Evaluation of the Umm Al Khabath copper prospect, Jabal Ibrahim quadrangle, sheet 20/41C, Kingdom of Saudi Arabia
<p>The Umm Al Khabath copper prospect (lat 20°10'N.; long 41°23'E.) was tested by 815 m of diamond drilling in three holes. Meager metallization of copper,…
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kya-`16' DIRECTORATE GENERAL OF MINERAL RESOURCES MINISTRY OF PETROLEUM AND MINERAL RESOURCES JIDDAH, SAUDI ARABIA ovetiM .Q4 . t ,,cp.,L , i "k N., iSse.prEGeNepooFiriotLgE:R LL. LU ''
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standards or nomenclature. sAuoi ARA. EVALUATION OF THE UMM AL KHABATH COPPER PROSPECT JABAL IBRAHIM QUADRANGLE, SHEET 20/41C cvlot_O !C KINGDOM OF SAUDI ARABIA - c, I N
‘" By Ronald G. Worl MAY 2 b With a section on E3 R
GEOPHYSICAL INVESTIGATIONS by Vincent J. Flanigan and Habib M. Merghelani SAUDI ARABIAN PROJECT REPORT 213 This report is preliminary and has not been edited or reviewed for conformity with U.S. Geological Survey standards and nomenclature. These data are preliminary and should not be quoted without permission. UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY
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1111111111111 1111111511,1111111,111111,1111 U. S. GEOLOGICAL SURVEY SAUDI ARABIAN PROJECT REPORT 213 /41, tr.au: taLs3 EVALUATION OF THE UMM AL KHABATH COPPER PROSPECT JABAL IBRAHIM QUADRANGLE, SHEET 20/41C, KINGDOM OF SAUDI ARABIA by Ronald G. Worl With a section on GEOPHYSICAL INVESTIGATIONS by ' Vincent J. Flanigan and Habib M. Merghelani U. S. Geological Survey Jiddah, Saudi Arabia
CONTENTS Page ABSTRACT INTRODUCTION Location and description Acknowledgments Purpose of study Diamond drilling program GEOLOGY Regional setting Lithologies and structure Mineralization and alteration GEOCHEMISTRY Surface sampling plan Core sampling plan Discussion GEOPHYSICAL INVESTIGATIONS by V. J. Flanigan and H. M. Merghelani Introduction Discussion of results Conclusions CONCLUSIONS AND RECOMMENDATIONS REFERENCES APPENDIX--Analytical results
ILLUSTRATIONS Page Figure 1. Geologic map of the Umm Al Khabath prospect showing sample locations 2. Vertical sections through diamond drill holes Kb-1, Kb-2, and Kb-3, showing relationship of geophysical data to geology 3. Self potential map, Umm Al Khabath prospect 4. Turam electromagnetic equiratio map, Umm Al Khabath prospect 5. Log of diamond drill hole Kb-3 showing relationship of electric logs to lithology TABLES Table 1. Diamond drill hole data, Umm Al KhAbath prospect 2. Summary geologic logs of drill holes Kb-1, 2, and 3, Umm Al Khabath prospect 3. Mean and range in analytical values of surface and split core samples, Umm Al Khabath prospect
EVALUATION OF THE UMM AL KHABATH COPPER PROSPECT JABAL IBRAHIM QUADRANGLE, SHEET 20/41C, KINGDOM OF SAUDI ARABIA by Ronald G. Worl ABSTRACT The Umm Al Khabath copper prospect (lat 20°10'N.; long 41°23'E.) was tested by 815 m of diamond drilling in three holes. Meager metallization of copper, zinc, gold, and silver is related to a distinct phase of quartz-pyrite veinlet stockworks and associated silicification, sericiti zation, and pyritization. Alteration and metallization are within a major north-trending shear zone, 10-50 m wide. Lithologies cut by the shear zone are pyroclastic agglo merate and tuff with intercalated ferruginous chert, wacke, and basalt flows, all belonging to the Precambrian Baish Group. The outcrop of the shear zone for a length of 1400 m contains scattered gossan, local zones of abundant malachite and chrysocolla veinlets, patches of malachite-rich calcrete cap, and several shallow ancient workings. Composite chip samples taken from the surface across the sheared and altered zone contain anomalous concentrations of copper and zinc in amounts greater than can be expected from the weathering of the slightly metallized rock of the sheared and altered zone. INTRODUCTION Location and description The Umm Al Khabath prospect is at lat 20°10'N. and long 41°23'E. (sheet 20/41C), 25 km north of the Emirate of Al Bahah and 1 km east of the macadam highway leading south from At Ta'if, 185 km northwest (fig. 1). The prospect is at the head of a small tributary near the top of the steep west rim of Wadi Bidah, a major north-draining wadi. Terrain in the vicinity is rugged with a total vertical relief of approximately 600 m in a distance of 2 km from the top of the west rim to the bottom of Wadi Bidah. Total relief within the prospect area is 130 m; the highest point is approximately 2200 m above sea level. Umm Al Khabath is just east of the densely populated and cultivated region of Bilad Zahkan located along the escarpment 8 km to the west. The village of Al Gawaur is 2 km west and the village of Bani Sar 6 km south. The prospect area is not terraced or cultivated, but serves as
320w EXPLANATION 2401; 160w Quartz vein Bow 88 0 N Andesite dike Diorite dike Zone of shearing 880N 800N and alteration Banded iron formation Contact 800N 720N Fault Strike and dip of foliation 720N 640N C:) Ancient workings CDs Ancient slag 640N 560N Ancient dump Kb- l
0-I Diamond drill hole 560N Sample location; last three 480N digits of 98000 series 480N 60 m 400N N
400N 320N 320N 240N 240N 160N 160N BON 80N 20000'N. Kb-i 80S Nr Al Taw 80S 160s Khabath Bahah 20030'N. 240w 20 KM 160W 320w 1-4-4-1-1J 80w INDEX MAP To At Ta i Figure 1. - Geologic map of the Umm al Khabath prospect showing sample locations.
