GEOLOGICAL SURVEY CIRCULAR 332 

THE KATHLEEN-MARGARET (K-M) 

COPPER PROSPECT ON THE ~~ ('~.), .-~ 

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Prepared in cooperation with the 

Department of Mines, Territory of 

Alaska. 

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UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary 

GEOLOGICAL SURVE.Y 

W. E. Wrather, Director 

GEOLOGICAL SURVEY CIRCULAR 332 

THE KATHLEEN-MARGARET (K-M) COPPER PROSPECT ON THE 

UPPER MACLAREN RIVER, ALASKA 

By Robert M. Chapman and Robert H. Saunders 

Prepared in cooperation with the 

Department of Mines, Territory of 

Alaska. 

Washington, D. C., 1954 

Free on application to the Geological Survey, Washington 25, D. C. 
...... 

...... 

146°20' 146.00' 145.40' 

N 

Mountain 

Mapted from U.S. Geological Survey map of the Delta River district, 

by R.H. Saunders, Department of Mines, Territory of Alaska 

Figure 1. -Map of upper Maclaren River, Alaska. 

63° 

20' 
THE KATHLEEN-MARGARET (K-M) COPPER PROSPECT ON THE 

UPPER MACLAREN RIVER, ALASKA 

By Robert M. Chapman and Robert H. Saunders 

CONTENTS 

Page 

Abstract..................................... 1 

Introduction. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Location and accessibility . . . . . . . . . . . . . . . . . . . . . 1 

Physical features 

and climate................................ 2 

Property and ownership....................... 2 

Page 

Geology and mineral deposits ............... ·. 2 

Geology................................ 2 

Mineral deposits. . . . . . . . . . . . . . . . . . . . . . . . 4 

Sampling and assays . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Conclusion and recommendations.............. 5 

Literature cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

ILLUSTRATIONS 

Page 

Figure 1. Map of upper Maclaren River, Alaska............................................. Faces page 1 

2. Sketch map of claims showing Albertson-Pettyjol:m copper prospect, Maclaren River............. . 3 

TABLE 

Pag: 

Table 1. Analyses of six samples assayed by the Department of Mines Assay Office at College, Alaska...... 5 

ABSTRACT 

The Kathleen-Margaret (K-M) prospect is in the 

Mount Hayes quadrangle on the west side of the Maclaren 

Glacler about 25 miles south of the peak of Mount Hayes. 

The proposed route of the Denali Highway is about 

9 miles south of the prospect. 

Several veins have been discovered on the prospect, but only one appears to be minable. The vein is 

about 10. 5 feet thick; it strikes N .. 3°-4° E. and dips 

70°-9oow. Along its east wall there is a zone of nearly 

barren quartz 1. 5 to 2 feet thick. The richest ore, 

samples from which have assayed 30 to 45 percent 

copper, is confined to a zone about 1. 5 to 2 feet thick 

adjacent to the nearly barren zone. Assays of samples 

from the remainder of the vein, about 7 feet thick, have 

ranged from 3. 5 to 12.5 percent copper. 

INTRODUCTION 

In 1950 E. 0. Albertson and F. S. Pettyjohn, Jr., 

of Big Delta, Alaska, formed a partnership and prospected the vicinity of Chistochina, a gold-placer 

district on the south slope of the Alaska Range about 

20 miles east of the Richardson Highway. From 

Chistochina they gradually worked westward until they 

reached the Maclaren River drainage. In 1952Pettyjo1:m 

discovered an outcrop of a copper-bearing vein on the 

west side of the Maclaren Glacier. 

From August 11 to 14, 1953, the copper-bearing 

outcrops and adjacent area were examined by 

R. M. Chapman of the U. S. Geological Survey and 

1 

R. H. Saunders of the Department of Mines, 

Territory of Alaska. This report is written from notes 

taken during that examination and from information furnished by Albertson and Pettyjohn. 

LOCATION AND ACCESSIBILITY 

The Kathleen-Margaret (K-M) copper prospect 

is in the Mount Hayes quadrangle at· latitude 

63°17' N. and longitude 146°35' W. By U. S. Geological Survey classification, it is in the upper 

Susitna valley district of the Cook Inlet region 

and by the U. S. Bureau of Mines classification, 

the prospect is in the Valdez Creek subdistrict 

of the Cook Inlet-Susitna region. The claims lie 

on the west side of the Maclaren Glacier about 

25 miles south of the peak of Mount Hayes. A 

glacial stream flows along the lower part of the 

west side of the glacier; it is fed by eastwardflowing tributaries that head in icefields on the 

ridge west of the glacier. The main outcrop is 

in the north wall of the gulch that has been 

eroded by Discovery Creek, named by Albertson 

and Pettyjohn, the first tributary upstream from 

the terminus . of the glacier. This outcrop is at an altitude of 4, 100 feet. 

