SA(IR)-243

UNITED STATES DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY

SAUDI ARABIAN MISSION

PROJECT REPORT 243

ANCIENT MINES OF THE FARAH GARAN AREA, 

SOUTHWESTERN SAUDI ARABIA

by 

C. W. Smith

with a section on

RECONNAISSANCE GEOPHYSICAL EXPLORATION

J. S. Geological Survey

OPEN FILE REPORT 7f~4fS& 

This report is preliminary4* 

not been edited or reviewed fcr

o o- u AW L°^!raUywlthGe 'loSi<>ai 

H. Richard Blan&andards or nomenclature

PREPARED FOR

DIRECTORATE GENERAL OF MINERAL RESOURCES 

MINISTRY OF PETROLEUM AND MINERAL RESOURCES 

JIDDAH, SAUDI ARABIA 

1979
U. S. GEOLOGICAL SURVEY 

SAUDI ARABIAN PROJECT REPORT 243

ANCIENT MINES OF THE FARAH GARAN AREA, 

SOUTHWESTERN SAUDI ARABIA

by 

C. W. Smith

with a section on 

RECONNAISSANCE GEOPHYSICAL EXPLORATION

by 

H. Richard Blank

»» « «HW«^ 

U. S. Geological Survey

OPEN FIL2 RE "CRT 

This report is ^rc n ' rr.inarr and has 

no i * -.; oditeu o- revievec Tor 

coiuonuity wiU: Q olcgical Survey 

standards or nomenclature

U.S. Geological Survey 

Jiddah, Saudi Arabia

1979
This report is preliminary and has not been edited or reviewed 

for conformity with U.S. Geological Survey standards and nomenclature.
CONTENTS

Page 

ABSTRACT................................................. 1

INTRODUCTION............................................. 2

REGIONAL GEOLOGIC SETTING................................ 4

FARAH GARAN MINE .................................^....... 7

Introduction........................................ 7

Geology............................................. 8

Structure........................................... 9

Mineral deposits.................................... 10

Sulfide deposits ............................... 10

North workings............................ 11

Central workings.......................... 11

South workings............................ 12

Gold-quartz veins.............................. 12

Sampling of gossans and veins.................. 12

Sulfide deposits .......................... 13

Gold-quartz veins......................... 13

Rock sampling for trace metal analysis.............. 15

Conclusions and recommendations..................... 15

AL ASHYAB................................................ 18

Introduction........................................ 18

Geology............................................. 19

Structure........................................... 21

Alteration.......................................... 21

Metallization....................................... 22
Page

Rock sampling for trace metal analysis.............. 23

Copper......................................... 23

Zinc........................................... 23

Conclusions and recommendations..................... 26

AL ASHARFAT.............................................. 27

Introduction........................................ 27

Geology and structure............................... 27

Metallization....................................... 29

Assay results.................................. 29

Conclusions and recommendations..................... 30

LEJOURAH................................................. 30

Introduction........................................ 30

Geology............................................. 30

Structure and metallization......................... 32

Assay results.................................. 32

Conclusions and recommendations..................... 33

HEMAIR................................................... 33

Introduction........................................ 33

Geology............................................. 35

Structure, metallization, and alteration............ 35

Assay results.................................. 36

Conclusions and recommendations..................... 36

PRELIMINARY STUDIES OF THE HEMAIR-AL ASHARFAT REGION..... 36

Introduction........................................ 36

The Hemair-Ethel region............................. 37

Geology........................................ 37

Metallization and alteration................... 37

ii
Page 

Rock sampling for trace metal analysis......... 38

Unnamed workings............................... 39

Ethel workings................................. 39

Assay results.................................. 39

Conclusions and recommendations................ 39

The East Al Ashyab area............................. 40

Geology........................................ 40

Assay results.................................. 40

Conclusions and recommendations................ 41

RECONNAISSANCE GEOPHYSICAL EXPLORATION................... 43

Introduction........................................ 4 3

Al Ashyab surveys................................... 4 3

Self-potential................................. 43

Results................................... 45

Turam.......................................... 4 7

Results................................... 47

Conclusions.................................... 49

Farah Garan surveys................................. 50

Self-potential................................. 50

Results ................................... 51

Turam.......................................... 5 3

Results................................... 54

Conclusions............................... 55

REFERENCES CITED......................................... 56

ILLUSTRATIONS 

Figure 1. Index map of western Saudi Arabia showing

location of the Farah Garan area............ 3

iii
Page 

Figure 2. Geologic map of the Farah Garan-Kutam area... 6

3. Geologic map of the Farah Garan ancient

mine.................................. Facing 8

4. Sample locality map, Farah Garan ancient

mine................................ Facing 12

5. Copper content of rock samples, Farah

Garan ancient mine.................. Facing 16

6. Zinc content of rock samples, Farah

Garan ancient mine.................. Facing 16

7. Vertical sections along proposed drill 

holes FG 1, 2, 3, and 4, Farah Garan 

ancient mine.............................. 17

8. Geologic map of Al Ashyab area.............. 20

9. Copper content of rock samples, Al Ashyab... 24

10. Zinc content of rock samples, Al Ashyab..... 25

11. Geologic and sample map of Al Asharfat...... 28

12. Geologic and sample map of Lejourah......... 31

13. Sketch geologic and sample map of Hemair.... 34

14. Geologic and sample map of the HemairAsharfat region..................... Facing 38

15. Self-potential map, Jabal Al Ashyab area., in pocket

16. Turam reduced-amplitude equiratio map,

660 Hz, Jabal Al Ashyab area............ in pocket

17. Turam reduced-amplitude equiratio map,

220 Hz, Jabal Al Ashyab area............ in pocket

18. Turam equiphase map, 660 Hz, Jabal Al

Ashyab area............................. in pocket

iv
Page

Figure 19. Turam equiphase map, 220 Hz, Jabal Al

Ashyab area............................. in pocket

20. Reduced-amplitude ratio and relative 

phase angle profiles, line 17S, 

Jabal Al Ashyab area.................... in pocket

21. Self-potential map, Farah Garan area...... in pocket

22. Turam reduced-amplitude equiratio map 

and ratio profiles, 220 Hz, Farah 

Garan area.............................. in pocket

23. Turam reduced-amplitude equiratio map and

ratio profiles, 660 Hz, Farah Garan area. . . in pocket

24. Turam equiphase map and phase profiles,

660 Hz, Farah Garan area................ in pocket

25. Turam equiphase map and phase profiles,

220 Hz, Farah Garan area................ in pocket

Table 

Table 1. Semi-quantitative spectrographic analyses

of samples................................. 14

v
ANCIENT MINES OF THE FARAH GARAN AREA, 

SOUTHWESTERN SAUDI ARABIA

by 

C.W. Smith

ABSTRACT

Ancient miners, in quest of oxidized copper minerals, gold, 

silver, and possibly zinc, mined gossans to approximately 20 m 

depth in an area 1.1 by 0.5 km in extent at Farah Garan. The 

gossans, derived from sulfides, are ordinarily found at 

contacts between marble lenses and metavolcanic-metasedimentary 

rocks, but in the southern part of the mined area, gossans are 

also within marbles. The gossans are generally lensoidal and 

discontinuous along strike. The same type of metallization, 

in similar rocks, was found at the Hemair ancient workings, 

about 3 km southeast. Both deposits are thought to be of 

epigenetic origin, and ore deposition was controlled by 

shearing along marble contacts. Drilling is recommended at 

Farah Garan.

Al Ashyab is 4 km south of Farah Garan, and similar rocks 

and structures extend through both areas but there are no 

ancient workings at Al Ashyab. The dominant geologic feature 

in the area is a high, narrow, light-colored ridge consisting 

of intensely silicified quartz porphyry. Pyritized 

metavolcanic rocks envelope the silicified rock, and geochemical 

sampling revealed weakly anomalous, erratically spaced concentrations of copper and zinc within these rocks. No further 

work is recommended for the area.

1
Quartz-filled fractures containing gold were mapped at 

Al Asharfat, Lejourah, and other locations where ancient 

miners worked the veins. The gold-bearing quartz veins are 

narrow and have short strike lengths, and potential tonnages 

are thought to be small. The veins are in younger, more 

massive rocks than the enclosing metamorphic rocks and are 

thought to be younger than the adjacent sulfide deposits. 

No further work is recommended.

Pyritized zones and associated sparse copper oxides 

extend intermittently about 6 km south of Hemair in metasedimentary rocks of the Jiddah group. Similar zones, 

associated quartz vein swarms, and minor magnetite and gold 

are found in mafic metavolcanic rocks adjacent to the contact 

with quartz porphyry about 1 km west of Al Asharfat. Further 

study of these areas is recommended.

INTRODUCTION

From May, 1975 to March, 1976 the author, assisted during 

part of that time by A.M. Helaby, mapped and sampled in detail 

four ancient mines and one altered zone within the area 

between lats 17°37 I 30"N. and 17°42'00"N. and between longs 

43°37 1 15"E. and 43°40'00"E. (fig. 1). In addition, 

reconnaissance mapping and sampling was done in two other 

areas; one is a north-striking belt of pyritized metasediments 

that extends from lats 17°34'15"N. to 17 0 40'00"N. and lies 

between longs 43°39'00"E. and 43°40'00"E., the other is an 

area of pyritized regional shear zones at lat 17°38'00"N. 

and long 43°38 I 00"E.

2
32° q 2'

20'-____

16

36* 39' 42* 45 e

Figure 1. Index map of western Saudi Arabia showing location of the Farah Garan area.

3

48°
R.E. Anderson, U.S. Geological Survey (USGS), mapped the geology of the Mayza quadrangle, including the Farah Garan area, in 

1974. He re-discovered the ancient workings at Farah Garan 

and recognized the altered zone at Al Ashyab. In his report 

the Farah Garan area was given the name of Wadi Al Maslulah 

area (Anderson, 1978). Rock unit names assigned by 

Anderson have been retained for the most part in the present 

report, and although we are not in complete agreement on the 

origin of the large body of quartzose rock (qp) which covers 

much of the study area (fig. 2), the name of quartz porphyry 

has been retained for the sake of simplicity.

H.R. Blank and USGS geophysical crew conducted ground 

geophysical surveys, using Turam electromagnetic and selfpotential methods, during the period November, 1975 to March, 

1976. Their findings are reported in the section of this report 

covering geophysical surveys.

This investigation is one of a series of mineral deposit 

studies conducted by the U.S. Geological Survey, made in 

accordance with a work agreement with the Ministry of 

Petroleum and Mineral Resources, Kingdom of Saudi Arabia.

REGIONAL GEOLOGIC SETTING

The layered rocks of the area, the erogenic events that 

affected them, and the plutonic rocks associated with or that 

followed orogenies, are summarized in the following hypothetical 

sequence of geologic events in the Farah Garan area, from 

oldest at the bottom to youngest at the top. Data are in part 

from Greenwood and others (1976).
Layered rock units Orogenic events Plutonic rocks

Jiddah group rocks 

and weakly foliated 

basalt in the Lejourah 

region intruded by 

pale-red to reddishgray quartz monzonite 

(qm) .

Late phase 

folding, faulting, 

and metamorphism.

Jiddah group layered 

rocks and mediumgrained quartz diorite 

syntectonically intruded by coarse-grained 

quartz diorite (qdc) 

at Al Asharfat.

Late phase 

folding, faulting, 

and metamorphism.

Jiddah group layered 

rocks syntectonically 

intruded by mediumgrained quartz 

diorite (qd) at Al 

Asharfat.

Basaltic lavas 

(ba) laid down 

in Lejourah 

area.

Late phase 

folding, faulting, 

and metamorphism.

Jiddah group 

metasedimentary 

and metavolcanic 

layered rocks. 

Possibly includes part of 

unit mapped as 

qp (quartz 

porphyry).

Aqiq orogenyisoclinal folding, 

faulting, metamorphism to 

amphibolite 

facies.

First diorite series. 

(Radiometric age 

960 million years.)

