Petrology, geochemistry, and source of the emplacement model of the Paleoproterozoic Tiébélé Granite Pluton, Burkina Faso (West‑Africa): contribution to mineral exploration

摘要

The Tiebele Granite Pluton (TGP) and the associated Pink Granite (PG), in southern Burkina Faso (West-Africa), are investigated based on petrology, geochemistry, and geochronology, to establish their relationship with volcanic-hosted mineral occurrences and their intrinsic capability to build up ore-forming metallic components. They can then be classified into either productive/fertile or nonproductive/barren intrusions with an approach using specific elements, such as Mn, Y, Rb, Zr, Sr, and Ta, as well as other discriminants including Fe2O3, Zn, and Sr/Y relative to SiO2. The TGP occurs as the main, single phase pluton, with the minor PG phase, which crosscuts the TGP. The CIPW normative Ab-An-Or and ternary K-Ca-Na indicate metaluminous (A/CNK similar to 1) "trondhjemite" and "granite" compositions. The TGP, with Sigma REE similar to 89-165 ppm, is relatively enriched in LREE (La to Eu), 10-100 times chondrite compared to HREE (Gd to Lu), 3-20 times chondrite, with a weak negative Eu anomaly (Eu/Eu* similar to 0.85-1.02). This is approximately parallel to the average of the upper crust (Sigma REE similar to 144 ppm) that shows a moderate negative Eu anomaly (Eu/Eu* similar to 0.74). This trondhjemitic to granitic pluton is an oxidized I-type granite related to partial melting of basalt and andesite from oxidized sources (based on magnetic susceptibilities), within an ensialic volcanic arc setting. In contrast to the PG, which is clearly nonproductive, based on the Y versus MnO discrimination, s the TGP seems fertile for porphyry-related Cu-Au deposits. U-Pb data on zircon yielded ages of 2147 +/- 12 Ma and 2121 +/- 47 Ma, respectively, for TGP and PG, whereas the rhyolite that hosts Zn-Cu-Pb Volcanogenic Massive Sulfide (VMS) occurrences occurs in an extensional setting dated at 2156 +/- 9 Ma, suggesting emplacement of the TGP pluton similar to 10 My later, possibly not synvolcanic to the volcanic package.