Ouiya P., Siebenaller L., Salvi S., Béziat D., Naba S., Baratoux Lenka, Naré A., Franceschi G.
Source
Ore Geology Reviews, 2016,
78, p. 623-630 ISSN 0169-1368
The Nassara-Au prospect is located in the Birimian Boromo Greenstone Belt in southwestern Burkina Faso. It is part of a larger mineralized field that includes the Cu-Au porphyry system of Gaoua, to the north. At Nassara, mineralization occurs within the West Bade Shear Zone that follows the contact between volcanic rocks (basalt and andesite) and volcano-sediments (pyroclastics and black shales) at the southern termination of the Boromo Belt. Gold is associated with pyrite and other Fe-bearing minerals that occur disseminated within the sheared volcanic and volcano-sedimentary rocks. In particular, highest grades are distinguished in alteration halos of small quartz-albite-ankerite veins that form networks along the shear zone. Here, pyrites are marked by As-poor and As-rich growth zones, the latter containing gold inclusions. Gold mineralization formed during D2(NA). Subsequent shear fractures related to D3(NA) related are devoid of gold. Nassara is a classical orogenic gold occurrence where gold is associated to disseminated pyrite along quartz veins.