Sulfide deposition, which is considered to be epigenetic, 

probably took place near the end of the Aqiq orogeny, possibly 

earlier than the nearby deposition of gold-quartz veins in 

fractures within younger rocks.
43 37'

EX

AS SARAT VOLCANIC R

WAJID SANDSTONE - C

17 40'

QUARTZ MONZONITE 

qd QUARTZ DIORITE - M

" FARAH GARAN . . .

ha BASALT - Weakly foliate

qp g:;: QUARTZ PORPHYRY - 

METAVOLCAN1C AND M

METAVOLCANIC ROCK

and flow breccia

METASEDIMENTARY R

graphitic schist, marble

CONTACT

FAULT

STRIKE AND DIP OF FO

y DRAG FOLDING 

X ALTERED ZONE 

X ANCIENT WORKINGS

MOTOR VEHICLE TRAI

5km

Modified from R. E. Andmon. 1975

Figure 2. Geologic map of the Farah Garan-Kutam area .
FARAH GARAN MINE 

Introduction

The ancient mining, milling, and smelting site of Farah 

Garan is at lat 17°41'00"N. / long 43°38'15"W. at an elevation 

of about 2000 m. The ancient workings were re-discovered in 

1974 by R.E. Anderson, and he and T.H. Kiilsgaard later 

examined the area and sampled mineralized outcrops.

Excavations by the ancient miners consisting of open cuts 

that average about 2 m in width extend discontinuously for 

1.1 km (fig. 3). Some of the open cuts may have reached 

depths in excess of 20 m along ore shoots. About 5000 tons of 

slag is in piles near the north end of the mapped area.

The mine area is drained by two tributaries of Wadi Kholan, 

and local relief is as much as 100 m. The northern part is 

only moderately rugged and drained by a tributary that flows 

west. The southern part is drained by a tributary that flows 

south and has deeply incised the rocks of the region so that 

access is difficult even on foot.

In May, 1975, an area 1.1 by 0.5 km was mapped by plane 

table at a scale of 1:2000 by the author and A.M. Helaby. A 

topographic base of the same area was compiled photogrammetrically 

by C.M. Robins. Geochemical rock chip samples were taken at 

10 m intervals on lines 50 m apart. Color photographs on a 

scale of about 1:12,000 and 1:20,000 aided in mapping.
Geology

The Farah Garan deposit is in metavolcanic and 

metasedimentary rocks of the Jiddah group. The western part 

of the mapped area is underlain by metavolcanic rocks of 

intermediate composition which contain marble lenses, whereas 

rocks in the eastern part are principally calcareous metasediments containing locally distributed graphitic schists 

(fig. 3). Metasediments are in contact with intrusive mafic 

volcanic rock of probable andesitic composition on the eastern 

edge of the mapped area.

Metavolcanic rocks are mainly green-gray quartz-chlorite 

schist that is interlayered with subordinate, more mafic, 

dark-green, feldspar-bearing schist. The quartz-chlorite 

schist, which is probably of dacitic composition, is 

characterized by clear quartz crystals as much as 3 mm in 

diameter, commonly shows good slaty cleavage, and is not 

obviously layered. The mafic, feldspar-bearing schist contains 

layers of volcanic breccia and massive lava/ which are locally 

interlayered with volcanic rocks of intermediate composition 

and with metasedimentary rocks. Andesite dikes intrude the 

metasedimentary rocks near the central workings. Sills or 

layers of a fine-grained rock of intermediate composition 

containing blue-gray quartz crystals (qp, fig. 2) were noted 

locally on both the eastern and western edges of the deposit 

but were not mapped separately. These rocks are undoubtedly 

outliers of the large mass of quartz porphyry that crops out 

a few hundred meters west of the ancient workings.

8
Metasedimentary rocks include marble, calcareous siltstones, 

graywacke and graphitic schists, all of which are interlayered 

with metavolcanic rocks. The marble is fine grained, 

brown-weathering, and is in beds a few centimeters to more than 

20 m thick. The layers of graphitic schist are commonly less 

than 5 m thick and are lensoidal. The various layers of graphite 

schist range from slightly graphitic to almost pure graphite.

All rocks have been metamorphosed to greenschist or 

amphibolite regional metamorphic facies. Chlorite and white 

mica form a well developed foliation that masks much of the 

original texture in all rocks, metasedimentary and metavolcanic 

alike. Typically, these rocks in thin section show strongly 

foliated fine-grained chlorite, epidote, white mica, and 

scattered ilmenite.

Structure

All rocks in the area were intensely folded isoclinally 

and now strike north and dip steeply west. Lenses of more 

competent marble were sheared only along their contacts. 

Later movement along a N.20°E.-striking regional fault caused 

local drag folding around fold axes that plunge 60° and bear 

S.40-60°E. Rotation and strike-slip displacement along the 

same fault then caused metavolcanic rocks to the west, which 

strike N.20°E., to be faulted against north-striking metasedimentary rocks on the east. A system of faults striking 

N.40-60°W. are the latest structures in the immediate area. 

These faults were later invaded by aplite dikes.
Mineral deposits

Mineral deposits at Farah Garan are of two types: 

zinc-copper sulfides and associated gold and silver along 

sheared contacts adjacent to marble lenses; and gold-quartz 

veins in shear zones not associated with marble lenses. Both 

types are thought to be of epigenetic origin, but age 

relationships between the two are not clear. The sulfide 

deposits are far more extensive.

Sulfide deposits

No sulfides were seen during the examination, except for 

minor pyrite found in quartz. All sulfides near the surface 

have been oxidized to form geothite, hematite, manganese 

oxides, copper carbonate, and zinc silicate within siliceous, 

cellular gossans along sheared contacts of marble lenses. In 

places, sulfides locally replaced marble and have undergone 

oxidation to form finely cellular, slightly siliceous 

medium-brown to maroon gossans composed mainly of iron 

oxides. Some small areas of gossan are heavily stained by 

copper oxides. Zinc minerals are ordinarily not visible in 

the field but assays of gossans indicate that zinc is ubiquitous 

Microscopic and X-ray diffraction studies of gossans, made by 

the USGS laboratories in Jiddah, have detected hemimorphite 

(H2 Zn 2 s i°5) ' Appreciable gold and silver were found in some 

of the gossan samples but the mineral form or association of 

these metals is not known. Lead minerals were not observed, 

even though some samples contained moderate amounts of lead.

10
Ancient workings in sulfide gossans are grouped in three 

zones, mainly the northern, central, and southern part of the 

area (fig. 3).

North workings.--Pits and open stopes have been sunk on 

gossans to depths as much as 20 m on both contacts of a marble 

lens that extends about 600 m N.20°E. and dips 65°W. The 

stopes average about 2 m in width and follow gossans averaging 

0.4 m in width. In some stopes, two or more gossans lie 

parallel, but the average width of mineralized rock on either 

contact probably does not exceed 2.0 m. Small workings within 

the marble lens reveal locally gossanized zones along fractures,

The central part of the marble lens has undergone 

fracturing, cavity filling, and partial replacement by milky 

quartz and calcite, and large parts of the lens are composed 

of these minerals. Quartz and calcite contain very minor 

amounts of cubic pyrite and no gold or silver. At least some 

of the quartz and calcite was deposited prior to the sulfides, 

as is revealed by the cross-cutting relationship of sulfide 

gossans to quartz.

The marble lens pinches and becomes discontinuous to the 

southwest and is accompanied by other lenses not exceeding 2 m 

in width.

Central workings. The largest stope in the central 

workings is 60 m long, 6 m wide, and 5 m deep, and reveals 

several discontinuous gossans in sheared metasedimentary rocks 

at the west contact of a marble lens. Other shallower, rubblefilled stopes on strike to the north indicate a sulfide zone,

11
which possibly extends 250 m in that direction. The marble 

lens pinches about 50 m south of the large stope, but 

quartz-filled shears continue south to an inclined shaft 

that shows copper-stained quartz. The entire sulfide zone is 

thus about 450 m long. Parallel marble lenses that have 

sheared, gossanized contacts indicate possible sulfide 

metallization intermittently across a 100 m width in this area.

South workings. The south workings consist of marble 

lenses honeycombed with irregular shafts, trenches, open cuts, 

and adits along a distance of 250 m. These workings are on 

gossans developed where sulfides locally replace marble. Two 

small marble lenses and minor gossans were mapped south of the 

workings, but obvious zinc-copper metallization terminates in 

this area.

Gold-quartz veins

Gold-quartz veins were worked by the ancients in the 

extreme north and central parts of the mapped area (fig. 3). 

The quartz is milky- to medium-gray and contains very sparse 

cubic pyrite. Free gold was not seen. Veins average about 

0.3 m in width but range up to 1.5 m wide, and are discontinuous 

and lenticular along strike. The quartz veins were deposited 

in shears not associated with marble lenses.

Sampling of gossans and veins

Thirty-six chip and grab samples were taken across mineral 

gossans in place and from waste dumps. In addition, Kiilsgaard 

and Anderson sampled at 28 localities, but information 

of sample widths is lacking for some of their sampling (fig. 4).

12
All samples were assayed for gold, silver, copper, lead, and 

zinc by both atomic absorption and semi-quantitative 

spectrographic methods. Spectrographic analyses also gave

semi-quantitative data for 25 additional elements (table 1). 

This work was done in the Directorate General of Mineral Resources (DG.MR) laboratories in Jiddah.

Sulfide deposits. Forty-two chip samples from gossans 

gave the following average width and grades:

Width (meters) Au Ag Cu Pb Zn

grams/ton(g/t) g/t percent(pet) pet pet

0.56 2.22 19.40 0.77 0.25 5.33

Ranges of widths and grades are as follows:

Width (m) Au Ag Cu Pb Zn 

g/t g/t pet pet pet 

12.0-0.05 44.8-0.03 130.0-0.75 2.05-0.04 2.15-0.004 23.60-

0.03

A weighted average from six continuous chip samples across 

the south end of the central workings gave the following width 

and grade:

Width (m) Au Ag Cu Pb Zn

g/t g/t Pct pet pet

2.85 0.47 10.30 1.14 0.09 5.64

Gold-quartz veins. The average content of gold and silver 

in 11 chip and dump samples is as follows:

Au Ag

g/t g/t

2.31 0.58

Average vein width where sampled in place is 1.2 m. Ranges of

vein widths and content of gold and silver are as follows:

Width Cm) Au Ag

g/t g/t

1.5-0.3 10.64-Trace 1.16-0.004

13
Table 1. Semi-quantitative spectrographic analyses of samples from Farah Garan ancient mine. Lower limit of detec

Data in parts per million, except for Fe, Ti, Ca, and Mg, which are in percent. N, element was looked for but not 

number indicates an amount less than the number was found; symbol > preceding a number indicates an amount greate

Samples 96159 through 96171 were assayed at a time when detectability limits were higher than at present.

