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A. M. Helaby

Publications and source records attributed to A. M. Helaby.

6 recordsLinked to original sources
USGS1990

Hamdah ancient gold mines, Kingdom of Saudi Arabia

The Hamdah prospect is a 1.5-km 2 area that includes ancient mine workings 15 km southeast of Hamdah in the southern Arabian Shield. The workings cluster at a gently dipping thrust contact between serpentinite (above) and hornblende schist (below) exposed in a window within the serpentinite. Aplite sills intrude the contact, and gold concentrations occur just above or below it. The ancient mine dumps cover >100,000 m 2 of the prospect and are estimated to be 1.5 to 1.8 m thick. They contain nearly 181,000 metric tons of material at an average grade of 4.5 g/t gold, thus having an estimated total gold content of 831 kg, or 26,726 Troy oz. Almost 100 percent of the contained gold is recoverable by cyanide acid leaching. Eleven new diamond-drill holes were completed to supplement information from 12 drill holes completed during an earlier drilling program, in order to enable more detailed evaluation of the prospect. The drill holes are grouped in the northeast, southeast, southwest, and west quadrants of the prospect. In the northeast quadrant, where 9 drill holes intersect gold at shallow (<27 m) depths, the quadrant is calculated to contain nearly 242,300 metric tons of gold-bearing material. The calculations show: (1) 19,144 metric tons high-grade material grading 21.4 g/t Au at 5 g/t cutoff; (2) 39,884 metric tons of material grading 8.5 g/t Au at 5 g/t cutoff; (3) 71,617 metric tons of material grading 3.9 g/t Au at 1 g/t cutoff; and (4) 111,641 metric tons low-grade material grading 2.0 g/t Au at 1 g/t cutoff. Total gold content of this selected block is 1,251 kg gold, or 40,234 Troy oz. The mineralized zone in 1 the northeast quadrant is open to the northeast, east, and southeast. Drill data are insufficient in detail to allow grade or tonnage estimates for the southeast, southwest, and west quadrants of the prospect. Gold is concentrated in surface alluvium in the southeast and southwest of the prospect, in amounts that are of possible economic significance. Ground geophysical surveys (CEM and VJJ7) revealed the presence of electrical conductors at shallow depths, some of which correlate with possible disseminated sulfide minerals, and others with the thrust contact. It is recommended that the thickness of the dumps be more accurately determined, and that the gold leachability of bulk dump material be tested. Shallow reverse-circulation drilling is recommended on 25-m centers in the northeast quadrant, and diamond drilling is recommended elsewhere at the prospect. Geophysical surveys are required to help establish depths to the serpentinite/schist contact on the northeastern, southern, and western margins of the prospect. Detailed mapping should be undertaken at the prospect, and a mineral-belt type of mapping program should be completed over the larger Hamdah region.

Open-File Report↗
USGS1983

Geological and geochemical studies in the Wadi Bidah District, Kingdom of Saudi Arabia

