaces as much as 50 centimeters wide were filled 

with crystalline wollastonite.

Vein minerals filled fissures and replaced both the igneous rock and 

altered limestone along fracture zones ranging in length from 5 to 

about 30 meters. The veins strike N. 10°-65° W. and dip steeply 

from 60° NE. to 80° SW. In the altered limestone, high-grade leadsilver ore occurs in lenses and irregular pods a few centimeters to 

1.5 meters wide and 1 to 5 meters long, whereas in the stock most sul-
HUALLANCA MINING DISTRICT 111

,</\ !>.!'/ iVT^-1 -. " \1,'~ ««. »',' » V- 1

'.V/'/C^^-XVx' ^-'v 'l^b '---

4600m4590m4580m4570m4560m4550m

Granodiorite porphyry

65| 

Vein, showing dip and thickness

Vein, less than 30 centimeters thick

90 

Vertical vein

Contact

v^8S

Strike and dip of joints

Open 

o

pit

Contour interval 10 meters 

Datum is mean sea level

Surveyed with compass and tape by G. E. Erlcksen and A. J. Indacochea, 

August 1949; base elevation established by altimeter

FIGURE 28. Geologic sketch map and section of the Sirena Encantadora mine, Huallanca

mining district.

fide minerals are localized as veinlets and small replacement pods of 

pyrite and galena along serpentinized fracture zones.

The richer ore consists of galena with disseminated grains of calcite, quartz, wollastonite, pyrite, and veinlets of very fine-grained 

argentite. Some of the galena is cubic, but most occurs as elongate 

grains 1 to 2 millimeters long oriented parallel to the vein walls. 

Argentite veinlets a few centimeters long and less than a millimeter
112 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

thick tend to parallel the elongate galena crystals. Parts of the veins 

contain crystals and veinlets of sphalerite.

Southeast of the area shown on the map (fig. 28) several veins along 

the contact have been explored, but only a small amount of ore was 

encountered. One of these veins contains a small amount of bladed 

stibnite.

Mining began in 1948. Ore is mined from surface pits and sorted 

by hand to produce a concentrate containing more than 50 percent 

of galena. Twelve miners were employed at the time of our visit, 

and production was approximately five tons of concentrate per month. 

The owner of the mine, Sr. Arnulfo Carbajal, stated that the concentrate yielded 4 kilograms of silver and 8 grams of gold per ton. The 

concentrates were hauled by burros and mules to Conococha and by 

truck from Conococha to Lima.

Although the ore bodies are small, they are the richest seen in southeastern Ancash and are equaled in grade by only one or two of the 

better veins of the Antamina mining district to the north.

Exploration to greater depths in the present mine area and around 

the contacts of the stock should discover other ore bodies which may 

sustain a very profitable small scale operation for several years. At 

least 50 tons of high-grade ore were in sight at the time of our examination.

BELEC PROSPECT

The Belec prospect is on the north side of Quebrada Chuspi, near 

the crest of the ridge between the Cuarto de Dormir and Quebrada 

Tanash to the north (fig. 4). A 4-meter adit, the principal opening, 

is about 3 kilometers northeast of the Sirena Encantadora mine at an 

altitude of 4,400 meters. A trail crossing the ridge between Quebradas Chuspi and Tanash passes a few hundred meters east of the 

prospect.

Three small fissure veins cut gray dense sandstone which strikes N. 

30° W. and dips 85° SW. to vertically. The contact with an overlying limestone is about 20 meters to the southwest. The north vein, 

explored by the adit, strikes about N. 65° E. and dips 85° S. to vertical. 

It contains a lens 10 to 25 centimeters wide and about 2.5 meters long 

of pyrite and quartz with pods and veinlets of galena and sphalerite. 

A second vein, exposed in a small prospect pit 50 meters to the southwest, strikes N. 45° E. and dips 65° NW. It is 20 to 30 centimeters 

wide and consists of sheared and fractured sandstone containing pods 

and veinlets of pyrite and lesser galena. A third vein, parallel to bedding in the limestone, is 75 meters farther to the southwest. It is 10 

to 40 centimeters wide and 4 meters long and consists of iron oxide 

with a few small pods of pyrite, quartz, and galena.

It is possible that the north vein yielded one or two tons of lowgrade lead concentrate before the prospect was abandoned. However,
HUALLANCA MINING DISTRICT 113

no ore remains in this vein, and the other two veins are essentially 

barren.

PERLA PROSPECT

The Perla prospect is on the south side and near the head of Quebrada Tanash about 5 kilometers west of the Huanzala mine at an 

altitude of about 4,360 meters. The trail distance to Huallanca via 

Quebrada Tanash and Quebrada Torres is about 23 kilometers.

Several small sulride veins are exposed in a contact zone between 

limestone and a diorite intrusive. The limestone in the zone is 

bleached, recrystallized, and partly replaced by garnet. Beds strike 

about N". 35° W, and dip nearly vertically. The mineralized contact 

zone trends east. Three principal veins, ranging from 20 centimeters 

to a mete$ in width and 5 to 15 meters in length, and many irregular 

pods and veinlets crop out along the contact for a distance of at least 

100 meters. The larger veins strike N. 75° W. to S. 70° W. and dip 

85°N. to vertically.

Sulfide minerals are concentrated along shears and fractures in the 

limestone which apparently was first recrystallized, then garnetized, 

and later replaced by pyrite, quartz, galena, and marmatite. Some of 

the veins contain coarsely crystalline white calcite. It was estimated 

that most of the veins contained 5 to 10 percent of marmatite and a 

smaller content of galena; one of the major veins carried 15 to 35 percent marmatite and 5 to 15 percent galena.

The veins have been explored by three or four prospect pits and 

trendies. A few tons of low-grade galena concentrate may have been 

mined and shipped.

About 500 meters to the northwest a second mineralized zone appears 

to be on the north contact of the same dioritic intrusive. However, the 

intervening area is covered with soil and rock debris, and it is uncertain whether the intrusive is one single body or two isolated dikelike 

bodies. The attitude of the limestone is the same as to the southeast. 

The irregular contact zone trends east.

Mineralization is comparable to that already described except that 

the veins contain more pyrite and less galena. Two major veins were 

seen: the east vein, striking N. 44° W. and dipping 80° SW., is 1 to 2 

meters wide and about 35 meters long;.the west vein, striking N. 66° E. 

and dipping 81° SE., is about 1 meter wide (maximum) and 10 to 15 

meters long.

The predominant ore mineral of both zones is dark-brown to black 

marmatite, which may contain too much iron to be mined profitably. 

However, selective mining of the zones richer in galena might prove 

profitable for a small scale operation. Further exploration of the covered contact zones of the intrusive might expose other ore bodies.
114 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

PROTECTORA MINE

The Protectora mine is high in the south wall of Quebrada Torres 

about a kilometer south of Hacienda Torres and near the crest of the 

ridge between Quebrada Torres and Quebrada Tanash. The portal of 

the adit is at an altitude of 4,550 meters. Trail distance to Huallanca 

is about 20 kilometers.

The country rock is silicified limestone near the core of a small 

anticline whose axial plane strikes N. 35° W. and dips vertically. Beds 

on the limbs of the anticline dip steeply. Three granodiorite porphyry 

sills, cropping out on the west limb of the anticline within 30 meters of 

the axis, range from less than a meter to about 5 meters in thickness. 

The limestone on the west limb of the anticline has been silicified and 

serpentinized, but that on the east limb is unaltered, fine grained, and 

dark gray.

The only vein carrying an appreciable amount of sulfide minerals is 

near the axis of the anticline and strikes N. 35°-50° W. and dips about 

35° SW. An ore shoot 20 to 80 centimeters wide and probably 10 to 15 

meters long consists of altered wall rock, barite, calcite, light-brown 

crystalline sphalerite, and cubic galena. The ore was estimated to 

contain 20 to 30 percent of sphalerite and galena combined. Ore is 

localized in short irregular lenses a few millimeters to 30 centimeters 

thick and as much as 4 meters long. Ore minerals appear to have been 

deposited both by fissure filling and by replacement of wall rock.

The vein was explored by a 6-meter adit and stoped upwards for 

about 3 meters. In 1949 the mine was worked intermittently on a small 

scale, and probably less than 1 ton of galena concentrates was produced per month.

The vein is small, and probably only a few additional tons of ore 

can be mined from the exposed ore shoot. However, further exploration may expose other small ore bodies.

OTUSCO PROSPECT

The Otusco prospect is near the top of the east wall of Quebrada 

Chogoracra about 0.5 kilometer west of the Protectora mine. The 

main prospect pit is at an altitude of 4,530 meters.

The country rock is dark-gray fine-grained limestone, which 

strikes N. 15°-25° W. and dips about 80° SW. The ore and gangue 

minerals were deposited in fractures and fissures and replaced the 

limestone along bedding shears. The main mineralized zone, about 

a meter wide and at least 12 meters long, is laced with veinlets and 

pods containing cubic galena and minor amounts of sphalerite and 

calcite. The zone was estimated to contain about 5 percent of galena. 

Along the west side of the zone an irregular limestone breccia zone 

3 to 6 meters in diameter contains many veinlets and pods of galena, 

sphalerite, and calcite.
HUALLANCA MINING DISTRICT 115

The veins were explored by three or four small prospect pits, and 

one or two tons of low-grade lead ore may have been mined. The 

prospect was not being worked at the time of our visit in 1949.

A few other small prospect pits in two or three gouge, breccia, 

and iron oxide zones to the northwest of the Otusco prospect expose 

veinlets of pyrite and quartz with minor amounts of galena and 

sphalerite.

A few tons of ore might be mined from the main vein, but reserves 

are very small, and the other veins are essentially barren.

REACCI6N PROSPECT

The Reaccion prospect is on the east side of Quebrada Pluiscaposada, a small tributary valley on the south side of Quebrada Pucaraju, 

the westAvarcl continuation of Quebrada Torres. The area is about 

2 kilometers southwest of Hacienda Torres. The trail from Huallanca 

to Pachapaqui via Paso Yanashallash passes by the mouth of Quebrada Huiscaposada. The prospect area lies between the altitudes of 

4,400 and 4,470 meters.

The country rock is very fine-grained fossiliferous, dark-gray limestone which strikes N. 25°-30° W. and dips 70°-80° SW. At least 

four veins crop out along the east side of the quebrada over a horizontal distance of about 500 meters. Three of the veins strike N. 

60°-75°E. and dip nearly vertically; one strikes N. 10° W. and dips 

75° SW. The veins range from 5 to 10 meters in length and in most 

places are only a few centimeters wide. They contain lenses of calcite, apparently deposited in solution cavities, which range from 1 

to 4 meters in length and have a maximum width of about a meter.

Vein material consists of coarsely crystalline, vuggy calcite in 

rhombs commonly several centimeters in diameter; some cleavage 

faces are as much as 20 centimeters across. Pyrite, sphalerite, and 

galena partly fill cavities in the calcite. These druses of sulfide 

minerals are few in number and seldom1 are more than 25 centimeters 

in diameter.

The veins were explored by three small prospect pits, but no ore 

was encountered, and the prospect was abandoned. The veins are 

small and nearly barren, and it is doubtful that further exploration 

is warranted.

CASUALIDAD MINE

The Casualidad mine is on the southeast side of Cerro Huallapata 

about 1 kilometer nortliAvest of Hacienda Torres. The main workings are between the altitudes of 4,280 and 4,300 meters. The mine is 

about 300 meters above the level of the pampa in Quebrada Torres.

Irregular veins cut coarse-grained light-gray sandstone which 

strikes about N. 40° W. and dips 40°-50° NE. The veins are on the 

east limb and near the crest of a large anticline in sandstone and 

overlying limestone. The axial plane of the anticline strikes
116 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

N. 30°-40° W. and dips nearly vertically. Vein minerals were deposited in fissures, fractures, arid breccia cavities along an irregular 

fault and shear zone trending N. 35° W. Within the fault zone many 

branching and curving shear planes dip steeply from 65° NE. to 60° 

SW. The zone is 1 to 2 meters wide and about 60 meters long.

Vein material consists of finely crystalline to massive stibnite, cubic 

galena, very fine-grained sphalerite, and fine-grained pyrite. Much 

of the vein material and wall rock is stained with iron oxide. Ore 

occurs in veinlets and pods which are concentrated in brecciated rock 

or in rock broken by numerous closely spaced fractures. These bodies 

are generally 1 to 1.5 meters wide and 1 to 5 meters long.

During 1949 the richest pockets of ore were being mined from small 

surface pits and three adits ranging from 2.5 to 8 meters in length. 

Three or four men, working by hand, probably produced between 1 

and 3 tons of stibnite and galena concentrate per month.

The ore pockets are small and low grade, and only a few tons of 

ore are in sight. Unless larger and richer ore shoots are encountered 

at depth, it is doubtful that mining will continue to be profitable.

VICTORIA MINE

The Victoria mine is at the head of Quebrada Quecurure, a small 

valley north of Quebrada Pucaraju and about 2.5 kilometers west of 

Cerro Huallapata. The mine workings are between the altitudes of 

4,410 and 4,420 meters.

Several short parallel veins crop out in an area 5 to 10 meters in 

diameter in a fractured and brecciated shaly limestone. The veins 

strike N. 70°-80° E. and dip 70°-80° SE. The area is on the east side 

of a broad anticline near the crest, where the limestone strikes N. 25° 

E. and dips 26° SE. A 3- to 5-meter dike of altered granodiorite 

porphyry crops out a few meters east of the mineralized zone and 

strikes N. 40° W. and dips 70° NE.

The veins range from less than a centimeter to as much as 5 centimeters in width and from a few centimeters to 4 meters in length. 

They contain bladed stibnite and fragments of soft, altered limestone. 

Numerous cavities are lined with crystals of quartz. The stibnite 

blades range from a few millimeters to 5 centimeters in length and 

form a porous meshwork of crystals and masses of radiating crystals.

The veins were explored by a shallow 4-meter trench and three or 

four small surface pits. One or two tons of stibnite concentrate may 

have been shipped. The mine was inactive at the time of our visit 

in 1949.

Veins are small and apparently disappear within a few meters of 

the surface. Total reserves of high-grade stibnite ore are probably 

less than 5 tons.
HUALLANCA MINING DISTRICT 117

Another vein area, about 150 meters to the northwest on the floor 

at the north side of the quebrada, is exposed in two old prospect pits. 

A fault zone, striking about N. 75° W. and dipping 55° SW., contains 

a few veinlets of pyrite and quartz. In places the veinlets contain 

grains of sphalerite and tetrahedrite but not in minable quantities.

BODOQTJE MINE

The Bodoque mine is south of a small lake on the west side of 

Quebrada Retama about 2.5 kilometers northwest of the junction with 

Quebrada Torres. The main workings are at altitudes of 4,500 to 

4,520 meters. The trail distance to Huallanca via Hacienda Torres is 

about 25 kilometers.

The country rock is interbedded sandstone, limestone, shale, and 

clay. The attitude of. the strata is irregular because of local faulting 

and crumpling, but in general beds strike about N. 10° W. and dip 85° 

NE. Several irregular breccia, shear, and gouge zones, trending about 

N. 25° E. and dipping nearly vertical, are exposed in an area about 

50 meters wide by 100 meters long. Much of the area is covered, and 

the zones are best exposed in the many prospect pits and trenches. 

One of the zones contained a few veinlets and small pods of crystalline 

quartz and bladed stibnite, but the other zones seem to be barren.

Inhabitants of the area reported that several tons of antimony 

concentrate were shipped from this mine but that it was abandoned a 

few years ago because of lack of ore.

GOTA DE ORO PROSPECT

The Gota de Oro prospect is 011 the east side near the mouth of 

Quebrada Retama about 1.5 kilometers southeast of the Bodoque mine. 

The altitude is between 4,240 and 4,250 meters.

A few veinlets and pods of sulfide minerals occur in a breccia and 

alteration zone in massive dolomitic limestone. Vein minerals consist 

of calcite with minor amounts of pyrite, galena, and sphalerite.

This prospect was discovered in August 1949, a few days before we 

visited the district. No ore is in sight, and it is doubtful that further

exploration is warranted.

ISPAC MINE

The Ispac mine is on the northwest side of Nevado Sacra about 6.5 

kilometers northwest of Hacienda Torres. Most of the veins and old 

workings lie south of Lake Ispac between the altitudes of 4,460 and 

4,500 meters. This mine, the northernmost of the Huallanca district, 

is west of the crest of the Cordillera Huayhuash and therefore in the 

Departamento de Ancash. It is one of the most inaccessible mines in 

the district. The trail to Quebrada Torres has largely been destroyed 

by slide rock or has disappeared in the swamps of the quebradas.
118 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

When the mine was active, it was also connected by trail to Chavin, 

about 30 kilometers airline to the northwest, and to Pachapaqui, 15 

kilometers to the south.

The country rock is finely crystalline gray to tan limestone with 

interbedded shale. Much of the limestone has been replaced by quartz 

and garnet or stained reddish brown with iron oxide, so that from a 

distance Nevado Sacra looks like a mountain of iron oxide. Regionally the strata strike N. 35° W. and dip 40° NE. At least one 

altered granitic dike, striking N. 40° W. and dipping 80° SW., passes 

through the main vein area. Several other dikes can be seen in tho 

walls of the valley around the lake.

Most of the veins are in an area about 100 meters long and 20 to 40 

meters wide. Veins strike both northeast and northwest and dip 

nearly vertically. However, the most persistent veins strike N. 20 °-45 ° 

E. and dip 65° SE. to vertically. They appear to be replacement zones 

in the limestone and range from a few meters to as much as 20 meters 

in length and from 50 centimeters to as much as 2 meters in width. 

In addition, the area is laced with numerous irregular veinlets of sulfide minerals.

Vein material consists largely of altered wall rock, pyrite, sphalerite, 

minor amounts of galena, and veinlets and pods of quartz and calcite. 

Most veins average more than 50 percent pyrite, either in solid masses 

or as a granular mixture with wall rock. The sphalerite is dark brown 

to black in color and may be the variety marmatite. It is either mixed 

with the pyrite and wall rock or forms solid lenses and stringers 10 

to 50 centimeters wide and 1 to 4 meters long. The richest vein seen 

contained many small lenses and stringers of galena in sphalerite and 

pyrite.