 Sample 

Number

106907

106908

106909

106910

106911

106912

106913

106914

106915

106916

106917

106918

106919

106920

106921

106922

106923

106924

106925

106926

106927

106928

106929

106930

106931

106932

106933

106934

106935

106936

106937

106938

106939

106940

106941

106942

96159

96160

96161

96162

96163

96164

96165

96166

96167

96168

96169

96170

96171

(.05) 

Fe%

3

0.7

0.5

0.7

0.5

0.7

0.3

0.7

1.5

0.5

3

7

3

7

7

7

7

3

7

10

5

5

10

5

5

5

10

7

5

1

1

7

>20

5

10

1.5

3

5

5

3

1.5

5

7

1.5

5

1.5

3

10

10

(.02) 

Mg%

1

0.3

0.02

0.02

0.02

0.02

0.02

0.02

0.7

0.15

3

3

0.5

5

3

3

5

0.5

1

1

0.3

3

1

0.07

0.1

0.03

0.07

0.15

0.1

0.15

0.05

1

1.5

10

7

10

3

0.7

0.7

0.7

5

0.5

0.7

3

0.5

0.05

3

1

1.5

(.05) 

Ca%

15

3

0.15

0.15

0.07

1.5

0.05

0.15

5

1.5

10

5

0.7

10

5

7

10

1.5

0.5

1

5

1

10

1.5

2

0.2

0.1

0.7

0.3

0.1

0.2

0.5

3

0.7

0.3

10

1

0.5

0.7

1.5

7

2

0.5

10

0.2

0.1

0.05

0.3

0.1

(.002) 

Ti%

0.15

0.005

0.01

0.03

0.005

0.007

0.005

0.03

0.07

0.007

0.1

0.01

0.3

0.005

0.03

0.01

0.03

0.05

0.1

0.5

0.03

0.1

0.03

0.01

0.02

0.01

0.03

0.01

0.01

0.03

0.05

0.03

0.07

0.003

0.08

0.007

0.1

0.5

0.07

0.01

0.003

0.5

0.2

0.01

0.03

0.003

0.15

0.005

0.1

(10) 

Mn

3000

200

20

100

70

70

50

200

300

200

3000

>5000

2000

>5000

5000

5000

3000

1000

1000

>5000

>5000

3000

5000

200

300

500

1000

3000

1500

1500

100

>5000

300

>5000

3000

>5000

1000

1000

1000

700

700

2000

700

3000

100

100

300

700

2000

(200) 

As

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

1000

1500

300

N

N

N

N

N

N

N

N

N

3000

N

N

200

300

200

<500

<500

<500

<500

<500

<500

700

<500

2000

1000

<500

1500

<500

(10) 

B

N

N

N

N

N

N

N

N

N

N

N

N

N

N

70

50

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

30

<50

<50

500

70

<50

<50

<50

<50

<50

<50

100

<50

<50

(20) 

Ba

300

<20

<20

20

<20

<20

<20

50

300

30

30

20

200

30

200

50

70

500

500

1500

1500

1500

70

<20

<20

<20

100

20

50

30

1500

500

70

<20

<20

20

200

300

50

<50

<50

1000

200

<50

3000

3000

5000

<50

150

(1) 

Be

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

(10) 

Bi

N

N

N

N

N

N

N

N

N

N

M

N

N

N

30

20

N

N

N

N

10

N

10

N

N

N

N

N

N

N

10

20

N

N

N

30

<20

<20

<20

20

<20

<20

<20

<20

50

<20

<20

150

<20

(20) 

Cd

N

N

N

N

N

N

N

N

N

N

N

N

N

200

100

200

500

N

N

150

100

N

20

N

N

N

N

N

70

N

70

30

30

50

50

200

<100

aOO

aOO

<100

<100

<100

aoo

aOO

aoo

aoo

aoo

aoo

aoo

(5) 

Co

5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

5

5

10

10

5

7

5

<5

10

10

<5

<5

<5

<5

5

<5

<5

<5

100

<5

10

<5

10

20

20

<20

<20 <20~

20

20

<20

<20

<20

<20

<20

30

(10) 

Cr

700

200

100

100

100

100

150

100

500

100

300

100

150

100

10

100

100

100

150

70

50

10

20

200

100

200

10

70

70

200

150

150

150

50

50

50

50

100

70

20

50

30

150

30

100

70

50

70

50

(20) 

La

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

(5) 

Mo

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

30

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

<5

70

<5

<5

<5

50

<10

<10

<10

<10

15

10

<10

50

<10

<10

20

^50

(20) 

Nb

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

<20

<20

<20

<20

<20

<20

<20

<20

<20

<20

<20

<20

<20

(5) 

Ni

70

<5

<5

5

<5

5

<5

5

30

5

5

<5

7

7

5

5

5

5

10

20

7

<5

<5

7

7

5

<5

<5

70

10

30

70

<5

10

5

20

20

30

20

<20

<20

50

50

30

50

30

50

70

50

(100) 

Sb

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

300

N

N

3000

300

N

<100

N

N

N

N

N

300

aoo

700

N

N

N

N

100

<200

<200

<200

<200

<200

300

<200

<200

1000

300

<200

500

<200

(5) 

Sc

30

<5

<5

<5

<5

<5

<5

<5

5

<5

<5

<5

15

<5

7

<5

7

15

20

15

<5

10

<5

<5

<5

<5

<5

<5

5

<5

<5

<5

5

< 5

< 5

< 5

15

20

10

ao

<10

20

30

<10

<10

<10

<10

<10

<10
Rock sampling for trace metal analysis

Four hundred rock chip samples were gathered for geochemical 

analyses along east-west lines across mineralized zones within 

an area of 1.1 by 0.5 km. Atomic absorption and semiquantitative spectrographic analyses were made on all samples. 

The two analytical methods gave similar results for Au, Ag, Cu, 

Pb, and Zn. Copper and zinc analyses were evaluated statistically, 

grouped into four frequency distributions, and plotted on figures 

5 and 6.

Generally, anomalous copper and zinc contents are confined 

to marble lenses and associated shear zones that have visible 

gossans (figs. 5, 6). Only a few scattered anomalous samples 

were found elsewhere. Although the metasedimentary and 

metavolcanic rocks are locally pyritized, they rarely contain 

anomalous amounts of copper or zinc. Likewise, the white 

quartz veins along marble lenses and along the trace of the 

Farah Garan fault are also barren.

Conclusions and recommendations

Zinc-copper-lead-gold-silver metallization is distributed 

intermittently throughout an area of 1.1 by 0.5 km at Farah 

Garan. Epigenetic sulfide minerals, accompanied by gold and 

silver, were deposited along sheared contacts of marble lenses 

and partly replaced the marbles. In addition, gold was 

deposited in quartz veins perhaps independently and in more 

restricted areas.

It is recommended that both types of metallization be 

tested by four diamond drill holes (figs. 3, 7).

15
Drill hole FG-1 is planned to intersect the downward 

projection of gossans exposed in the large central workings. 

In addition the hole will explore at depth a zone 100 m wide 

where other gossans were mapped at contacts with marble lenses; 

samples of these rocks contain anomalous amounts of zinc and 

copper, and geophysical studies found a 400 millivolt, negative, 

self-potential anomaly. Proposed length of the drill hole is 

200 m.

FG-2 is planned to intersect the downward projection of 

copper-zinc metallization found at the south workings and also 

to explore the continuation at depth of other gossans associated 

with marble lenses across a zone 100 m wide. The south 

extension of the self-potential anomaly would also be explored. 

In addition, this drill hole may provide information concerning 

the shape and plunge of folded marble lenses and their effect 

on sulfide deposition. Its proposed depth is 200 m.

FG-3 is laid out to intersect drag-folded marble lenses 

locally replaced by sulfide. In addition, it would explore the 

projection of other thin marble lenses and a gold-quartz vein 

worked by the ancients. Geophysical studies outlined a 

negative self-potential anomaly trending along the hanging 

wall of the Farah Garan fault. The drill hole would intersect 

this anomalous zone and penetrate the Farah Garan fault. If 

continued to 350-400 m depth, it would also explore 

metallization projected 250 m below the surface at the central 

workings.

16
Zone anomalous in Zn and Cu

METERS r

2100

2000-

E w

METERS

2100-

Zones anomalous in Zn and Cu

N70°W

2000

7 METERS

2100

2000-

N7Q°W 

METERSp

2100-

2000-

1900

Zones anomalous in Zn and Cu (projected)

Farah Garan fault 

quartz vein

EXPLANATIO

ANDESITE Massive, weakly foliated. Contai

Metamorphosed to greenschist facies

METAVOLCANIC ROCKS - Predominantly o

ad APLITE DIKES - Fine-grained

quartz crystals as much as 3 mm in diameter

METASEDIMENTARY ROCKS - Includes gra

schist. Some non-metasedimentary rocks

METASEDIMENTARY MARBLE - Fine-grain

color

MAJOR FAULT 

POSSIBLE SULFIDES 

QUARTZ VEINS

50 100n

Figure 7. Vertical sections along proposed drill hole FG 1,2,3, and 4, Farah Garan anc
FG-4 is planned to intersect the downward projection of 

metallization found at the north workings and also to further 

test the self-potential anomaly trending parallel to the 

hanging wall of the Farah Garan fault. It would also explore 

the northerly projection of metallization found along sheared 

contacts of marble lenses at the central workings. The hole 

is estimated to be 250 m in length.

The four proposed drill holes would aggregate about 

1050 m in length and would adequately test metallization at 

depth. Depending upon results, the drilling program could be 

expanded if desirable.

AL ASHYAB 

Introduction

Al Ashyab was recognized as having possible mineral 

potential by R.E. Anderson during his mapping of the Mayza 

quadrangle. An inspection of the area was later made by 

T.H. Kiilsgaard and Anderson. The area of interest is at 

lat 17°30'13"N. and long 43°37 I 11"E. and is accessible by 

4-wheel drive vehicle via a Bedouin truck-trail leading from 

the Najran-Khamis Mushayt highway (fig. 2).

Work in the area by the author during November 1975, and 

February 1976, assisted by A.M. Helaby, consisted of laying 

out a base line, rock chip sampling on a 25 and 50 m grid, and 

geologic mapping on an aerial photographic base at a scale of 

1:5000.

Al Ashyab is named from a prominent north-south ridge rising 

120 m from the valley floor. There are no ancient workings in

the area.

18
Geology

The oldest rocks at Al Ashyab are interbedded metasedimentary and metavolcanic rocks of the Jiddah group 

(figs. 2, 8). Metasedimentary rocks are sparse and consist of 

shaly, calcareous rocks in lenses as much as 4 m wide interlayered 

with silicic to intermediate tuffs and flows that contain quartz 

crystals to 3 mm in diameter and with dark-green mafic volcanics^ 

which in places contain feldspar phenocrysts. All rocks have 

been metamorphosed to the greenschist or amphibolite facies.

In thin section the intermediate metavolcanic rocks are 

quartz-sericite schist and the mafic metavolcanics are 

chlorite-epidote-quartz schist that contain finely scattered 

ilmenite. The shaly-calcareous metasedimentary rocks display 

fluffy chlorite on fresh surfaces, and in thin section are finegrained chlorite-epidote-quartz schist containing a little 

coarse-grained ilmenite. The rocks are similar to those mapped 

at Farah Garan, 4 km north. They occupy the valley floors at 

Al Ashyab.

Metasedimentary and metavolcanic rocks of the Jiddah group 

were syntectonically intruded by quartz porphyry in thin sills 

and probably are interlayered with flows and tuffs of the same 

rocks. The quartz porphyry is part of a large mass that extends 

south to Kutam and well north of Farah Garan (fig. 2). It 

contains blue-gray quartz phenocrysts as much as 1 cm in 

diameter in a fine-grained groundmass of garnet-bearing 

sericite~quartz-chlorite schist. Evidence for intrusive origin 

consists of dikes and thin sills of quartz porphyry within the

19
Hi

EXPLANATION

ALLUVIUM

QUARTZ PORPHYRY - Siliceous to intermediate rocks. Gametiferous, strongly 

foliated. Blue quartz phenocrysts as much as 1 cm in diameter

MET A VOLCANIC ROCKS - Flows or tuffs of r-afic composition

META VOLCANIC ROCKS - Flows or tuffs of intennediate composition. 

Non-layered. Quartz crystals as much as 3 mm in diameter

METASEDIMENTARY ROCKS - Mostly calcareous, strongly chloritized 

SILICIFIED QUARTZ PORPHYRY

QUARTZ VEIN

CONTACT - Dashed where location is uncertain 

FAULT SHOWING DIP 

STRIKE AND DIP OF CI.EAVAGE 

A ROCK CAIRN FOR GEOCHEMIC ALAND GEOPHYSICAL GRID

Figure 8. Geologic map of Al Ashyab area.

20
same rock type. Some outcrops show evidence of.extrusive 

origin, however, and quartz porphyry appears to lie in 

conformable contact with layered metavolcanic rocks. The 

quartz porphyry occupies the high valley walls and the central 

ridge within the mapped area.

Structure

All rocks were isoclinally folded and sheared. Layering 

and strong foliation strike north and dip steeply west. 