The prospect is about 9 miles north of the 

proposed route of the Denali Highway between 

Paxson and Cantwell. The highway is now under construction. The extent of the road at the end of 

the 1953 · working season is shown on figure 1. 

By the end of 1954 the road probably will be 

completed as far as the Maclaren River. 
An access road from the prospect to the Denali 

Highway would be 9 to 10 miles long. The. flood plain 

of the Maclaren River probably would provide the best 

route for the first 7 or 8 miles of the access road. The· 

flood plain consists mostly of coarse well-drained 

gravel and it appears that the building of a road on the 

grave1 would require little more than clearing boulders 

from the roadway. A mile or two south of the prospect 

the road would leave the flats and would be built on the 

lower_slopes on the west side of the river. This part 

of the road would be more difficult to build, but there 

are no obstacles that would make the cost of construction prohibitive. 

After the necessary roads are built, the prospect 

will be 50 miles from Paxson, 245 miles from Valdez, 

and 450 miles from Seward by road. Shipping over the 

Alaska Railroad would require a truck haul of 105 miles 

to Cantwell; the distance by rail from Cantwell to Seward 

is 320 miles. 

There are only a few small lakes within 10 miles 

of the copper prospect, and the nearest lake that is 

suitable for use by small pontoon-equipped aircraft is 

situated near the west bank of the Maclaren River about 

2. 5 miles south of the terminus of the Maclaren Glacier 

and about 5 miles sout.h of the prospect. Several large 

lakes, 12 to 20 miles southeast of the prospect area, 

would be suitable for larger pontoon aircraft. 

A landing field large enough for multiengine aircraft could be constructed on the braided flood plain of 

the Maclaren River. Many stretches of the alluvial gravel 

between Cottonwood Creek and Maclaren Glacier are 

nearly smooth and clear enough in their natural state 

to serve as a landing strip. If a permanent strip is 

built on the flood plain, it will be necessary to raise 

the level of the runway surface and possibly to build 

protective dikes to prevent flooding during extreme 

high water stages, as channel shifting is frequent in 

the braided channel areas. 

The prospect can be reached c"Onveniently by 

small pontoon aircraft from one of the lakes along the 

Richardson Highway to the small lake on the west side 

of the Maclaren River. Pontoon planes are available 

for charter at Summit and Meier Lakes. 

PHYSICAL FEATURES AND CLIMATE 

The upper Maclaren River area is a part of the 

rugged glaciated south slope of the Alaska Range. The 

altitudes range from about 3, 000 to 8, 000 feet and the 

copper-bearing veins are exposed at altitudes of 

3, 800 to 4, 100 feet. The mountain slopes are predominantly steep, and the average relief is about 2, 000 feet. 

The main Maclaren River valley and the other large 

valleys are wide, flat floored, typical glacial valleys, 

and_the smaller tributary valleys are either small 

glacial valleys with moderate gradients, or small, 

sharp postglacially eroded valleys with gradients steep 

enough to produce cascades and small waterfalls. Many 

of the small glacial hanging valleys are connected to the 

main valley by a postglacial notch in their lip. Discovery Creek is an example of this. 

There are several glaciers in the vicinity of the 

copper prospect. The large Maclaren Glacier is about 

10 miles long and occupies the head of the main Maclaren 

2 

valley. A number of cirque glaciers and small icefields, remnants of larger tributary glaciers, are 

present at altitudes of 5, 000 feet and higher in the 

peaks between the Maclaren River and the West Fork. 

A flow of water adequate for the needs of a camp 

and mining operations is available during the summer 

months from any of the small streams that are fed by 

snowfields and glaciers. In addition to the melt water, 

precipitation is frequent in this area during the summer, 

according to Pettyjohn's report and the writers' experi~nce during the field examination. The Maclaren 

River carries a large volume of water, but much of 

its upper course is braided, and fordings with tractors 

and other equipment can be made in the braided stretches 

if reasonable care is used. 

The area within several miles of the copper prospect and the--Maclaren Glacier is devoid of timber. The 

vegetation consists of scrub willows and alders in the 

main valley floor and in a few protected valleys, and 

low brush and small tundra plants, mosses, and lichens 

on the slopes and .mountains. Timberline in this part 

of the Alaska Range is at an altitude of 2, 500 to 3, 000 feet. 