Local inhabitants reported that the area was worked formerly for 

silver but was abandoned about 1925. Only one of the veins, explored by a shaft, contains enough galena to be mined and sorted by 

hand.

The mineralized area is fairly large, and reserves may be adequate 

to support a small mining operation for several years. It is possible 

that further exploration would expose other galena-rich veins which 

could be mined and concentrated by hand.

DEPOSITS OF QUEBRADA CASACANCHA

Several prospects and small mines are in the headwater region of 

Rio Vizcarra, along Quebrada Casacancha, and at the heads of small 

tributary valleys to the west. The region is east of Quebrada Azulmina and therefore is not shown on the sketch map of the Huallanca 

district (fig. 4). The deposits are accessible from Huallanca. Mr. 

Frank S. Simons examined the deposits of this region in July 1952 

and gave the following data about the mines and prospects.
HUALLANCA MINING DISTRICT 119

Prospects at the head of Quebrada, Casacancha. The high glaciercapped peak (Nevado Tutococha) at the head of Quebrada Casacancha is underlain by an irregular stocklike mass of light-gray rhyolite or dacite porphyry. Along its north and west margin, at an altitude of about 4,800 meters, the porphyry is in contact with gray wellbedded limestone, which strikes north and dips steeply east. Small 

bodies of pyrite and subordinate galena crop out at several places in 

the limestone along the contact, and many narrow sulfide veinlets cut 

the limestone at some distance from the contact. A few of the sulfide 

bodies have been explored by small prospect pits, but no ore was exposed and the prospect was abandoned. To judge from the size and 

tenor of the veins in this area, it is doubtful that further exploration 

would reveal ore.

The area seems to be undergoing a very rapid deglaciation. According to local residents, the deposits were covered by ice until fifteen or twenty years ago; at present the ice has retreated several tens 

of meters above the deposits. However, a short distance to the south 

a large tongue of ice extends well below the level of the contact of the 

limestone and the porphyry.

Pucarodeo prospect. The Pucarodeo prospect is on the west side 

near the bottom of Quebrada Casacancha about 1 kilometer south of 

Hacienda Casacancha and 15 kilometers by trail south of Huallanca. 

The workings are between the altitudes of 4,050 and 4,060 meters. 

Country rock is interbedded quartzite and phyllite which strikes N. 

30° W. and dips 80° NE.

Two short adits, 10 meters apart vertically, and a raise to the surface from the upper adit have explored a vein striking N. 60° E. and 

dipping 70° NW. The vein is some 50 centimeters wide and consists of 

ankerite and minor amounts of pyrite, galena, and tetrahedrite (?). 

Apparently very little ore was found, and the prospect has been 

abandoned.

Arteria and Reserva mines. The Arteria and Reserva mines are on 

the north slope of Nevado Chaupijanca at the head of Quebrada 

Churuco about 5 kilometers south of Quebrada Casacancha and 15 

kilometers by trail south of Huallanca. The old mine camp is at 4,320 

meters, and the veins crop out between the altitudes of 4,440 and 

4,580 meters. Rocks of the mine area are limestone cut by an intricate 

network of dikes composed of gray porphyritic andesite and andesite 

breccia and light-gray rhyolite or dacite. The limestone strikes east 

and dips steeply.

The Arteria vein is exposed over a strike distance of about 200 

meters and ranges in width from less than 1 centimeter to 3.5 meters; 

on the average the width ranges from 1.0 to 1.5 meters. The vein 

strikes east and dips 65°-75° S. In the lower and easternmost exposures the vein consists of a pyritized breccia zone 1.0 to 1.5 meters
120 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

wide, interlaced with many veinlets of pyrite, galena, and sphalerite. 

These veinlets are as much as 30 centimeters wide but average less 

than 5 centimeters. The intrusive rocks north of the vein are andesite, 

and those to the south are rhyolite or dacite. Rock in the vein walls 

is heavily pyritized.

Toward the west the vein widens to 3.5 meters and then pinches out. 

The west half of the vein consists largely of quartz and pyrite with a 

few small pods or lenses of sphalerite and galena. Wall rocks are 

andesite, andesite breccia, and limestone.

The Arteria vein probably contains on the average less than 10 

percent of combined galena and sphalerite. Sufficient ore is available 

to support a small operation producing a few tons of hand-sorted lead 

and zinc concentrate per month. As fresh vein material is well exposed through a vertical zone of 40 meters and over a horizontal distance of 200 meters, the outcrop should give a fair indication of the 

grade and amount of ore available. The average ore is rather low 

grade, and the tonnage is inadequate to sustain a large-scale 

operation.

The Reserva veins are south of the Arteria vein. One vein, about 

200 meters south of the west end of the Arteria vein, strikes N. 60° W. 

iind dips steeply southwest. It is 30 to 40 centimeters wide and consists of pyrite with a little galena and sphalerite. The vein cuts 

through limestone and dikes of rhyolite or dacite. A second vein about 

150 meters farther south cuts gray porphyritic andesite. This vein 

strikes N. 70° W. and dips 80° SW. It is as much as 1.7 meters wide 

and has an outcrop length of 20 to 30 meters. Vein material is pyrite 

with considerable sphalerite and minor amounts of associated galena 

along the footwall. Several other small veins on the Reserva claim 

appear to be essentially barren.

The Arteria-Reserva group of veins may possibly be worked profitably on a small scale, but grade of ore and possible tonnage are low.

El Sol prospect, El Sol prospect is on the west shore of Azulcocha 

Lake in a small cirque at the head of Quebrada Yanajirca, an eastern 

tributary of Quebrada Churuco. The prospect is about 5 kilometers 

east of the Arteria-Reserva deposits and is near the altitude of 4,390 

meters. Country rock is limestone which strikes N. 10° E. and dips 

65° NW. A small opencut exposes irregular pods of sphalerite, pyrite, 

and minor amounts of galena, which appear to have replaced limestone 

along the bedding. The mineralized zone crops out for 20 meters along 

the strike and ranges in width from 60 centimeters to nearly 2 meters; 

it lenses out to the south and is covered to the north. The largest pod 

is about 30 centimeters thick. Although some high-grade zinc ore is 

available, the tonnage is very small, and it is doubtful that additional 

exploration would reveal much more ore.
HUALLANCA 'MINING DISTRICT 121

Near the outlet of Lake Azulcocha one contact of a small rhyolite 

intrusive in limestone is marked by a little iron oxide and copper carbonate with small amounts of galena. Neither the carbonate nor the 

galena occurs in mlnable quantities.

DEPOSITS AT THE HEAD OF QUEBRADA AZULMINA

Of the following mines located at the head of Quebrada Azulmina, 

the Danubio-Diamante mine was examined by G. E. Ericksen in 1949, 

and the others by F. S. Simons in 1952. Mr. Simons also saw veins 

at the Danubio-Diamante mine in 1952. Location of the DanubioDiamante mine, as shown in figure 4, is approximate.

Danubio-Diamante mine. The Danubio-Diamante mine is near the 

Pachapaqui-Huallanca trail about 1.5 kilometers southeast of Paso 

Burro and at the extreme western end of Quebrada Azulmina. It lies 

east of the crest of the Cordillera Huayhuash in the Departamento de 

Huanuco. By trail the mine is about 15 kilometers from Pachapaqui 

and about 20 kilometers from Huallanca. The workings are between 

the altitudes of 4,530 and 4,580 meters.

Principal mineralization occurs within or along the contacts of an 

irregular porphyritic granite dike several hundred meters long and 

from 2 to 20 meters thick. The dike trends N. 60°-85° W. and clips 

nearly vertically. The country rock is thin-bedded fine-grained darkgray limestone which has been complexly folded. The many large 

and small folds have amplitudes ranging from a few meters to more 

than 100 meters. Axial planes trend N. 30° W. and are nearly vertical.

Sulfide minerals are disseminated in irregular replacement bodies 

2 to 20 meters long and 0.5 to 3 meters wide, which crop out along the 

dike for more than 75 meters. One or two of these bodies cut across 

the dike, but most are near the contact and tend to be nearly parallel 

to it. The limestone near the dike contains a few veins of sulfide min - 

erals and commonly is crisscrossed with calcite veinlets.

The replacement bodies consist of irregular pods of high-grade 

lead, zinc, copper, and silver ore separated by intervening areas of 

low-grade ore. The vein minerals are galena, sphalerite, chalcopyrite, tetrahedrite, realgar, rhodonite, pyrite, and quartz. Of these 

minerals, galena and chalcopyrite are most common, tetrahedrite 

occurs in minor amounts, and realgar was seen in Armlets of only 

one mineralized body. Disseminated grains of rhodonite give the ore 

bodies a pinkish color. During the deposition of the minerals, vugs 

as much as 20 centimeters in diameter were lined with massive rhodonite and then filled Avith crystalline quartz.

A short distance from the dike galena, chalcopyrite, and sphalerite, 

in a gangue of quartz and rhodochrosite, replace limestone along an 

irregular vertical fracture zone which trends roughly N. 15° W. The

321628 55 9
122 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

limestone strikes N. 30° W. and dips vertically. Tetrahedrite and 

realgar associated with coarse-grained milky quartz occur sporadically along the walls of the mineralized zone. The ore body was explored and mined by means of a shallow inclined shaft and an adit 

(now caved) about 10 meters below the head of the shaft. The ore 

in this vein is moderately high grade, but the amount in sight and 

reasonably expectable is very small.

The present operation was begun in 1948, and the veins were worked 

by hand entirely from surface pits. The owner employs three to 

six men, and production between 1948 and 1952 was about a ton of 

hand-sorted lead-copper-silver concentrate per month. The area had 

been explored previously by means of two or three, adits which were 

inaccessible in 1949 and 1952.

Parts of the mineralized bodies are amenable to hand mining and 

concentrating. It seems probable that the reserves throughout tht 

Danubio-Diamante area are large enough to support the present operation for several years.

Eweka mine. The Eureka mine is at the head of Quebrada Azul 

mina several hundred meters south of the Danubio-Diamante mine.

A number of veins crop out on the lower slopes of Cerros Portachuela and Inca at altitudes ranging from 4,670 to 4,760 meters. 

These veins cut limestone that strikes N. 20°-30° W. and dips steeply 

northeast. They range in width from less than a millimeter to about 

1 meter, but most are 10 to 20 centimeters wide. Vein material consists of pyrite, chalcopyrite, reddish-brown sphalerite, and galena in 

a gangue of quartz, calcite, rhodonite, and rhodochrosite; late veinlets of manganiferous calcite and pyrargyrite (?) occur in one vein. 

Two short adits and one moderately long adit expose the veins. The 

longest adit, at an altitude of 4,760 meters, was driven south to explore the veins at depth. Two veins were cut, at 90 and 93 meters 

from the portal. Both veins strike N. 70°-80° E. and dip 75°-SO° 

S. The northern vein ranges from a few centimeters to about a meter 

in width. The widest part of the vein, exposed in a drift to the east 

of the adit, was stoped, and apparently considerable amounts of highgrade copper-lead-zinc ore were extracted. The southern vein and 

other veins tend to be narrow but locally contain small bodies of minable material.

Although the mine was inactive in July 1952, enough ore is available and inferred to sustain a small-scale operation for several years. 

However, the veins in general are very narrow, and the possibilities 

of obtaining large amounts are remote.

Excelsior prospect. The Excelsior prospect is about 3 kilometers 

southeast of Paso Burro near the summit of Cerros Portachuelo and 

Inca, between the altitudes of 4,880 and 4,920 meters. Limestones
HUALLANCA MINING DISTRICT 123

striking N. 30° W. and dipping steeply northeast largely have been 

converted to pale-green garnet in the prospect area.

The Excelsior vein strikes east and its dip is vertical. It is exposed 

over a strike distance of about 120 meters and attains a maximum 

width of two meters. The vein pinches out to the east and is covered 

by ice to the west. Vein material is largely coarse-grained calcite cut 

by veinlets of quartz, rhodonite, and pyrite with small amounts 

of chalcopyrite, galena, and sphalerite. Although the vein is 

persistent and moderately Avide, the tenor is too IOAV to Avarrant farther 

exploration.

OTHER DEPOSITS

In addition to the mines and prospects already described a feAv 

others, whose names are unknoAvn and which have not been worked 

for several years, are described briefly in the following section and 

are given numbers for purpose of reference.

Prospect 1. A small prospect lies about 100 meters northeast of 

a small lake in the east Avail of Quebrada Pucaraju Pampa at an altitude of 4,360 meters. Sandstone striking N". 35° W. and dipping 85° 

SW. is cut by a mineralized fracture zone striking N. 85° W. and dipping 85° S. The zone is about 50 centimeters Avide and is exposed for 

about 10 meters. It is stained with iron oxide and contains a feAv 

veinlets of galena averaging less than 2 millimeters in width and 10 

centimeters in length.

There is no ore in sight, and it is doubted that further exploration 

Avill reveal minable material.

Mine 1. An old silver mine is on the south side of Cerro Huallapata, 

about 250 meters south of the Casualidad mine and about a kilometer 

northwest of Hacienda Torres. The portal of the loAvest major adit 

is at an altitude of 4,200 meters and is 50 to 100 meters above the pampa 

in Quebrada Torres. The Avorkings are old and the mine has been 

abandoned for many years.

A single fissure vein, striking about N. 30° W. and dipping 85° NE., 

is parallel to bedding of light-gray sandstone on the east limb of the 

anticline of Cerro Huallapata. The vein contains gouge and breccia 

with disseminated crystals and veinlets of pyrite but seems to be barren of ore minerals. A careful search of the dumps revealed a feAv 

specimens containing crystals of proustite and galena.

The vein was mined and explored by means of 4 major adits and 

several shorter adits and surface pits through a horizontal distance of 

about 100 meters and a vertical distance of 50 meters. The major 

adits are from 10 to 30 meters long and are noAv partly caved or filled 

with water. An upper adit is stoped to the surface, a distance of 10 

to 20 meters, and possibly a shoot of enriched silver ore \vas mined. 

The loAver adits are smaller and have no stopes; they may have been 

driven to explore the vein at greater depth.
124 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

The vein appears to be barren, and the adequate exploratory work 

indicates little chance of finding more ore.

Mine 2. A small group of workings of another old mine is on the 

south side of Quebrada Torres about 500 meters southwest of Hacienda Torres and about a kilometer southeast of mine 1. The workings 

lie between altitudes of 4,140 and 4,150 meters and are 65 to 75 meters 

above the pampa.

Several small mineralized zones crop out in sandstone on the east 

limb of the same anticline as is exposed at Cerro Huallapata. They 

contain much gouge and breccia with veinlets of pyrite and quartz. 

One principal zone strikes N. 40° W. and dips 55° SW., and the other, 

10 meters to the north, strikes N. 70° E. and dips 80° SE. No ore 

minerals were observed in place, but a few specimens on the dumps 

contained veinlets of galena.

The area was explored by a 7-meter inclined shaft with a 7-meter 

drift, a 10 meter adit, and a few prospect pits. Apparently no ore 

was encountered.

PACHAPAQUI MINING DISTRICT

The Pachapaqui mining district is in the northeast part of Bolognesi Province in the Departamento de Ancash. The district takes its 

name from the town of Pachapaqui at the south edge of the area, 22 

kilometers airline north of Chiquian. The main trail from Chiquian 

to Huallanca via Quebrada Burro passes through Pachapaqui. The 

trail distance to Chiquian is 30 to 35 kilometers, and that to Huallanca 

via Quebrada Tunacancha and Quebrada Torres is 35 to 40 kilometers.

The area lies west of the Cordillera Huayhuash at the headwaters of 

the Rio Pativilca. Three major valleys lying to the north join at 

Pachapaqui, and their streams join to form the Rio Pativilca. The 

northwestern valley, Quebrada Piscapaccha, heads on the eastern 

slope of the Cordillera Blanca near Nevado Raria and trends southeast about 16 kilometers to Pachapaqui. The central valley, Quebrada 

Tunacancha, trends approximately south and is about 11 kilometers 

long. The eastern valley, Quebrada Cara, is 3 to 4 kilometers long 

and trends southwest. At the east end of Quebrada Cara is the junction of three smaller valleys, Quebrada Burro, Quebrada Nupocuta, 

and Quebrada Shier a Shier a. Most of the mines and prospects are in 

these three smaller valleys (fig. 5).

Most valleys of the district are U -shaped. Their heads are cirquelike and contain much recent morainal material. A small lake has 

formed behind a recent recessional moraine at the head of Quebrada 

Burro. The higher peaks along the crest of the Cordillera Huayhuash 

are covered with active glaciers, and tongues of ice extend down into 

the mine areas. Nevado Burro, one of the highest peaks in the north-
PACHAPAQUI MINING DISTRICT 125

ern part of the Cordillera Huayhuash, rises sharply from the north 

end of Quebrada Burro.

The sedimentary rocks are complexly folded, and it was not possible to work out details of the stratigraphy. Most of the folds are in a 

medium- to thick-bedded fine-grained dark-gray limestone that is underlain by medium-grained light-gray sandstone. Between these units 

is a sequence of interbedded shale, limestone, and shaly sandstone, 

which may be several hundred meters in thickness. On the whole the 

rocks seem to be similar to those in the Huallanca district.

The only igneous rocks are irregular dikes and stocks of granite 

porphyry, which occur in greatest number near the crest of the Cordillera Huayhuash.

Many small faults appear to have caused only minor displacement 

of the rocks. Most of them appear to be steeply dipping normal 

faults and contain veins of sulfide minerals.

Both fissure and replacement veins are found. The predominant 

minerals of the fissure veins are quartz and pyrite with lesser amounts 

of galena, sphalerite, chalcopyrite, and tetrahedrite. The replacement 

veins contain, much quartz, rhodochrosite, and rhodonite with pods, 

veinlets, and disseminated grains of galena, sphalerite, chalcopyrite, 

and pyrite.

Some of the fissure veins might be Avorked profitably on a small scale 

for several years. However, the future of the district depends on the 

possibility of large-scale exploitation of one or two large low-grade 

replacement veins; at present we do not know whether these veins can 

be mined profitably.