Regional shears extend north and south outside of the mapped 

area and diverge around a large silicified mass of quartz 

porphyry at Jabal Al Ashyab, indicating that at least part of 

the shearing is post-silicification.

Some of the silicified rocks are sheared, although little 

horizontal displacement has taken place. In the south-central 

part of the mapped area, a major north-south shear zone has 

been intruded by quartz porphyry, indicating that some of the 

shearing is pre-quartz porphyry, and was later silicified. 

Consequently, the regional shears are thought to have been 

active over a long time period.

Complimentary east-trending faults of little displacement 

are reflected by drainage systems. They are younger than the 

northerly shearing and in places are intruded by fine-grained 

mafic dikes.

Alteration

In the northern part of the mapped area, quartz porphyry 

has been almost totally silicified along the general northerly 

shear direction for a distance of approximately 600 m, forming

21
a high, narrow ridge (fig. 8). Quartz phenocrysts are visible 

within the silicified zone, indicating that the original rock 

was quartz porphyry. In thin section the rock exhibits granular 

quartz and relicts of muscovite and epidote from an earlier 

generation of alteration minerals. Very fine pyrite is 

sparsely disseminated throughout the quartz.

A zone of quartz-sericite alteration extends out from the 

silicified mass at least 200 m to the west and north, but only 

a few meters to the east and south. Limits of the quartz-sericite 

mass are not shown on figure 8 because of the difficulty in 

mapping gradational boundaries. In thin section the rock is 

fine-grained quartz-sericite-chlorite schist that contains very 

fine-grained pyrite crosscutting foliation.

Metallization

Two types of metallization were recognized in the

south^-central part of the Al Ashyab area: prominent pyritization 

within metavolcanic rocks and quartz veins containing minute 

copper stains.

Pyritized metavolcanics are best exposed in the wadi 

bottoms (fig. 8). Within these areas, disseminated cubic pyrite 

as much as 0.5 cm across is weathered to hematite. The greatest 

concentrations of pyrite appear to be along major shear zones, 

especially along the north-northeast striking shear in the 

southwest part of the area. Drainages crosscutting this zone 

display intensely pyritized metavolcanic rocks. One chips sample from this area contained 0.26 percent zinc. No other indication of metallization was seen.

22
A north-striking quartz-carbonate vein was mapped in the 

south-central part of the area. The vein is as much as 3 m 

wide and consists mainly of milky quartz and lesser brownweathering calcite. The quartz contains very sparse cubic 

pyrite, and vein selvages show very weak copper staining. 

Chip samples from the vein indicate low concentrations of all 

metals.

Rock sampling for trace metal analysis

Rock chip samples were taken at 556 sites on a grid whose 

spacing was 25 m in the south and 50 m in the north and that 

covered an area of 1 km by 0.5 km (figs. 9, 10). Samples were 

analyzed for gold, silver, copper, lead, and zinc by both atomic 

absorption and semi-quantitative methods. Analytical data for 

copper and zinc were grouped statistically and their frequency 

distribution determined.

Copper

Copper content below 41 ppm is considered to be background, 

and amounts greater than 325 ppm are considered to be anomalous.

The quartz porphyry, including the silicified ridge, is 

generally low in copper. A poorly defined, weakly anomalous 

zone coincides with pyritized metavolcanics south and east of 

the silicified ridge, but anomalous values are scattered. A 

pyritized shear zone sampled at the extreme south contains no 

anomalous copper.

Zinc

Zinc content of less than 49 ppm is considered to be 

background, and amounts greater than 480 ppm are anomalous.

23
4337"M"

17 38'13"

x x x 

 x x o 

 

x * xx O<

^ X X X

. x. °

 * x x x

x 

x x0 x 

 x x 

x ax

 > O X X >

A x °

 x\x OO o >

)* V

Sfe 0 X 0 

 xV x x x

O X >

 Q. x

x v"'-^o"*-^o

 x*

 X 

^x-f-^*~*'^-*-~V

X X

 x 

EXPLANATION

<41 PARTS PER MILLION 

* (ppm) - Background

X 41 -125 ppm

O 126- 3 25 ppm

O >325 ppm

A ROCK CAIRN

___ - " - * 

^*~-~~~~^

0

1

 X w 

 x 

 X A x 

0,0

 

> »xx x

, xo» o x x x x

0

 XXxx^ X O x X x O x

 xO x xO x x«x»

 xo» 0 °* x 

X XX

QXXX»X X

Oxxoxx xOx»O»

 xxxOO Oxxo*/^

 OxOx xx^ O» x x 

x x x J 

xxx»»o xx ..-/» 

x x ( 

XOX» ^ 

x x o x x *>

i x OOO* xxx »PX**

^. x x O x \

0Vxx. o xX X *

xTo O O OOfc x»

,^ 0 o ^^5S-°

x\ \ \

O^QAO o x \»

\ X O *

O ^X 

o a o o x x

X

5_ ^^- 

300m

1 1 1

 

 

X O

x 0

 

 o

/x

 

 

 

 

^r

 /

 -xs"" 

\I *

V

X 

* ^x'^D0 *^/^

/o

s

Figure 9. Copper content of rock samples, AI Ashyab.

24
4337'11"

17 38'13"

V

O««xx« x ****

. '

V * ? 

% xV * [

 X X 0 0 O

X J

 \ X 4

4 

O ^ X X X >

x. x 

X * *

X ^ X X X

/ 0 C

*-xV.

*^1K

X O

00 x 0 

,.__/^x~ xV """""bo ° *

X

x x x

d/\r FVPI L,f\Ftt\ ANATION 1 Iv/IN

<49 PARTS PER MILLION

(ppm) - Background

X 49- 116 ppm

O 11 7- 480 ppm

O >480ppm

A ROCK CAIRN

^ "" ~~ ----t.

^ """ "

0 

1

 x x x x

 O X X

 

v« v v * * * ^VW J\ ^\ ^ ^ ^

 X A O» X XX 

0,0

 OX X OXXX««

>t, .«0*x 

:» * QX * *XXOO

X

. *OX X X« x 0 .OX 0 0 « X

O

oo«

« ««X x X x * X

V NX V <^ V V w ^». V y 

A. W XAV^ XAX C\ X A w

y v O X v v /"

 oooo «*«oO x x > ' x

 xOOOX X.' 

 X X xg X«X>«**

x x x x o y^

ooo*°o oo >< ».

00 o t

OQOX o «\ x x 

x O x x x/: x

JsDxOo 0 000,U««x« 

o\> o xx - xx /" * X

\0 X O O X ..' 

.... VooOO Oo A^S.O x /

°\ \ X .. ^

x C^P x 0 0 0 x \- r~

x'^ x x ° X ° *W°

o o o x \x x x "X^ 

\ /^

7/ 

x y

^^~

-! ____ _____^^^ 

300m 

1

Figure 10. Zinc content of rock samples, Al Ashyab.

25
Most of the quartz porphyry, including the silicified 

ridge, does not contain anomalous zinc. However, anomalous 

zinc samples are more numerous and more closely grouped than 

are those anomalous in copper. Samples with higher zinc 

contents are concentrated within the pyritized shear zone south 

of the ridge, as are those of high copper content.

Other anomalous samples are widely scattered and do not 

appear to be significant.

Conclusions and recommendations

Al Ashyab is 4 km south of Farah Garan and similar rocks 

extend through the two areas, except that the marble lenses 

mapped at Farah Garan are less common at Al Ashyab. Folds, 

faults, and quartz veins strike north and dip steeply west in 

both areas. Identical metavolcanic rocks are altered to 

quartz-sericite-chlorite schist and are pyritized within shear 

zones at both places. Strongly silicified quartz porphyry 

occurs only at Al Ashyab.

At Farah Garan, visible copper- and zinc-bearing minerals 

are confined to sheared, gossanized contacts with marble lenses, 

and geochemical studies confirm this relationship. Pyritized 

quartz-sericite alteration zones contain no anomalous amounts 

of copper or zinc. At Al Ashyab, the metavolcanic rocks 

affected by quartz-sericite-pyrite alteration are strongly 

anomalous in copper and zinc in closely confined areas, whereas 

weakly anomalous zones are broader and poorly defined. The 

silicified quartz porphyry is not anomalous in either metal.

26
Metallization in both areas is believed to be epigenetic 

and related to shears within metavolcanic rocks but at Al 

Ashyab, visible zinc-copper metallization is lacking, and the 

erratically spaced, moderately anomalous mineralized zones 

encountered in geochemical studies suggest that economic 

mineral deposits probably are not present at depth.

No further work is recommended for the area.

AL ASHARFAT 

Introduction

The Al Asharfat ancient workings are at lat 17 0 37'00"N., 

long 43°39'00"E. and are accessible via a Bedouin truck-trail 

(fig. 2). They consist of 10 shallow workings along a distance 

of approximately 1.5 km. The largest working is 50 m long and 

8 m deep at the deepest part. A sorting area with a few 

grinding stones is adjacent to the largest workings. Most of 

the workings are partly filled with mine waste.

The author, assisted by A.M. Helaby, sampled veins and 

dumps and mapped the area using aerial photographs during 

February 1976.

Geology and structure

Rocks of the Jiddah group here are isoclinally folded, 

faulted, and strongly foliated, and are intruded by two 

syntectonic phases of quartz diorite. All rocks are cut by 

faults which strike N.10°E. and dip steeply west. The latest 

faults, which strike N.50°W., are filled by fine-grained 

mafic dikes (fig. 11).

27
43 39'

to

00

Sample 

number

109200

109201

109899

109910

109911

109912 

109913

109914

109915

109916

109917

109918

109945

109946

109948

109949

109983

109984

Description

Quartz, with iron oxid

cubic pyrite

Quartz, with iron oxid

cubic pyrite

Quartz, clear, white

Pillar in workings--f a

Schist, pyritic, seric

Minor quartz, iron oxi

On shear, siliceous, 

stained

Shear, silicified

Shear, weakly silicifi

Sparse iron oxide

Weak copper stain in f

Quartz with manganese

oxide

Dump, selected, silice

 n «

Shear in fresh quartz

diorite

Quartz with manganese o

Shear, sparse iron oxi

E

md I MAFIC DIKES - Fine-gr

qdc QUARTZ DIORITE - Sy

qdm QUARTZ DIORITE - S

jmv

METAVOLCANIC AND 

MET A VOLCANIC ROCK

METASEDIMENTARY R

cherty conglomerate, 

CONTACT - Dashed wh

FAULT SHOWING DIP 

/ STRIKE AND DIP OF FO

<H!37r^> ANCIENT WORKINGS 

- = = = = MOTOR VEHICLE TRAI

109200 SAMPLE LOCALFTY AN

Figure 11. Geologic and sample map of Al Asharfat.
The intrusive rocks are massive and less foliated than the 

enclosing metavolcanics. Both phases of quartz diorite contain 

subhedral, blue-gray quartz intergrown with plagioclase, 

amphibole, fine-grained biotite, and scattered ilmenite. The 

later phase, which intrudes the earlier, is petrographically 

similar but coarser grained.

Metallization

Trenches along the N.10°E. fault system expose narrow 

fractures along which wall rocks are silicified and locally 

stained by hematite derived from cubic pyrite. The width of 

silicified wall rock does not exceed 0.5 m. In places the 

fractures contain narrow stringers of milky pyritic quartz. 

Dump material from a trench at the south end of the area 

studied contained minor copper stain but none was seen in place. 

The silicified wall rock apparently was the material sought by 

ancient miners and probably contains free gold, but none was 

seen by the author.

Assay results

Assay results and sample locations are shown on figure 11. 

Silicified fault zones exposed in workings were sampled at 

18 localities and two grab samples were gathered from dumps.

The highest gold assay was 38.8 grams per ton, in a sample 

across 0.05 m of silicified, faulted material in the deepest 

workings. A sample of selected siliceous rock from the dump 

of the same workings contained 22.0 grams gold per ton. Samples 

cut across narrow silicified fault zones in other workings

29
assayed as much as 6.86 grams gold per ton. No significant 

amounts of silver, copper, lead, or zinc were found in the 

samples.