Geological and geochemical followup studies of airborne electromagnetic anomalies in the Wadi Bidah district, southwestern Saudi Arabia, did not reveal metals of economic grade. Investigation of an anomaly enclosing the Rabathan ancient mine disclosed tightly folded and sheared Proterozoic tuffaceous rocks interlayered mostly with chert, dolomite, carbonaceous rocks, and volcanic wacke including cherty iron-manganese formations slightly anomalous in copper and zinc. Three drill holes placed to test anomalies within these formations yielded negative results. Studies of a long, narrow anomaly north of the Rabathan area indicated a similar geological environment. This northern area also contains limited zones that are highly anomalous in copper and zinc and extensive zones that are slightly anomalous in those metals. Drilling was not undertaken in this area. The Bilajimah airborne electromagnetic anomaly west of Wadi Bidah coincides with a broad synclinorium of layered felsic turfs and gossans. Geochemical studies indicated slightly anomalous copper, zinc, and silver values in gossans within the anomaly area. Two drill holes intersected carbonaceous rock that contained approximately 15 percent pyrrhotite and traces of sphalerite and chalcopyrite. Two geophysically anomalous areas west of Wadi Bidah surround ancient mines at Mahawiyah and Khayal al Masna'ah. Results of geochemical sampling at these workings were positive. An airborne electromagnetic anomaly located in the Assifar area in the southwestern corner of the Wadi Bidah district is underlain principally by metasedimentary rocks that include large linear zones of cherty iron-manganese formation and a few gossans .containing secondary base metal minerals. Detailed mapping and sampling of the Mulhal ancient mine, located west of Wadi Bidah, revealed two types of polymetallic gossans : (1) stratiform deposits interlayered with ignimbrites and mafic volcanic rocks and (2) barite-bearing gossanous material in shear zones that grade into hydrothermally altered shear zones and extend beyond the mine area. The gossans and gossanous shear zones contain anomalous amounts of gold, silver, lead, copper, zinc, barium, and selenium. Two gossans west of Wadi Bidah were mapped and sampled in detail; both gossans are interlayered, with siliceous volcanic rocks. Although the gossan at Jabal Mohr covers a large area, it contains low amounts of precious and base metals. The gossan at Mulhal No. 2 contains moderate to high amounts of gold, silver, copper, lead, and zinc.

Open-File Report↗
USGS1981

Iron sulfide deposits at Wadi Wassat, Kingdom of Saudi Arabia

Massive and disseminated iron sulfide deposits in Wadi Wassat form lenticular, stratabound deposits in cherty Precambrian sedimentary rocks interlayered with Precambrian calcareous sedimentary rocks, pyroclastic rocks, and andesitic flow rocks. These rocks have been cut by a wide variety of plutonic and dike rocks including gabbro, diorite, granodiorite, diabase, rhyolite, and granite. The zone containing the sulfide lenses is nearly 16 km long and is cut off by granitic rocks at both the northern and southern ends. The lenses are as much as 200 m thick; one can be traced along strike for more than 4 km. The lenses consist mostly of iron sulfides. Pyrite is the principal sulfide mineral; near intrusive bodies the pyrite has been partially converted to pyrrhotite and locally mobilized into fractures. The sulfides have been oxidized to a depth of about 25 m. Preliminary calculations indicate that about 107,500,000 tons of sulfides, averaging 40 percent iron and 35 percent sulfur, are available to a depth of i00 m. Small amounts of nickel, cobalt, zinc, and copper are also present, but at metal prices prevailing in early 1981, these do not constitute significant resources.

Open-File Report↗
USGS1977

The Jabal Guyan ancient gold mine, Wadi Malahah quadrangle (sheet 18/43D), Kingdom of Saudi Arabia

Gold occurs in quartz veins and associated altered country rocks at the Jabal Guyan ancient mine in southern Saudi Arabia. The gold-bearing veins follow northwest-trending fault zones which cut the Precambrian metavolcanic rocks of the area. The veins are brecciated, and gold may have been remobilized during cataclasis. A second generation of unbrecciated, barren quartz cements the earlier quartz and also occurs in north-northeast-trending veins. Gold values are greater in waste in the mine area than in vein quartz remaining in the ancient workings, and it is believed that considerable gold was extracted from high-grade ore by the ancient miners. Exploration drilling to determine if veins and alteration zones persist at depth at the Jabal Guyan mine and examination of other ancient mines in the region are recommended.

Wadi Malahah quadrangle↗
USGS1975

Mineralization in the Uyaijah-Thaaban area, west-central part of the Uyaijah ring structure, Kingdom of Saudi Arabia

Anomalous amounts of tungsten, molybdenum, and bismuth were found previously in surficial debris collected from the Uyaijah-Thaaban area in the west-central part of the Precambrian Al Uyaijah ring structure. The area is mostly underlain by quartz monzonite. Countless quartz veins ranging from a knife edge to more than 3 m in thickness cut the quartz monzonite; many of these veins contain molybdenite. Detailed mapping and intensive sampling of the molybdenite-bearing quartz veins indicate that their grade and quantity are probably inadequate to permit present-day mining; however, they represent a potential future resource. The tungsten of the area appears to be negligible.

Open-File Report↗