Mines showing most promise for future production are:

Patria, Esperanza, and Otito: low-grade lead-zinc-copper ore, largest mineralized zones in the four southern mining districts. Detailed sampling 

and diamond drilling might disclose very large reserves of low-grade ore.

Sinchi Roca: lead-zinc-copper ore, reserves may be large enough to support a small scale operation for a few years.

San Antonio and Abandonada: lead-zinc copper ore, moderately large but 

low-grade mineralized zone, worthy of further exploration.

San Judas Tadeo: lead-zinc-copper ore, reserves may support a small-scale 

operation for several years.

PACHAPACtUI CONCENTRATION PLANT

The Pachapaqui concentration plant is on the north side of Pachapaqui at an altitude of 3,800 meters.

The mill, rated at 30 tons per day, is owned and operated by the 

Compania Minera Argenta Bolognesi. Construction was completed 

early in 1949, and operation began in March 1949. In August 1949 the 

plant was operating at less than one-half capacity because of shortage
126 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

of ore. Five to ten men were employed, and production was about 

three-fourths of a ton of lead-copper-silver concentrates per 8-hour 

day. However, only two or three mines were furnishing ore, and the 

mill operated less than four days per week; probably output was less 

than 10 tons of concentrate per month.

The plant is powered by a 75-horsepower Frances turbine which 

furnishes direct (pulley) power to the machines. Water for the turbine comes from the stream in Quebrada Cara and is brought to the 

plant by a canal about 1 kilometer long. Other equipment of the mill 

included a Kisdon Iron Works jaw crusher rated at 100 tons per 24 

hours, a Krupp ball mill rated at 30 tons per 24 hours, a Dorr Simplex 

classifier, and 6 wooden flotation cells, Denver type No. 15.

PATRIA, ESPERANZA, AND OTITO MINES

Two large, nearly parallel mineralized zones along the east side of 

Quebrada Piscapaccha have been explored and worked at the Patria, 

Esperanza, and Otito mines. The principal workings of the northernmost mines, Patria and Esperanza, are in Quebrada Quenhuaracra between the altitudes of 4,320 and 4,350 meters. Patria is on the eastern 

zone and Esperanza on the western zone about 300 meters distant. 

These mines are about 9 kilometers airline and 12 kilometers by trail 

north of Pachapaqui. Two prospect areas of the Otito mine are on 

the eastern mineralized zone 2.5 and 3 kilometers southeast of Patria. 

The Otito workings are between the altitudes of 4,330 and 4,510 meters.

The mineralized zones are in brecciated limestone on two sides of a 

complexly folded structure which in Quebrada Quenhuaracra consists 

of two anticlines separated by a syncline. At most places the zones are 

10 to 30 meters thick, but at Otito the eastern zone attains a thickness 

of nearly 50 meters. The zones have an outcrop length of more than 4 

kilometers and an exposed vertical extent of at least 200 meters. They 

are underlain by light-gray sandstone and overlain by a sequence of 

alternating beds of limestone and shale. At Patria the beds strike 

N. 15° W. and dip 70°-85° NE., and at Esperanza they strike N. 

20°-30° W. and dip about 80° SW., whereas at Otito bedding is more 

irregular, striking N. 25°-55° W. and dipping 45°-75° NE.

It is probable that a limestone bed resting on sandstone was irregularly faulted and brecciated during folding and later was mineralized. 

The resulting mineralized zones have a sinuous outcrop and regionally 

are parallel to beds but locally cut across beds of the underlying sandstone. Irregular brecciated areas and veins of sulfide minerals within 

the principal zones trend parallel to them.

Much of the limestone is silicified and contains finely disseminated 

pyrite. At places the zones are capped with porous and cavernous 

gossan, which may be several meters thick, and at other places
PACHAPAQUI MINING DISTRICT 127

weathered surfaces are encrusted or stained with iron oxide, so that it 

is difficult to examine the zones except in prospect pits or in valleys 

where streams have kept the surfaces clear of iron oxide. The more 

intensely brecciated areas contain pyrite, calcite, siderite, and quartz 

with blebs, veinlets, and disseminated grains of sphalerite, galena, and 

chalcopyrite. Unbrecciated limestone contains scattered grains and 

veinlets of these minerals. Apparently minerals were deposited both 

by fracture filling and by replacement of the limestone.

The degree of mineralization varies considerably at the different 

mines. The richest lead ore is exposed at Patria and is mixed with 

pyrite and altered limestone. Several veins and lenses of pyrite and 

sphalerite with lesser galena are exposed at Esperanza. The zone at 

Otito contains much pyrite, ankerite, and minor amounts of galena 

and sphalerite.

In the underlying sandstone at Patria and within 30 meters of the 

principal zone a few small irregular galena veins crop out along fracture and breccia zones parallel to bedding. At Esperanza a vein in 

the sandstone strikes N. 45° E. and dips 35° SE. and contains 10 to 20 

centimeters of quartz and pyrite with a few blebs of chalcopyrite.

Veins at the three mine areas have been explored and mined in pits, 

trenches, and short adits. The vein in sandstone at the Esperanza 

mine was explored by means of several inclined shafts up to 5 meters 

long and a drift about 10 meters long. At the time of our visit in 1949 

the Patria mine was being worked by two men, and the other mines 

were inactive.

These mineralized zones are the largest and most persistent seen in 

the region. On the whole they are of low grade, and detailed 

sampling would be necessary to determine the quantity and grade of 

minable material. If blocks of the zones could be mined in toto, the 

reserves should be very large. Some small veins of galena can be 

mined profitably by hand, but selective mining on a larger scale would 

not be profitable.

PACIENCIA PROSPECT

The Paciencia prospect lies near the mouth of a small tributary valley extending southward from Quebrada Car-a. In airline distance 

the prospect is 4.1 kilometers east of the Pachapaqui concentration 

plant, and the trail distance is 6 to 7 kilometers. The prospect is at 

the level of the stream at an altitude of 4,120 meters.

Two veins about 10 meters apart are exposed in a 3-meter adit and 

a pit in an area covered by slide rock and soil at the south side of the 

stream. The north vein strikes N. 45° W. and dips 85° NE., and the 

south vein strikes N. 65° W. and dips 80° SW. The veins range from 

50 to 80 centimeters wide and contain breccia fragments, quartz, and 

white coarsely crystalline calcite with pods and veinlets of pyrite,
128 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

sphalerite, and galena. Because of the poor exposures, the horizontal 

and vertical extent of the veins could not be determined, but they are 

probably not more than a few meters long.

The content of galena and sphalerite is insignificant, and it is doubtful that further exploration would reveal minable material.

ARABIA MINE

The Arabia mine is on the west side of Quebrada Burro 4.9 kilometers airline distance northeast of the Pachapaqui concentrator. 

The main workings are between the altitudes of 4,310 and 4,430 

meters. The trail distance to Pachapaqui is 8 to 10 kilometers.

The country rock is coarse-grained light-gray sandstone striking 

N. 40° W. and dipping 80° NE. to vertically. Several irregular 

fissure veins 20 to 40 centimeters wide and 10 to 50 meters long crop 

out in a fault or shear zone 5 to 10 meters wide and more than 150 

meters long. The veins strike N. 10°-45° W. and dip 80° NE. to 

Arertically, nearly parallel to bedding. Vein material consists of 

vuggy white quartz with some rhodonite and with small lenses, 

irregular pods, veinlets, and disseminated grains of pyrite, chalcopyrite, sphalerite, galena, and tetrahedrite.

According to local inhabitants the mine was worked during 

Colonial times, and throughout the area are many surface pits, shafts, 

drifts, and open stopes. The main adit, more than 300 meters long, 

is the lowest and the easternmost opening. It exposes several pyritequartz veins that in places contain disseminated chalcopyrite. 

Although there is no record of production, the size of the Avorkings 

indicates that several thousand tons of vein material were removed.

It is probable that the mine was operated for a number of years and 

that most of the ore has been mined. The remaining vein material 

seems to be of low grade, and reserves are small.

VETILLA MINE

The Vetilla mine is on the east side of Quebrada Tunacancha, near 

the crest of the ridge between Quebrada Tunacancha 'and Quebrada 

Burro and about a kilometer northwest of the Arabia mine. The 

main workings lie between the altitudes of 4,300 and 4,400 meters. 

The trail distance to Pachapaqui via Quebrada Tunacancha is 6 to 1 

kilometers.

The country rock is thin-bedded dark-gray quartzite with interbedded phyllite, striking about N. 35° W. and dipping 85° SW. The 

veiii area is largely covered with slide rock and waste material from 

several adits. Almost all the waste material consists of barren 

quartzite, and a careful search of the dumps revealed only a few fragments of vuggy, crystalline quartz with disseminated grains of 

pyrite, galena, sphalerite, and tetrahedrite.
PACHAPAQUI MINING DISTRICT 129

A few veinlets of quartz and pyrite trending parallel to the strata 

are exposed in one adit 75 meters long. Several short crosscuts intersect a bedding fault zone as much as a meter wide containing altered 

wall rock and gouge with veinlets of pyrite. The drifts along this 

zone are completely caved.

Local inhabitants could not give any information about the mine, 

but the workings are old, and the area may have been explored at the 

time the Arabia mine was operating. There are at least three caved 

or flooded adits which, to judge by the size of the dumps, were from 

50 to 100 meters long.

No lead, zinc, or copper minerals were observed in the exposed 

veins, and the small quantity of sulfide minerals on the dumps suggests that practically none were encountered during mining.

ABANDONADA PROSPECT

The Abandonada prospect is about 150 meters north of the Arabia 

mine, in the west wall of Quebrada Burro. The altitude at the adit is 

4,340 meters.

The country rock is massive gray limestone which strikes about N. 

15° W. and dips nearly vertically. Several irregular replacement 

bodies and veinlets of quartz, rhodonite, and rhodochrosite are in a 

zone up to 15 meters wide and more than 50 meters in horizontal and 

vertical extent. The replacement'bodies tend to be elongate parallel 

to the bedding of the limestone. Both ends of the mineralized zone 

are covered with slide rock.

Most lenses are not more than 1 to 2 meters Avide and 5 to 10 meters 

long. They consist of compact and tough masses of intermixed wall 

rock, white quartz, and pink rhodonite and rhodochrosite, with disseminated grains of pyrite, chalcopyrite, sphalerite, galena, and tetrahedrite.

The area was explored by a prospect pit and a 6-meter adit. The 

prospect was abandoned prior to 1949, and it is doubtful that any ore 

was shipped.

The veins are low grade and visible reserves small. However, this 

zone may be a continuation of the San Antonio vein and might warrant further exploration. The vein material is too low grade to be 

mined and concentrated by hand.

SANTA ELENA, MINE

Two veins have been worked on the Santa Elena property. Santa 

Elena I, the southern vein, is on the west side of Quebrada Burro 300 

meters east of the Arabia mine, and Santa Elena II is 250 meters to 

the northeast. The adit at Santa Elena I is at an altitude of 4,200 

meters, and that at Santa Elena II is 4,170 meters.
130 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

The country rock at Santa Elena I is light-gray crystalline limestone which strikes N. 30° W. and dips nearly vertically. Sulfide 

minerals occur in a main vein a few centimeters to a meter wide and 

about 20 meters long as well as in a shorter off-shoot vein. The major 

vein strikes N. 45° W. and dips 90°, and the off-shoot strikes N. 70° 

W. and dips 65° SW. The veins contain vuggy quartz and pyrite with 

veinlets and pods of galena, sphalerite, and tetrahedrite. The ore is 

banded and crustified and contains open cavities lined with calcite 

crystals.

The principal vein was worked from a 10-meter adit, and possibly 

several tons of ore were extracted. Although small-scale mining 

might produce an additional few tons of ore, reserves appear to be 

very small. The mine was inactive at the time of our visit.

The country rock at the Santa Elena II vein is gray crystalline limestone striking N. 40° W. and dipping 70° SW. The vein minerals 

were deposited in fissures along a fault zone striking N. 35° W. and 

dipping 50°-75° SW. The zone has an average width of 1 meter and 

horizontal and vertical ranges of more than 30 meters. It consists 

largely of limestone breccia, gouge, and pyrite, with pods and grains 

of galena, sphalerite, chalcopyrite, and tetrahedrite. At places it contains bodies of moderate- to high-grade ore, ranging from one to two 

meters long and as much as one meter wide. Much of the vein is 

webbed with veinlets of quartz and calcite.

An adit 25 meters long was driven on the Santa Elena II vein, and 

probably several tons of copper-lead-silver ore were extracted. The 

mine was not operating in 1949, but it seems likely that small scale hand 

mining of the vein would be profitable for a few years.

PRIMAVERA PROSPECT

The Primavera prospect is in a small gorge cut by the main stream 

near the center of Quebrada Burro, 4.5 kilometers northeast of Pachapaqui. The altitude of the adit is 3,960 meters.

A mineralized fault and shear zone, striking N. 20° W. and dipping 

55° SW., crops out near the stream level in a light-gray sandstone 

which strikes N. 35° W. and dips 55° SW. The most persistent vein 

in the shear zone, about 5 centimeters wide and 10 meters long, contains quartz and pyrite with minor amounts of galena and sphalerite. 

Small stringers and pods of these minerals also occur in the shear zone 

within 1 meter above and below the vein. The zone was explored by 

a 2-meter adit, but no ore was encountered and the prospect was 

abandoned.

A second vein is exposed in a small outcrop about 75 meters- to the 

southwest. The vein is about 20 centimeters wide and contains calcite 

with disseminated sulfides. It is largely covered but at the outcrop 

strikes N. 65° W. and dips 75° SW.
PACHAPAQUI MINING DISTRICT 131

Both veins are small and nearly barren, and further exploration does 

not seem justified.

DOS COMPADRES PROSPECT

The Dos Compadres prospect is on the east side of Quebrada Burro 

about 700 meters northeast of the Primavera prospect. Several small 

prospect pits are between the altitudes of 4,100 and 4,110 meters.

The prospect is a new discovery and was being explored by three 

or four small pits at the time of our visit. The vein seems to be a tabular body 25 to 40 centimeters thick and 5 to 15 meters long, parallel 

to bedding of silicified limestone striking N. 25° W. and dipping 45° 

SW. The vein parallels a dip slope and is covered with about 50 centimeters of limestone which is cut by veinlets. Vein material is predominantly pyrite, calcite, and gouge with pods and disseminated 

grains of galena, sphalerite, and chalcopyrite.

The vein is small and low-grade and probably cannot be worked at 

a profit.

SINCHI ROCA MINE

The Sinchi E-oca mine is on the east side of Quebrada Burro 400 to 

600 meters east of the Primavera prospect. The main lower adit is at 

an altitude of 4,050 meters, 75 to 100 meters above the pampa.

The country rock is gray crystalline limestone which strikes N. 25° 

W. and dips 80° SW. Vein minerals were deposited in fissures and 

also replace wall rock along an irregular fault zone which strikes 1ST. 

25°^i5 0 W. and dips 45° SW. to nearly vertically. The vein is more 

than 150 meters long and has an exposed vertical range of about 125 

meters. Ore shoots are lenticular, generally 10 to 20 meters long, and 

have a maximum width of 1 to 1.5 meters. The areas between ore 

shoots are altered and contain veinlets of sulfide minerals.

The ore shoots contain much pyrite, gouge, quartz, and calcite with 

pods and disseminated grains of galena, sphalerite, and chalcopyrite. 

Much of the vein material is stained red-brown with iron oxide. Outcrops show some copper stain, and numerous open cavities contain 

crystals of azurite and malachite. The ore shoots were estimated to 

contain 5 to 15 percent of combined lead, zinc, and copper sulfides.

The main adit is 15 meters long, and the vein has been stoped upwards for 2 to 3 meters. A second adit about 150 meters southeast is 

5 meters long, and stopes extend upward about 3 meters to the surface.

Probably as much as 100 tons of vein material were mined, but the 

grade of the ore and amount of concentrate shipped are not known.

The Sinchi Koca vein is one of the more accessible of the district, 

and reserves are probably large enough to support a profitable smallscale operation for several years.
132 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

SANTA BENITA PROSPECT

The Santa Benita prospect is near the head of Quebrada Burro 

about 200 meters southeast of Laguna Burro. The altitude of the adit 

is 4,320 meters.

Many vein lets of sul.fi.de minerals are in closely spaced, parallel 

fractures and in breccia along a fault zone striking N. 35° W. and dipping 90°. The wall rock is recrystallized and silicified limestone that 

strikes N. 55° W. and dips 55° S.

The veinlets are'vuggy and consist largely of pyrite and quartz 

with minor amounts of galena, sphalerite, chalcopyrite, and tetrahedrite. Many of the vugs are lined with quartz and tetrahedrite 

crystals. On the average, the mineralized zone is 20 centimeters wide 

and has a horizontal and vertical extent of more than 20 meters. The 

richest part was explored by a 4-meter adit, but the vein material 

appears to be too low in grade to.be mined.

RASCACIELO MINE

The Rascacielo mine is on the east side of Quebrada Burro, 300 

meters south of the Santa Benita prospect. At the portal of the adit 

the altitude is 4,360 meters. The main trail from Pachapaqui to 

Huallanca passes by the mine.

Minerals were deposited in a gouge and breccia zone, striking N. 

Y0° W. and dipping 55° N., in silicified limestone which strikes N. 

45° W. and dips 80° NE. Much of the area is covered with soil, and 

the zone is best exposed in an old adit about 40 meters long. Here it 

ranges in width from 50 centimeters to a meter and extends more 

than the full length of the adit.

Irregular fractures along the fault zone contain calcite and quartz 

with disseminated grains of sulfide minerals. A few larger bodies 

of sulfide minerals, as much as a meter wide and 1 to 3 meters long, 

consist largely of pyrite with lesser amounts of chalcopyrite, galena, 

and sphalerite.

The adit appears to be very old, but the face was extended a few 

meters in recent years. The mine was not being worked at the time 

of our visit in 1949. Most of the vein is barren, but a few tons of ore 

are exposed in the richer sulfide bodies.