It is reported that some spruce timber of usable size 

can be obtained on the Maclaren River about 9 miles 

south of the terminus of the Maclaren Glacier, but 

most of the timber would have to be hauled from greater 

distances. 

The climate in this area is moderately severe. 

Weather records for 7 years between 1914 and 1944 

taken at Paxson, about 36 airline miles east-southeast 

of the copper prospect, show 18.36 inches mean annual 

precipitation, most of which falls during the period of June 

through September. The snowfall ranges from about 10to 

22 inches per month during the period from October through 

April. Written records, and personal observations indicate that cloudy skies and strong winds are common. The 

mean temperature at Paxson is 25.3° F. The mean maximum temperature during June, July, and August is about 

65° F, and during December and January is about 8 degrees. 

The mean minimum temperature is about 37° F·during June, 

July, and August, and about -12° FduringDecember and 

January. 

PROPERTY AND OWNERSIDP 

The two owners have staked 10 claims to cover 

the veins that they have discovered. The claims are 

designated Kathleen-Margaret Nos. 1 to 10. The locations of the claims are shown on figure 2. Each 

claim is owned jointly by the two partners. The location certificates are recorded in the records of the 

U. S. Commissioner at Talkeetna, Alaska. 

GEOLOGY AND MINERAL DEPOSITS 

Geology 

Little time was available for general study of the 

rock formation during the visit to the copper prospect, 

and only the rock exposed in the immediate area of 

the prospect was examined. The formations have been 

generally defined and mapped by Moffit (1912) and 

distant observations and examination of aerial photographs confirm his reconnaissance mapping. 

The country rock in which the copper-bearing 

quartz veins occur is chiefly a green diabasic lava. 
Samples 14,15,16. 

EXPLANATION 

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Outcrop of copper- bearing vein, 

showing dip 

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Vertical copper- beori ng vein 

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1200 Feet 

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en 

From compass survey by R.M.Chopmon,U.S.Geologicol Survey, 

and R.H. Sounders, Deportment of Mines, Territory of Alaska, 

September 1953 

Figure 2. -Sketch map of claims showing Albertsen-Pettyjohn copper prospect, Maclaren River, Alaska.. 

3 
Moffit assigned · a late Carboniferous or early or 

middle Triassic age to this unit, which is exposed in a west-trending range of low mountains 

that lies between Summit Lake and the Susitna 

River. Capps (1940, pl. 2) shows the same unit 

as pre-Cretaceous (Mesozoic). As described by 

Moffit (1912, p. 29-30): 

"The rocks consist largely of diabase and locally are 

amygdaloidal. They are associated with argillites, 

tuffs, and tuffaceous conglomerates in a number of 

places and are intruded by diabases and by dikes of 

less basic, light-colored porphyritic rock.· Intrusions 

of pe~idotite have taken place in the Tangle Lakes vicin~ty, and probably also in other places, for 

boulders of this character were found in same of the 

younger conglomerates near the glacier at the head of 

the east fork of Maclaren River. The lava flows have 

been deforme~ in the general folding of the region so that steep d~ps are common, and schistosity is occa- sionally developed. 11 

Apparently the oldest rocks in the area lie 

east of the Maclaren Glacier and northeast of 

the copper prospect. These rocks, correlated by 

Moffit with the Chisna formation of Mendenhall 

(1905), lie in a west-trending belt on the south 

side of the Alaska Range. This formation extends eastward from the Maclaren Glacier to the 

Summit Lake area, but has not been recognized 

west of the Maclaren valley. The Chisna formation was not examined in the field, but 

Pettyjohn reports that he found no mineralization 

in the parts of it that he prospected. As described by Moffit (1912, p. 27-28), the formation 

consists of quartzite, tuffaceous beds, and metamorphosed limestone containing associated granular 

intrusives. Many of the weathered surfaces of 

this formation have a rusty red color that is 

particularly conspicuous. 

Rocks of probable Triassic age include limestone, conglomerate, and thick units of slate 

having intercalated basic igneous flows or intrusives, all of which are cut by granular intrusives 

of dioritic or related compositions. These rocks 

are exposed on the west side of Maclaren valley 

about 2. 5 miles north of Discovery Creek, and 

they form an outcrop belt that extends westsouthwestward from this point. Triassic rocks 

apparently are not exposed in the area between 

the Maclaren Rivar and the Richardson Highway. 

