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 SiO2 and CaO in the wall-rocks but rather that ferromagnesian elements (FeO, MgO) and K2O 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.
Highlights
The Irbiben gold deposit, formerly operated by the Akka Mine, is located in the Akka Tagragra inlier
The host formations of the Irbiben deposit are composed of rocks generally metamorphosed in the green schist facies
The hydrothermal activity has led to the formation of secondary minerals such as calcite, sericite, chlorite or quartz QIII. These mineralogical changes are reflected in the chemical composition of the rocks, resulting in a much higher silica and calcium grade, much more important in the hanging walls accompanied by an increase in iron
Summary
The Irbiben gold deposit, formerly operated by the Akka Mine, is located in the Akka Tagragra inlier It is located about 160 km Southeast Tiznit city, in the Western part of the Moroccan Anti-Atlas. In addition to the deformation caused by the placement of the gold-bearing quartz veins in the host rocks, a change, minor, affects these in their mineralogy and their chemistry This is why this paper proposes to identify and characterize this hydrothermalism through a petrographic and geochemical study of alteration. Several studies [1] [2] [3] [4] have shown that there are close links between the development of gold mineralization and hydrothermal alterations This type of association occurs in deposits of the Tagragra of Akka [3] [5] of which Irbiben is a part of.
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