SOCORRO PROSPECT

The Socorro prospect is at the northeast end of Quebrada Burro 

near the Pachapaqui-Huallanca trail, about 0.5 kilometers west of 

Paso Burro and 7 kilometers northeast of Pachapaqui. The altitude 

of the lowest adit is 4,400 meters.

Thin-bedded gray limestone striking N. 40° W. and dipping 

45°-TO° SW. is cut by at least three small mineralized shear zones. 

One of the zones strikes N. 45° W. and clips 55° NE., and the other
PACHAPAQUI MINING DISTRICT 133

two are parallel to bedding. The zones, ranging from 5 to 30 meters 

in length and a few centimeters to 75 centimeters in width, are within 

an area less than 35 meters long and 10 meters wide. Vein material 

consists largely of rubbly, soft, reddish iron oxide and shattered gray 

limestone with veinlets and pods of galena, sphalerite, pyrite, and 

quartz. A few crystals of tetrahedrite were seen in specimens on the 

dumps.

The area was explored by 3 adits ranging in length from 5 to 7 

meters, and it is possible that a few tons of low-grade lead-silver 

ore were mined before the prospect was abandoned. There is no ore 

in sight, and further exploration is not warranted.

RIftUEZA MINE AND PRADO PROSPECT

The Riqueza mine is about 200 meters west of the crest of the Cordillera Huayhnash, on the east side of Quebrada Burro. The workings are between the altitudes of 4,650 and 4,700 meters. The Prado 

prospect is about 400 meters to the southwest and 50 to 100 meters 

lower in altitude. A trail about 700 meters long, which originally 

connected the Riqueza mine with the Pachapaqui-Huallanca trail 

near the Eascacielo mine, has been largely destroyed by rockslides.

The country rock is silicifiecl and pyritized limestone which in the 

Riqueza area strikes N. 55°-75° E. and dips nearly vertically and in 

the Prado area strikes about N. 30° W. and dips 70° SW. A small 

irregular intrusive of porphyritic granite crops out southeast of ths 

vein areas near the crest of the cordillera.

At Riqueza the main vein is along a bedding shear or fault zone 

striking N. 60° E. and dipping nearly vertically, which is 40 to 70 

centimeters wide and is exposed throughout the length of a 70-meter 

adit. The vein minerals, consisting of vuggy quartz and rhodonite 

with veinlets and disseminated grains of pyrite, chalcopyrite, tetrahedrite, galena, and sphalerite, were evidently deposited in fissures 

and cavities in the zone. A second vein cropping out about 200 

meters to the southwest is on another shear zone striking N. 75° E. 

and dipping 85° N"., nearly parallel to bedding in the silicified limestone. This vein was opened by a trench 10 meters long and 5 meters 

deep, from which a lens of lead-copper ore seems to have been mined. 

The vein now exposed in the trench is as much as 70 centimeters wide 

and consists of many irregular veinlets in silicified limestone. The 

minerals are essentially the same as in the vein to the northeast but 

occur as both wall rock replacements and cavity fillings.

At Prado three small irregular fissure filling and replacement veins 

crop out; one is parallel to the bedding of the limestone, and the others 

strike nearly east and dip 80° to 90° S. The veins, ranging from a 

few centimeters to a meter wide and 1 to 10 meters long, contain 

stringers and irregular bodies of quartz, calcite, and pyrite with disseminated grains and pods of chalcopyrite, galena, and sphalerite.
134 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

The veins at Prado were explored by small prospect pits, and a few 

hundred pounds of ore were extracted and stockpiled at the mine. 

Several tons of ore were probably extracted from the Riqueza 

workings.

The area is one of the most inaccessible of the Pachapaqui district, 

and transportation of ores and supplies would be difficult and expensive. No ore was in sight at the time of our visit, but further exploration, especially around the contacts of the intrusive body, might expose pockets of ore which could be mined on a small scale.

SAN ANTONIO PROSPECT

The San Antonio prospect is 100 to 200 meters north of the ridge 

between Quebrada Burro and Quebrada Nupocuta and 800 meters 

southeast of the Sinchi Roca mine. The workings are between the 

altitudes of 4,370 and 4,380 meters.

The country rock is metamorphosed and silicified limestone which 

strikes N. 40° W. and dips 85° SW. Ore and gangue minerals form 

irregular replacement lenses and veins, ranging from a few centimeters to 2 meters in width and less than a meter to 15 meters in 

length, along irregular fractures within a large shear zone. The general trend of the lenses and veins is N. 40° W., and average dip is 80° 

NE. These lenses are restricted to a zone about 5 meters wide which 

can be traced northwestward about a kilometer, almost to the pampa 

in Quebrada Burro. The zone, if projected northwest, would include 

the Abandonada prospect, and mineralization at both mines is similar.

Between the San Antonio workings and a second area of strong 

mineralization 400 to 500 meters northwest the zone contains only a 

few mineralized lenses and irregular pods. This second area is near 

the west contact of a small intrusive body of granite.

The vein material is largely an altered limestone and consists of 

calcite, rhodochrosite, rhodonite, and quartz with veinlets, disseminated crystals, and blebs of pyrite, chalcopyrite, galena, and sphalerite. 

Some of the lenses contain a moderate amount of sulfide minerals, 

whereas others are almost barren. Many cavities in the veins, as large 

as 20 centimeters in diameter, are lined with quartz crystals.

Prospect pits have been opened on several of the mineralized bodies, 

and one of the largest lenses was explored by a short inclined shaft. 

Most of the vein material appears to be too low in grade to be mined 

and concentrated by hand, and it is doubtful that concentrates have 

been shipped.

This mineralized zone is more extensive than most and contains 

moderately large tonnages of vein material. Mining of isolated lenses 

probably would be expensive, and the tenor may be too low to pay 

mining costs. However, if roads are built into the Pachapaqui district, 

the San Antonio and Abandonada areas should be worthy of further 

investigation.
PACHAPAQUI MINING DISTRICT 135 

SANTA CLARA MINE

The Santa Clara mine lies on the north side of Quebrada Nupocuta 

5.2 kilometers east of the Pachapaqui concentration plant. The workings 011 the main vein lie between the altitudes of 4,200 and 4,210 

meters.

At least three small quartz-sulfide fissure veins crop out in silicified 

limestone which is nearly horizontal. Only one vein, with an outcrop 

length of about 25 meters and a maximum width of 75 centimeters, 

contains an appreciable amount of sulfide minerals. It strikes east 

and dips 75° S. Vein material consists of massive quartz with small 

irregular pods of pyrite, galena, and sphalerite. Most sulfide bodies 

are not more than 0.5 meter long and 20 to 30 centimeters wide. Two 

other quartz veins are exposed in prospect pits about 200 meters to 

the west. One vein strikes N. 25° W. and dips 75° NE., and the other 

strikes N. 65° E. and dips 85° SE. They contain iron oxide and quartz 

but practically no sulfide minerals.

During 1949 the su]fide pockets in the main vein were mined from 

small surface pits, and a few tons of concentrate was shipped to the 

Pachapaqui concentrator. It is doubtful that the hand-sorted ore contained enough lead and silver to pay mining and shipping costs. The 

remaining vein material is low-grade, and the reserves are small.

SAN MIGUEL I AND II PROSPECTS

The two San Miguel properties are near the pampa in Quebrada 

Nupocuta about 5 kilometers east of the Pachapaqui concentration 

plant at altitudes near 4,000 meters.

At San Miguel I a few small prospect pits explore the top of a low 

hill on the south side of the valley. The country rock is massive darkgray limestone cut by a mineralized fault or shear zone striking N. 

70° E. and dipping nearly vertically. Numerous veinlets and small 

lenses of calcite and pyrite with pods and disseminated grains of 

galena and sphalerite fill cavities and partly replace the sheared and 

brecciated limestone along the fault and irregular fractures and 

shears on both sides of the fault. The mineralized zone is 5 to 10 

meters wide and more than 20 meters long. The largest mineral lens 

has a maximum width of about a meter and is several meters long. 

The other lenses are less than 30 centimeters wide and 1.5 meters long.

At San Miguel II a 43-meter adit on'the north side of the valley 400 

meters north of San Miguel I exposes a fault zone striking N. 20°-30° 

W. and dipping from 85° to 90° NE. The zone contains sheared and 

brecciated limestone and gouge with veinlets and pods of calcite, pyrite, galena, and sphalerite.

Both areas are largely covered with alluvium and soil. No ore was 

seen in the workings, and it 'is doubtful that further exploration 

would disclose minable material. Probably no ore has been shipped.
136 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

FORTUNA MINE

The Fortuna mine is in the west side of Quebrada Shicra Shier a 

about 600 meters southeast of San Miguel I. The portal of the adit 

is at an altitude of 4,200 meters.

Two veins crop out in silicified dark-gray limestone which strikes 

N". 20° W. and dips 85° NE. The principal vein, striking N. 70° W. 

and dipping 70° SW., contains quartz and sulfide minerals which have 

tilled irregular fissures and replaced wall rock along a fault zone. 

This vein is more than 50 meters long and ranges from 10 centimeters 

to a meter in width. It contains pyrite, quartz, chalcedony, and sphalerite with minor amounts of galena and arsenopyrite. Limestone in 

the footwall is silicified and contains disseminated sulfide minerals.

The second vein, exposed in a prospe'ct pit to the east of the main 

vein, strikes N". 55° E. and dips 70° NW. This vein is about 40 centimeters wide and contains veinlets and disseminated grains of pyrite 

and sphalerite.

The principal vein was explored and mined from an adit 19 meters 

long. The mine was opened around 1940, and probably several tons 

of lead-silver concentrate were shipped. The mine was not operating in 1949. Ore is low grade, and reserves are small.

LUIS ADOLFO PROSPECT

The Luis Adolf o prospect is about 200 meters northeast of the Fortuna mine on the east side of Quebrada Shicra Shicra. The vein is 

exposed between the altitudes of 4,120 and 4,130 meters.

A mineralized shear and breccia zone in massive dark-gray limestone strikes N. 35°-75° E. and dips 65° SE. to vertical. The zone has 

a maximum width of a meter and can be traced on the surface for 15 

to 20 meters. Minerals were deposited in fractures and cavities and 

also appear to have replaced part of the limestone. The zone contains 

much sheared and brecciated limestone and pyrite with lesser marmatite and minor amounts of galena. Locally it is webbed with veinlets 

of calcite and quartz.

The zone was explored by two or three prospect pits, but no ore was 

encountered, and further exploration would probably not be remunerative.

GABY PROSPECT

The Gaby prospect is on the ridge between Quebrada Shicra Shicra 

and Quebrada Nupocuta about 1 kilometer east of the Fortuna mine. 

One prospect area is north of the ridge crest at an altitude of 4,270 

meters, and the other is 400 meters to the south in Quebrada Shicra 

Shicra between the altitudes of 4,220 and 4,230 meters.

The country rock is thin-bedded dark-gray limestone with shaly 

and sandy layers, striking N. 35°-60° W. and dipping 20°-25° SW.
PACHAPAQUI MINING DISTRICT 137

Some of the limestone beds have been silicified and serpentinized. A 

dike or irregular intrusive body of porphyritic granite, cropping out 

near the south prospect area, is as much as 8 meters wide, strikes about 

N. 20° W., and dips nearly vertically.

At the north prospect an irregular replacement body about 2 meters 

in diameter, of serpentine, quartz, and sulfide minerals, is exposed in 

an adit 2.5 meters long. The ore body is in the footwall of a normal 

fault striking N. 40° W. and dipping 55° SW. SIickensides on the 

fault plunge 40° SW. In the replacement body veinlets of calcite 

strike N. 40° W. and dip vertically; they appear to have formed along 

tear fractures in the footwall of the fault. The ore consists of serpentinized limestone with disseminated crystals, pods, and veinlets of 

chalcopyrite, pyrite, galena, sphalerite, and pyrrhotite.

At the southern prospect several irregular replacement bodies and 

veins crop out in limestone near the west contact of the granite intrusive. The three largest veins are 5 to 10 meters long and 25 centimeters to 3 meters wide. They appear to have formed by fissure 

filling and partial replacement along irregular shear and fracture 

zones striking N. 5°-55° E. and dipping nearly vertically. The mineralization is similar to that at the northern prospect, but veins contain more sphalerite an.d less galena.

During 1949 the northern prospect was worked, and a few tons of 

hand-sorted ore were sent to the Pachapaqui concentration plant. 

The southern prospect was explored and mined from 4 or 5 pits, and 

a few tons of hand-sorted ore may have been shipped.

The veins may contain enough chalcopyrite and galena to support 

the present scale of operation for a year or two. However, individual 

lenses contain only a few tons of ore, and once the surface area is 

mined, exploration costs may be prohibitive.

LUCERO PROSPECT

The Lucero prospect is near the mouth of a small valley on the 

east side of Quebrada Shicra Shicra about 500 meters southeast of 

the Gaby property. The workings lie between the altitudes of 4,320 

and 4,330 meters.

Silicified limestone striking N. 85° W. and dipping 80° N. is cut 

by a fissure vein which strikes N. 70° W. and dips nearly vertically. 

The vein contains much soft iron oxide, quartz, and rubbly and crystalline calcite. Within this material are disseminated grains of 

pyrite, galena, and tetrahedrite. The vein is about TO centimeters 

wide and 60 meters long.

The prospect area is largely covered with talus, but the vein is 

exposed in an 8-meter shaft and several small prospect pits. No 

minable material was seen.

321628 55 10
138 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

EXITO PROSPECT

The Exito prospect is about 400 meters to the east of the Lucero 

prospect and in the same valley. A single prospect pit in the area 

is at an altitude of 4,350 meters.

A fissure vein, exposed in a vertical cliff of silicified limestone, 

strikes N. 35° W. and dips nearly vertically. The vein has a maximum width of 25 centimeters and a vertical range of at least 30 meters. 

It contains quartz and pyrite with disseminated grains of tetrahedrite, 

galena, and sphalerite. Apparently no ore was encountered in the 

prospect pit. The vein is too small and the mineral content too low 

to warrant further exploration.

PERU MINE

The Peru mine is in cliffs about 200 meters southeast of Exito. 

The portal of the upper adit is at an altitude of 4,450 meters, and a 

lower adit is 30 to 40 meters below.

Country rock is silicified limestone near the west edge of a complexly folded area along the crest of the cordillera. At the mine the 

limestone strikes N. 15° W. and dips 80° SW. A fissure vein of 

massive and crystalline quartz, about 40 meters long, strikes N. 85° 

W. and dips nearly vertically. The vein was explored and mined 

from two adits 7 and 10 meters long respectively. In the lower 

7-meter adit the vein is about 10 centimeters wide and contains only 

quartz, whereas in the upper adit the vein is 35 to 40 centimeters wide 

and contains minor amounts of pyrite, galena, sphalerite, and 

tetrahedrite.

Local inhabitants stated that this mine was worked for silver, and 

it is possible that several tons of low-grade concentrates Avere shipped. 

The material now exposed in the vein cannot be mined profitably.

TRES REYES MAGOS PROSPECT

The Tres Reyes Magos prospect is at the east side of Quebrada 

Shicra Shicra 600 meters south of the southern workings at the Gaby 

prospect. The main prospect pit is at an altitude of 4,240 meters.

The mineralized area is along the north contact of a granitic dike 

cutting dark-gray metamorphosed limestone. The limestone strikes 

N. 40° W. and dips nearly vertically, and the dike strikes east and 

dips 65° N. A small lens of sulfide minerals was mined from a pit 

about 2 meters deep. The vein exposed in the pit is about 10 centimeters wide and contains quartz with disseminated crystals of pyrite. 

One or two tons of vein material on the dump is largely pyrite and 

quartz with lesser sphalerite and minor galena. A smaller pit about 

10 meters to the east along the dike exposes a few quartz veinlets.

No ore has been shipped from the prospect. The veins'are very 

small and barren, and no additional exploration is justified.
PACHAPAQUI MINING DISTRICT 139' 

SAN JUDAS tfADEO PROSPECT

The San Judas Tadeo prospect is at the south end of Quebrada 

Shicra Shicra about 600 meters south of the Tres Reyes Magos 

prospect. It is the southernmost mine in the district and is about 7 

kilometers southeast of Pachapaqui. The workings on the veins are 

between the altitudes of 4,350 and 4,420 meters.

Several mineralized shear and fault zones occur on both sides of a 

contact between recrystallized limestone and an overlying sequence 

of thin- to medium-bedded phyllites and quartzites. Beds strike 1ST. 

45° W. and dip 60° SW., and most veins are nearly parallel to bedding. One major cross vein strikes N. 80° E. and dips nearly vertically. Sulfide minerals occur in pods, irregular veins, and well-defined 

lenses along shear zones in the phyllite and quartzite and apparently 

were deposited in open fissures and cavities. Sulfide minerals in the 

limestone occur as pods, veinlets, and scattered grains in irregular 

zones up to 5 meters in diameter, and most apparently were deposited 

by replacement. The bodies of sulfide minerals crop out over an area 

1 to 10 meters wide and at least 300 meters long.

The ore minerals are sphalerite, galena, and chalcopyrite in a gangue 

of wall rock, quartz, pyrite, and calcite. Dark-brown to black sphalerite, possibly the variety marmatite, is the most common ore mineral, 

and in a few places forms nearly solid lenses 1 to 2 meters long and 

as much as a meter thick. Galena appears to be more abundant in 

replacement bodies in limestone than in the fissure veins. The mineralized zones in limestone have associated irregular patches and disseminated crystals of epidote, and at places the limestone is transected 

by veinlets of white crystalline calcite, which locally make up 30 to 

40 percent of the rock. The calcite was evidently the last mineral to 

be deposited.

Several veins along the zone have been explored by small prospect 

pits, but no ore has been shipped. The prospect was inactive at the 

time of our visit in 1949.

Although the area has not yet been prospected adequately, smallscale mining of the richer pockets of galena and chalcopyrite should 

v be profitable for several years. Further exploration, especially of the 

limestone zones now covered with glacial debris, may reveal additional 

ore bodies.

OTHER DEPOSITS

Prospect 1. This prospect is reported to have been explored in 1948 

or 1949, but the name was not known to the inhabitants of the district. 

