Hydrothermal alteration patterns surrounding the Yalea Au deposit as reflected by mica chemistry

摘要

Patterns in muscovite, paragonite, and phengite Al-Si chemistry, and biotite Mg-Fe chemistry were examined for the Lower Proterbzoic Yalea gold deposit in the Kedougou-Kenieba Inlier, Western Mali. The structurally , controlled deposit forms part of the ~25 km long Loulo-Gounkoto gold district, a >17 Million ounce gold camp and is hosted in greenschist-facies quartz wackes, argillites and marbles. Superimposed metasomatic hydrothermal alteration halos extend for up to ~15 km from the economic zone. This includes an envelope of plagioclase-biotite-sericite alteration extending ~1060 m into the hangingwall, overprinting regional pre-mineralisation albitisation and tourmali-nisation (Lawrence et al. 2015). The mineralogy of this envelope was investigated to better constrain the development of the hydrothermal system at Yalea.