grazing ground for herds of goats and sheep ranging out of nearby villages. The prospect consists of several malachite-stained gossans and ancient workings scattered along an altered shear zone for a distance of 1400 m. Umm Al Khabath(mother of slag), the local name, comes from the great abundance of large slag dumps left from the ancient smelting operations in the central part of the area (fig. 1). Much of the slag is copper-stained and some contains small beads of native copper. An extensive ancient village site is in and around the slag dumps. Fragments of copper-glazed pottery and partly devitrified green bottle glass can be found among the ruins. Mining and smelting activity was probably greatest in the eighth and ninth centuries during rule of the Abbasid Caliphate. This was a period of extensive mining activity in many parts of the Arabian Shield. The slag dumps and ancient workings were reported by Murryyi bin Bunayan Almutayri of the U. S. Geological Survey Saudi Arabian Project staff in September of 1973, following a reconnaissance of the general area for ancient mines. Goldsmith (1971) mentions the prospect (number 31 in his table 2, p. 31), but gives no information other than to mention the copper-stained slag. No other mention of the prospect was found in the literature. The prospect is in the Jabal Ibrahim quadrangle which has been mapped at a scale of 1:100,000 by Greenwood (1975). A summary of all known prospects in the quadrangle is included in Greenwood's report. Acknowledgements The work was performed in accordance with a work agreement between the U. S. Geological Survey and the Ministry of Petroleum and Mineral Resources, Kingdom of Saudi Arabia. The guidance and discussions concerning this study by T. H. Kiilsgaard, R. J. Roberts, D. L. Schmidt, and W. R. Greenwood, of the U. S. Geological Survey and W. K. Liddicoat of the Directorate General of Mineral Resources, all of whom visited the area, are gratefully acknowledged. Topographic surveys were conducted under the field direction of K. S. McLean, while F. G. Lavery handled the aerial photographic mission and prepared the 1:2,000 topographic base map. Prospectors, guides, surveyors, and samplers Murryyi bin Bunayan Almutayri, Meghim Selmi Al Murtaryyri, and Murdi Mabsouk Almtari made important contributions. Acknowledgement is extended to the field services section of the USGS Saudi Arabian Project for providing excellent logistical support. All samples were analyzed in the Directorate General of Mineral Resources-USGS laboratory, Jiddah.
Purpose of study Umm Al Khabath is one of several ancient mines and prospects examined during a reconnaissance study of parts of the Al 'Aqiq (20/41D) and Jabal Ibrahim (20/41C) quad rangles during the fall of 1973. Four of the prospects, including Umm Al Khabath, were selected for further economic evaluation. The prospect was selected as the best of several similar potential areas. If Umm Al Khabath were to prove to be of potential economic value numerous other sheared and altered zones throughout the Jabal Ibrahim and Al 'Aqiq quadrangles also might warrant extensive prospecting. The geology of the prospect area was first mapped at a scale of 1:10,000, using enlarged aerial photography as a base. Geochemical and geophysical surveys were conducted using a 1:1,000-scale Brunton and tape base map. Sheared and altered rocks also were mapped on this base. Later all information was transferred to a 1:2,000-scale topographic map prepared from low-altitude aerial photography. Following the geologic, geochemical, and geophysical investigations the prospect was tested by three diamond drill holes. This paper presents the geological, geochemical, and geophysical evaluations of the prospect and outlines the results of the diamond drilling program. Diamond drilling program The Arabian Drilling Company drilled a total of 815 m of diamond drilling in three holes at the Umm Al Khabath prospect during the period March 1 to June 1, 1974 (table 1) Table 1. Diamond drill hole data, Umm Al Khabath prospect Hole No. Depth Azimuth Inclination Map coordinates Kb-1 275° 35° 48N./46E. Kb-2 95° 40° 408N./34SW. Kb-3 275° 70° 630N./128W. The purpose was to test the major sheared and altered zone for sulfide potential, either massive lodes or disseminations. The drill hole locations were based upon a combination of geologic, geochemical, and geophysical information. Drill holes Kb-1 and Kb-2 were designed to test a geophysical anomaly that coincides with ancient workings and surface geochemical anomalies within the main sheared and altered zone. The holes were laid out to explore rock adjacent to the main sheared and altered zone and to intersect the sections at nearly right angles to the structure. Drill hole Kb-3 was designed to test a down-dip length of the main sheared and altered zone below an ancient working and a surface geochem ical anomaly. Complete logs of each drill hole including
complete drilling and geologic information are on file with the Directorate General of Mineral Resources, Jiddah. Analyses of split drill core samples are listed in Appendix A, drilling data and locations are in table 1, summary geologic logs in table 2, and zones of metallization on fig. 2. GEOLOGY Regional setting Umm Al Khabath is near the west edge of the Bidah mineral belt, a north-trending zone of tectonism, plutonism, and base metallization (Greenwood, Roberts, and Bagdady, 1974). This belt which extends approximately 100 km east, 70 km north, and 120 km south, is defined by strong northtrending shear and fault zones, intrusive bodies of diorite and quartz diorite, ancient copper and gold mines, and the outcrop pattern of the Precambrian layered rocks. Massive sulfide deposits composed of pyrite, chalcopyrite, and sphalerite occur 25 to 50 km north in the Wadi Bidah district (Earhart and Mawad, 1970; Greenwood and others, 1974). The largest Wadi Bidah deposit defined to date by diamond drilling is a steeply dipping lenticular tabular body at least 200 m long and as much as 19 m thick. This conformable body (the Rabathan deposit) forms the nose and east limb of a steeply north-plunging fold and contains at least 1.5 million metric tons averaging 2.14 percent copper. Massive sulfide deposits in the Wadi Bidah district are mainly in carbonate-quartz sericite schist in close proximity to graphitic schist of the Precambrian Baish Group. One deposit, the Gehab mine, is in part within the quartz porphyry. The eastern part of the Jabal Ibrahim quadrangle is underlain mainly by rocks of the Precambrian Baish Group and plutonic bodies of diorite and quartz diorite with minor exposures of rocks of the Precambrian Bahah Group and sills and dikes of quartz porphyry (Greenwood, 1975). The Baish and Bahah Groups comprise a metabasalt-graywacke-chert assemblage that is the oldest of three major assemblages recognized in the southern Arabian Shield (Greenwood and others, 1976). Baish Group rocks in this area are composed predominantly of basalt pyroclastic rocks with volcanic and sedimentary breccias. Much of the rock is blocky breccia suggestive of near vent facies, or alternatively submarine slide deposits (Greenwood, 1975). The younger Bahah Group, exposed mainly to the west .1nd south of Umm Al Khabath, is characterized by graywacke, arkosic graywacke, chert, and marble with local beds of graphitic chert and marble. Both groups are metamorphosed to the greenschist regional meta morphic facies and locally to the amphibolite regional metamorphic facies. The major shear and fault zones, foliation,
