Orogenic gold mineralisation associated with Birimian Shear Zones in the Sanankoro District (southern Mali): A litho-structural and geochemical approach

Abstract

This study provides the first integrated geological assessment of the Sanankoro gold district (southern Mali), aimed at identifying the lithological, structural, and geochemical controls on orogenic gold mineralisation. Field mapping, drill-core logging, petrography, and whole-rock geochemistry (FUS-ICP-AES/MS) were combined on 11 representative samples. The district is composed of felsic tuffs, graphite-rich metasediments, trachyandesites, dacites, and altered granodiorites. Major-element contents (SiO 2 = 30.7–73.1 wt-%; Al 2 O 3 = 6.35–20.92 wt-%), and high LOI values (≤25.6 wt-%) indicate strong hydrothermal alteration, reflected also by CIA values ranging from 47 to 88. Elevated As concentrations (≤171 ppm) confirm the association of sulphides with gold zones. REE patterns show LREE-enriched, calc-alkaline signatures consistent with a volcanic-arc setting. Structurally, the NNE-SSW Sanankoro Main Shear Zone focused auriferous fluids, with gold concentrated in felsic tuffs, graphite-bearing metasediments, and fractured granodiorites, especially at Selin. The SMSZ therefore represents the principal mineralising conduit, and the primary control on both fluid pathways, and the localisation of high-grade zones. These results refine the metallogenic model and strengthen exploration criteria for the district.