An evaluation and geochemical survey of the Farah Garan East Prospect, Southeast Asir, Kingdom of Saudi Arabia

The Farah Garan East prospect (MODS 4886) is located in the southeastern part of the Precambrian Arabian Shield of Saudi Arabia, about 15 km east-northeast of Zahran Al Janub and 1 km northeast of the ancient mines at Farah Garan. Ore minerals at the Farah Garan East prospect are pyrite, tennantite, galena, and sphalerite. These are sparsely and erratically distributed in west-dipping beds of dolomite, dolomite-talc breccia, and carbonate-sericite phyllite, and in associated breccias and zones of carbonate-altered mafic metavolcanic rocks, all of Precambrian age. Concordant beds of dolomite and carbonate-sericite phyllite are interlayered with metavolcanic rocks and are interpreted as volcanic-related submarine hydrothermal deposits of Precambrian age. Funnel-shaped bodies of dolomite-talc breccia that crop out near the north and south ends of the dolomite beds are interpreted as submarine hot-spring vent breccias. Aprons of exhalative dolomite thin laterally outward from these vents. Discordant and concordant zones of carbonate-altered metavolcanic rocks, east of and structurally below the hot-spring vents, probably represent pathways of hydrothermal circulation along networks of fractures in volcanic rocks, subjacent to these Precambrian submarine hot-spring vents.

Ore minerals in outcrops, and geochemically anomalous concentrations of gold, silver, copper, lead, zinc, arsenic, antimony, and tellurium are present in carbonate-rich rocks of the hot-spring assemblage. This indicates that the ore minerals and elements were deposited originally as constituents of the hot-spring assemblage. However, exposed ore-mineral occurrences are small and sparse, and geochemical anomalies are small, irregularly distributed, and of subeconomic grade. Furthermore, weak electromagnetic anomalies do not indicate the presence of subsurface bodies of concentrated, conductive ore minerals. Therefore, no drilling is recommended.