/ E M amplitude ratio METERS 1.2 -j 1.1 EM METERS 2 METERS H- 1940 Kb- 3 METERS --100 cn r 2000 Kb-1 Kb-1: 196-204m - .14% Cu EMamplitude ratio METERS 1.4 1.3 1.2 - METERS EM r 0 SPmillivolts (mV) Quartz vein Contact METERS SP Andesite dike Fault 6r6r;g15‘r Diorite dike t-111 Ar7 Zone of metalization / Zone of shearing and alteration Attitude of foliation Kb-2: 180-184m. - .45% Zn 187-190rri - .10% Cu, .43% Zn J 190-194m - 11 ppm Ag, .35% Cu, 1.11% 198-199m - 22 ppm Ag, .44c7oCu, 2. 76.% Zn
/ r Banded iron formation 0 20 40N1 Contorted foliation Figure 2. - Vertical sections through diamond drill holes Kb-1, Kb-2, and Kb-3 showing relationship of geophysical data to geology for Kb-1 and Kb-2
Table 2. Summary geologic logs of diamond drill holes Kb-1, 2, and 3, Umm Al Kabath prospect Summary log Kb-1 From To Description Weathered tuff Andesitic tuff. Four intergradational types interbedded throughout drill hole. 1. massive fine grained 2. pyroclastic 3. banded carbonate-rich 4. clastic Diorite dike Andesitic tuff .Siliceous tuff, large diffuse siliceous pyroclasts in subordinate chloritic groundmass Ferruginous chert Siliceous tuff, overprint of chlorite along -shear planes Andesitic tuff Ferruginous chert Quartz-sericite schist, nil to abundant carbonate Andesite dike Chlorite schist, dense gray groundmass of fine-grained quartz, sericite and pyrite, abundant talc, zone of strongly sheared rock extends from 165 to 200 Siliceous tuff Quartz-sericite schist, crenulated a Andesitic tuff Andesite dike
Table 2. Summary geologic logs of diamond drill holes Kb-1, 2, and 3 (continued) Summary log Kb-2 From To Description Weathered tuff Andesitic tuff. Four intergradational types interbedded throughout drill hole. 1. massive fine grained 2. pyroclastic 3. banded carbonate-rich 4. clastic Andesite, amygdaloidal, intercalated with andesitic tuff Shear zone Andesitic tuff Andesite dike Andesitic tuff, mostly pyroclastic Siliceous tuff Fault zone 87.80 101.60 Andesitic tuff 101.60 111.79 Diorite dike 111.79 179.86 Andesitic tuff, carbonate-rich locally 179.86 192.60 Quartz-sericite schist, crenulated, diss. pyrite, zone of slightly to strongly sheared rock. 192.60 194.25 Massive pyrite in siliceous groundmass 194.25 198.85 Quartz sericite schist 198.85 208.56 Andesitic tuff 208.56 220.47 Quartz-sericite schist, zone of slightly to strongly sheared rock 220.47 299.45 Intercalated massive andesitic tuff and sheared and crenulated quartz-sericite schist
Table 2. Summary geologic logs of diamond drill holes Kb-1, 2, and 3 (continued) Summary log Kb-3 From To Description C) Massive andesitic tuff Siliceous tuff, diffuse gray siliceous pyroclasts in chloritic groundmass. Local zones ferruginous chert Fault zone Siliceous tuff Andesitic schist, massive, pyroclastic, and banded carbonate-rich types interbedded Quartz-sericite schist, zone of intensely sheared rock Several post-shearing fault zones 154.9r:, Siliceous tuff Quartz-sericite schist, zone of intensely sheared rock iliceous tuff Quartz-sericite schist, zone of strongly sheared rock Mainly quartz-sericite schist interbedded with less sheared and altered andesitic tuff and siliceous tuff Andesite dike Andesite dike
and schistosity in the eastern part cf the Jabal Ibrahim quadrangle are dominan,Lly north-trending and nearly vertical. Layering and foliation within the units is generally parallel to the regional trends although tight shear folding of competent beds is common. Lithologies and structure Rocks of the Umm Al Khabath prospect are mainly pyro clastic volcanic rocks, tuff to agglomerate, with intercalated basaltic flows, wacke and ferruginous chert formation. All rock types have been metamorphosed to the greenschist facies and are composed of varying amounts of plagioclase (albte oligoclase?), chlorite, epidote, quartz, and calcite with locally abundant amphibole, probably actinolite, pyrite, hematite, and magnetite. The metamorphic effects combined with ubiquitous shearing tend to mask the original rock types; however, enough relict textures remain tc make reasonably accurate determinations of the original lithologies. Pyro clastic fragments range in size from ash to bombs and blocks as much as 10 cm in diameter. Many of the pyroclasts seem to be rounded, and detrital quartz is a minor constituent in the tuff and agglomerate. Clasts of plagioclase crystals and aggregates of plagioclase, commonly with pyroxe.ne or epidote and chlorite are in most rock types with the exception of the basaltic flow rocks. The larger pyroclasts are dark gray, locally vesicular, siliceous in places with abundant carbonate or pyrite. Clots of chlorite and epidote probably represent mafic pyroclasts but have been sheared, stretched, and recrys tallized beyond recognition. Groundmass of the pyroclastic rocks is composed of varying amounts of untwinned plagioclase (albite-oligoclase?), quartz, chlorite, and epidote. Calcite is a common but variable constituent as 1 to 10 mm long lenses, layers, and interstitial grains in all rock types except the ferruginous chert. Ferruginous chert composed of quartz and magnetite or hematite with locally abundant pyroclasts and minor chlorite is well- to poorly-bedded and occurs as lenses within the tuff and agglomerate. The tuff is finely laminated, crenulated, locally sorted and contains small amounts of detrit,11 quartz. Minor lenses of wacke composed of quartz, feldspar, and lithic fragments occur within the tuff and agglomerate. Crosscutting the volcanic-sedimentary assemblage are small dikes of diorite that trend northeast and cut the north-trending foliation of the country rock, but are sheared out along the northtrending shear zones. Lenses of massive andesite, probably dikes or sills, are conformable to the foliation and shearing. The main structure at the prospect is a north-trending zone of shearing 10 to 50 m in width (Fig. 1) that extends several kilometers north and south of the map area. Several