For purposes of reference it is designated Prospect 1. The prospect is 

on the north side of Quebrada Nupocuta, about 500 meters north of the 

Santa Clara mine. The workings are between the altitudes of 4,240 

and 4,270 meters.
140 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

Two veins occur along shear zones in a dark-gray metamorphosed 

limestone which strikes N. 25° W. and dips 70° SW. On one vein, 

striking N. 30° W. and dipping 75° SW., a lens of sulfide minerals 

about 5 meters long and 1 to 1.5 meters wide was mined from a small 

trench. Ore on the dump consists of quartz and rhodonite with 5 to 

15 percent of chalcopyrite, galena, and sphalerite. A 5-meter crosscut 

to the vein 8 meters below the trench does not expose sulfide minerals.

Another shear zone, about 50 meters to the northeast, strikes N. 85° 

W. and dips 75° NE. It contains two lenses of vein minerals, each 

about 5 meters long and a meter in maximum width, which consists 

of rhodonite, quartz, and pyrite with minor amounts of galena, chalcopyrite, sphalerite, and tetrahedrite.

It is possible that a few tons of copper and lead concentrates were 

shipped. The tenor of the remaining ore is low, reserves are small, and 

it is doubtful that further mining would be profitable.

PACLLON-LLAMAC MINING DISTRICT

The Pacllon-Llamac mining district is about 20 kilometers southeast of Chiquian in the southeastern part of Bolognesi Province in the 

Departamento de An cash. Most of the mines are on the ridge between 

Quebrada Pacllon on the south and Quebrada Llamac on the north. 

Five kilometers east of the mine area the Pacllon-Llamac ridge intersects the Cordillera Huayhuash about 5 kilometers north of Nevado 

Yerupaja. The buildings of Hacienda Palca are near the east end of 

Quebrada Llamac and at an altitude of approximately 3,680 meters; 

the east end of Quebrada Pacllon is somewhat higher. A trail from 

Hacienda Palca to Quebrada Pacllon crosses the Pacllon-Llamac ridge 

at an altitude of nearly 4,570 meters. Fig. 6 shows the location of 

mines in the district.

The mining district is accessible from Chiquian by a trail which 

passes through the towns of Llamac and Pocpa to Hacienda Palca, a 

distance of about 35 kilometers. From Palca the mines are all within 

2 hours' ride on horseback.

The major valleys of this area are U-shaped, as is best shown in 

Quebrada Llamac (fig. 19), and trend westerly to drain into the Rio 

Pativilca. A small pampa at Palca appears to be a filled-in glacial 

lake, and several small glacial lakes still exist in Quebrada Pacllon. 

Nevado Yerupaja and surrounding peaks of the Cordillera Huayhuash 

are covered with active glaciers.

The sedimentary rocks exposed in the Pacllon-Llamac ridge consist 

of sandstones of early Neocomian age; a sequence of limestones, shales, 

and sandy shales of Barremian age; and more massively bedded limestones with minor amounts of shale, which probably represent the 

Machay and Jumasha. The base of the lower Neocomian was not 

seen but exposed beds are several hundred meters thick. A massive
PACLLON-LLAMAC MINING DISTRICT 141

limestone immediately overlying the sandstone, probably the lower unit 

of Steinmann's Barremian sequence, is about 200 meters thick. The 

heterogeneous sequence is considered as the middle unit of the Barremian and is of the order of several hundred meters thick. The upper 

limestone unit of the Barremian was not differentiated in the field 

from the more massive overlying Machay and Jumasha limestones. 

Most of the veins occur in the lower limestone unit, directly overlying 

the lower Neocomian, but several are also found in the lower Neocomian sandstone and in the shales and shaly sandstones of the middle 

unit of the Barremian.

Throughout the entire region southeast of Chiquian few igneous 

rocks are visible. The only intrusions seen in the mine area were a 

diorite dike, an andesite sill, and a rhyolite sill. At a distance Nevado 

Yerupaja and nearby peaks appear to consist of folded and steeply 

dipping sedimentary rocks (fig. 11), and prominent igneous masses 

seem to be absent.

The outstanding features of the regional structure are large upright 

anticlines and synclines characterized by sharp crests and troughs and 

steeply dipping limbs. The axial planes trend N. 20°-30° W. and dip 

nearly vertically. On the Pacllon-Llamac ridge, faults cutting across 

the strata are rare, whereas bedding faults are many. Fissure veins 

are on cross faults, and most replacement veins are along bedding 

faults.

The predominant vein minerals are pyrite, marmatite, and quartz. 

A little galena occurs in nearly all veins, and chalcopyrite is found in 

many. A few veins contain tetraheclrite and arsenopyrite, and one or 

two others have pyrrhotite or magnetite. Limestone near most replacement veins is silicified and garnetized.

Most of the veins have a surface coating of iron oxide. Rocks on 

the Pacllon-Llamac ridge contain enough red iron oxide to give them 

a prominent reddish color. In the Susana mine area streams and 

springs have deposited iron oxide in the alluvium, forming breccialike 

masses 1 to 3 meters thick and as much as 50 meters in diameter.

The mines in the Pacllon-Llamac district most worthy of further 

exploration are:

Susana low-grade zinc-lead ore, many short veins and mineralized 

zones, large mineralized area.

San Samuel low-grade zinc-lead ore, two principal veins 50 to 100

meters long.

BONANZA MINE

The Bonanza mine is in a small gully in the cliffs at the south side 

of Quebrada Llamac about 0.5 kilometer south of the buildings of 

Hacienda Palca and 4 kilometers east of Pocpa. The principal workings are between the altitudes of 3,970 and 4,010 meters.
142 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

The gully is cut in a thin sequence of black shales and argillites 

within light-gray sandstone. The strata, striking N. 25°-30° W. and 

dipping 60°-65° NE., are on the east limb of a large upright anticline 

whose crest lies between this mine and the Susana mine about 1 kilometer to the southwest. A single outcrop of a narrow sill of altered 

andesite in the shale was seen at the north end of the mine area. The 

sill is covered with soil and talus elsewhere in the gully.

Several irregular fault and shear zones containing short sulfide 

veins crop out in the sandstone below the shale. Most of the veins 

contain gouge and breccia, and sulfide minerals appear to have been 

deposited in cavities and fissures. A major vein strikes N. 65°-80° E. 

and dips from 50° to 90° SE. Other small mineralized shear zones 

strike N. 35°-60° W. and dip 55° SW. to vertically. The veins occur 

through an area about 50 meters wide and 75 meters long.

Only the major vein, 20 to 50 centimeters wide and 25 meters long, 

contains a significant quantity of sulfide minerals. This vein consists 

of crystalline to massive quartz and pyrite with veinlets, pods, small 

lenses, and disseminated grains of marmatite, galena, and tetrahedrite. 

The vein material is banded and contains many small cavities lined 

with quartz crystals. The more massive lenses of ore minerals are 

webbed with quartz veinlets. Other veins of the area are small and 

nearly barren.

Six adits ranging in length from 6 to 35 meters and a few surface 

pits have been opened on the veins. Of the three adits on the major 

vein, the middle one exposes the widest part of the vein and the highest 

grade ore. The size of workings on this vein indicates that nearly 100 

tons of vein material were extracted, and it is possible that this material yielded several tons of hand-sorted concentrate. Apparently most 

of the ore had been extracted in these workings when the mine was 

abandoned.

A few more tons of lead-silver concentrate might be mined at a 

profit from the present workings, but the reserves appear to be small, 

and it is doubtful that new ore bodies will be found.

SUSANA MINE

The Susana mine is in a broad gully in the south wall of Quebrada 

Llamac, 3.5 kilometers southeast of Pocpa and about 1.5 kilometers 

southwest of Hacienda Palca. Veins are exposed in the Susana claims 

over an area about 900 meters long and 200 meters wide between the 

altitudes of 4,000 and 4,500 meters (pi. 11). Veins also crop out for at 

least an additional 500 meters to the southeast of the Susana area and 

can be traced into the veins at the Monte Cristo mine. A trail from 

the mine meets the Pocpa-Hacienda Palca trail 2 to 3 kilometers east 

of Pocpa.
PACLLON-LLAMAC MINING DISTRICT 143

Most veins are in a fine-grained dark-gray limestone and a 

hydrothermally altered limestone having a thickness of more than 150 

meters. This sequence is underlain by coarse-grained light-gray sandstone and grades upward into a sequence of interbedded calcareous 

shales, phyllites, and shaly sandstones. The sedimentary rocks are 

locally crumpled but in general strike N. 35°-40° W. and dip 

65°-85° SW.

A rhyolite sill 1 to 4 meters thick was intruded into the upper part 

of the limestone. Although this intrusive is essentially parallel to the 

strata, it is somewhat irregular in strike and locally cuts across limestone beds. The rhyolite consists of feldspar crystals and quartz grains 

as much as a centimeter in diameter in a microcrystalline groundmass. 

Feldspars have been bleached and partly altered to clay. Mafic minerals are completely decomposed, and their former presence is indicated only by small cavities filled or stained with limonite.

The upper part of the limestone and lower part of the overlying 

sequence are silicated and contain much garnet, quartz, and epidote. 

Limestone was most intensely altered near the sill. Some of the altered 

rock is pale green and only partly replaced, whereas some consists 

entirely of green massive and crystalline grossularite garnet and 

quartz or epidote and quartz. Stringers and pods of unreplaced but 

recrystallized limestone are preserved within the altered limestone. 

The most conspicuous body of this type is an irregular stringer from 

2 to 10 meters wide which crops out a few meters west of the sill and 

extends nearly the length of the mine area (pi. 11).

Mineralized zones containing lenses, pods, veinlets, and scattered 

grains of sulfide minerals occur in the altered limestone near the sill 

and along the contact between limestone and underlying sandstone. 

Although the zones are irregular in attitude, most tend to parallel the 

 strata. They range from less than a meter to as much as 80 meters in 

length and from a few centimeters to 2 meters in width. Apparently 

most of the sulfide minerals were deposited by replacement of the 

altered limestone along bedding shears.

The contact between the limestone and the underlying sandstone is 

marked by a layer of altered thin-bedded calcareous shale 2 to 3 meters 

thick, as is shown in fig. 29.- This layer, as well as material along 

bedding planes and cross fractures in the overlying limestone, is partly 

replaced by sulfide minerals (figs. 30 and 31).

The vein material consists largely of pyrite, sheared and brecciated 

wall rock, limonite, and marmatite with minor amounts of quartz and 

galena. At places lenses and irregular bodies of marmatite with finely 

disseminated grains of pyrite and galena are 1 to 2 meters wide and 

several meters long. A small mass of magnetite crops out at the limestone-sandstone contact near the south end of the area.
144 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

FIGURE 29. Mineralized zone at contact between sandstone

and overlying limestone, Susana mine. :

All of the veins are covered with a crust of iron oxide, which ranges 

from a few millimeters to several centimeters in thickness. Beneath 

the crust the pyrite, and to a lesser extent the marmatite, are altered 

to limonite. At most places oxidation does not extend to depths of 

more than 1 or 2 meters.

According to local inhabitants several of the pits and small adits 

date from Colonial times. These are now largely caved or filled with 

rock debris. It is not known whether any ore was shipped from the 

older workings. The Northern Peru Mining and Smelting Company 

explored the area in 1948 and opened the four adits shown in fig. 32 

but did not ship any concentrate.

Probably several thousand tons of low-grade lead ore are available 

in the Susana property, but ore shoots are mostly small and isolated, 

and underground mining would be expensive. The galena is disseminated and would be almost impossible to concentrate by hand. The 

principal ore mineral is marmatite, generally intermixed with pyrite, 

and it might contain too much iron to yield a saleable zinc concentrate.

If this region were made accessible by road, the Susana mine, and 

several other mines of the district probably could supply a small mill 

with lead ore for a number of years.
PACLLON-LLAMAC MINING DISTRICT 145

FIGUUE 30. Sullide minerals replacing limestone along bedding planes, Susana mine. 

Veins near right side of photograph are about 5 cm. thick.

FIGURE 31. Sulfide minerals replacing limestone along cross fractures, Susana mine.

Scale is 22 cm long.
146 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

EXPLANATION

Veinlets and disseminated 

grains of sulfides .

Contact, dashed where 

approximately located

t 50

Fault, showing dip; dashed 

where approximately located

Opencut at portal of adit

ADIT 3 ADIT 4

20 Meters

Surveyed with compass and tape by G. E. Ericksen 

and A. J. Indacochea, September 1949

FIGURE 32. Geologic sketch maps of exploratory adits at Susana mine, PacllCu-Llaraac

district.

MONTE CRISTO MINE

The Monte Cristo mine is about 500 meters south of the Susana mine 

and near the top of the Pacllon-Llamac ridge. Two mineralized zones 

lie at altitudes of about 4,570 and 4,700 meters. The trail distance to 

Hacienda Palca is 4 to 5 kilometers.

The principal sulfide vein, apparently along the southern extension of the western mineralized zone at Susana, strikes N". 35° W. and 

dips 55° SW. This vein is lenticular in shape and ranges from less 

than a meter to about 7 meters wide and from 70 to 80 meters long. 

Wall rock is garnetized limestone or calcareous shale striking 1ST. 

25°-35° W. and dipping 65°-75° SW. The rhyolite sill of the Susana 

mine area crosses the ridge 30 to 50 meters to the northeast.

The second mineralized zone southeast of the principal vein and at 

the lower altitude (fig. 6) consists of several short veins and irregular 

bodies of sulfide minerals extending through an area 15 to 20 meters 

wide and 25 to 30 meters long. Most of the veins strike N. 15°-30°
PACLLON-LLAMAC MINING DISTRICT 147

W. and dip 65°-90° SW. The veins range from less than a meter to 

about 5 meters long, and' most are less than 50 centimeters wide. The 

country rock is dark-gray fine-grained limestone striking N. 15° W. 

and dipping 65° SW. An anticline and a syncline, exposed in a cliff 

100 meters south of the vein area, have vertical axial planes which 

strike N". 25° W. These folds seem to be on the southern extension 

of the large anticline between Susana and Bonanza mines, and they 

continue southward, passing through the Aida and San Samuel mine 

areas.

The Monte Cristo veins seem to have resulted from replacement of 

limestone along bedding faults and irregular shear zones. The vein 

material, consisting largely of a granular mixture of pyrite and wall 

rock, contains pods and irregular bodies of marmatite with disseminated grains of galena and is similar to the material of the Susana 

veins. The weathered outcrops of the veins are pitted and encrusted 

with dark-red to black iron oxide.

A pit on the principal vein, said to date from Colonial times, is 

about 10 meters long, 5 meters wide, and 5 to 7 meters deep. A few 

veins in the second area have been explored more recently by a pit and 

a room, each about 5 meters in diameter. The main vein is large but 

contains no ore, whereas the veins of the eastern mineralized zone contain low-grade ore but are small. It is doubtful that any of the veins 

could be worked at a profit.

AiDA MINE

The Aida mine is on the south side of the Pacllon-Llamac ridge, 

about 500 meters south of the pass. The main workings are at an 

altitude of 4,490 meters. The trail from Hacienda Palca passes 

through the mine area.

The veins are on the east limb of a small open anticline in finegrained light- to dark-gray limestone striking N. 10°-25° W. and 

dipping 50°-65° NE. A syncline and a second anticline are exposed 

a short distance to the east. The axial planes of the folds strike N. 

15°-20° W. and dip nearly vertically.

Several short veins and irregular bodies of sulfide minerals crop out 

in an area 15 to 20 meters wide and 120 meters long parallel to the 

strike of the limestone. These veins strike N. 25°-80° W. and dip 

45° to 90° NE. Most are small, but one irregular body is about 20 

meters long and as much as 4 meters wide. A few zones of limestone 

breccia and iron oxide lie parallel to the bedding, the largest 1 to 2 

meters thick and about 30 to 50 meters long.

Mineralization is similar to that at the Susana and Monte Cristo 

mines. The sulfide bodies range from pure pyrite to a granular mixture of limestone and pyrite containing irregular pods and lenses of 

marmatite with disseminated grains and veinlets of galena. One of
148 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND IIUAYHUASH

the veins contains pyrrhotite. The iron oxide and breccia zones appear 

to contain no sulfide minerals.

Recently several veins have been explored and mined in surface pits. 

One of the owners reported that a few tons of galena concentrate was 

extracted from one vein.

One or two of the galena-bearing ore bodies might be mined and 

concentrated by hand and probably would yield a few additional tons 

of concentrate. However, most of the veins are of too low-grade to 

be mined at a profit.

SAN SAMUEL MINE

The San Samuel mine is on the south side of the Pacllon-Llamac 

ridge about 500 meters southeast of Aida mine. The main vein area 

lies between the altitudes of 4,370 and 4,400 meters. Two major veins 

with associated splits and irregular replacement bodies crop out in 

an area 50 to 60 meters wide and more than 100 meters long.

The veins are in the same folded limestone complex as those at the 

Aida mine and strike N. 15°-30° W. nearly parallel to the bedding 

and dip T0°-90° SW. The crest of an anticline lies along the east 

side of the vein area; its axial plane strikes N. 20° W. and dips 65° 

NE.

The two principal veins are about 60 meters apart, and range in 

width from less than a meter to as much as 4 meters. Part of the limestone in and near the veins is brecciated, suggesting that the minerals 

were deposited along bedding faults. Some of the vein material may 

have been deposited in fissures, but irregular and gradational contacts 

Avith wall rock and irregular patches of limestone along the veins indicate that mineralization took place largely by replacement.

Most of the vein material is a granular mixture of pyrite and altered 

limestone which contains irregular bodies of marmatite with disseminated grains and veinlets of galena. The western vein contains many 

lenses, pods, and disseminated grains of marmatite and was mined 

in trenches and shafts throughout its exposed length. The east vein 

at its northern end consists of pyrite and altered limestone with almost no ore minerals; the southern extension is iron-stained recrystallized limestone with disseminated pyrite. The north ends of the two 

veins curve toward each other, and between them are several irregular 

replacement bodies of sulfide minerals. One of these bodies, 5 to 7 

meters wide, contains many veinlets and small pods of galena associated with marmatite, forming the richest lead ore seen at the mine.