Conclusions and recommendations

Ancient miners worked gold deposits to shallow depths in 

the Al Asharfat region, where gold occurs in narrow, silicified 

zones bordering faults. Potential gold reserves of the area are 

small and no further study is recommended.

LEJOURAH 

Introduction

Lejourah is accessible by motor vehicle via a Bedouin 

truck trail that passes through the village of Talhah and 

joins the Khamis Mushayt-Najran highway nearby (fig. 2). Five 

ancient workings within a small area are at lat 17 0 42'6"N., 

long 43°37 I 28"E. in relatively flat terrain. They are filled 

with mine waste, and no bedrock is exposed in them. A great 

number of grinding stones and sorting piles are near the workings,

The area was mapped in February 1976 on color photographs 

at a scale of approximately 1:12,600, and dumps, sorting piles, 

and a few unmined quartz veins were sampled.

Geology

Volcanic rocks of the Jiddah group, principally interlayered 

basalt and andesite, are isoclinally folded, sheared, strongly 

foliated, and metamorphosed to greenschist facies in the mine 

area (fig. 12). Foliation and layering strike N.45°E. and dip 

steeply northwest. Later basalt flows are massive, weakly 

foliated, and cut by quartz veinlets that contain associated

30
43 37'28"

qm

EXPLANATION

QUARTZ MONZONITE Pale red to reddish-gray. Mesocratic to leucocratic. 

Weak flow foliation locally

OS BASALT - Fine-grained, weakly foliated

; JIDDAH GROUP - Layered mafic volcanic locks metamorphosed to greenschist tacies

CONTACT 

REGIONAL FAULT

STRIKE AND DIP 

OF FOLIATION

QUARTZ VEIN 

ANCibNT WORKINGS

ba grinding, stones *~

Sample 

number

114023

114024

114025

114026

114027

114028

114029

114030

114032

114033

114034

114035

114036

114038

114039

114040

114041

114042

114043

Description

Quartz, white, with iron stain;

from dump; no vein in place

visible

As above

As above

Quartz veinlet-5 cm wide,

adjacent to mafic dike

Quartz with iron oxide

Quartz with iron oxide

Quartz with iron oxide

Quartz vein in augite porphyry

about 5 cm wide

Quartz vein, irregular, adjacent to marble lens

Quartz vein adjacent to 1140'32

Quartz vein, width as ouch as

0.75 m

Quartz vein on major shear

Quartz vein on major shear

Quartz vein within basalt

Weak shear

QUartz monzonite on major

fault

Quartz vein in basalt

Quartz vein in raetaroorphic

rocks

Quartz vein in basalt

Au 

g/ton

12.00

10.00

0.90

--

3.88

6.60

13.40

0.31

6.60

 

 -

0.10

' 0.10

0.08

0.08

0.04

0.04

Ag 

g/ton

0.4

0.8

0.2

0.1

0.5

1.3

0.8

0.8

0.8

0.1

0.1

0.1

0.1

iO.l

0.5

0.1

 0.1

--

0.4

Cu 

ppm

15

42

9

12

25

33

14

6

10

5

6

9

15

9

55

5

7

8

253

Zn

ppm

8

44

6

7

26

16

8

5

14

5

3

9

10

43

20

8

13

37

26

300 

I

Figure 12. Geologic and sample map of Lejourah.

31
ilmenite. The youngest rock is a pale-pink to gray, mediumto coarse-grained quartz monzonite pluton that intrudes the 

basalt to the northwest.

Structure and metallization

Regional faults that strike slightly north of east and 

dip steeply north transect all rocks. Ancient workings are 

within basalt along the trace of fault zones and on the contact 

between basalt and metavolcanic rocks. The open cuts are small, 

and the orebodies worked apparently had short strike lengths. 

Piles of sorted quartz on waste dumps must represent the 

material the ancients were mining. The quartz is milky and iron 

stained, and contains sparsely scattered free gold in grains as 

much as 0.5 mm across. The gold occurs typically in small 

clusters of chloritic material. Cubic pyrite is also disseminated 

sparsely within the quartz.

Unmined quartz veins deposited as fracture fillings in 

basalt were mapped about 250 m southwest of the workings. The 

veins average 0.4 m in width and have strike lengths of only a 

few meters.

Assay results

Sample locations, descriptions, and analyses are shown on 

figure 12. Among vein samples only sample 114032, cut 

across an irregular quartz vein, contained gold in significant 

amounts, 6.60 grams per ton. Samples from other quartz veins 

and faulted zones contained only negligible gold. Of six 

samples collected from sorting piles, the richest contained 

13.40 grams per ton and the poorest 0.90 grams per ton. The

32
average grade of these six samples is 7.80 grams gold per ton. 

No other metals were found in significant amounts. 

Conclusions and recommendations

Ancient miners at Lejourah worked gold-bearing veins in 

small open cuts within an area 150 by 500 m. Quartz from 

sorting piles near the open cuts bears visible free gold. 

The numerous grinding stones confined to a small area adjacent 

to the ancient workings indicate that the gold veins were 

intensively worked.

Geologic mapping and sampling of the ancient mine sites 

indicate that the possibility of finding extensions of the 

gold-bearing quartz veins is remote. Even though free gold 

was found in quartz on dumps, and significant gold was found in 

sampling, the potential tonnage of ore is too small to merit 

further consideration.

HEMAIR 

Introduction

The Hemair ancient mining site is on the steep valley walls 

of Wadi Kholan at lat 17 0 40'00"N., long 43°39 I 00"E., where a 

line of workings trends nearly due south and extends 

intermittently more than 500 m. The workings are very narrow, 

averaging less than a meter in width, but some are extremely 

deep where ancient miners evidently followed ore shoots. Mine 

dumps have been completely eroded away.

The nearest approach to Hemair via land vehicle is from 

Al Ashyab, about 5 km southwest (fig. 2). The area was reached 

by helicopter in February 1976, at which time mineral outcrops

were mapped by use of Brunton and tape and were sampled.

33
65 ^

fold noses?

, work ings interconnected?

white quartz on sheared contact 

of calcareous lens

/

,workings 1m deep

'114013 

,114014

eo .^workings about 0.5m wide, 

very sparse copper stain

75w" 114015

Jnr stope about 4m deep.

on quartz vein?

stope 4-5 m deep, average 0.75m wide-

/ M//N14016

deep stope, interconnecting?^

/ ^-114017 

ffir~\ 14018

deep stope average 0.75m wide

/ open cut 

very deep stope average 0.75m wide

interconnects with stope to north 

graphitic schist65

\ '

S intensely folded; isolated 

blocks of marble

EXPLANATION 

MARBLE 

QUARTZ VEIN 

FAULT SHOWING DIP 

STRIKE AND DIP OF FOLIATION 

 0- STRIKE OF VERTICAL FOLIATION 

<SS ANCIENT WORKINGS 

114019 SAMPLE LOCALITY AND NUMBER

65

o

c

sparse copper stain on walls . 

of trench 5-6m deep /

74*XXY^ /shallow workings on shear; / 

sparse copper stain on walls '

114008 /

gray-green sericite schist with 

abundant fine-grained pyrite

mine, very deep

114011-& / °

w_ / __

50 METERS

Sample

number

114005

114006

114007

114008

114009

114010

114011

114012*

114013

114014

114015

114016

114017

114018

114019

114020

114021

114022

Width

met

0.

6.

1.

0.

0.

1.

2.

0.

1.

0.

0.

0.

0.

0.

0.

0.

0.

0.

:ers

.45

.00

.00

,50

.50

00

00

.10

.50

.50

,05

,10

45

,45

,75

,15

.45

.30

Au

a/

1.

0.

0.

0.

42.

0.

0.

0.

0.

0.

1.

0.

3.

2.

6.

0.

3.

0.

>_t

.00

,17

.17

.17

.40

,32

.17

.17

.17

.08

.40

.20

.20

.50

.60

.50

.88

.04

Ag

a/

6.

1.

0.

9.

160.

11.

1.

0.

1.

1.

31.

14.

70.

16.

30.

8.

8.

3.

/t

.20

.30

.70

.80

.00

.10

.70

.40

.00

.20

.80

.80

.00

.50

.00

.50

.00

.20

Cu

percent

0.34

0.005

0.01

0.10

1.42

2.65

0.04

0.004

0.009

0.007

0.32

0.73

2.35

0.19

1.25

0.03

0.18

0.02

Pb

pei

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0,

0.

2.

0.

0.

0.

0,

0

rcent

.90

.003

.002

.40

,99

.24

.02

.001

.or

.003

.70

.14

.00

.48

.78

.03

.41

.14

Zn

pei

3.

0.

0.

0.

1.

0.

0.

0.

0.

0.

0.

0.

1,

0.

0.

0.

0,

0

rcent

.75

.02

,004

.08

.85

.60

,09

.001

.004

.009

,51

.14

.50

.36

.94

.09

.20

.09

* Not shown on map

Figure 13. Sketch geologic and sample map of Hemair.

34
Geology

Metasedimentary and metavolcanic rocks of intermediate 

composition and assigned to the Jiddah group were isoclinally 

folded, faulted, and metamorphosed to greenschist facies within 

the Hemair region. Metasedimentary rocks consist of fine-grained, 

nonbedded, brown-weathering marble, graphitic schist, and 

calcareous siltstone. These rocks are interbedded with massive 

metavolcanics containing crystals of clear quartz as much as 

3 mm in diameter. The metavolcanics are part of the same rock 

unit as that mapped at Farah Garan and Al Ashyab. 

Structure, metallization, and alteration

Foliation and layering of the metasedimentary rocks strike 

north and dip steeply west. The rocks, particularly the 

marble-graphite contacts, were sheared by a regional fault along 

bedding planes. The shear zone was then weakly silicified and 

the enclosing metavolcanic rocks were pyritized. Copper, lead, 

and zinc sulfides with accompanying gold and silver were then 

deposited. Milky quartz was later deposited within the main 

shear zone and along subordinate shears. Slight postsilicification movement along the major fault weakly brecciated 

the silicified zones (fig. 13).

Sheared, silicified, and metallized rock along the fault 

averages less than one meter in width and is absent in the center 

of the mapped area where the fault is expressed only by thin 

fractures. Gossans are best developed on sheared contacts of 

marble, where they are sparsely copper stained. Silicification 

is stronger at the south end of the area, where black, flinty,

35
fine-grained, siliceous material may be silicified graphitic 

rock.

Assay results

Eighteen continuous chip samples were cut across the 

metallized fault and their positions are indicated on figure 13. 

Analyses of gold, silver, copper, lead, and zinc indicate that 

metal is erratically distributed along the fault zone. Ranges 

of metal contents and sample widths are as follows:

Width (m) Au Ag Cu Pb Zn 

g/t g/t pet pet pet 

5.0-0.05 42.40-Trace 70.00-0.40 2.65-0.004 2.00-0.001 3.75-

0.001

Average width and assays are as follows:

Width (m) Au Ag Cu Pb Zn

g/t g/t pet pet pet

0.82 3.50 20.9 0.54 0.40 0.57

Conclusions and recommendations

Rock formations, structure, content of sulfides and 

precious metals , and ore contacts at the Hemair deposit are 

in many respects similar to those of Farah Garan, 3 km northwest, 

and these deposits are probably genetically related. The Hemair 

deposits themselves are small and merit no further investigation, 

but the general area contains rocks and structures favorable for 

ore deposition and warrants additional study.

PRELIMINARY STUDIES OF THE HEMAIR-AL ASHARFAT REGION

Introduction

During January and February of 1976 the author mapped and 

sampled by reconnaissance methods a belt of metasediments 

extending south from Hemair, as well as shear zones parallel 

to the contact between quartz porphyry and mafic metavolcanics

36
(fig. 2). Several small ancient workings were found and 

examined. Mapping was done on low-level, color aerial 

photographs.