episodes of shearing can be recognized in the zone. The effects of shearing are evident in all lithologes and range from slight rotation of feldspar clasts and development of chlorite along a preferred orientat:on to the develooment_ of massive mylonite. All gradations between slightly foliated greenstone to mylonite composed of quartz and serIcite can be found, and remnants of less sheared and altered greenschist with relict tuff and agglomerate textures are common within the shear zone. All lithologies are foliated, generally, but not strictly parallel to layering, and in some sections of drill core two slightly divergent foliations can be detected. Shear folding on a minor scale is common and probably exists on large scales but is indistinguishable in the area. At Wadi Mandahah, 20 km north, the same sequence of rocks is strongly shear folded at all scales. Mineralization and alteration The main shear zone (fig. 1) contains numerous ancient workings which explore limonitic (hydrous iron oxides that have not been specifically identified) gossans and locally abundant malachite and chrysocolla stringer zones. The gossans are not strong but are large and indicative of mainly fine-grained disseminated sulfides and stringers of sulfides with scattered small lenses of massive sulfides. Malachite and chrysocolla stringers 1 to 10 mm in width occur along shear planes and cross fractures and are also common in less sheared rock along the edge of the sheared and altered zone. Malachite is locally very abundant as stringers and masses in a calcrete cap that covers parts of the shear zone. Ancient workings consist of one trench about 60 m long, 1-2 m wide, and 2-3 m deep: several smaller pits and trenches: and a pit 20 by 30 m and unknown but shallow depth, A shaft about 1.5 m square leading to shallow underground workings was exposed by caving of a rain water tilled sample trench. The shaft, of unknown depth, is within a 60 m long ancient trench now filled with alluvion and silt, Several thousand tons of ancient slag are found scattered along parts of the shear zone. The amount of slag present seems greater than could have been produced from ancient workings, suggesting that either large amcunts of ore were hauled in from elsewhere, or that there are extensive working in the near vicinity that have not been discovered. However, another likely source is the malachite-rich calcrete cap that covers parts of the sheared and altered zone. The ancients may have stripped large areas of formerly extensively malachite-rich calcrete cap and malachite-bearing gossans and hand cobbed the material to a depth of several meters. Remnants of malachite-rich calcrete caps and the nature of
the rock found in spoil piles supports this idea. Collec tively these sources would provide a large tonnage of ore easily obtained with crude tools, and this may have been the source of the copper ore, and thus the slag. Drilling penetrated wide zones of altered and slightly mineralized rocks in the shear zone. The major shear and altered zone is largely silicified, pyritized, and sericitized. The rocks have possibly been subjected to hydrothermal propylitization, but shearing and greenschist facies meta morphism mask the effects. Hydrothermal alteration in the shear zone is centered around veinlets of gray quartz and sulfides and spreads laterally from the veinlets as a flooding of gray quartz, very fine-grained pyrite, and sericite. Some parts of the shear zone are entirely altered with minor remnants of greenschist while in other parts the alteration occurs as irregular patches in sheared and mylonitized green schist. This alteration obliterates or greatly subdues the mylonitic texture. The altered zones are cut by veinlets of carbonate, veins of milky white quartz, which in turn are cut by talc-rich shears. Two generations of quartz veins have been noted. The older is in northeast-trending structural features outside the main sheared and altered zone and as boudins and lenses within the shear zone. The younger milky white veins are both inside and outside the main sheared and altered zone. The older generation may be the source of the local gold and silver anomalies. Pyrite, a common but minor constituent of the sheared, but unaltered greenschists, is most abundant within the altered rock where, along with lesser amounts of chalcopyrite and sphalerite, it forms fine disseminations, stringers, veinlets, and 1 to 10 mm layers conformable to the shear foliation. The sulfides are locally very abundant, but do not form massive bodies more than 5 cm thick.. The only massive sulfide body found was intersected in drill hole Kb-2 at 192.60 to 194.25 m, where approximately 80 percent of the core was stratabound sulfide layers. Chalcopyrite and sphalerite generally occur in veinlets and stringers in the altered rock; however, their abundance is low and distribution sporadic. This is reflected in the generally low ond quite variable copper and zinc values obtained by analyses of split drill core (Appendix I). GEOCHEMISTRY Surface sampling plan Four groups of surface geochemical samples were taken to test the sheared and altered zone for metal content; a) rock chip samples across 10 m intervals within the main
sheared and altered zone, b) selected gossan samples from the main sheared and altered zone, c) chip samples from the bottom of ancient workings cleared of debris, and d) rock chip samples taken at regular intervals along traverses across the major structural trend. Sample locations are on figure 1 and analytical results are given in Appendix A. Each sample was a rock chip sample composed of approximately 3 kg of 3-6 cm sized chips taken from outcrops along the length of the sample zone. Analyses were performed at the Directorate General of Mineral Resources-USGS laboratory, Jiddah. Other elements besides those listed, were checked, but occur in nil or minor amounts and include Mo, W, B, Be, Bi, Cd, La, Nb, Sb, Sc, Sn, Sr, and W. Twenty-six composite rock chip samples were taken along 10 m lengths across the main sheared and altered zone at intervals of 40 m (fig. 1). The samples contained nil to anomalous concentrations of Au, Ag, Cu, and Zn. The mean and range in values are given in table 3. Copper occurs as secondary malachite and chrysocolla stringers; zinc in part as finely disseminated smithsonite and probably in part adsorbed on limonite. The nature of occurrence of the other elements is unknown. Twenty-six selected gossan samples that correspond to the above composite chip samples were taken, one from each composite sample interval. Each sample consisted of several chips of the strongest gossan present within the sample interval. Because the samples were selected high-grade material their metal contents are not characteristic of the main sheared and altered zone. The purpose was to check for the suite of elements present and to obtain a rough estimate of the metal content of sulfide stringers, the probable source of the seams of gossan. Results of analyses are given in Appendix A, and the mean and range in values are given in table 3. The metals present are the same as detected in the 10 m interval chip samples but are present in greater abundance. No other metals were detected. Three trenches were hand dug across the largest and most obvious ancient working (fig. 1) and surrounding sheared and altered rock. The depths of the trenches were 30-50 cm over sheared and altered rock and 1 to 2.5 m over the ancient workings. The sample material collected, although weathered, was from below the obvious surface carbonate and oxide enriched zone. Results of analyses of the fifteen samples are given in Appendix A and the mean and range in values in table 3. The same suite of metals are present, but in lesser concen trations than in the surface samples. Malachite and chryso colla are nct obvious in this rock, nor are sulfides.
