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Scientific Research
NATURE OF GOLD MINERALISATION IN ILESHA SCHIST BELT SOUTHWESTERN NIGERIA
Akindele, O. Oyinloye
Olusola A. Olaolorun
The geochemistry of the country wall rock, the alteration selvage and common Pb chemistry of feldspar, host rock, and pyrite which associates with the Iperindo gold deposit have been studied and presented in this paper. The country wall rock contains low U/Pb and Th/Pb ratios and upper crustal lead below 50ppm implying that metamorphism might not have affected common Pb in this rock. The AFM plot, homogenous PbPb ratios in the country wall rock, feldspar and pyrite all indicate derivation from a subduction tectonic setting (an orogen) akin to a back arc environment. On further analysis, common Pb in pyrite yielded an average age of 550 Ma. On the whole, the petrography, chemistry and PbPb data of the materials studied in this research indicate that the protolith of the host rock, gold and its associated suiphides were all formed in an orogen. Au was possibly leached from the volcanics in the belt by an invading hydrothermal fluid, transported through the same medium as thiocomplexes and deposited in the quartz veins in a shear zone. Native gold was liberated from these thiocomplexes through ore fluidspinel interaction at the loci of mineralization.
11 Pages
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