The metallogeny of gold deposits in Saudi Arabia and its significance in gold exploration and exploitation

الملخص EN

Met allogenic studies relating to gold deposits in the Saudi Arabian Shield show that gold is hosted mainly by two broadly-recognized geologic environments, namely vol- canosedimentary successions and plutonic complexes, within which tour principal types of gold mineralization have been recognized on the basis of rock-facics association, morphologi- cal setting and mineral assemblages.

1.

Gold mineralization associated with oxidized sulfide zones, as at Al Hajar and Shaib at Tair prospects (Wadi Shwas-Wadi Bidah areas), comprising breccia ted, silicificd, ferruginous and sandy-textured fades, in which free gold is finely disseminated in supergene alteration minerals and associated siliceous gangue.

2.

Gold mineralization in zones of massive sulfides, in close association with vol- canosedimentarv facies (cherts, carbonates, graphitic tuffs), as at AI Masani and Nuqrah.

forming a concordant mineralized interval commonly at the top of the sulfide body This mineralization, which is also locally enriched in silver, displays a complex gold-silver-telluridc- sulfide and silver sulfosalt mineral assemblage.

3.

Gold mineralization occurring in vein-like bodies and/or stockworks hosted by chloritized and siliceous volcanic facies and subvolcanic intrusions, as at Mahd adh Dhahab and Al Amar.

where the mineralization is characterized by relatively high gold content, ex- pressed both by the notable concentration of free gold in sulfides, chlorite and quartz, and by the relative abundance of gold and gold-silver tcllurides.

4.

Gold mineralization related to plutonic complexes as at Sukhaybarat.

Zalim.

Bari and Jabal Ghadarah that is typically characterized by close association of gold with arsenopyrite and pyrite, general scarcity of basc-metal sulfides and a marked depletion in gold tcllurides.

These metallogenic studies in conjunction with detailed geological and geochemical investi- gations led to the redefinition of exploration targets for gold mineralization in the Saudi Ara- bian Shield, and the re-examination of known gold occurrences and ancient mines of small di mensions.

following the recent improvements in gold extraction by heap leaching and cyanida- tion techniques.