The Hemair-Ethel region 

Geology

A belt of metasedimentary rocks of the Jiddah group extends 

south through Hemair and passes under Wajid Sandstone near the 

Ethel mine (fig. 14). The rocks include black to brown, massive, 

fine-grained marble, cherty conglomerate, graywacke, calcareous 

mudstone, and graphitic sediments. The sedimentary rocks are 

interbedded with layered quartz crystal tuffs, massive 

unlayered quartz crystal metavolcanic lavas, and metavolcanic 

flow breccias. Many of the metasedimentary rocks contain 

graphite and associated cubic pyrite. The metasediments strike 

north and dip steeply west. They are in contact with 

thick-bedded andesitic to basaltic metavolcanics on the east and 

with mafic metavolcanic flows and interbedded thin metasedimentary 

rocks on the west.

Metallization and alteration

Quartz crystal metavolcanics and calcareous metasediments 

are pyritized, sericitized, and weakly silicified in broad zones 

along the belt of metasedimentary rocks. Fine-grained cubic 

pyrite is heavily disseminated in some zones and is probably 

not genetically related to the more coarse-grained pyrite 

associated with graphitic rocks. The pyrite is generally found 

in strongly sheared zones. Weathered pyritized rocks are 

unevenly stained by iron oxide.

37
A small ancient workings named Degarth is adjacent to a 

marble lens about 1 km east of Al Asharfat (fig. 14). The 

open cut is 9 m long, 4 m wide and 4 m deep and is on sheared 

and pyritized metavolcanic rock containing copper carbonates 

and copper pitch. Pyritization extends at least 1 km north 

of the open cut, and within the pyritized rock, sparse copper 

carbonates were noted along thin fractures and small amounts 

of copper-stained float rock were found in wadis. Strongly 

pyritized rocks extend at least 1 km south of Degarth, and 

small amounts of chalcopyrite were found in sparsely copper 

stained, calcareous rock. Farther south, rocks are pyritized 

locally but no copper minerals were found.

Rock sampling for trace metal analysis

Preliminary rock chip sampling for geochemical study was 

done at 35 locations along a length of about 6 km of the belt 

of metasedimentary rocks. Locations were chosen to represent 

all rock types; however, pyritized shear zones were especially 

tested. Sample localities and their respective descriptions 

and grades are shown on figure 14.

Three samples anomalous in copper and zinc were taken from 

sites where copper minerals were locally visible. Samples from 

north of Degarth, where copper minerals also are locally visible, 

contained copper and zinc in amounts just above background. 

Samples from the region south of Degarth contained moderately 

anomalous amounts of copper and zinc in two samples each.

38
Unnamed workings

At lat 17°36 I 15"N. / long 43°40'20"E. (fig. 14), veins 

and veinlets of milky quartz in mafic metavolcanic rocks strike 

north, dip steeply west, and are about 5 m wide. Shallow ancient 

workings on the east contact of the quartz veins are about 

200 m apart, but quartz is discontinuous between the two workings

Three samples taken across the quartz vein in workings 

contained no significant amounts of metals.

Ethel workings

Massive veins and narrow stringers of milky quartz were 

worked in shallow open cuts by ancient miners at lat 17 0 33'50"N., 

long 43°40 I 10"E. (fig. 14). The vein system strikes north, dips 

steeply west, and ranges from massive quartz as much as 4 m wide 

to a series of narrow stringers along a strike distance of about 

200 m. The quartz is unevenly stained by iron oxides derived 

from pyrite. Workings are along selvages of massive quartz 

within swarms of quartz veinlets.

Assay results

Six samples were cut across massive quartz and quartz 

veins within workings. One sample from a selvage of a massive 

quartz vein contained 1.64 grams of gold per ton. The remaining 

samples contained negligible amounts of valuable metals. 

Conclusions and recommendations

Sparsely copper-stained, pyritized shear zones within 

interbedded metavolcanic and metasedimentary rocks occur in an 

area about 3 km south of the Hemair deposit. The intervening 

area has not been studied. It is recommended that more detailed

39
studies be made of the metasedimentary and interbedded metavolcanic rocks and of their genetic relation to sulfide deposits 

in the area. The small quartz veins merit no further study.

The East Al Ashyab area 

Geology

About 1.5 km southeast of Al Ashyab at lat 17°38 I 00"N., 

long 43°38 I 00"E., a series of lensoidal, weakly folded quartz 

veins strike north and dip steeply west. They are within 

strongly foliated mafic metavolcanic rocks of the Jiddah group 

near the contact with quartz porphyry (fig. 14). The entire 

vein swarm is about 0.5 km wide by 2 km long, but the veins are 

discontinuous along strike. The quartz veins locally contain 

specular hematite, in places contain sparse copper staining in 

vein selvages, and are barren of sulfides. Strongly sheared 

metavolcanic rocks are pyritized in parallel zones. Bands of 

magnetite as much as 0.1 m wide and a few meters long are 

parallel to foliation within metavolcanics near the contact with 

quartz porphyry at a point 0.5 km south of the vein swarm. 

About 2 km farther south, a small, deep ancient working on the 

contact between metavolcanics and quartz porphyry exposes a blue 

to gray quartz vein as much as 0.45 m wide. The vein contains 

sparse crystalline pyrite and a little gold.

Assay results

Quartz veins were sampled thoroughly to test for precious 

metal content. Assays indicate no significant amounts of either 

gold or silver in the quartz vein swarm. Some samples of 

pyritized sericite schist in the same area have high contents

40
of copper and zinc (fig. 14). Two samples of quartz vein from 

ancient workings contained 14.0 grams of gold and 1.3 grams of 

silver per ton, and 22.0 grams of gold and 1.0 gram of silver 

per ton, respectively.

Conclusions and recommendations

The area studied is a very small part of an extensive 

contact zone between mafic metavolcanic rocks of the Jiddah 

group and a large body of quartz porphyry. Although many of 

the sampling data are negative, positive factors include:

1. Sparse copper staining in vein selvages.

2. Scattered anomalous copper-zinc contents in samples 

from pyritized shear zones.

3. Magnetite in thin bands along foliation.

4. Significant gold analyses in quartz from ancient 

workings.

The large quartz porphyry mass was interpreted by Anderson 

as being intrusive into rocks of the Jiddah group (Anderson, in 

prep.), but the present author believes that much of it is 

interlayered with the Jiddah group and is extrusive, in part 

perhaps tuff. It is obvious that the origin of the quartz 

porphyry is important in respect to the genesis of sulfide 

deposits in the area and to a logical approach to exploring for 

them. Therefore, it is recommended that this and other contact 

zones of quartz porphyry be studied in detail in order to clarify 

contact relationships if possible; gathering of further data on 

metallization could be done concurrently with such a study.

41

RECONNAISSANCE GEOPHYSICAL EXPLORATION

by 

H. Richard Blank

Introduction

In late 1975 and early 1976 a limited program of 

geophysical work was carried out at Al Ashyab and Farah 

Garan by the combined USGS/DGMR Geophysics section, in 

support of base metal exploration by C.W. Smith. The work 

consisted of approximately 35.2 line-km of self-potential (SP) 

surveys and 9.0 line-km of Turam electromagnetic surveys. 

Altogether about one crew-month was spent in the field, about 

two-thirds of which time was at Al Ashyab. Production at both 

locations was hampered to some extent by the ruggedness of the 

terrain.

The geophysical surveys were essentially reconnaissance 

in scope and aimed at identifying the gross electrical 

characteristics of the altered zones. It was intended to 

follow up this work at a later time with additional surveys 

to delineate specific drilling targets if warranted by the 

combined results of the integrated exploration program. To 

date, however, the work reported here remains the only 

geophysical prospection in either area.

Al Ashyab surveys

Self-potential

The Jabal Al Ashyab altered zone was the first target 

surveyed. Smith's camp immediately south of the Jabal served

43
as a base of operations for the field party. The SP survey 

was made during November 1975 under conditions of high 

surface aridity (there had been no rains in the recent past). 

Readings were taken at 50-m intervals along east-west traverse 

lines laid out by tape and compass normal to Smith's surveyed 

base line.

Initially the three-pot (leapfrog) method was used, but 

because of the need for greater accuracy it was decided to 

switch to the two-pot (fixed pot, moving pot) method, keeping 

one pot stationary on the base line. Traverse lines were 

then tied together by surveying the base line with one pot 

fixed at station (0,0) . To facilitate the measurements an 

auxiliary base line 0.5 km long was established west of Jabal 

Al Ashyab and exactly 0.5 km west of Smith's line. The 

measuring device used was a BRGM model RUE electronic millivoltmeter. Although this type of instrument has a very high 

input impedance, and differences of potential can be read with 

an accuracy of + 0.2 millivolt in all operating environments, 

line-closure errors were in some cases as high as 20 millivolts 

Pot potentials were compared several times each day and pot 

polarization drifts can account for at most a few millivolts 

generally less than 1 millivolt of uncertainty at any time 

during the survey. Excessive closure errors occurred with 

both the two-pot and three-pot methods, and their origin has 

not been unequivocally determined. It seems likely to be 

related to rapid dessication of the immediate electrode environment, which was watered some hours prior to each traverse and

44
then charged with saturated copper sulfate solution just prior 

to the actual measurement.

Results. The SP data were eventually reduced to an 

assumed datum of zero millivolts at station (15S,OE) on the 

Smith base line, and contoured to produce the equipotential 

map of figure 15. This map contains, in addition to errors 

described above, spatial distortions associated with the lack 

of slope corrections in the tape-and-compass station locations, 

which have been plotted as a rectilinear grid. Such distortions are generally negligible but may amount to as much as 

half a grid interval in the vicinity of the cliffs of Jabal Al 

Ashyab.

The total SP relief of the surveyed area is 115 millivolts. Equipotential contours show virtually no relation to 

mapped geological structures (fig. 8). The central part of 

the surveyed area, a zone of silicified and in some places 

pyritized metasedimentary and metavolcanic rocks of the Jiddah 

group, is mostly a relative SP high. Quartz porphyry terrane 

east of the Smith base line is characterized by low average 

SP values, whereas quartz porphyry terrane in the western 

part of the area has generally lower SP values than the 

central part but contains strong high and low SP anomalies.

The dominant SP anomaly grain does not trend north, 

following the strike of geological units, but nearly east. 

This is the direction of the SP traverse lines and therefore 

could be accounted for by datum offsets between stations on 

the base line. However, it is doubtful that the easterly

45
direction of anomaly trend is an artifact of the survey. Very pronounced easterly SP, IP (induced polarization), and ground magnetic trends 

have been delineated in the vicinity of the Kutam mine, 7 km 

to the southwest of Al Ashyab, notwithstanding the absence 

of such geologic trends in that area (Blank and others,

) . Moreover, the regional aeromagnetic pattern throughout much of the southern Arabian Shield is characterized by 

nearly east-west anomalies that seem to transect first-order 

geologic structures.

A system of topographic lineaments that have trends a 

few degrees south of east is clearly distinguishable on 

aerial photographs of the Kutam - Al Ashyab region and suggests 

control by a set of fractures trending nearly east. At Al 

Ashyab the strongest linear SP anomaly, a sharply bounded low 

of almost 90 mv amplitude, trends slightly south of east and 

more or less follows the principal alluviated wadi. Several 

lesser SP trends are also roughly aligned with wadis. The 

drainage and associated anomalies may reflect the existence 

of a shear system that influences ground water disposition and 

hence potential gradients. No evidence was found relating SP 

anomalies to superficial indications of mineralization.

From the point of view of the explorationist the SP 

results are not encouraging; no negative SP anomaly appears 

to be associated with the Al Ashyab alteration zone. In the 

light of experience with the SP method elsewhere in the 

southern shield this must be regarded as contra-indicative of 

base metals at shallow depths.

46
Turam

The electromagnetic survey at Al Ashyab was carried out in 

December 1976 using a newly delivered ABEM TS-4 type 5280 system 

operating at 660 Hz and 220 Hz. A linear current cable was laid out 

oriented north approximately along the line of stations 8E, about 

400 m east of Smith's base line. Its south end was grounded in sandy 

soil on the left bank of the main wadi, where the wadi bends sharply 

to the east, about 250 m south of the southernmost SP traverse (line 

24S), and the north end was grounded in a rock gully about 150 m 

north of line OS. Traverses were made at 100 m intervals starting 

with line 5S and extending to line 19S; receiver staffs normally 

separated by 40 m were positioned midway between SP stations and 

moved in 50 m increments.