The Jurassic rocks, as described by Moffit, 

consist of gray quartz diorite and hornblende 

diorite that in part show well developed cleavage 

and schistosity. They occur as dikes, silJ.s, and 

large, irregular, intrusive masses. Several small 

masses of Jurassic rocks were mapped by Moffit 

(1912, pl. 11) .on both sides of the Maclaren valley 

in the area just north of the copper prospect. An 

igneous mass of batholithic size lies in the Susitna 

River drainage about 5 to 12 miles west of the 

Maclaren Glacier. 

The geologic mapping of this region is of 

the general reconnaissance type. Additional reconnaissance and semidetailed geologic mapping of 

the· south slope of the Alaska Range between the 

Richardson Highway and the Alaska Railroad should 

be done to provide basic geologic and economic 

data. 

4 

Mineral deposits 

Several quartz veins bearing bornite and chalcopyrite with malachite surface alteration occur in the 

vicinity of Discovery Creek, a western tributary of the 

Maclaren River near the terminus of the Maclaren 

Glacier (fig. 2). The largest and richest vein is located on the steep north slope of Discovery Creek about 

3, 200 feet upstream from the mouth. This vein is 

about 10. 5 feet thick, strikes N. 3°-4° E., and dips 

70°-90°W. Mineralized talus from this vein can be 

traced down the slope to Discovery Creek and 

downstream in the creek gravel. The best exposure 

of the vein is near the top of the slope about 180 feet 

above the bottom of the valley. It is from this outcrop, 

which had been dug out for sampling and examination, 

that the authors obtained samples. The vein crops out 

at several places down the slope within a vertical distance of about 80 feet, and the width and mineralization 

appear to be fairly uniform throughout this distance. 

The richest ore, samples from which have assayed 

30 to 45 percent copper, is confined to a zone about 

1. 5 to 2 feet thick within the vein. Assays of samples 

from an adjacent zone about 7 feet thick have ranged 

from 3. 5 to 12.5 percent copper. Appreciable amounts 

of silver and traces of gold also are present in the 

samples from both zones. The gold content seems 

to be higher in the lower grade copper bearing material 

than in the rich zone . 

Two small quartz veins about 30 feet apart containing bornite and chalcopyrite with malachite surface alteration crop out on the south side of Discovery 

Creek about 200 feet downstream from the 10. 5-foot 

thick vein. These veins are 0. 75 to 1. 0 foot thick. 

Several barren quartz veinlets associated with them are 

1 to 2 inches thick. One vein strikes N. 35°E. and dips 

60° south. Samples taken from widths of 0. 75 foot in 

these veins assayed 1. 58 percent copper (sample 12) and 

2. 95 percent copper (sample 13) with only traces of gold 

and silver. The bedrock in this zone is a highly fractured, 

dark grayish-green flow(?) rock and includes light applegreen pods and small dikes that are composed largely of 

epidote(?). Thin, sheared zones of blackish-green serpentine and/or chlorite are associated with the quartz veins. 

Some brick-red iron staining is present in this fractured zone. 

A small quartz vein, banded with bornite and 

calcite, crops out on the south side of Discovery Creek 

about 1, 000 feet above the mouth. Chalcocite, chalcopyrite, and epidote have been identified in other 

specimens from this vein. This vein, which is 

0. 4 foot thick, strikes N. 15°-20° E., and is vertical, 

apparently continues northeastward for at least 100 feet 

to another small vein outcrop. Sample 11, taken across 

the width of the vein, assayed 1. 33 percent copper, a 

trace of gold, and no silver or nickel. Albertson and 

Pettyjohn reported that their sample from this vein 

showed 2 percent copper and a trace of nickel. 

Another small quartz vein is exposed on a rock knob 

on the eastside of Spray Creek about600feetdownstream 

fromDiscoveryCreek. This vei:p. strikes N.30°E. and 

dips 75°-90° southeast. It contains traces of copper 

minerals and has some greenish-black serpentine .streaks 

and pockets and some epidote within the quartz. 

A quartz vein bearing some chalcopyrite and 

bornite with malachite surface staining is exposed in 
a small gully tributary to Discovery Creek about 

600 feet upstream from the 10. 5-foot vein. The 

quartz vein is 3 to 5 inches thick and can be 

traced laterally for at least 20 feet. The rock exposed 

in the gully has slumped, but the vein appears to 

strike N. 20° W. and to dip 60° north. 

