Wallrock alteration categories and their geochemical signatures in gold-bearing Neoproterozoic granitoids, Batouri gold district, southeastern Cameroon.

Hydrothermally altered granitoids in the Batouri district host gold mineralization. Gold and associated metals occur as disseminated, stockwork and veins. The granitoids range from quartz-alkali granitoids sensu stricto to diorite with various types of wallrock alterations including K-feldspar alteration, sericitization, silicification, and sulphidation/ferruginization. Most gold-bearing samples are extensively brecciated. Gold mineralization is accompanied with sericitization, silicification, and sulphidation/ferruginization alterations. Gold concentrations reach a high of 103.7 ppm. The granitic rocks are sub-alkaline. They show enrichment in the LREE, a negative Eu anomaly and a depletion in the HREE reflecting the breakdown and mobility of the initial plagioclase feldspar bearing HREE during fluid-rock interaction. On multielement variation diagrams, spikes at K, Ba, Pb, and Th are depicted resulting from selective enrichment during alteration. Mass gains/losses during alteration calculated using the immobile element method indicate, amongst others, gains in SiO₂ (silicification), K₂O (K-feldspar alteration), SO₃ and Fe₂O₃ (sulphidation/ferruginization) with losses in Na₂O linked to sericitization. The samples show Pd and Pt as high as 2 ppm. Gold mineralization is associated with wallrock alteration zones with elevated contents of As-Ba-Cu-Pb-Rb-Sr-Zn and Zr due to the neominerals developed during hydrothermal alteration. Au-Ag-Zn defines a potential pathfinder element cluster in the Batouri district. [ABSTRACT FROM AUTHOR]