Geology, geochemistry, and genesis of gold mineralization in the Chifumbazi deposit of the Tete Province, Irumide Belt, Mozambique

Abstract

AbstractThe Chifumbazi gold deposit is located in the Chifunde District, Tete Province, northwestern Mozambique. The geology of the study area is composed of the Proterozoic Mualadzi Group comprising ultramafic metavolcanic rocks, quartzite, biotite‐schist, Macanda Mafic Metavolcanics, conglomerate, and granitoid of the Furancungo Suite. The geological characteristics and metallogenesis of gold mineralization in the Tete Province are poorly understood. This study describes the gold mineralization and associated hydrothermal alteration in the Chifumbazi deposit on the basis of petrography, whole‐rock geochemistry, mineral chemistry, fluid inclusion and sulfur isotope analyses. The mineralization in the Chifumbazi deposit includes auriferous quartz, calcite, dolomite and ankerite quartz‐chlorite, and chlorite‐pyrite veins and veinlets as well as sulfide dissemination hosted by altered meta‐granodiorite along shear zones and fracture zones. On a larger scale, the mineralized veins and veinlets occur along a discordant fracture system within a Pan‐African shear zone. The meta‐granodiorite host‐rock of the mineralization consists mainly of plagioclase, biotite, actinolite, and quartz, and alteration minerals calcite, dolomite, sericite, and chlorite. The meta‐granodiorite is enriched in LREE compared to HREE and shows negative Eu anomalies. The mineralization in the Chifumbazi deposit formed through three hypogene mineralization stages (Stages I–III) and one supergene stage (Stage IV). Stage I comprises quartz, calcite, dolomite, ankerite, pyrite, chalcopyrite, pyrrhotite and galena. Stage II comprises quartz, pyrrhotite, pyrite, chalcopyrite and native gold. Stage III comprises chlorite and pyrite; and Stage IV comprises secondary minerals goethite, bornite and covellite. Bulk chemical analysis of ores detected gold contents up to 5 ppm for a quartz vein of Stage II, where visible native gold is present in pyrite. The δ34SCDT values of pyrite and chalcopyrite of the Stages I–III range from +0.9 to +2.4 ‰. On the basis of the geological setting, mineralogy, and sulfur isotope signatures, the Chifumbazi deposit can be classified as orogenic.