Minor amounts of malachite are found on weathered exposures of the copper-bearing veins, but 

azurite occurs only rarely. Chrysocolla has been 

identified in at least one sample that was collected by 

the owners. 

In addition to the above-mentioned veins that 

were examined by the writers, Pettyjohn reports that 

there are several copper-bearfng veins about 2. 5 miles 

southwest of Discovery Creek on the slopes of Cottonwood Creek valley. Several specimens from veins 

are reported to assay 0. 5 to 1. 5 percent copper' and 

one piece of float assayed 40.85 percent copper. Samples from a 51-inch thick quartz vein near the highgrade float had copper assays ranging from nil to 

1. 43 percent. The 51-inch vein reportedly is cut off 

at one end by a fault. Pettyjohn plans further prospecting in the Cottonwood Creek and West Fork ·area. 

Pettyjohn also reports that he found no metallization 

on the east side of the Maclaren valley or on the west 

side north of Spray Creek. 

SAMPLING AND ASSAYS 

Six samples taken during the field examination 

were assayed by the Department of Mines Assay Office 

at College, Alaska, and the results of the assays are 

shown in table 1. The sampling points are shown on 

figure 2. 

Table 1.--Analyses of six samples assayed by 

the Department of Mines Assay Office at 

College, Alaska 

Sample Width Ounces per ton Copper no. sampled gold silver (percent) (feet) 

ll 0.40 ( 1) (2) 1.33 

12 -75 ( 1) ( 1) 1.58 

13 -75 ( 1) (1) 2.95 

14 2.00 ( 1) (2) .27 

15 1.75 ( 2) 2.55 30.45 

16 7-00 0.-18 1.20 8.99 

Samples 14, 15, and 16 are rough channel 

samples that were taken across the uppermost outcrop 

of the main 10. 5-foot vein. · Sample 14 represents a 

band of barren quartz 2 feet wide on the east side of 

the vein. Sample 15 represents a band of 11 high grade 11 

5 

9.djacent to the barren quartz; it ranges in width from 

1. 5 to 2 feet. The high-grade band consists mostly of 

bornite and contains minor amounts of chalcopyrite 

and quartz probably with a few other minerals. The 

remainder of the vein, represented by sample 16, 

ranges from 6. 5 to 7. 5 feet in width. It consists of 

quartz impregnated with bornite and chalcopyrite. 

The three bands in the vein appear to be consistent in 

width. The vein is exposed at several points over a 

distance of about 150 feet on the slope. 

Samples 11, 12, and 13 were tested for nickel; 

none was present. The owners reported that there 

was a.trace of nickel in a sample that they took from 

the vein from which sample 11 was taken. The owners 

have taken several samples across the high-grade band 

in the main vein. All have assayed more than 40 percent copper. Samples taken by the owners from the 

7 -foot band of quartz, bornite, and chalcopyrite on 

the west side of the vein have assayed from 

3. 5 to 12.5 percent copper. 

CONCLUSION AND RECOMMENDATIONS 

The 10. 5-foot bornite-chalcopyrite-quartz vein 

on Discovery Creek is worthy of further exploration. 

The tenor and the apparent downdip continuity of the 

vein indicate a minable deposit if the vein has sufficient continuity along its strike. Unfortunately the 

ridge top to the north of Discovery Creek is completely covered by vegetation, and no surface indications of the vein or bedrock can be found without 

trenching or underground exploration. 

In addition to exploration of the 10. 5-foot vein, 

further prospecting is recommended in the Discovery 

Creek area and the westward extension of the outcrop 

belt of basaltic lavas. The headwaters of Cottonwood 

Creek and the West Fork are a virtually unknown area, 

and the basaltic lava formation 'continues westward 

to the Susitna River. Moffit {1915, p. 76) points 

out that a vein of chalcopyrite was found on Butte Creek, 

just west of the Susitna River, and that copper-bearing 

minerals have been found in the lava flows between 

Butte and Wachana Creeks and the Susitna River. 

LITERATURE CITED 

Capps, S. R., 1940, Geology of the Alaska Railroad 

region: U. S. Geol. Survey Bull. 907. 

Mendenhall, W. C., 1905, Geology of the central 

Copper River region, Alaska: U. S. Geol. Survey 

Prof. Paper 41. 

Moffit, Fred H., 1912, Headwaters of the Gulkana and 

SusitnaRivers, Alaska: U.S. Geol. SurveyBull. 498. _____ 1915, The Broad Pass region, Alaska: 

U. S. Geol. Survey Bull. 608. 

INT.-DUP. SEC., WASH., D.C.6lS 27