Planned traverses along lines 21S and 23S had to be abandoned 

due to carburetion problems with the 3.2 Kv JLO motor-generators.

Results. Reduced-amplitude equiratio maps and equiphase maps 

for each frequency have been prepared from profiles along the eight 

traverses and are presented in figures 16-19. Reduced ratios are 

obtained by correcting the observed ratios for the different distance of each receiver from the source cable, which is assumed to 

be of infinite length; phase angles represent the phase lead of 

the signal induced in the far receiver over the received in the 

near receiver, Over a uniform half-space the reduced ratio 

would be 1:0 and the phase angle zero degrees.

 Because phase anomalies obtained in the Al Ashyab and Farah 

Garan surveys are positive rather than negative, as is usual with 

the procedures followed, it is possible that the new Turam equipment is wired for the opposite convention.

47
In contrast to the SP results, the Turam anomaly map 

pattern for the Al Ashyab area strongly mirrors the generally 

north-trending structural grain. No east-trending anomalies 

were detected. Results at 660 Hz and 220 Hz are quite similar, 

an indication that surficial conductivities do not contribute 

substantially to the Turam response.

Two main linear anomalies appear to be present in the 

area covered, each of which is within or at the margin of the 

belt of rocks of the Jiddah group. The stronger of the two, 

with a maximum reduced ratio of 1.65 at 220 Hz and 1.73 at 

660 Hz, follows the western boundary of the Jiddah rocks 

closely at 220 Hz and somewhat less closely at the higher 

frequency. At 220 Hz the ratio anomaly is remarkably uniform 

along strike and sharply asymmetrical perpendicular to the strike, 

due to the primary cable. The anomalous source is probably steeply 

dipping or vertical. Moderately high ratio values are 

accompanied by fairly large phase angle differences (maximum 

of + 8.5° at 220 Hz and + 14.7° at 660 Hz), thus implying a 

source of moderate conductivity. The depth to the top of the 

induced current system is probably no greater than the depth 

to the water table (about 20 m). Because neither base metal 

mineralization nor graphitic rocks were seen in the vicinity 

of the Jiddah group-quartz porphyry contact, whereas minor 

pyrite and considerable cataclasis can be seen, the source is 

inferred to be a pyritized, wet shear zone.

The second and slightly weaker anomaly reaches a peak 

ratio of 1.60 at 220 Hz and 1.70 at 660 Hz and has a maximum

48
phase anomaly of +4.3° at 220 Hz and +12.4° at 660 Hz. Its 

maximum coincides rather closely with the eastern border 

of the Jiddah group. This anomaly lacks the continuity of 

the western anomaly, however, and is not present north of the 

southern tip of Jabal Al Ashyab. The Jiddah rocks are 

pyritized where the anomaly is most intense.

Typical Turam profiles are shown in figure 20, in which 

values of amplitude ratio (increasing toward the top of the 

page) and phase angle (increasing toward the bottom of the 

page) at 660 Hz and 220 Hz are plotted for line 17S. The 

location of both principal anomalies can be seen in relation 

to the quartz porphyry contacts. The asymmetry of the western 

anomaly is less distinct here than on profiles farther north. 

Smaller anomalies situated between the two flank anomalies 

have larger amplitudes north and south of the profile chosen. 

These and other anomalies within the central part of the 

surveyed area are probably also related to localization of 

conductive solutions along shears rather than to conductive 

bedrock. However, the central part of the area appears to be 

the area of maximum Cu-Zn enrichment (see figs. 9 and 10), 

and it is possible that the associated Turam anomalies in 

part reflect the presence of sulfides.

Conclusions

Geophysical reconnaissance at Jabal Ashyab has demonstrated that no substantial SP effect is associated with the 

generally north-trending lithologic belts in the zone of

49
alteration. The highly silicified quartz porphyry of the 

Jabal proper seems to produce a positive SP anomaly. Easterly 

trends of anomalies with amplitudes up to 90 mv that traverse 

the target area across the structural grain are as yet unexplained, but are consistent with a similar SP anomaly 

pattern at the nearby Kutam ancient mine; both may reflect an 

east-trending shear set. Turam surveys show the existence of 

linear conductive zones that seem to be produced by northtrending shear zones within and especially near the margins 

of the central belt of metamorphic rocks. The principal 

Turam anomalies are open to the south and require further 

field work for complete delineation. The possibility exists 

that the Turam anomalies are due to base metal mineralization, 

but geochemical support for such an interpretation is weak at 

best. Further geophysical work might consist of additional 

Turam traverses in the southern part of the target, accompanied by reconnaissance induced polarization profiles.

Farah Garan surveys

Self-potential

The base of operations for Farah Garan surveys was the 

USGS camp at Kutam. Field work was carried out with the aid 

of a helicopter for the commute across Wadi Kohlan (Wadi 

Maslulah), and a spike camp was set up for overnight storage 

of equipment. The SP survey was made in January 1976, when 

surface conditions were similar to those prevailing at Al 

Ashyab. Measurements were again made along east-west lines

50
surveyed by tape and compass in 50 m increments from a 

north-south base line established by Smith, but at Farah 

Garan the traverse spacing was increased to 100 m. The 

two-pot (fixed pot, moving pot) method was used exclusively, 

and the instrument was the same as before. On this occasion 

the SP readings appeared to be quite stable: no difficulties 

were encountered in making ties and repeats. All values were 

subsequently reduced to an assumed datum of zero millivolts 

at station (ION,O) on the base line.

Results. SP results at Farah Garan are shown as an 

equipotential contour map in figure 21. Once again, spatial 

distortion is present due to lack of slope corrections, particularly along the several southernmost profiles (lines 2, 

4, 6, 8, and 10S), where the topographic relief is extreme, 

but the maximum distortion is less than at Jabal Al Ashyab. 

Figure 21 also shows the location of six Turam profiles.

The relative self-potential values range from +171 to 

-520 millivolts, and the maximum difference of potential, 

nearly 0.7 v f is the largest we have yet measured. Most of 

this difference is embodied in an extensive SP low that trends northnortheast across the prospect area, more or less parallel 

to the trend of the trunk wadi draining the flattish area of 

old high-level alluvium. The close association of the SP 

low with an area of low topographic relief suggests a genetic 

relationship. However, such a relationship is probably 

secondary; both SP low and low topographic relief are associated with the belt of predominantly metasedimentary rocks of

51
the Jiddah group containing the central and south ancient mine 

workings (fig. £). A very steep gradient bounding the SP low 

on the northwest lies just northwest of and parallel to the 

Farah Garan fault, a shear zone interposed between the predominantly metasedimentary formation and a predominantly metavolcanic formation also belonging to the Jiddah group. The 

gradient lies wholly within the metavolcanics. A weaker 

gradient bounds the southeast side of the SP low and lies 

largely within meta-andesites , roughly following the eastern 

contact of the metasedimentary formation.

These relations do not obtain in the southern part of the 

map area, where the geologically inferred trace of the Farah 

Garan fault and the SP gradient trends diverge, and the SP 

anomaly contours transect the metasedimentary-metaandesite 

contact at a high angle.

Ancient mine workings are disposed within, on the flanks 

of, and outside the SP anomaly but the anomaly itself is not 

directly associated with any known distribution of mineralization, and probably results instead from oxidation of graphitic 

members of the metasedimentary formation, and only in relatively 

minor part from oxidation of ore. Within this formation the 

potential is more or less uniformly low. Where no graphite is 

present (that is/ in the metavolcanic formations), the potential 

increases to values that are more or less uniformly high: the 

metasedimentary rocks seem to behave as a single, negatively 

charged electrode. However, the graphite content of the metasedimentary unit must drop off sharply at the southern end of

the SP anomaly.

52
Inspection of the SP map shows that there are in fact a 

number of discrete minima within the principal low. In most 

cases the shapes of these minima are not well represented by 

the contours because of the wide traverse spacing (100 m), 

and therefore their geologic association is difficult to 

judge. Some or all may result from oxidation of local concentrations of sulfides. However, it is equally likely that 

they too are produced by graphite.

Two sets of northerly SP trends seen on the equipotential 

map may reflect the influence of secondary structural elements 

auxiliary to the Farah Garan fault. The more westerly of the 

two extends south from Smith's base line and is closely associated with the central and south ancient workings. The more 

easterly set is not associated with any known mineralization 

but extends into an area not yet mapped. It may coincide in 

part with a strong Turam anomaly found on the traverse of line 

A, although the validity of the latter anomaly is suspect (see 

next section). In any case the area covered by both sets of 

northerly SP trends should probably be thoroughly prospected.

Turam

The six reconnaissance Turam lines labelled A-F in figure 

21 were surveyed in February 1976 as a test of the Farah Garan 

shear zone. A source cable 2.3 km in length was laid out on 

a bearing of 023°, about 100 m offset from the first station 

on the traverse lines. The Turam system was again the new ABEM 

TS-4. Grounding at the southwest end was accomplished easily

53
in wet sands of a rock-walled wadi tributary to Wadi Kohlan, 

and the north-northeast electrode was buried with much more 

difficulty in a rocky gully. In spite of the relatively short 

length of the traverse lines, it was not possible to obtain an 

accurate null in all cases at their eastern extremities due to 

loss of signal strength.

Results. The Turam data are shown as combined contour 

maps of reduced amplitude ratio and relative phase angle in 

figures 22-25. Plot points on the traverses are very approximate owing both to lack of slope correction, which particularly 

affects position on lines E and F where the terrane falls off 

quite rapidly towards Wadi Kohlan, and to the fact that the 

line was oriented by hand-held Brunton compass as the receivers 

were advanced from station to station by the length of the 

standard 40 m connecting cable. Also the rendering of contour 

lines from widely spaced traverse data is hazardous. Nevertheless, the inductive response of the target area can be qualitively evaluated.

The anomaly at the eastern end of line A is the strongest 

recorded but because of the weakness of the signal received it 

is possibly in error, as stated previously. This aside, two 

major Turam anomalies were delineated. The more intense anomaly 

appears on both lines A and B, and opens to the north, whereas 

the weaker of the two is apparently centered on line D. These 

anomalies are colinear but discrete. The current concentrations are located on or just east of the Farah Garan fault; the 

northern anomaly and perhaps both anomalies, are directly associ54
ated with layers of graphitic schist in the metasedimentary 

formation. For line A the association was established by 

successively halving the receiver separation, until it was 

revealed that the anomaly source coincides with a near-vertical 

bed of graphitic schist 5-10 m thick with surface outcrops. 

Therefore the anomaly is caused either by the graphite or by 

concealed sulfides in the graphitic zone its source could be 

no deeper than about 20 m or approximately the depth to the 

base of the zone of oxidation (or water table).

Rocks traversed in the vicinity of the ancient workings 

did not produce any appreciable disturbance of the Turam field. 

Metavolcanic rocks west of the Farah Garan fault produce 

almost no reponse even where mineralized.

Conclusions. The combination of highly conductive graphite 

beds and sulfide mineralization is a particularly difficult 

challenge for geophysical investigations, and on the basis of 

work to date, the possibility of sulfide contributions to 

either the Turam or the SP anomalies cannot be ruled out 

entirely. On the other hand the outlook is not favorable. 

It must be considered likely that both effects are produced 

by the graphite schist component of the predominantly metasedimentary formation of the Jiddah group.

A Turam survey at closer traverse spacing might provide 

better evidence on the relation of inductive anomalies to 

geochemical anomalies and to mappable graphitic units. If 

preliminary drilling results are encouraging, consideration

55
should be given to completing the Turam or another electromagnetic survey, and to carrying out a mise-a-la-masse IP 

(induced polarization) survey.

REFERENCES CITED 

Anderson, R. E., 1978, Geology of the Mayza quadrangle, sheet

17/43 B, Kingdom of Saudi Arabia: Saudi Arabian Directorate General of Mineral Resources Geologic Map GM-31, 

scale 1:100,000.

