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.
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.
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USGS Numbered Series
Ancient mines of the Farah Garan area, southwestern Saudi Arabia