Abstract
The Sabodala gold deposit in the Mako volcanic Belt (SE-Senegal, West African Craton) occurs in mafic and ultramafic rocks overlain by clastic sedimentary rocks and felsic volcanic-volcaniclastic sequences. It is a structurally controlled mesothermal vein gold deposit developed in deformed rocks units near the Falombo pluton. The Sabodala Goldfield comprises several faults systems striking N-S to NE-SW. New structural evolution consisting of both thrusting and transcurrent events has been defined for the Sabodala Goldfield. The majority of the gold at Sabodala occurs on the western flank of a large, doubling plunging dome (the Sabodala Antiform) and is also associated with sinistral wrenching that overprints early structures within the Sabodala Mine. The gold bearing veins are hosted by flat lying and NW-trending shear zones. The NW-trending faults acted as transfers syn-gold mineralization, although only discrete segments of these faults were active during the main stage of gold mineralization. Late exhumation resulted in extension along fault zones was responsible for the juxtaposition of medium and low grade metamorphic rocks. The granitic suite of the Falombo pluton is linked to exhumation. Final dextral transpression postdating exhumation produced shearing and folding. Gold lodes developed during brittle deformation are associated with high fluid pressures in a northwest-southeast shortening regime. These are termed mainly the Sabodala deposit, and secondary the Niakafiri and Masato deposits.
Highlights
Gold mineralization in many deposits of the WAC (West African Craton) is empirically associated with shear zones domes and regional antiforms (e.g. Damang, Loulo, Yatéla, Sadiola...)
This phase of deformation is associated with regional apparent left-lateral displacement on shear zones, including Ayoub’s thrust, which was associated with early, premineralization carbonate alteration
This is stressed by the following points: the presence of relicts of mylonitic rocks in the auriferous Sabodala shear zones suggests that ductile D2 shear zones were reactivated in a strike-slip to oblique-slip system during the D3 event
Summary
Gold mineralization in many deposits of the WAC (West African Craton) is empirically associated with shear zones domes and regional antiforms (e.g. Damang, Loulo, Yatéla, Sadiola...). These deposits are structurally controlled, and are deposited from mesothermal syn- to post-metamorphic fluids in D2 deformation zones (Eisenlohr and Hirdes [1]; Blenkinsop et al, [2]; Mumin and Fleet [3]; Oberthür et al, [4] [5]; Yao et al, [6]; Allibone et al, [7]; Feybesse et al, [8]; Harcouët et al, [9], Gueye et al, [10]). This article presents a revised structural interpretation for a component of the world class Sabodala Goldfield in the Birimian Craton of Western Africa and a revised structural map for a major segment of the Sabodala Goldfield to provide a framework for the revised geological model
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