Table 3. Mean and range in analytical values of surface and split core samples Umm Al Khabath prospect. , IA - Composite IB - Selected I C&D - Composite I E&F - Composite I -E&F - Composite I IA - Split IIB - Split M C - Split I IA, B, C, & chip samples, gossan chip samples chip traverse chip traverse core samcore samcore samD - All split Sample core sheared and samples from trenches samples samples minus pies from pies from pies from group altered zone samples taken in Hole 3 Hole 2 Hole 3 sheared and altered zone Number of 52 & 34 128 & 13 15 & 15 58 & 38 samples .151* ppm range .05-6.40 .04-17.60 (-)-2.00 (-)-0.41 (-1-0.26 (-1-1.06 (1-1.88 (/-128 Au mean .51 .07" .021* .101* .091* .221* Ag mean 5.83 1.151* .961* 3.21* 2.631* 1.871* ppm range .40-38.2 (-) -11 .6 (1-5.3 (1-3.3 (-)-52.0 (1-52.0 Cu mean .43 .081 .021 .031 .061 ppm range .01-1.88 .04-26.25 (1-1.85 (-1-.23 (1-.63 (-1-.04 (1-.63
Zn mean .25 .061* .071* .311* .031* A2" % range .01-1.73 (-1-6.00 (1-.41 (1-.45 (-)-2.76 (-).44 (1-6.00 Mn mean 568 1,902 1,930 1,573 ppm range 80-1,870 20-1,100 200-1,300 200-5,600 200-5,600 50-5,000 Fe mean % range 3.91-17.3 Mg mean % range Na20 mean % range K20 mean % range Si02 mean % range 42.98-76.48 2.98-71.02 Ba 1,600 mean G5000 ppm range censored 70-5,000 mean ppm range Y mean ppm range Zr mean ppm range
- Data censored-a number of concentrations below detection limits
Sixty composite chip samples were taken along four traverses across the trend of the main sheared and altered zone. The samples were taken at 20 m intervals from random starting points. Each sample was composed of chips taken from an area approximately 10 m in diameter. Results indicate no other metal concentrations other than in the main sheared and altered zone. Analytical results are given in Appendix A, and the mean and range in values in table 3. Core sampling plan Altered and mineralized core was split with one half being retained, and one half submitted for analyses. Sample intervals ranged from 1-2 m of core length. The mean and range in values are given in table 3 and all analytical results are listed in Appendix A. As the samples were selective in that only altered and mineralized rock was included the analytical results are an adequate estimate of the metal content of the sheared and altered zone at depth. Metallized zones encountered in the diamond drilling were very few, and of low grade. They are listed below: Drill Hole Depth Metal content Kb-1 196-240 m 14% Cu Kb-2 180-184 m 45% Zn 187-190 m 10% Cu, .43% Zn 190-194 m 35% Cu, 1.11% Zn 198-199 m 44% Cu, 2.76% Zn Discussion Distribution of anomalous concentrations of the metals copper, zinc, gold, and silver is centered upon the main sheared and altered zone. Overall primary concentration within the zone is slight, but higher metal values, corres ponding to massive silicification with disseminated to massive pyritization, occur scattered throughout. Secondary concentration of copper, zinc, gold, and silver at the surface of the main and altered zone is significant. This concentra tion is at or just under the surface as evidenced by the low metal values of samples obtained from shallow trenches dug across the zone (table 3). Much of the copper and presumably also the zinc in the surface zone occurs as pods and lenses within the calcrete cap that covers part of the zone. The high values of copper, and zinc in the carbonate-rich surface rocks are misleading and represent false or dispersed hydromorphic anomalies. Metals migrating along the shear zone
would be trapped, by deposition, in the alkaline environment forming the calcrete cap. Source of the materials for the calcrete cap is the locally abundant carbonates in the sur rounding tuffs, especially where cut by the shear zone. In this arid to semi-arid environment a strong upward percolation of the Ca++ and HC0-charged water combined with evaporation and transpiration of the surface would form the calcrete cap above or near the source carbonate. Source of the metals is not so clear. The anomalous values could represent a progres sive concentration of the metals weathered in place; and retained relatively immobile by the alkaline environment. More likely the values represent an enrichment of metals from other parts of the sheared and altered zone that were deposited and trapped upon encountering the alkaline environment. Oxida tion of the siliceous sulfide bodies would release the metals in an acid environment in which zine especially, but also copper, are highly mobile. These elements would then be relatively mobile until they either reached the surface, probably alkaline everywhere in this climate, or encountered a zone of alkaline waters around weathering carbonates. The copper and zinc may have migrated a few meters, many meters, or perhaps many hundreds of meters. Although these anomalies do not reflect metallization directly at depth they do point to a source somewhere within the hydromorphic system. Detailed surface and subsurface geochemical studies of several prospects in the Wadi Bidah district by Allcott (written commun.) have pointed out the need to use elements other than copper and zinc for geochemical exploration in this area. The geologic setting of the Wadi Bidah district is similar to that at Umm Al Khabath. Massive sulfide bodies are along sericitized, silicified, and pyritized altered shear zones and are commonly associated with larger zones of disseminated and stringy sulfides. Some of the occurrences at Wadi Bidah have massive limonite gossans but the weak, malachite-bearing calcrete covered gossan over the largest deposit, Rabathan, is not unlike the leached and gossan zone at Umm Al Khabath. Allcott (written commun.) suggests that anomalous concentrations of Au, Ag, Ba, and an Fe/Mg ratio greater than 5 are significant indications of metallization and may more exactly define targets than copper and zinc. At Umm Al Khabath, samples taken from trenches across the main sheared and altered zone contain anomalous concentrations of Au, Ag, and Ba and the Fe/Mg ratio on half the samples is 5 or greater. Most of the samples from the zone contain slightly anomalous concentrations of gold and silver. However analyses of Ba, Fe, and Mg were determined on too few of these samples to be meaningful.