Greenwood, W. R., Hadley, D. G., Anderson, R. E., Fleck, R. J., 

and Schmidt, D. L., 1976, Late Proterozoic cratonization 

in southwestern Saudi Arabia: Royal Society of London 

Philosophical Transactions, A, v. 280, p. 517-527.

56
CONTACT - Dashed wnen location fc 

MAJOR FAULT SHOWING DIP

-o- STRIKE AND DIP OF FOLIATION

«- - FOLD PLUNGING 90'

e e o- QUARTZ VEIN SHOWING Ds?

GOSSANS - Dashed where projected 

ANCIENT WORKINGS AND DUMP 

ANCIENT SLAG PILE 

A SURVEY POINT

ANDESrTE - Massive, weakly foliated. Contains minor feldspar phenocryita.

Metamorphosed to greenachitt facial

METAVOLCANIC ROCKS - Predominantly of intermediate competition. Moat

contain quartz crystals as much as 3 mm in diameter. Strongly foBatMl

METASEDIMENTARY ROCKS - Includes graywacke, calcareous afltttone. ROCK CAIRN FOR GEOCHEMICAL AND GEOPHYSICAL GRID and graphitic schist. Some non-metasedimentary rocks PROPOSED DRILL HOLE SHOWING HORIZONTAL PROJECTION

METASEDIMENTARY MARBLE - Fine-grained, texturelen. Weathen to

S^QalN<»>Jins>

(cP^£&^

Figure 3. Geologic map of the Farah Garan ancient mine.
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EXPLANATION 

LOCATION AND NUMBER OF SAMPLE

APPROXIMATE LOCATION AND NUMBER OF SAMPLE TAKEN BY 

T. H KlILSCAARD AND R. E. ANDERSON

ANCIENT WORKINGS

SURVEY POINT - . "* " ^:

ROCK CAIRN FOR CEOCHEMICAL AND GEOPHYSICAL GRID

95332.

95333

95334

95335

95336

106939'

&

96169

106936

9

17

40' 

44'

4338*16*

100I

200 METERS

Figure 4. Sample locality map, Farah Garan ancient mine.
EXPLANATION

<41 PARTS PER MILLION (ppm) 

- Background

X

V 

O

y

X

O 

X

x 

x

X 

X x^

~ J - ..

X*° 0 

0

0 

0 1 

&

-5 ! -i J o 

v °x x 

x

» ° 

0 

o

r 

o

0

- 

o 

X 

*

x 

X ^F

^£

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g0 

x

X

X

X

o

1

0

X

:~

X

0

1

X 

X 

X

X

X

1^ 

«^

XX

o

%

o

X

o

X

-

;

X

AJ

f\

gx 

/

o

V

i

X '.

X/> l"*^^^ /\l ^^.

X

o

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X x

. .--' 

o

8 A"

X

Q

^

!j. , ( w '

i ift-;

x

\

.

>o

o

X - . i.

X 41- 120 ppm

O 121-llOOppm 

O ¥, ^ O >1 100 ppm

< X 

0 A ROCK CAIRN

* 

*

J X v A SURVEY POINT

-. 

^*

y ! 0 

*

X 

y A 0 100 200 METERS

r

x x i i i i i

/ . x 

x* : ! / : o 

x j ; o x I/O 0 x 

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X *./ ^v ! *

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v xiV X \ A £ s .x \ I 

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IV J 1 

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1 X X Jr'v / 

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^

Figure S. Copper content of rock samples, Farah Garan ancient mine.
xx°

X

X

OX

!

X

o 

X

X X

X 

X

o 

o

A

O

X

o

X

o

o 

X

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X

X 

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X

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X 

X

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o 

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X o 

X

X

ft

o 

o

X

X

o

o

X

o

X

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X

X

X

X

X

X

EXPLANATION

<41 PARTS PER MILLION (ppm) 

- Background

X 41-120 ppmO 121-1100 ppm

 ] O >HOOppm

A ROCK CAIRN

A SURVEY POINT

100 2DC*ETERS 

I_______|_______I

X 

X

: 

x

*

> x

~ - X 

Figure 6. Zinc content of rock samples, Farah Garan ancient mine.
4340' 1740'

QUARTZ DIORITE - Syntectonic, missive, coane-griined. Contains blue-gray quart/.

EXPLANATION

OGW WAJID SANDSTONE

Qdm QUARTZ PORPHYRY - Siliceous to intermediate rocks of quartz dioritic " composition. Characterized by blue-gray quartz phenocrvsts

QUARTZ PORPHYRY -Siliceous to Intermediate rocks of quartz diorite

composition. Characterized by blue-gray quanz phenocrysis

:: METAVOLCANIC AND METASEDIMENTARY ROCKS-_undMdod,____

METAVOLCANIC ROCKS - Massive to schistose andesite and basalt lava and

flow breccia. Minor interbedded sedimentary rocks

CuOx

METASEDIMENTARY ROCKS - Chert pebble conglomerate, calcareous mudstone, 

graphitic schist. InterbeddeU with meuvolcanic rocks of ir.tiraiediate composition

METASEDIMENTARY ROCKS - Mostly calcareous

CONTACT - Dashed where location Is uncertain

STRIKE AND DIP OF FOLIATIONSTRIKE AND DIP OF BEDDING

PYRITIZED ZONE

COPPER STAINANCIENT MINING SITESAMPLE LOCALITY AND NUMBER

MOTOR VEHICLE TRAIL

FOCAL CENTER OF PHOTOGRAPH

ANALYTICAL DATA.

1000m

Sample number

109891109900

109901

109902

109903109904

109905

109906

109907109908109909

109919

109920109921109922109923109924

109925109926

109927

109928109929109930109931109932109933109934

109935

109936109937

109938

109939109940109941109942

109943

109944

109954

109955109956

109957

109958

109959 

1099CO

109961

1099C2

109963

1099(4 1099C51Q99CC

10996710996810997510997C

109977109978

109979

109980

109981

109982109915

10998C109987109988109989

103930

10999110999210999410999510999C

109997

109998

109999114000114001114002114003

114004

114053

114054

114062114063114064

Description

Milky quartz about 1 * wide Sericite schist, pyritized, brown iron oxids

Quartz vein, 5 cm wideQuartz vein, sparse copper carbonate in selvage

Quartz vein, IS cm wide

Quartz vein, 10 cm wide

Quartz carbonate veinlets

Quartz carbonate veinlets across 3 

Quartz sericite schist, pyritizedQuartz sericite schist, pyritizedQuartz sericite schist, pyritizedQuartz-carbonate vsin, to 40 cm widsQuartz-csrbonate stringers across 5 

Milky quartz, contains moderate iron oxidsMilky quartz, folded, contains mangansse oxideSericite schist, pyritized

Ions of quartz veinlets, 2 widelone of quartz veinlets, 1.5 wide

lone of quartz veinlsts, copper oxids in selvages

Quartz veinlets in sericite schistQuartz vsinlets, 2 t» wideQuartz ssricite, pyritizedQuartz veinlets in sericite schistQuartz veinlsts in sericits schistQuartz ssricite, strongly pyriticQuartz sericits, strongly pyriticQuarts ssricite, strongly pyriticQuartz stringers in sericits schistQuartz with hematite (aftsr magnstite?)Quartz vein, 20 cm wide, copper oxide in selvageQuartz vein, 30 cm wideQuartz vein, 30 cm wide

Quartz porphyry, silicified

Quartz-carbonate veinlets, 1 m Wide

Quartz with tremolite, 20 cm'wide

Quartz-carbonate veinlstsQuartz in marble lensQuartz-carbonate velnletsQuartz-carbonate veinlsts

Copper carbonate in ssricite schistQuartz schist, pyritized, sericiteQuartz schist, pyritized, sericiteMetavolcanic rocks, silicifiedGraphitic schist containing cubic pyrite Marble, copper stained

Sericite quartz schist containing pyrite

Milky quartz, 30 cm wideMilky quartz, 60 cm wide Milky quartz, 4 cm widsMilky quartz, 2.5 m wide

Milky quartz, 3.0.m wideQuartz stringsr zone, 2 m wide

Metavolcanic rocks, weakly pyritizedMetavolcanic rocks, weakly pyritizedContact metavolcanic rocks, graphitic schistContact metavolcanic rocks, graphitic schist

Graphitic schist, pyritiferous

Marble, dark-gray to black

Graphitic schist, calcareousGraphitic schist, calcareous

Mudstone, calcareous, containing chalcopyriteMuds tone, calcareous, containing chalcopyrite

Quartz sericite schist, pyritiferous

Quarts sericite schist, pyritiferous (

Quarts- sericite schist, pyritiferous

Siliceous, calcareous, black, mottled

Cherty conglomerate

Grsphitio schist, containing coarse cubic pyrite '

Sericite schist, containing iron oxide stain

Metavolcanic rocks, containing calcareous lenses, cubic pyrite Sericite schist, weakly pyritiferous

Sericite schist, weakly pyritiferous

Quarts-carbonate vein in workings, 45 cm wideQuartz, gray-blue with pyrite, 20 cm wide

Quarts-sericite schist, pyritiferousQuartz-carbonate in schistQuartz veinlsts in tightly folded schistMetasedimentary rocks, calcareous Metasedimentary rocks, calcarsous adjacent tographits

Marble, medium gray-brown with quartz stringers

Marble, medium gray-brownQuartz vein swarmQuartz vein swarm, 0.5 m wide in deep workingsQuartz, iron-stained grab sample from dump

Au

q/ton

a. 10

0.100.08

0.080.05

0.100.04

0.080.050.070.110.070.040.100.080.09

0.040.07

~

0.100.10

0.10

0.10

0.10

0.100.100.100.100.100.100.100.100.10

0.10

0.100.130..130.13

0.140.*4 0.140.15

0.180.140.15 

1.C4

0.14

0.14

0.140.130.130.130.130.130.130.140.36

0.64

0.200.140.15

0.13

fl.13

0.15

0.15

0.100.140.140.17

14.0022.00

0.240.140.17

0.17

0.17- __ 0.08 -- ** q/ton __0.2 0.6 0.2 0.2 0.8 0.9 1.0 0.6 0.2 0.2 0.3 0.3 0.3 --2.0 0.5 1.2 1.0 0.4 O.X 0.3 0.2 b.s 0.4 0.6 0.6 1.2 2.1 0.6 0.2 0.7 1.7 0.3 0.7 0.7 2.2 0.8 11.4 1.1 0.4 0.6 0.9 1.5 0.6

~

o.c "

1.1«

~

0.6

2.0C.S

0.41.6

1.3

1.7

10.9

5.1

0.5

1.11.0

0.4O.C

1.5

0.3

0.70.40.6

1.3

1.00.50.90.51.0

1.00.10.9

Cu

jp»

9

169

543

38

33

56

116

45

482257

27

16

30

80

200

4630

550888

60

60

2013

22

SO

87

131

903

6400

200

2743

1810163738

. 19

15800

34

44

35

109

68

58

5

12 20

5

30

7

9

6792

21IS1229

218

7800

4110

46

168

3036

554226

112

7t1064

105

9*

363

30

33

54

99

«

8

28

11

Pb

ppn

11

~--10

1213

13

11

11

10

29

- 

18

1417

- ----10--42

141129

151125142218

27

_1C

1523

2411

38

2522

32

22--19

1424

2123

13

1010

1219

27--21

30

2510~~

Zn

ppm

9

178

318

34

2895

5444

5

13

145

15

17

20

2027

1010

67

178

30 .

5

32

26

66 

138

263

480

338

130

66

18

12

552010

30

1416

1500

31

256559 ______ 455310 n%

4 *-

46 

58

59

3431

7

37

37

5075

5600

1680

43

. 53

59

133

8327

250

CS

44 (. 47 

V

42 * 57 c 36 ;

92 <-'

46 ( 99 t43

78

7

4

IS

3

Figure 14. Geologic and sample map of the Hemair-Asharfat region.