Hydrothermal Alterations in Irbiben Gold Deposit (Tagragra Akka, Western Anti-Atlas, Morocco): Petrographic and Geochemical Characterization

Abstract

Irbiben is a small gold deposit of the Precambrian inlier Tagragra d'Akka located in the Moroccan western Anti-Atlas, approximately 160 km southeast from Tiznit. Petrographic study shows that host rocks of Irbiben deposit are green schist facies metamorphic rocks, like metamorphic sandstone and schist, meta-pelite and quartzite. Gold is located in quartz veins or host rock with frequent injections of quartz. The petrographic characterization of alteration through the description of the alteration profiles and the comparative study of protolith and altered rocks showed a development of dominant quartz and calcite in mineralization wall-rocks. In moving away from it, there is rather sericite and chlorite. These phenomena are materialized respectively by the development of SiO 2 and CaO in the wall-rocks but rather that ferromagnesian elements (FeO, MgO) and K 2 O away from the mineralization. These trends were demonstrated by the geochemical study through Harker diagrams, description of alteration profiles, comparative study of protolith and altered rocks, and use of a new alteration index, MIA, elaborated during this work.