Chemical variations in biotites—an exploration tool to distinguish between mineralized and barren rocks in the Nigerian tin bearing province

Geochemical and Geochronological Discrimination of Biotite Types at the Detour Lake Gold Deposit, Canada

“…Comparatively, lower Mg contents in biotite from mineralized rocks, relative to biotite from barren rock, was reported from the Afu Younger Granite complex of central Nigeria [46]. These chemical variations in the biotite were attributed to primary magmatic or subsolidus processes that result in the re-equilibration of earlier formed mineral compositions [46]. This model predicts that an initially low f O2 reduces the activity of MgO, which causes the late crystallization of magnetite.…”

“…However, Mg-loss is not observed in the mineralized biotite at Detour Lake; instead, we observe a subtle Mg-loss in the barren biotite type, which further complicates the reliable use of biotite chemistry as a vector to Au ore at this deposit. Comparatively, lower Mg contents in biotite from mineralized rocks, relative to biotite from barren rock, was reported from the Afu Younger Granite complex of central Nigeria [46]. These chemical variations in the biotite were attributed to primary magmatic or subsolidus processes that result in the re-equilibration of earlier formed mineral compositions [46].…”

“…As illustrated in Figure 1, the mineralized samples are hosted within mafic volcanic rocks, whereas barren samples are hosted within more felsic plutonic rocks. Based on the model from the Afu Younger Granite complex [46], the Mg variation in mineralized and barren biotite at the Detour Lake deposit could potentially be attributed to the f O2 of their magmatic source, rather than hydrothermal alteration. To pursue this model, we first need to determine whether biotite at Detour Lake are primary magmatic, re-equilibrated, and/or represent new growth (neoblastic) during hydrothermal activity.…”