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 (SiO₂ = 30.7–73.1 wt-%; Al₂O₃ = 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.

Keywords

Orogenic gold Sanankoro main shear zone Birimian terranes hydrothermal alteration whole-rock geochemistry

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References

Ledru

Piqué

Milési

J-P

, et al. Orogenic gold deposits in French Guiana and West Africa: a plate tectonic model. Econ Geol 1991; 86: 234–240. https://doi.org/10.2113/gsecongeo.86.3.234

Milési

J-P

Ledru

Feybesse

J-L

, et al. Early proterozoic ore deposits and tectonics of the birimian orogenic belt. Precambrian Res 1992; 58: 305–344. https://doi.org/10.1016/0301-9268(92)90123-5

Goldfarb

Baker

Dubé

, et al. Distribution, character, and genesis of gold deposits in metamorphic terranes. Econ Geol 2005; 100: 407–450.

Groves

Goldfarb

Santosh

, et al. A holistic model for the origin of orogenic gold deposits and its implications for exploration. Geological Society, London, Special Publications 2020; 502: 89–118. https://doi.org/10.1144/SP502-2020-11

Goldfarb

Groves

Gardoll

. Orogenic gold and geological time: a global synthesis. Ore Geol Rev 2019; 113: 103011. https://doi.org/10.1016/j.oregeorev.2019.103011

Vearncombe

. Structural controls on gold mineralization in shear zones: a review. Applied Earth Science 2019; 128: 1–22. https://doi.org/10.1080/25726838.2018.1560477

Blenkinsop

Doyle

Groves

. Structural controls on fluid flow in shear zones: implications for orogenic gold deposits. J Struct Geol 2018; 108: 167–187. https://doi.org/10.1016/j.jsg.2017.12.004

Feybesse

J-L

Milési

J-P

Deschamps

, et al. The paleoproterozoic Ghanaian province: geodynamic model and ore controls. Precambrian Res 2006; 149: 149–196. https://doi.org/10.1016/j.precamres.2006.06.003

Groves

Goldfarb

Gebre-Mariam

, et al. Orogenic gold deposits: classification and crustal distribution. Ore Geol Rev 1998; 13: 7–27. https://doi.org/10.1016/S0169-1368(97)00012-7

10.

Goldfarb

Groves

Gardoll

. Orogenic gold and geologic time: a global synthesis. Ore Geol Rev 2001; 18: 1–75. https://doi.org/10.1016/S0169-1368(01)00016-6

11.

Perrouty

Jessell

Aillères

, et al. Shear zone architecture and gold mineralization in paleoproterozoic terranes. Precambrian Res 2018; 304: 349–368. https://doi.org/10.1016/j.precamres.2017.11.012

12.

Coragold. Sanankoro Gold Project: Technical Report. Corral Resources Ltd., 2024, 78 pp.

13.

Lawrence

Treloar

Rankin

. Fluid inclusion and stable isotope constraints on birimian gold mineralization. Ore Geol Rev 2018; 98: 1–18. https://doi.org/10.1016/j.oregeorev.2018.05.003

14.

Nesbitt

Young

. Early proterozoic climates and plate motions inferred from major element chemistry. Nature 1982; 299: 715–717. https://doi.org/10.1038/299715a0

15.

Sun

S-S

McDonough

. Chemical and isotopic systematics of oceanic basalts. Geological Society, London, Special Publications 1989; 42: 313–345.

16.

Bessoles

. Géologie de l’Afrique: le Craton Ouest-Africain. BRGM, 1977, 120 pp.

17.

Abouchami

Boher

Michard

, et al. A major 2.1 Ga event of mafic magmatism in West Africa: an early stage of crustal accretion. J Geophys Res 1990; 95: 17605–17629. https://doi.org/10.1029/JB095iB11p17605

18.

Ennih

Liégeois

J-P

. The boundaries of the West African craton. Geological Society, London, Special Publications 2008; 297: 1–17. https://doi.org/10.1144/SP297.1

19.

Chardon

Gapais

Castaing

, et al. A structural map of the southern West African craton. Precambrian Res 2020; 340: 105561. https://doi.org/10.1016/j.precamres.2020.105561

20.

Boukari

Tegyey

Ouattara

, et al. Gold distribution and structural controls in the paleoproterozoic of West Africa. J Afr Earth Sci 2008; 50: 133–149. https://doi.org/10.1016/j.jafrearsci.2007.09.014

21.

Rollinson

. Using immobile elements in altered volcanic rocks: strengths and pitfalls. Geochem Explor Environ Anal 2021; 21: 1–16. https://doi.org/10.1144/geochem2020-066

22.

McDonough

Sun

S-S

. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition. Geological Society, London, Special Publications 1989; 42: 313–345. https://doi.org/10.1144/GSL.SP.1989.042.01.19

23.

Roser

Korsch

. Determination of tectonic setting using SiO₂ content and K₂O/Na₂O ratios. J Geol 1986; 94: 635–650. https://doi.org/10.1086/629071

24.

Bhatia

Crook

KAW

. Trace element characteristics of greywackes and tectonic setting discrimination of sedimentary basins. Contrib Mineral Petrol 1986; 92: 181–193. https://doi.org/10.1007/BF00371452

25.

Winchester

Floyd

. Geochemical discrimination of different magma series and their differentiation products. Chem Geol 1977; 20: 325–343. https://doi.org/10.1016/0009-2541(77)90057-2

26.

Crook

KAW

. Classification of sandstone types. J Geol 1986; 94: 1–15.

27.

Ross

P-S

Bédard

. Magmatic affinity of volcanic rocks using immobile trace elements. Chem Geol 2009; 262: 57–74. https://doi.org/10.1016/j.chemgeo.2009.02.008

28.

Large

Bull

Maslennikov

. A carbonaceous sedimentary source-rock model for orogenic gold deposits. Econ Geol 2019; 114: 161–183. https://doi.org/10.5382/econgeo.2019.4614

29.

Bourassa

Perrouty

Jessell

. Controls on gold mineralization in West African shear zones: implications for exploration. Minerals 2021; 11: 162. https://doi.org/10.3390/min11020162

30.

Blenkinsop

. Structural controls on gold mineralization: examples from greenstone belts and shear-zone systems. Applied Earth Science 2017; 126: 120–133. https://doi.org/10.1080/03717453.2017.1283572

31.

Boadi

Dunphy

. Structural controls on gold mineralization in birimian terranes. J Afr Earth Sci 2019; 158: 103569. https://doi.org/10.1016/j.jafrearsci.2019.103569

32.

Perrouty

Jessell

Aillères

, et al. Revisiting the geology and geodynamic evolution of the paleoproterozoic birimian belts of West Africa. Precambrian Res 2012; 220–221: 304–319. https://doi.org/10.1016/j.precamres.2012.08.003

33.

Oberthür

Vetter

Davis

, et al. Age constraints on gold mineralization and crustal evolution in West Africa. Precambrian Res 2002; 118: 213–248. https://doi.org/10.1016/S0301-9268(02)00113-2

34.

Sillitoe

. Styles of gold deposition in metamorphic terranes and the role of hydrothermal alteration. Applied Earth Science 2010; 119: 67–81. https://doi.org/10.1179/174327510X12772912411023