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

Abstract

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 SiO 2 (silicification), K 2 O (K-feldspar alteration), SO 3 and Fe 2 O 3 (sulphidation/ferruginization) with losses in Na 2 O 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.

Emplacement timing, temperature, and redox conditions of the Kambélé auriferous pluton, Batouri gold District, SE Cameroon

“…The AYD is dominated by a NE-SW regional-scale felsic calc-alkaline plutonic complex intruded into a Palaeoproterozoic basement (Tchameni et al, 2006). Lithologically, the AYD is underlain by a variety of granitic rocks including alkali-feldspar granite, quartz alkali granitoid, syeno-monzogranite, granodiorite, diorite, monzodiorite and tonalite (Asaah et al, 2014;Tata et al, 2018). These granitoids intrude high grade gneisses that represent a Palaeoproterozoic basement which was likely dismembered during the Pan African assembly of western Gondwanaland (Toteu et al, 2004;Van Schmus et al, 2008).…”

“…1) pluton lies within the Adamawa Yadé Domain (AYD) in the eastern region of Cameroon. It forms part of the Central African Fold Belt well known for its gold mineralization associated with felsic granitic plutons (Ateh et al, 2017;Tata et al, 2018;Ngatcha et al, 2019). Plutons within the Adamawa Yadé Domain have been charac-terized based on their petrochemistry, as well as their significance in the genesis of gold mineralization (Asaah et al, 2014;Tata et al, 2018, Ngatcha et al, 2019.…”

“…It forms part of the Central African Fold Belt well known for its gold mineralization associated with felsic granitic plutons (Ateh et al, 2017;Tata et al, 2018;Ngatcha et al, 2019). Plutons within the Adamawa Yadé Domain have been charac-terized based on their petrochemistry, as well as their significance in the genesis of gold mineralization (Asaah et al, 2014;Tata et al, 2018, Ngatcha et al, 2019. Within this domain granitic plutons hosting mineralization reveal a mean age of 620 ± 2 Ma in the Batouri gold district (Asaah et al, 2014).…”

Features of gold-bearing quartz veins in an artisanal mining-dominated terrain, Batouri gold district, Eastern region of Cameroon

“…The Adamawa Yade Domain extends eastwards from Cameroon into the Central African Republic where it is known as the Yade massifs (Van Schmus et al, 2008) and is bounded to the north by the Tcholliré-Banyo fault and to the south by the Yaoundé Domain. The Adamawa Yade domain is underlain by a variety of granitic rocks including alkali-feldspar, granite, quartz alkali granitoids, syeno-monzogranite, granodiorites, diorites and tonalite (Asaah et al, 2014;Tata et al, 2018). The granites are Pan African, metaluminous, I-type granites.…”

“…In the Batouri area, gold is hosted by hydrothermally altered granitoids with concentrations reaching a high of 103.7 ppm (Tata et al, 2018). Gold mineralization is accompanied by sericitization, silicification and sulphidation/ferruginization.…”