The veins were explored by short shafts, pits, and trenches. The 

largest working, a shaft on the west vein, is about 10 meters deep. 

Twenty to thirty meters east of the main mine area surface pits and an 

inclined shaft, 10- to 15-meters long, explore a breccia and iron oxide 

zone striking north and clipping 40° E. This zone appears to be bar-
PACLLON-LLAMAC MINING DISTRICT 149

ren of sulfide minerals. All the workings are old and are said to 

date from Colonial times.

The veins are mostly low grade but are more persistent than most 

others of the district, and together with the Susana veins might furnish ore for a small concentration plant. The galena from one or two 

of the sphalerite bodies probably could be concentrated by hand, but in 

most of the veins the galena is too finely disseminated for hand 

concentration. FABULOSA PROSPECT

The Fabulosa prospect is on the south side of the Pacllon-Llamac 

ridge about 500 meters Avest of San Samuel. Veins crop out in an 

area about 100 meters long and 40 meters wide between the altitudes 

of 4,470 and 4,490 meters. Trail distance from the mine to Hacienda 

Palca is about 6 kilometers.

Many short veins and lenses are enclosed in limestone near the contact with overlying thin-bedded metamorphosed shales and sandstones. The sedimentary rocks strike N. 0°-35° W. and dip from 75° 

to 90° SW. Most veins lie nearly parallel to the strata. The veins 

range from a few centimeters to as much as 2 meters wide and from 

less than a meter to 10 meters long. Most veins are near the south 

end of the property and are scattered through a thickness of 30 to 40 

meters of limestone along a strike distance of 15 to 20 meters. The 

veins contain pyrite, quartz, and altered limestone with minor amounts 

of marmatite, galena, chalcopyrite, arsenopyrite, and calcite. The 

mineralization is similar to that at the Aida mine. Much of the limestone near the veins has been silicified and garnetized.

Parts of the veins have been explored recently by pits and trenches, 

but no ore was encountered and the prospect was abandoned.

LA ESPERANZA MINE

La Esperanza mine is on the south side of the Pacllon-Llamac ridge 

about 200 meters west of the Fabulosa prospect. The workings are 

between the altitudes of 4,480 and 4,490 meters. The main trail from 

Hacienda Palca to Quebrada Pacllon passes by the mine.

Two fissure-filling veins crop out in fine- to medium-grained gray 

sandstone interbedded with thin shale layers. The strata strike N. 

25° W. and dip 85° SW. The major vein, striking N. 55°-70° E. 

and dipping 60°-70° NW., appears to intersect or cut off the second 

vein which strikes N. 60° W. and dips 60° SW. However, the junction of the veins, as shown in fig. 33, is covered, and their true relationship is not known. Vein material consists principally of clear 

crystalline quartz with well-crystallized pyrite, arsenopyrite, rhodochrosite, and calcite. Crystalline light-brown sphalerite and finegrained argentite are the only-ore minerals; galena appears to be 

absent. The vein material is vuggy and porous, consisting of a mesh
150 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

\

T^'-i'-'. ' '.' ''. ' '.'.' ' ';' 

' '.' ° '.-' '' ' ' : ' \*- ^^-^

;V.; -: ; .: ^:^;:^X:. Wr

Raise to surface

10 0 . 30 Meters 

L , i i i I______I______I______I

Vein, showing dip and thickness

Vein, projected through covered area

Indefinite contact

Strike and dip of beds

Projection of 

underground workings

0

Surveyed with compass and tape by D. Brambilla 

and U. Petersen, September 1949

FIGURE 33. Geologic sketch map of La Esperanza mine, Pacll6n-Llamac mining district.

of quartz crystals with lesser amounts of sulfide minerals. Crystals 

range from less than a millimeter to 2 centimeters in length.

The main vein is at least 80 meters long and from 20 to TO centimeters wide. The other vein is exposed only in the cliffs about 50 

meters west of the mine workings. The ore shoot on the major vein 

pinches out a few meters east of the workings, but an irregular shear 

zone continues eastward for at least 200 meters. A small vein at the 

north end of the Fabulosa mine area appears to be in this zone.

The main vein was worked from pits and an open stope about 5 

meters deep, which bottoms at a 10-meter drift. A few tons of handsorted silver concentrates were shipped before the mine closed down 

in 1942. It appears that the richest ore has been mined, but further 

exploration might show other small ore shoots which could be worked 

profitably by hand mining methods.

MISERICORDIA PROSPECT

The Misericordia prospect is on the south side of the PacllonLlamac ridge about 500 meters north of La Esperanza mine. The 

workings lie between the altitudes of 4,620 and 4,650 meters.

Sulfide minerals occur in two small irregular shear zones and alonoa diorite dike south of these zones. The country rock consists of in-
PACLLON-LLAMAC MINING -DISTRICT 151

terbedded fine-grained iron-stained sandstones and dark-gray shales 

striking N. 25° W. and dipping 80° SW. The mineralized part of 

the eastern shear zone, as much as a meter wide and 10 to 15 meters 

long, strikes N. 85° E. and dips 60° S. It contains many quartz veinlets with associated pyrite and arsenopyrite. The second shear zone, 

about 200 meters to the west, strikes N. 80° W. and dips 80° S. It 

contains a lens 3 meters long and up to 60 centimeters wide consisting largely, of an open mesh of small quartz crystals with cavities 

partly filled by crystalline pyrite, rhodochrosite, argentite, galena, 

and sphalerite. The diorite dike is about 2 meters wide and strikes 

N". 65° E. and dips 85°-90° NW. Small irregular fractures at the 

contacts of the dike contain crystals of sulfide minerals.

The shear zones and the dike contacts have been explored by small 

prospect pits, but apparently no ore was found and the prospect was 

abandoned. The veins are small, and it is doubtful that further exploration would reveal ore bodies.

BLANQUITA PROSPECT

The Blanquita prospect is about 100 meters south of La Esperanza 

and about 30 meters lower in altitude.

Two small irregular bodies of quartz and arsenopyrite occupy shear 

zones in sandstone. The shears are parallel, striking N. 65° W. and 

dipping 80° SW., and are about a meter apart. The mineral bodies 

are from 20 to 60 centimeters wide and, although largely covered, 

seem to be only a few meters long.

Both veins Avere exposed in a small prospect pit, but ore minerals 

appear to be absent.

AGUSTfN PROSPECT

The Agustin prospect is about 300 meters southwest of La Esperanza, at an altitude of 4,440 meters.

Two small parallel quartz veins, striking N. 75°-800 W. and dipping from 85° NE. to vertical, are exposed in an outcrop of lightgray sandstone in a slide rock area. The veins, each from 10 to 40 

centimeters wide and from 10 to 20 meters long, are about 4 meters 

apart and appear to have formed by fissure filling within a fault zone. 

The quartz contains a minor amount of arsenopyrite and lesser pyrite 

and galena.

During prospecting, part of the weathered surfaces were stripped 

from the veins, revealing them to be essentially barren of sulfide minerals. It is doubtful that further exploration would reveal ore.

ROSITA PROSPECT

The Rosita prospect is 150 to 200 meters southwest of the Agustin 

prospect and near the east rim of a broad, deep canyon on the south
152 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

side of the Pacllon-Llamac ridge. The main prospect pit is at an altitude of 4,400 meters.

Veinlets and lenses of sulfide minerals fill fissures and partly replace 

altered limestone along a zone nearly 150 meters long. The veins and 

lenses are parallel to the bedding of the limestone which strikes N. 

15°-20° W. and dips 70°-80° SW.

Most veins and lenses are less than 50 centimeters wide and 3 meters 

long. The largest lens has a maximum width of 60 centimeters and 

is about 15 meters long. It contains up to 50 percent marmatite with 

lesser amounts of pyrite, galena, and chalcopyrite. Other lenses and 

veins are similar but contain less sulfide minerals and more altered 

wall rock. The altered limestone and fractures near the veins contain 

crystals of grossularite garnet. On the whole, mineralization is 

similar to that at the Susana mine.

The veins have been explored by three or four pits and trenches, but 

probably no ore has been shipped. A few small pockets of high-grade 

galena Avithin the marmatite might be mined and concentrated by 

hand. Otherwise, the veins are too small and too low-grade to be 

mined at a profit.

CCORIDELIA MINE

The Ccoridelia mine is near the head of a small valley north of 

Quebrada Llamac. The mine is about 2 kilometers airline distance 

northeast of Hacienda Palca and 5 to 6 kilometers by trail. The workings are between the altitudes of 4,400 and 4,450 meters.

The country rock is medium- to thick-bedded fossiliferous finegrained gray limestone which overlies medium-bedded fine-grained 

gray sandstone. Bedding strikes N. 25°-35° W. and dips 55°-65° SW. 

At least ten small fissure veins are along faults, striking N. 20°-60° E. 

and dipping from 55° to 90° SE., which cut the limestone. Most of 

the faults cut across the contact of the limestone and the sandstone 

and displace it from a few meters to as much as 40 meters. They seem 

to persist in the limestone for distances of 50 to 200 meters, but most 

die out in the sandstone within a few meters of the contact.

The veins consist of lenses, irregular pods, and veinlets of crystalline 

stibnite and calcite, most of which lie within 50 meters of the contact. 

The larger bodies are from 5 to 30 centimeters wide and 30 centimeters 

to 1.5 meters long. Stibnite forms either radiating masses or open 

meshworks of crystals which developed in open cavities. The larger 

crystals are as much as a centimeter in diameter and 20 centimeters 

long. Large radiating stibnite crystals in one vein appeared to have 

penetrated the silicified limestone Avail rock, indicating that they had 

groAvn by replacement of the limestone. White coarsely ciystalline 

calcite fills spaces betAveen stibnite crystals and along the faults. One 

vein yielded calcite rhombs 5 to 10 centimeters across cleavage faces.

The veins crop out along the limestone-sandstone contact for a
TUCO-CHIRA MINING DISTRICT 153

distance of nearly a kilometer. In the lower workings the veins contain less stibnite than in the upper workings, and the few7 veins which 

continue to the floor of the valley about 50 meters below contain only 

calcite.

The veins have been explored and mined from small pits, trenches, 

and three adits 2 to 6 meters long. The mine has been worked intermittently for several years,.although it was not operating at the time 

of our visit. Ore is mined and concentrated by hand, and several tons 

of high-grade stibnite concentrates have been shipped. Several tons 

of high-grade ore in the exposed veins could probably be mined at a 

profit. However, mineralization extends only to a shallow depth, and 

possible reserves are small.

TUCO-CHIRA MINING DISTRICT

The Tuco-Chira mining district is at the south end of the Cordillera 

Blanca about 20 kilometers airline northeast of Conococha. The district has been named for the two major quebradas of Tuco and Chira 

which drain the area. (See fig. 7.) The north end of the pampa in 

Quebrada Tuco at the old smelter is at an altitude of 4,330 meters, and 

the bottom of the valley near the Chira mine in Quebrada Chira is at 

about 4,230 meters. The trail from Quebrada Tuco to Quebrada Chira 

crosses the ridge between the quebradas at an altitude near 5,000 meters. 

Nevado Tuco, at the north edge of the district, reaches an altitude of 

5,487 meters. . The ridge separating Quebrada Tuco from Quebrada Chira trends 

parallel to the main mass of the Cordillera Blanca and forms the local 

drainage divide between the Rio Santa and Rio Pativilca. Quebrada 

Tuco drains southwestward into the Rio Santa near the outlet of 

Laguna Conococha, whereas Quebrada Chira drains southeastward 

into the Rio Pativilca. Both quebradas originate on the flanks of 

Nevado Tuco, and glaciers furnish most of the water to the streams.

The sedimentary rocks consist of a sequence of interbedded shaly 

sandstones, shales, calcareous shales, and a feAv beds of limestone, overlain by massive limestone. Part of the shaly sandstones have been 

metamorphosed to quartzite, and shales and calcareous"shales to phyllite or hornfels; some of the limestone has been recrystallized. We 

believe that the heterogeneous sequence of shales, sandstones, and calcareous shales are equivalent to the middle unit of the Barremian of 

Steinmann. In Quebrada Tuco the exposed sequence is several hundred meters in thickness. Because of complex folding the thickness of 

limestone which overlies the Barremian sequence could not be estimated. However, several hundred meters of massive limestone are 

exposed and may be equivalent to the upper limestone unit of the 

Barremian, the Machay, and part of the Jumasha.

321628 55 11
154 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

These sedimentary rocks have been intruded by a ]arge granodiorite 

stock, several small irregular granite porphyry stocks and dikes, rhyolite porphyry sills, and andesite sills and dikes.

The sedimentary rocks have been complexly folded, as is shown in 

fig. 13, and time was not available to make a complete study of the 

structure. However, large folds with complex secondary folds are the 

most prominent structural features, and most faults appear to be small. 

The regional strike of sedimentary beds is about N. 30° W.

The most common vein minerals are pyrite and quartz with lesser 

amounts of galena, sphalerite, chalcopyrite, tetrahedrite, calcite, barite, and fluorite. Most veins are vuggy, and the minerals are well 

crystallized.

Some of the veins were mined extensively during the early part of 

the present century, when the smelter at the north end of Quebrada 

Tuco was in operation. Two of the mines were worked in 1949 by 

small-scale hand-mining methods. Yearly production from the district probably averages less than 35 tons of lead-silver-copper concentrate. Output could be increased by more extensive mining, but most 

of the veins are small and low grade. Unless larger ore bodies are discovered, it is doubtful that reserves are large enough to maintain increased production for more than a few years.

Of the mines and prospects of the district, only the Cosmos mine 

has possible reserves of lead-zinc-copper ore to sustain a small-scale 

operation for more than a year or two.

COSMOS MINE

, The Cosmos mine, the largest in the district, and the Cascajal mine 

probably were the principal sources of ore for the smelter. The mine 

is on the west side of Quebrada Tuco 200 to 270 meters vertically 

above the pampa and 1.5 to 2 kilometers southwest of the smelter. 

The principal workings are between the altitudes of 4,550 and 4,620 

meters. A trail leads directly from the smelter to the mine.

Veins occur along a recrystallized limestone bed in a metamorphosed 

shale-sandstone sequence near the contact with massive limestone. The 

area is on the upper or west limb of an overturned syncline (pi. 12), 

so that older shale rests on younger limestone. Massive limestone cropping out about 100 meters northeast of the map area (pi. 12) is near 

the axis of the syncline. The axial plane of the syncline strikes 

N. 20°-30° W. and dips 2°~12° SW., and strata on the overturned limb 

strike N. 10°-30° W. and dip 24°-60° SW. Three andesite sills, which 

strike about N. 30° W. and dip 50°-60° SW., crop out 75 to 130 meters 

west of the recrystallized limestone bed. Sills of similar lithology 

crop out on the east limb of the syncline several hundred meters east 

of the vein area. It is possible that these sills are continuous through
TUCO-CHIRA MINING DISTRICT 155

the syncline and that therefore they were intruded before the sequence 

was folded.

Many fissure filling and replacement veins occur over a distance of 

more than a kilometer in or near a layer of light-gray recrystallized 

limestone which averages about 10 meters in thickness. However, this 

layer is somewhat irregular in thickness and, as exposed in one of the 

principal adits (pi. 12), consists of two stringers separated by a lens 

of impure limestone, giving an aggregate thickness of nearly 20 

meters. At some places the contact between the recrystallized limestone and surrounding rock is gradational, whereas in other places the 

contact is sharp. Irregular breccia zones are found at many places 

within the recrystallized limestone and at the contacts, suggesting in 

part tliat the irregularity in thickness is due to faulting. It seems 

possible that the recrystallized limestone represents a relatively pure 

limestone layer in the shale-sandstone sequence that was shattered and 

recrystallized during folding and metamorphism.

Most of the veins strike N. 20^-30° W. and dip 35°-70° SW. They 

contain breccia and gouge with irregular to lenticular sulh'de bodies, 

most of which are less than a meter wide and 5 to 10 meters long. 

These bodies consist largely of pyrite with irregular pods and veinlets 

of galena and sphalerite, but many of them also contain minor 

amounts of chalcopyrite, tetrahedrite, calcite, barite, and fluorite. The 

veins in the main Cosmos area have been worked from several inclined 

shafts and adits, many of which are now either caved or flooded. The 

total length of underground workings probably exceeds 600 meters.

About 500 meters south of the main Cosmos area shown in the map 

(pi. 12) and between the altitudes of 4,610 and 4,620 meters two other 

veins crop out in the recrystallized limestone layer. One is a zone of 

iron oxide and limestone breccia from 1 to 1.5 meters wide and about 

50 meters long, striking N. 80° W. and dipping vertically. It contains 

pods and veinlets of malachite and azurite. The second vein, about 10 

meters to the north, strikes N. 80 c W. and dips 80° S.; it consists of 

pods and stringers of iron oxide and galena in a shear and fracture 

zone 50 to 75 centimeters wide and about 10 meters long.

A third mineralized zone about 150 meters east of the main Cosmos 

area was explored by an adit more than 50 meters long. Here an ir« 

regular zone of iron oxide and silicated limestone contains a few veinlets of galena and sphalerite.

During 1949 two or three men were hand-mining ore pockets in the 

old workings and may have been producing as much as 2 to 3 tons of 

low- to medium-grade hand-sorted lead-copper-silver concentrates per 

month. Enough ore is probably available to sustain this operation for 

several years, but as the ore bodies are small and generally low grade, 

it is doubtful that potential reserves could support a larger operation.
156 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

CASCAJAL MINE

The Cascajal mine is on the west side of Quebrada Tuco about a kilometer south of the main Cosmos area. Several old workings lie between the altitudes of 4,510 and 4,600 meters. The trail distance from 

the old smelter is about 3 kilometers.

Veins in the Cascajal area are associated with the same layer of 

recrystallized limestone exposed at Cosmos. However, here the beds 

swing around the nose of the overturned syncline, as shown in figure 

12, and the strata are in normal position, striking N. 55°-85° W. and 

dipping 40°-75° NE. About 50 meters northwest of the uppermost 

vein, beds are overturned and strike N. 20°-30° W. and dip 50°- 

70° SW.