GEOPHYSICAL INVESTIGATIONS by Vincent J. Flanigan and Habib M. Merghelani Introduction Geophysical surveys were carried out at the Umm Al Khabath copper prospect to provide geophysical data that might assist in understanding the structure, geology, and mineral potential of the area. The geophysical surveys covered an area of approximately 1.4 x .25 km along the main sheared and altered zone (fig. 1). This zone presumably associated with regional faulting ranges from 10-50 m in width and can be traced for several kilometers through the area. Metavolcanic rocks of the Baish Formation have been largely altered to quartz-sericite schist in the altered zone. Non metallic conductors such as graphitic schist, are not present in the prospect area. Discussion of results The results of the geophysical surveys are shown on figures 3 and 4. Five distinct lens-shaped anomalies were outlined by the self-potential (SP) method. These anomalies, located along the zone of shearing and alteration, range in size from 10-13 m wide and 100 240 m long. The maximum amplitude of the SP anomalies is -150 milli volts (mV), as referenced to base station 80S. The self-potential method (fig. 3) measures spontaneous or natural voltages developed in the earth. The source of the selfpotential determinations is not dependent upon any definite rock physical property but is due to chemical activity associated with the oxidation process (Parasnis, 1966). Sato and Mooney (1960) suggest that certain common conditions have been observed to exist where the source of self-potential values have been studied. Among these are factors that affect the oxidation process and the transfer of elec trons in the ore body and surrounding country rocks. When ideal conditions are attained in nature, the self-potential will be large, reaching values on the order of 500 mV. A deterioration in one or more of these factors affecting the SP phenomena will result in lower amplitude measurements. Just how much each factor affects the overall process is not clearly understood, but this probably explains why some ore bodies can be outlined reasonably well by the SP method, whereas known extensions of the same ore body, apparently not elec trically connected, reflect none or very small self-potential measurements. The electromagnetic (EM) method (fig. 4) also outlined the altered zone where locally, values of up to 1:1.6 amplitude ratio where attained. The maximum EM values generally coincide
EXPLANATION SELF-POTENTIAL CONTOURS - Lines of equipotential referenced from the 80S base station. Contour interval 25 millivolts; hachures indicate closed area of lower self potential N 60 m SCALE Figure 3. - Self-potential map, Umm al Khabath prospect.
EXPLANATION ELECTROMAGNETIC CONTOURS - Represent area of subsurface conduction as defined by the amplitude ratio of the 660 cps electro magnetic signal induced into two detectors 20 m apart. Contour interval 0.1; hachures indicate closed areas of lower ratio N 60 in SCALE KbFigure 4. - Turam electromagnetic ratio map, Umm al Khabath prospect.
with the maximum SP values, except that the EM maxima are offset to the west in reference to SP maxima suggesting that the EM method may be more susceptible to the dip of the conductor than is the SP method. Phase angle differences (not shown on fig. 4) coupled with the amplitude ratio values indicate that the body centered about station 400N and 160W is a moderate to good electrical conductor. The diamond drill holeq penetrated the sources of the highest T-!c>physical anomalies. The relationship of the geo physical data to the drill core log of the hole KB-1 is shown on figure 2. Generally the drill intersected tuff and agglomerate mineralized by disseminated pyrite. Along the zone of alteration the tuff and the agglomerate are altered to quartz sericite schist. The highest geophysical data values seem to be associated with this quartz sericite schist and may be related more specifically to the degree of altera tion associated with more intensely sheared sections of the zone. Drill hole KB-2 (fig. 2) generally shows the same relationship, that is, the highest geophysical data values are associated with the zone of shearing and alteration in which the tuffs and agglomerates are silicified, sericitized, and pyritized in varying degrees. Pyrite is abundant locally in the altered zone. The relationship of the drill core log of hole KB-3 to the relative self potential, and to the apparent resistivity of the rocks intersected by the drill is shown in figure 5. The self potential as well as the apparent resistivity values are relative to an arbitrary datum and cannot be related to the results of the surface SP survey. However, it is apparent that within the sheared and altered zone several zones of higher self-potential exist. Anomalous zones also are reflected at 10 m intervals at 165 m and 232 m where lower apparent resistivity measurements were recorded. These anomalies may be associated with the degree of alteration, but this cannot be correlated directly. Conclusions The self-potential and electromagnetic anomalies of Umm Al Khabath are directly associated with the zone of shearing and alteration. Within the zone of alteration there are noncoincident zones of higher self potential and lower resistivity. The degrees of metallization and alteration, as well as the factors affecting the oxidation-reduction SP phenomena, probably account for the caw-;e of the geophysical anomalies. The main source of the SP anomaly is probably the dark gray siliceous pyritic alteration product.
Surface Massive, fine-grained tuff Water table Disseminated magnetite Pyroclastic tuff agglomerate with disseminated pyrite Steel casing + + 4, in meters P08C 000,4 Weak to : intense shearing o„ 000, 0, %., cS -250 1)01 t
SCALE RELATIVE SELF POTENTIAL Quartz-sericite schist with dark-gray groundmas. Siliceous tuff 7Quartz-sericite schist Siliceous tuff Quartz- sericite schist with disseminated pyrite
ohms SCALE RELATIVE APPARENT RESISTIVITY Figure 5. - Log of diamond drill hole Kb-3 showing relationship of electric logs to lithology.