Several old dumps and pits extend along the limestone layer for a 

distance of more than 200 meters northeast from the nose of the syncline. All the old workings are caved, and most of the vein outcrops 

are covered with slide rock or waste. An upper vein, exposed near the 

nose of the syncline, strikes N. 65°-TO° W. and dips 65° NE. and appears to be a replacement zone within the recrystallized .limestone. 

The mineralization, similar to that at Cosmos, shows predominant 

pyrite and quartz with minor tetrahedrite, galena, and sphalerite. At 

a caved adit 150 to 200 meters to the northeast another vein in the recrystallized limestone trends east and dips 40°-60° N., nearly parallel 

to the bedding. It consists of soft, crumbly pyrite and altered limestone with a few disseminated crystals of sphalerite.

A few other prospect pits and two small adits to the northeast on 

the same limestone layer lie within 400 meters of the principal Cascajal mine area. The prospects expose small irregular veins or pods 

of sulfide minerals.

The Cascajal mine was probably worked at the same time as the 

Cosmos mine. The production of the mine is unknown, but the size 

of the dumps indicates that several thousand tons of rock were removed. It is possible that the veins were worked out and then 

abandoned.

VENUS MINE

. The Venus mine is on the east side of Quebrada Tuco, almost due 

east of the Cascajal mine. The portal of the main adit is at an altitude 

of about 4,430 meters and is about 100 meters above the pampa.

A mineralized fault zone striking about N. 60° W. and dipping 

20°-40° NE., cuts metamorphosed calcareous shale striking N. 75° E. 

and dipping 30° NW. The zone, 20 centimeters to 1 meter wide and 

more than 50 meters long, consists largely of gouge, breccia, and quartz 

with disseminated grains of pyrite, chalcopyrite, arsenopyrite, and 

calcite. A fine-grained andesite dike cropping out in the mine area 

strikes N. 50° W. and dips 20° NE.
TUCO-CHIRA MINING DISTRICT . 157

Four small adits have been opened on the vein. The two lower adits 

are caved, the main adit is 50 meters long, and the upper adit is 9 

meters long. The main adit has two sm^all raises but no stopes. Production from the main adit could not have been more than a few tons 

of copper concentrates. The upper adit and dumps of the lower adits 

are barren. The mine was not operated in 1949. No ore is in sight, 

and it is doubtful that further exploration would reveal new ore 

bodies.

MERCEDES MINE

The Mercedes mine is on the east side- of Quebrada Tuco 1.5 to 2 

kilometers south of the Venus mine and about 200 meters above the 

pampa. The altitude at the portal of the main adit is 4,530 meters. 

A one-half kilometer trail connects the mine with the road about 4.5 

kilometers south of the old smelter.

Several veins crop out in light-gray recrystallized limestone above 

the contact with the granodiorite stock. Bedding in the limestone is 

obscure but seems to be nearly horizontal. The contact of the limestone and the granodiorite strikes N. 55° E. and dips 10°-20° NW.

The veins appear to have formed both by fissure filling and by replacement along short irregular fractures in the limestone along the 

contact for a distance of 75 to 100 meters. Veins strike N. 60°-75° E. 

or N. 30°-75° W. and dip either 15°-45° N. or 55°-65° S. The major 

vein is arcuate, striking from N. 75° E. to N. 75° W. and dipping 

55°-65° S. It has a maximum width pf 50 centimeters and is more 

than 20 meters long. The predominant mineral is calcite which contains small pods and vemlets of galena, sphalerite, and pyrite. Mineralogy of the other veins is similar.

During 1949 the ore was hand-mined and concentrated by three or 

four men, and a few tons of galena concentrates were shipped. The 

veins were worked from a 22-meter adit arid several small pits. The 

veins are small, and most are low grade, but small scale mining of 

richer pockets may continue to be profitable for a few years.

SIBERIA MINE

The Siberia mine is in the low hills along the west side of Quebrada 

Tuco about 4 kilometers south of the old smelter. Mine workings 

are near the floor at the west side of the quebrada between the altitudes 6f 4,300 and 4,320 meters.

Several small veihs cut recrystallized and partly silicated limestone 

near the contact with the granodiorite stock. Beds strike N. 15°-25° 

E. and dip 20°-30° NW. One or two small aplite dikes have been 

intruded into the limestone.

Veins appear to replace altered limestone along irregular fractures 

and faults occurring along the contact for a distance of 50 to 75 

meters. The most prominent veins lie nearly parallel to the lime-
158 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

stone beds and range from 5 to 60 centimeters in width and 1 to 10 

meters in length. Many of the veins consist only of altered limestone with disseminated grains of pyrite and chalcopyrite, but a few 

contain small pods and lenses of high-grade galena and sphalerite. ' 

The veins have been explored and worked in several small pits and 

two or three adits ranging from 2 to 15 meters in length. Sulfide 

pockets may have yielded a few tons of lead concentrates, but the 

remaining material appears to be too low in grade to be mined 

profitably.

RUSIA PROSPECT

The Rusia prospect is on the east side and near the mouth of 

Quebrada Tuco, about 1 kilometers south of the old smelter. The 

workings are between the altitudes of 4,420 and 4,430 meters. The 

trail distance from the Quebrada Tuco road is about 1 kilometer.

A narrow vein in altered sandstone near the contact with the 

granodiorite stock strikes about N. 50° E. and dips 70° SE. Bedding 

planes of the sandstone strike N. 60° W. and dip 30° SW. The vein 

is largely covered but may be as much as 50 meters long. It consists 

of wall rock and quartz with disseminated crystals and veinlets of 

pyrite and is essentially barren of other sulfide minerals. Only a 

few grains of galena were seen in specimens on the dumps. A few 

pits and three small adits are now completely caved, and the prospect 

has been abandoned.

CHIRA MINE

The Chira mine is on the west side of Quebrada Chira about 3.5 

kilometers east of the old smelter in Quebrada Tuco. The workings 

lie between the altitudes of 4,240 and 4,420 meters. A trail about 6 

kilometers long connects the mine to the smelter.

Many irregular veins, short thick lenses, and irregular pods of 

quartz and pyrite are found in a contact-alteration zone between limestone and the granodiorite stock. This zone is from 25 to 50 meters 

wide and can be traced westward from near the floor of the quebrada 

for more than a kilometer. The limestone in the zone, striking N. 

40° E. to east and dipping 10°-15° N., has been silicified, garnetized, 

pyritized, and partly recrystallized, and in places it contains irregular pods and disseminated crystals of wollastonite. One bed near the 

contact is schistose and originally may have been shaly limestone 

or shale. Within the granodiorite are several small aplite dikes.

Most of the larger veins and lenses of quartz and pyrite, ranging 

from 5 to 15 meters in length and 1 to 2 meters in width, strike east 

and dip 15°-25° N. A few are 15 to 20 meters long and as much as 

4 meters wide. Apparently the bodies formed both by replacement 

and by fissure-filling along fractures and cavities in the altered limestone. Some of the veins are a granular mixture of fine-grained
TUCO-CHIRA MINING DISTRICT 159

quartz and pyrite, whereas others are massive quartz dotted with 1- 

to 2-centimeter cubes of pyrite. A few of the veins contain minor 

amounts of chalcopyrite and sphalerite.

The contact zone has been explored thoroughly by prospect pits 

and short adits over a width of about 25 meters and a length of about 

150 meters. Four major adits range from 20 to 25 meters in length. 

Also along the deposit to the west of this area for a distance of several 

hundred meters are several other prospect pits and short adits. The 

mine has been abandoned for several years, and as the veins appear 

to be nearly barren, it is doubted that further exploration will discover minable material.

OTHER DEPOSITS

Two prospects not previously discussed are on the east side of 

Quebrada Tuco. They are 300 and 450 meters north of the Venus 

mine and slightly higher in altitude.

At the southern prospect two parallel replacement veins, ranging 

from 50 centimeters to 2 meters in width and from 50 to 70 meters 

in length, strike N. 50°-60° W. and dip 50°-60° NE. The veins contain pyrite, iron oxide, and altered limestone. The wall rock is very 

fine-grained dark-gray limestone which strikes N. 35° W. and dips 

4-5°-60° NE. The veins were explored by a 21-meter adit, but no ore 

was encountered.

The northern prospect was explored by a 30-meter adit which exposes recrystallized limestone and one or two small veinlets of pyrite.
160 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

LITERATURE CITED

Bateniah, A. M., 1942, Economic mineral deposits: 912 p., New

York, John Wiley and Sons. 

Boit, Bernando, 1926, Algunos datos sobre la geologia de

Ancashs: Soc. Geol. del Peru Bol., v. 2, p. 47-74. 

Borchers, Philipp, (editor), 1935a, Cordillera Blanca, Cordillera

Blanca-Expedition des Deutschen und Osterreichen Alpenvereins: Munchen, Klein and Volbert, topographic map (scale

1:100,000).

 I935b, Die Weise Kordillera: Berlin, Verlag Scherl.

Broggi, J. A., 1943, La desglaciacion actual de los Andes del 

Peru: Soc. Geol. del Peru Bol., v. 14-15, p. 59-90.

Comstock, W. J., 1879, Analysis of tetrahedrite from Huallanca, 

Peru: Am. Jour. Sci., ser. 3, v. 17, p. 401-402.

Dana, E. S., 1932, A textbook of mineralogy, 4th ed., 851 p., New 

York, John Wiley and Sons.

Dana, J. D. arid Dana, E. S., 1944, The system.of mineralogy, 7th 

ed., v. 1, 848 p., New York, John Wiley and. Sons.

Direccion de Minas, 1950, Estado del patron general de minas 

al segundo semestre de 1949: Ministerio de Fomento y Obras 

Publicas del Peru, Lima.

Duefias, E; I., 1904, Recursos minerales de los distritos de Chacas 

y San Luiz : Bol. ;Cuerpo de Ing. de Minas 'del Peru, v. 15,142 p.

Dunbar, C. O., and others, 1942, Correlation charts prepared by the Committee of Stratigraphy, National Research 

Council: Geol. Soc. America Bull., v. 53, p. 429-434.

Dunstan, G. D., 1909, La mineria en Cajatambo y Bolognesi: 

Bol. Direc. Fomento (Lima), Aiio 7, p. 49-74.

Flint, R. F., 1947, Glacial geology and the Pleistocene epoch, 

589 p., New York, John Wiley and Sons.

Garbin, L., 1904, Apuntos sobre los minerales de Huallanca, 

Chonta y Queropalca: Bol. Soc. Ing. (Lima), v. 6, p. 1-17.

Geological staff of the (Cerro de Pasco) Corporation, 1950, 

Lead-zinc deposits of the Cerro de Pasco Corporation in central Peru, in The geology, paragenesis, and reserves of the 

ores of lead and zinc: 18th Int. Geol. Congress, Report of the 

eighteenth session, pt. 7, p. 154-186 (London).

Harrison, J. V., 1943, The geology of the central Andes in part 

of the Province of Junin, Peru: Geol. Soc. London Quart. 

Jour., v. 99, p. 1-36.

Heim, Arnold, 1947, Observaciones geologicas en la Cordillera 

Blanca, Peril: Bol. Soc. Geol. del Perti, v. 20, p. 111-118.

 1949, Observaciones geo!6gicas en la region del terromoto de Anchash de noviembre de 1946: Soc. Geol. del Peru,

Volumen Jubilar, fasc. 6, 28 p. 

Huff, K. F., 1949, Sedimentos del Jurassico Superior y Cretacico

Inferior en el Este del Perti: Soc. Geol. del Peru, Volumen

Jubilar, fasc. 15,10 p. 

Indacochea, Angel, and Iberico, Mariano, 1947, Aluvionamiento

de Chavm de Huantar el 17 de enero 1945: Bol. Soc. Geol.

del Peru, v. 20, p. 21-28. 

Jenks, W. F., 1951, Triassic to Tertiary stratigraphy near Cerro

de Pasco, Perfi : Geol. Soc. America Bull., v. 62, p. 203-220.
LITERATURE CITED 161

Kinzl, Hans (editor), 1939a, Cordillera Blanca (Peru) Siidteil, 

topographic map (scale 1:100,000) : Anden-Kundfahrt des 

Alpenvereins, Innsbruch.

 1939b, Cordillera de Huayhuash (Peru), topographic map 

(scale 1: 100,000) : Anden-Kundfahrt des Alpenvereins, Innsbruch.

Kinzl, Hans, 1942, Gletscherkundlich Begleitworte zur Karte de 

Cordillera Blanca (Peru) : Zeitschr. Gletscherkunde, v. 

28,19 p.

Kinzl, Hans; Schneider, Erwin; and Ebstar, Fritz, 1942, Die 

Karte de Kordillera von Huayhuash (Peru) : Zeitschr. 

Gessell. Erdkunde Berlin, 35 p.

Knechtel, M. M.; Richards, E. F.; and Rathbun, M. J., '1947, 

Mesozoic fossils of the Peruvian Andes: Johns Hopkins Studies in Geology, 15, p. 1-150.

Kummel, Bernhard, 1948, Geological reconnaissance of the Contamana region, Peru: Geol. Soc. America Bull., v. 59, p. 1217- 

1266.

Lindgren, Waldeinar, 1933, Mineral deposits, 4th ed., 947 p., 

New York, McGraw-Hill.

McLaughlin, D. H., 1924, Geology and physiography of the Peruvian . Cordillera, Departments of Junin and Lima: Geol. 

Soc. America Bull., v. 35, p. 591-626.

Miller, B., L.; and Singewald, J..T., Jr.; 1919, The mineral deposits of South America, 598 p., New York, McGraw-Hill.

Ministerio de Fomento, 1948, Anuario de la industria mineral en 

el Peru : v. 84, 279 p. Lima, Peru.

Raimondi, A., 1873, El Departamento de Ancashs y sus riquezas 

minerales: 651 p., Lima, Peru. El Nacional.

Spann, H. J., 1947, Informe sobre el origen de la catastrofe de 

Chavin de Huantar: Bol. Soc. Geol. del Peru, v. 20, p. 29-33.

Steinmann, Gustav, 1930, Geologia del Peru: 462 p., Heidelberg, 

Carl Winters, Universitatsbuchhandlung.

Stose, G. W., and others, 1950, Geologic map of South America, 

G. W. Stose (editor) (scale 1:5,000,000), Geol. Soc. 

America.

Szpessy Schaurek, All de, 1949, Contribuci6n al conocimiento 

de las lagunas glaciares en la Cordillera Blanca: Soc. Geol. 

del Peru, Volumen Jubilar, fasc. 10, 5 p.

Velarde, C. E., 1908, La mineria en el Peru: Ministerio de Fomento, 410 p., Lima, Peru.

Weaver, C. E., 1940, A general summary of the Mesozoic of 

South America and Central America: Eighth Am. Sci. 

Gong., Washington, D. C., Proc., v. 4, p. 149-193.

Welter, Otto, 1913, Eine Tithonfauna aus Nord-Peru, in Steinmann, G., Beitriige zur Geologic und PaUiontologie von Siidamerika XIX: Neue Jahrbuch 1913, Band I. p. 28-42.

Winchell, A. N., 1933, Elements of optical mineralogy, 477 p., 

New York, John Wiley and Sons.

Yates, R. G.; Kent, D. F.; and Fernandez Concha, Jaime; 1951, 

Geology of the Huancavelica quicksilver district, Peru: U. S. 

Geol. Survey Bull. 975-A, p. 1-45.
METRIC EQUIVALENTS

TEMPERATURE

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 30

 20

_

 10

_

n

1 cm. = 0.3937 inch 1 meter = 3.2808 ft. 1 km. = 0.6214 mile 

1 inch = 2.5400 cm. 1 ft. = 0.3048 meter 1 mile = 1.6093 km.

1 sq. meter = 1.20 sq. yd. 

1 hectare = 2.47 acres 

1 cu. meter = 1.31 cu. yd.
INDEX

Abandonada deposit..........._.....__.. 129

Abstract....__..__.__._____..._ 1-2

Acknowledgments___.. ......__...... 15-17

Agglomerate__.... ......... .._. 27

Augustm deposit....... ..__...__ 151

Aida mine.......---..---------.----------.. 147-148

Albian stage, strata..__.. ..______ 23 

Algal structures in limestone....... __ 26

Alteration.. 27,29,31-32,39,40, 51-52,56-58,88-89,143 

Altitudes, accuracy of measurements... 16,67-68,90 

Aluviones..__ ....-.---------.---.---_. 45-47

Ancash, Departamento de, location and extent..---.-----------.----.--.... 3

Andalusite.......-.--------.------------..-.- 18,39

Andean mineral province ...------. .... 2

Andesine.........-.....------....-..--..-- 29,31,32

Andesite.................................. 27,31,32

Anglesite...__ -------------------- _ 60

Animus vein.._______'.________ 50,82-84 

Antamina-Contonga mining district...___ 6-8,

26,30,63,87-89 

Antamina area........... 31,32,40,50,63,89-100

Contonga area....__.__.____ 38,100-104

Apash deposit..... -------------------- 87

Apatite... . 29,30,31

Aplite........-..---..------------------..---. 30

Aptian stage, strata......... 23

Arabia mine__----.---.-----.-.--------__. 128

Arequipa deposit..--------------...---.-.-..- 73

Argentite.....------------------------------.- 52

Arsenopyrite._. - . .-.--.. 51,52,141 

Arteria deposit..-....---.---------. 119-120

Augite.._. - 24

Atlante mine and vein.------ 38,41,49,50,59,77-80

Azurite__..__------ . . 55

o B

Barite-.-.----_--_---_-------- 52

Barremian sequence of Steinmann, lower 

limestone unit.------.-------.---- 23-24,140-141

middle heterogeneous unit___ ._ 23,24,141 

upper limestone unit... _ . 25,141

Barren deposit... . - 91

Base-metal sulflde deposits, Peru______ 2,48 

Belec deposit__...._. _..- __ 112

Benavides, V. E., work cited........ 17,22,23,26,27

Bibliography............ .... ......... 160-161

Biotite.................... .......... 29,30,32,39

Blanquita deposit....._.....____..... 151

Bodoque mine_......._ _... 117

Boit, Bernando, cited.__.__________ 19 

Bonanza deposit_.__..-..--.-......_ 141-142

Bornite...... _.__.-.......................... 52

Page 

Boundary between Jurassic and Cretaceous

strata............................. 20

Bournonite. - __ ____..__-------- 52

Breccia .... ...... 48,49,50,99,127

zones........................... 33, 52,126-127

Cahuide mine. See Condor mine. 

Calcite... 51,52,53,56,89

Carbajal, Arnulfo, cited.... ...__........ 112

Carlsbad twins.....-.-.-------...-.-....-.-.- 31

Carmen del Macizo deposit ._...... 55,105-106

Carmen del Pclarte deposit....________ 75

Cascajal deposit....___ _.._... 156

Casualidad deposit_____.______ 96,115-116 

Ccoridelia mine...._____.__.._. 152-153

Cerussite............_..--. .... 55,66

Chaco mine..---.--....---_.___.._... 72

Chalcanthite._...-_------------- _ 55

Chalcedony..-.----.-..---_----.------..-.- 55

Chalcopyrite............. .. .. 51,53,141

Chile deposit.....-....-------.-.-------..-- 87

Chira deposit_............................. 158

Chloritization.. . ...- ... - 29,30,31-32 

Chulec limestone member.....__------_.. 22,26

Clay........-.-.....--.-.-...----..-, 57-58

Climate....---.-...-.---.....---........... 11

Coal beds.... - ......... ,. 20,22,23

Coastal batholith__...___._.______ 32 

Concentrating plants--------..---. 59,80,105,125

Condor mine, inaccessible.................... 71

Contact zones....--....------..-. 18,39, 49, 51, 57, 99

Cooperative program... .... ........ 2

Copper. 2,99-100,103

Cordillera Blanca.................... 5,18,40

batholitic core..... .... 18, 28-29,32,48,65

Cordillera Huayhuash......... ... 5,40

Cordillera Negra...................... 3,4

Cosmos deposit... . - 32,154-155

Cretaceous system__. .-- . 21-27

correlation chart_............. ....... 21

threefold division by Steinmann.......... 22

Cross faults...-------------------------- 48

Cruzada vein..__...___ .__.__._ 38,78 

Cusca deposit...-.. -.------... .-----._ 71

D

Damelemano deposit...-------_...__ 72

Danubio-Diamante deposit._. 54,121-122

Diabase.-......--..-...--....-.------..- 30

Dikes.........--..... 28,88,89,90,96,97,99,137,141

Diopside................. .... . ..... 40

Diorite................. 30,31

163
164 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

Page 

Discovery of deposits..--------............... 66, 67

Disseminated deposits in limestone....... 89,99-100

Dolomite_..__.._..............._..... 53

Dos Compadres deposit..___._.____ 131 

Duenas, E. I., work cited........ 15,18,19, 20,87,101

Dynamic metamorphism___.______ 18,102

E

Earthquakes................................. 38

El Sol prospect.......................____. 120

Epeirogenic uplift stage__..........__.... 32,33

movement__...................._. 27,47,48

Epidote.......................... 29,31,32,40,52,57

Epsomite__-.-.-....__-------____1_. 55

Esperanza deposit_____...______1. 126-127 

Estrella de Oriente deposit......______.. 71

Eureka deposit................____.... 122-123

Excelsior deposit................___.... 122-123

Exchange, rate of_.....__..___....... 60

Exito deposit................................. 138

Fabulosa deposit.-._.---._............ 149,150

Faulting, block..___.____________ 47

Fault scarps.________________._ 38

zones................._--.....---___ 50,51

distinguished from shear zones__--.-. 49 

Faults........................................ 32

bedding....................... .... 33,48,141

contact_____...____._______.. 38,48 

economic importance.-.--..___.--.-.. 39 

movement along__..._____....... 35

normal...-.-........-.---.........----.-. 33,38

reverse............................_... 32,33,88

Field'work................................... 15-16

Fluorite...................................... 53

Flowage....._._______________ 33

Folding............................... 25, 47,141,154

Folds, character in central Ancash_ ____. 33 

isoclinal....... 18,33

overturned............................... 33

Foliation______..._._________ 18,29 

Fortuna deposit, of Antamina-Contonga district.....-..-.-.-..---.---.------. 90-91

of Pachapaqui district._____'.. __ 136 

Fossils.............................. 18,19, 20, 23, 25

Fractures._--.-..__.__..._____._ 40,89 

Future of mining................ 3,62,63,67,141,144

O

Gaby deposits________________.. 136-137 

Galena............................ 50,51,53,81,141

Gangue minerals... .._...--.-..--__.... 51,66

Garnet..--.-....... .......... 40,52,56

Geology, summary....___................. 17-18

Glacial deposits.__.__________ 40-41,45-47 

Glaciers.-..-....---.-.. 28,40,75,77,124-125,140

Gold...... ................................ 112

Goslarite. __.__._______._._ 55 

Gossan..___.................___..'._.. 56

Gota de Oro deposit.. ----------_--... 117

Gouge...-.-......-.--.........--.-.- 33

Goyllarisquisga formation.........______ 23, 23

Granite....-...-.....-.--....... 30,31,51,125,137

Page 

Granodiorite......__.___._ 28, 29, 30, 31, 32,39

porphyry_ ..._______._.__.___.__._._ 30

Gypsum..____.________..._____ 55

Harrison, J. V., work cited. __.___.-.- 22,23,32 

Hornfels ................................ 18, 20, 39

Hornblende._._.__________.__ 29,30,32 

Hot springs__...__....._............. 28

Huallanca mining district....__..--.-.---. 8-9,

19-20, 24, 25, 26, 30, 51, 61, 63 

HuamanS deposit ....._ 38,39,50,56,59,57,80-85

Huanuco, Departamento de, location and extent....__....__............ 3

Huaras..._____.-._____......._____ 5

disaster at____...___ 46

formation of Weaver. See Barremian sequence of Stcinmann. 

Hydrothermal solutions.-.....-..---. 27,29,39,56

Ichu. . - 11-12

Idocrase__.__...________.__.... 40

Imlay, R. W., cited....... 26

Inactive mines. -------- 106-110,107

Incaic orogeny of Steinmann... 32

Inclusions...-.-.----.-------.------------ - 29

Intrusive rocks......... 17, 28-32,39,47,125,141,154

Ispacmine.___..._____._...... 55,117-118

Italia deposit..........:...... ........... 80

Joints-- -----------------------------. 38

Judas deposit. . . 80 

Julia Eloisa deposit___........... ..... 97

Jumasha limestone._.__....____.. 22-23,26 

Jurassic(?) strata 18-20,65

La Esperanza deposit..,._..... ......... 151

Laurion deposit...... ----- 86

Lava flows____ ...--....-- ...... 27

Lead..- . 2

Lewis, R. V. cited-........-- --- 40

Limestone. 22, 23, 25, 26,33,

39, 50, 51, 52, 56, 57, 88, 99-100,141,143,153 

Limonite. _-------_____----_-- -,--. 55-56

Lower Neocomian sequence of Steinmann.- 23-24,

140-141 

Lucero deposit--. .... . .-..-..-.. 137

Liiis Adolfo deposit...._... ...._....... 136

M

McLaughlin, D. H., work cited........... 22,23,32

Machay limestone.....---------- ... .- 22,26,41

Magnetic declination......_ . . 16

Magnetite 51,53

Mapping . 15-16,90

Marl. 25

Marmatite.........-... - - 51,62,141,143

Merced deposit....._____.... 77,106

Metamorphism_....._-------_--------- 39-40

as a boundary between rock systems..... 19-20

Microcline--.---. 29
INDEX 165

Page 

Microperthitc.._.__._....._.____". 29

Minerals, gangue.............._.._....... 51

primary......................._........ 65,125

secondary................................ 66

Minerals, texture...___.................... 51,89

Minerals, vein__.............._...... 51,141

Mines, active.....___.__......_...... 61

Mine-timber supply....................._.. 13

Mining, districts, location......__.......... 6-11

history....................... 66,80,83,86,89,90

methods............................ 13,58-59,90

Misericordia deposit...._.....___... 32,150-151

Monte Cristo deposits...........-.-...-.----. 146

Moraines.----.--..-.-.-..--.-...--........_ 40

Muscovite_.___....._..._..__.... 29,39

0

Occupations.................................. 12-13

Oligoclasc.............................. 29,30,31,32

Ollanta deposit..__._._..._.__... 71 

Opal......................................... 55

Ore, concentration_........................ 59-CO

deposition of.........___.._...... 48,59,99

lenses.-..._........................ 51,90,152

localization.............._.............. 49

shipment____......_____....... 14, 59, 60

Ore deposits, altitudes of..___............. 6,8,9

banding_._..._______........... 51,130

displacement of__..----.-._.......... 48

fissure filled................... 49-50,89,125,141

genesis.- _.. . ___ 55

largest............................ 52,62,97,127

mineralogy..-.--....._---....._...--.._ 52-56

replacement--......-......-.... 49, 50-52, 58,141

tenor......-.----......----..........--.-. 50, 75

Ore minerals.................. 51, 52, 53, 54-55, 65-66

Ore shoots........... 49, 51, 66, 79,81, 89, 90, 97-98,131

Orogenesis. ................................ 32

Orogeny._.............___............... 27,47

Orthoclasc....--------..------------...- 29,30,31,32

Otito deposit..----...-...-.-.---.-.-.-..---.- 120

Otusco deposit......_..--------..-...-.-- 114-115

Outwash deposits........................._ 17,28

Oxidation....----------.--------.----....---- 144

Pachapaqui mining district................... 9,

10,25,26,30,31,62,124-140 

Paciencia deposit..........-...-..-......--. 127-128

Pacllon-Llamac mining district.-.........---. 9,

10,11, 24, 25,32, 61, 62, 63,141-153 

Pallares deposit...__.._-_.____........... 98-99

Pariatambo limestone member...-------....- 22,26

Pampas....---..--.__...................... 41

Patria deposit..____..._............. 120-127

Peaks.... -_-- --- _- 3-4,18,29

Perla deposit-..................-.-,---...-.- 31,113

Peru mine.---.--.........-___...___... 138

Phyllito.. - ......... .-....-. . 18,33,39

Physiography.___....___.___....._ 3

Plagioclase....--..--....----.-...-...-. 29,30,32,39

Planes of shear..._..............._..---.. 89,99

Pleistocene deposits.......................... 28

Poderosa deposit............................. 94-96

Polybasitc. --..---.-..----------.---.---.-- 53

Page

Population..........--.-...-.-.-..---........ 5-6

Port facilities.....---------..--.-...._____ 14

Power plants.--------------.-------------.... 46

Prado deposit....-.---.---.-...-.......-... 133-134

Prascondu vein._...._....._._..-...._.___ 81,84

Previous geologic studies...-...-.----........ 14-15

Primavcra deposit_...._.................. 130

Pi eduction, concentrates.__....._...... 61,154

Protectora deposit......._......__._... 114

Proustite__.........._......_____.. 50,53

Purfsima mine.....---.-......--.-.-..-.-.... 106

Putapuquio deposit.................... ... 98

Pyrargyrite. _._.--------.-__-_- ......... 53

Pyrrhotite...-...---------.---.-------. 51, 54, 58,141

Pyrite-... ................ 20, 24, 51, 53-54, 57,141

Pyroxene_...___.._......_.......... 32

Q

Quartz.... 24, 29,30,31,32, 39,40,51, 52, 54, 56,99,141

Quartzite --_- -- 18,33,39,153

Quebrada Antamina, deposits at head........ 99

Qucbrada Casacancha, deposits at head.... 118-119

Quebrada Honda-Vcsuvio mining district.... 6,

13,18-19, 20, 24, 28, 32, 39, 63, 64-87, 89 

Quebrada Illauro, deposits in.....-...---..... 87

Quebrada Pacllash, deposits in._._.___ 71 

Qucbrada Piscapaccha, deposits in....__. 120-127

O.uebrada Quenhuaracra, deposits in.______ 120-127

Quebrada Tucapac deposits...------- .... 106-107

R

Railroad-.....-.----------------------------. 13-14

Raimondi, A., work cited........._____ 18,19, 20

Rataquena deposit...----------.-------...... 68

Rascaciolo deposit.. ..-.---.-..-------..- 132

Reaccion deposit.... ..-...-.-.-- ... 115 

Realgar ......--.--..-.-..........-.-.-.-- 53

Recent deposits__------- .-.-.----------. 28

Recompensa deposit, Antamina-Contonga

district.......................... 94,95

Quebrada Honda-Vesuvio district... .._ 71

Reserva deposit.......-.--.--.---------- 119-120

Reserves..... - - 62,63,

67, 69,87, 89, 90,110,1.12,113,127 

Rhodochrositc... ___... - 51, 54 

Rhodonite . ' .. . 51,54

Rhyolite ...................-.-. 27,39, 51,143

Ribordesia vein.......................... 81,83-84

Richest ore bodies........ _ _ .._._ 51,112

Rfo Santa....-...-.......-.....----.------ 5,41,46

Riqueza deposit......-----.---.-------------- 133

Roads, access, recommended...__..._.... 62-63

Roads, main.._ .- _ _ - -------.. 13

Roads, secondary__............-.-...-.----- 13-14

Rocks, aspect__. ._. __._ ----. .-- 18

Rosita deposit..... .- . ---- -- ---. 151-152

Rosita do Oro deposit....._____._____ 97-98

Rusia deposit__..... ......-...-.-.-.... 158

San Antonio deposit.---------.-.------------- 134

Sandstone. ... . 22, 23, 24, 25,33,39, 56,153

San Francisco deposit, Antamina area.._... 92-93

Huallanca area...._ _ _ - . 100

San Josfe vein_.............................. 84
166 LEAD-ZINC DEPOSITS, CORDILLERAS BLANCA AND HUAYHUASH

Page

San Jos6 de Huanzala deposit__.___.. 108-110 

San Jose del Banco mine.....________ 107-108

San Judas Tadeo deposit....___.__..._ 139

San Miguel deposits___...._...__.... 136

San Pedro vein......______.__.___ 84

San Samuel deposit.._._.___.... 147,148-149

Santa Barbara deposit__.------.---...-... 71

Santa Benita deposit...-...__-.-.-._.. 132 

Santa Clara deposit...._.-.--.-...-----_. 135

Santa Elena deposit........................ 129-130

Santa Kosa deposit, Antamina area_........ 92

Huallanca area...._.___............ 106

Santa valley....--... ............ 24, 25, 27, 28,46

Sedimentary rocks. ... 17,18-28,33, 38, 49,47, 51-52 

Sericite......______...___.__--.-.... 24

Sericitization.. _ ... . 29,31-32,52,57 

Serpentine...___.____.__.-.--. 40, 51, 52,57 

Serpentinization___.-...--.-_----..-..-. 39,137

Sextri deposit......._._________.__ 66,85

Shale_.----- 18, 20, 22, 23, 24, 25, 26, 33,39, 50, 56,153

Shear zones...___........_......_ 49,50,65,81

Sheeted zone(s)..._.. ... ...... 38

Siderite.._._____.__...__...__.... 54

Silica ted limestone --. 39-40,88-89,143 

Siliciflcation.............-.-.-.----.---.-.- 39, 56, 57

Sills..---..------- . 28, 88, 89, 98,141,143,154-155

Silver-------...----. ------- 2, 50, 51,106,112

Simons, F. S., work cited................... 118-121

Sinchi Roca deposits...___ .....-.... 131

Sirena Encantadora deposit... _- 51,57,110-112 

Size, mineral grains_ 30

Slickensides. ... 48,137

Smelter, Huallanca__________._ 59-60,105 

Smithsonite.__...____________.... 56,66

Snowline...-------- -.-.-----.-------------- 40

Socorro deposit......_____._____._ 132-133

Soledad deposit___ _...-.-.-----.---.-.. 75

Sphalerite. ...................... 50,51,54,67,81

Sphene___.______._________.. 30 

Steinmann, Oustav, work cited____.... 15,19-20

Stibnite.. .................. 51,55,61,81,103,153

Stocks.................................. 29, 30-31, 32

in Contonga area..--------------- 38,101,103

in Quebrada Honda..._.._ 28,29,30,38,65 

in.Tuco-Chira district.------------------ 30

Streams..-.-.---...--.------------------.-- 5,13

Susana mine. _ --._ 51,53,54,57,142-145 

Tennantite. ._.__ ._.-__ 55

T Page

Tertiary rocks. ____....____._... 17-18,27

Tetrahedrite.___. ____. ____. _ 50, 51, 55,141 

Thrust faults__________._________ 32 

Thermal metamorphism___-.._......... 17,18

Till ... 17, 27

Tithonian stage............__..........__ 19-20

Tomelemano deposit........_..._..... 67,68-70

Topography.. _______________ gs 

glacial.--.---..--.......-.-.-....-...- 41-45, 64

valleys related to fault zones_..._..... 38

Towns. .. ..... __..........._..._- 6

Trails..--.-.- ........ 9,10, 64,124,127,133,140

Tram, aerial_............................... 13,86

Transportation of ore..._................... 14,60

Travertine-...- .-_...___........_. 28

Tres Reyes Magos deposit_______.__ 139 

Tuco-Chira district..... 9,10, 20, 24,30,31,32,153-159

Tuff 25, 27

U

Unnamed deposits..______ 123-124,139-140,159 

Urano deposit.._.-----.---................. 80

Valanginian stage, strata...-..________ 23 

Vegetation........ ............... 11-12,13,64-65

Venus deposit______.....___.... 32,156-157

Vetilla deposit...-............. ... . 128-129

Victoria deposit...-----...-.-.-..-..--..-. 116-117

Volcanic rocks...------..-......----. 17,18, 25, 27, 47

Vugs ... a - 40,51,132

W

Water supply-- - _------- 13

Wollastonite-. ...... 39,40,51

Workings, inaccessible........-.-..------ 71,106-107

Yanez Leon, work cited.-------- .. 23

Zinc. 2,67

Zircon...-.--.-.-..-----....-.---------.... 29,30,39

Zoisite 18,39

Zoning of plagioclase-......-. ..-.-.. 29,30

o