CONCLUSIONS AND RECOMMENDATIONS Primary metallization at Umm Al Khabath consists of chalcopyrite and sphalerite with trace quantities of silver and gold related to a distinct period of quartz veinlet stock-working silicification, sericitization, and pyritiza tion. Metal content within the altered rock is erratic and higher concentrations are mainly confined to zones of high pyrite content. The alteration and related metallization were later events in the geologic history of this region. The origin of the deposits was probably by deposition from waters derived from deep-seated sources; migrating upward along the shear zone; perhaps during a late metamorphic stage. A partial geologic history of the mineralized belt is summarised below: A - Period of minor shearing and development of hydro thermal(?) talc along shears. B - Emplacement of andesitic dikes. This event may have preceded the shearing and alteration . C - Emplacement of milky white quartz veins. D - Emplacement of quartz veinlet stockworks with asso ciated silicification, sericitization, pyritization, and metallization in the main shear zone. This event crosscuts and obliterates the mylonite. E - Shearing along north-trending surfaces with develop ment of foliation and schistosity in all lithologies and intense mylonite in the shear zones. F - Emplacement of diorite dikes and quartz veins along north-east trending fractures. U) G - Development of foliation and presumably metamorphism bH of the Baish Group basaltic tuffs and agglomerates. The surface geochemical copper and zinc anomalies along the main sheared and altered zone are supergene hydromorphic and reflect more the presence of an alkaline environment than an underlying metalliferous deposit. The metals may have migrated long distances along the shear zone before being precipitated in the alkaline, near surface environment. Geo physical electromagnetic (EM) anomalies outline the zone of shearing and the SP anomalies probably outline the areas of strongest pyritization and associated alteration. Investigations at Umm Al Khabath have identified geolog ical factors that should be considered in any future explora tion in the general area. Any surface anomalies of copper
and zinc must be evaluated carefully in terms of the environ ment of secondary transportation and deposition. Selective sampling of altered and gossan zones from shallow trenches may give more accurate approximations of the metal content of the unweathered rock. However, in the case of copper and zinc, they would be depleted if the environment were acidic and enriched if it were alkaline. Other pathfinder elements such as Ba, Au, Ag, and the Fe/Mg ratio as suggested by Allcott (written commun.) may prove to be more useful. Although electro magnetic (EM) anomalies generally outline sheared zones, a SP anomaly may outline massive sulfides, finely disseminated sulfides, (weathering) graphitic schists, pyritiferous slates, ferruginous jasper dikes, or iron-bearing beds. Other electrical geophysical methods may prove to be more useful. The fact that large zones of mineralization or massive sulfide bodies were not detected by drilling Umm Al Khabath does not negate their presence in the general area. The results of work at Umm Al Khabath suggest that if massive or disseminated sulfide deposits do occur in the Baish Group rocks an integreated program of geochemistry, geophysics, lithofacies studies, and regional geology will be needed to detect them. REFERENCES Earhart, R. C., and Mawad, M. M., 1970, Geology and mineral evaluation of the Wadi Bidah district: U. S. Geol. Survey 04) S 119, 110 p. Goldsmith, Richard, 1971, Mineral resources of the Southern Hijaz quadrangle, Kingdom of Saudi Arabia: Saudi Arabian Dir. Gen. Mineral Resources Bull. 5, 62 p. Greenwood, W. R., 1975, Geology of the Jabal Ibrahim quadrangle, Sheet 20/41C, Kingdom of Saudi Arabia, with a section on Economic Geology by R. G. Worl and W. R. Greenwood: Saudi Arabian Dir. Gen. Mineral Resources Geol. Map GM-22 (scale 1:100,000) with text. Greenwood, W. R., Roberts, R. J., and Bagdady, Abdulaziz, 1974, Mineral belts in western Saudi Arabia: U. S. Geol. Survey /-L-kja-/ (/re) sof-. 177, 26 p. Greenwood, W. R., Roberts, R. J., Kiilsgaard, T. H., Puffett, Willard, and Navi, I. M. 1974, Massive sulfide deposits in the Wadi Bidah mining district: U. S. Geol. Survey 175, 17 p.
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 Soc. London Phil. Trans., v. A280, p. 517-527. Parasnis, D. S., 1966, Mining geophysics: Elsevier Pub. Co., p. 74-93. Sato, Motoaki, and Mooney, H. M., The electrochemical mechanism of sulfide self-potentials: Geophysics, v. 25, no. 1, p. 226-249. APPENDIX - Analytical results Surface sample locations are given on fig. 1, and drillcore sample intervals and depths are on logs on file at the Directorate General of Mineral Resources. This listing contains results of the following: I. Surface composite chip samples A. Along 10 m sample intervals across main sheared and altered zones. B. Selected gossan samples that correspond to sample set A. C. From trenches across ancient workings, atomic absorp tion results. D. From trenches across ancient workings, spectrographic results. E. At 20 m intervals along traverses across structure, atomic absorption results. F. At 20 m intervals along traverses across structure, colorimetric and atomic absorption results. II. Subsurface split drill-core samples A. Drill hole Kb-1, atomic absorption results B. Drill hole Kb-2, atomic absorption results C. Drill hole Kb-3, atomic absorption results D. Drill holes Kb-1, Kb-2, and Kb-3, spectrographic results.
I. Surface composite chip samples A. Along 10 m sample intervals across main sheared and altered zone, atomic absorption results, Sample number Au ppm Ag ppm Cu Pb Zn 1/ Ba ppm 1/ Fe/Mg ratio As ppm Mn ppm 98,300 98,301 98,302 98,303 98,304 1,300 98,305 98,306 98,307 98,308 98,309 1,870 98,310 98,311 98,312 98,400 98,401 98,402 98,403 98,404 98,405 98,406 1,440
I. Surface composite chip samples A. Along 10 m sample intervals across main sheared and altered zone (cont'd.) 1/ Sample Au Ag Cu Pb Zn Ba Fe/Mg1/ As Mn number ppm ppm ppm ratio ppm ppm 98,407 98,408 98,409 98,410 98,411 98,412 Mean Range .05-6.40 .40-38.2 .01-1.88 80-1,870 1/ — Spectrographic analyses
I B. Selected gossan samples that correspond to sample set A. Atomic absorption results. Bad Au Ag Cu Pb Zn Ba Fe/Mg-1/ As Co Mn number ppm ppm ppm ratio ppm ppm ppm 98,300 1,000 98,301 98,302 98,303 98,304 1,000 98,305 98,306 N, 98,307 -.1 98,308 98,309 98,310 98,311 98,312 98,400 98,401 125 1,370 98,402 98,403 99,404 98,405 98,406
I B. Selected gossan samples that correspond to sample set A (cont'd.) Sample Au Ag Cu Pb Zn Ba1/ Fe/Mg-1/ As Co Mn number ppm ppm ppm ratio ppm ppm ppm 98,407 98,408 60 1,100 98,409 98,410 98,411 98,412 m Mean Range .04-17.60 .7-396.0 .04-26.25 (-)-.74 (-)-6.00 20-1,100 1/ - Spectrographic analyses
I C. From trenches across ancient workings, atomic absorption results Sample Au Ag Cu Pb Zn Fe/Mg As Co Mn number ppm ppm ratio ppm ppm ppm 98 5161/ " / 98,517- 2,180 98,518I: 98,519-2-, 98,5201 / 98,5211 98,5221 98,5237 1,300 98,525-11 98,5261/ 98,527 / 98,5282, 98,5292/ 98,530 Mean Range .04-.88 .6-43.2 .01-.18 200-2,180 / one meter sample interval / five meter sample interval
I D. From trenches across ancient workings, spectrographic results Sample number Fe Mg Cu Ti Ba ppm ppm Y ppm Zr ppm CA) C:D I/ 98,516I/ 98,5171 98,518 -/ 2/ 98,519 / 98,5201 I/ 98,521 / 98,5221/ 98,5231I/ 98,524 / 98,5251 I/ 98,5262/ 98,527 / 98,5282/ 98,529 / 98,530-?- G5,000 G5,000 G5,000 G5,000 G5,000 G5,000 G5,000 G5,000 G5,000 G5,000 G5,000 3,000 G5,000 3,000 Mean G5,000 Range 1.0-5.0 .3-.7 <.05-1.5 .1-.3 50-200 20-100 20-70 one meter sample interval 2./ five meter sample interval G - Greater than value given
I E. At 20 m intervals along traverses across structure, atomic absorption results Sample Au Ag Cu Pb Zn Bali Fe/Mg1/ Co Ni Mn number ppm ppm % % % ppm ratio ppm ppm ppm 98,340 98,341 98,342 98,343 98,344 3,000 1,580 1,440 1-, 98,345 98,346 98,347 98,348 98,349 1,870 98,350 98,351 98,352 98,353 98,354 1,000 1,480 98,355 98,356 98,357 98,358 98,359 1,500 98,360 98,361 98,362 98,363 98,364 5,000 61'
I E. At 20 m intervals along traverses across structure, atomic absorption results (cont'd.) / / Sample Au Ag Cu Pb Zn Bal Fe/Mg1 Co Ni Mn number ppm ppm % % % ppm ratio ppm ppm ppm 98,365 98,366 98,367 98,370 5,000 2,040 98,371 3,640 98,372 3,840 98,373 4,320 98,374 4,000 98,375 2,520 w 98,376 2,000 98,377 2,060 98,378 98,379 2,000 98,380 3,000 5,600 98,381 3,560 98,382 3,120 98,383 4,840 98,384 2,520 98,385 3,260 98,386 3,000 98,387 3,480 98,388 3,920 98,389 2,220 98,390 2,680 98,391 2,400
I E. At 20 m intervals along traverses across structure, atomic absorption results (cont'd.) Sample Au Ag Cu Pb Zn Ba"Fe/Mgl/ Co Ni Mn number ppm ppm ppm ratio ppm ppm ppm 98,392 3,000 98,393 2,990 98,394 2,400 98,395 2,680 98,396 2,320 98,397 2,880 98,398 2,520 w 98,399 2,600 w Mean 1,902 Range (-)-2.00 (-)-11.6 (-)-1.85 200-5,600 1/ Spectrographic analyses
I F. At 20 m intervals along traverses across structure, colorimetric and atomic absorption results Sample Na20 K20 SiO2 Fe number °A 98,360 98,361 98,362 98,363 98,364 98,365 98,366 98,367 98,370 98,371 98,372 98,373 98,374 98,375 98,376 98,377 98,378 98,379 98,380 98,381 98,382 98,383 98,384 98,385 98,386 98,387 J.06 66.()8 98,388 98,389 98,390 98,391
I F. At 20 m intervals along traverses across structure, colorimetric and atomic absorption results (cont'd.) Sample Na2O K2O SiO2 Fe number °A 98,392 98,393 98,394 98,395 98,396 98,397 98,398 98,399 Mean Range .04-5.67 .24-2.70 42.98-76.48 3.91-17.3
II. Subsurface split drill-core samples A. Drill hole Kb-1, atomic absorption results Sample (m) Au Ag Cu Pb Zn Ca Mo As number From To ppm ppm ppm ppm 101,300 101,301 101,302 101,303 101,304 rn 101,305 101,306 101,30101,308 101,309 101,310 101,311 101,312 101,313 101,314 101,315 101,316 101,317 101,318 101,319 101,320 101,321 101,322 101,323 1n1,324
II. Subsurface split drill-core samples A. Drill hole Kb-1, atomic absorption results (cont'd.) Sample Interval (m) Au Ag Cu Pb Zn Ca Mo As number From To ppm ppm ppm ppm 101,325 101,326 101,327 101,328 101,329 w 101,330 101,331 101,332 101,333 101,334 101,335 101,336 101,337 101,338 101,339 101,340 101,341 101,342 101,343 101,344 101,345 101,346 101,347 101,348 '01.349
II. Subsurface split drill-core samples A. Drill hole Kb-1, atomic absorption results (cont'd.) Sample number Interval (m) From To Au ppm Ag ppm Cu Pb Zn Ca Mo As ppm ppm 101,350 101,351 101,352 101,353 101,354 w 101,355 101,356 101,357 101,358 101,359 101,360 210 211 101,361 101,362 101,363 101,364 .38 20 10 101,365 101,366 101,367 Mean Range
II B. Drill hole Kb-2, atomic absorption results Sample Interval (m) Au Ag Cu Pb Zn Ca Mo As number From To ppm ppm % ppm ppm 101,368 101,369 101,370 101,371 101,372 =.02 101,373 101,374 101,375 101,376 101,377 101,378 101,379 101,380 101,381 101,382 101,383 101,384 101,385 101,386 101,387 101,388 101,389 101,390 101,391 101,392
II B. Drill hole Kb-2, atomic absorption results (cont'd.) Sample number Interval From (m) To Au ppm Ag ppm Cu Pb Zn Ca % Mo ppm As ppm 101,393 101,394 101,395 101,396 101,397 101,398 101,399 Mean Range (-)-1.06 0.7-22.0 (-)-2.76
II C. Drill hole Kb-3, atomic absorption results Sample number Interval From (m) To Au ppm Ag ppm Cu Pb Zn Ca % Mo ppm As ppm 101,400 101,401 101,402 101,403 101,404 101,405 101,406 101,407 101,408 101,409 .p. 1-, 101,410 101,411 101,412 101,413 101,414 101,415 101,416 101,417 101,418 101,419 ,13 101,420 101,421 101,422 101,423 101,424 101,425 101,426 101,427 Mean (-) Range (-)-1.88 (-)-52.0 (-)-.04
II D. Drill holes Kb-1, Kb-2, and Kb-3, spectrographic results Sample Fe Mg Ti Mn Ba Y Zr c., number ppm ppm ppm ppm ppm 101,300 101,310 101,320 1,000 101,330 101,340 3,000 101,350 5,000 1,000 101,360 3,000 5,000 101,370 3,000 5,000 101,380 3,000 3,000 N 101,390 1,000 101,400 1,000 101,410 1,500 101,420 Mean 1,573 1,600 Range .5-5.0 .2-.7 50-5,000 70-5,000
937 z1
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