Restricted accessResearch articleFirst published online 2025-6
Tracing the source of the Mineralization Fluid,and metamorphism of the Nampala Gold Deposit,southern Mali: Constraints from stable (oxygen and hydrogen) isotopes and Raman Spectroscopy
The Nampala gold deposit is a sub-world-class occurrence in Mali's Birimian Terrain. Although numerous detailed investigations have been conducted on Mali's gold deposits, the debate on the origin of the mineralizing fluid remains unresolved. To address that knowledge gap this study presents oxygen, and hydrogen isotope data for auriferous quartz veins, along with Raman spectroscopy analysis of graphitic schist, to investigate the genesis and evolution of the mineralizing fluid of the Nampala gold deposit and the associated metamorphic grade. The isotopic signatures of quartz veins and their fluid inclusions reveal δD values ranging from −48 to 0.3‰ (mean −25.98‰, n = 15) and δ18O values from 15.23 to 16.57‰ (mean 16.14‰, n = 15). The narrow δ18O range of auriferous quartz veins indicates a common hydrothermal fluid source, while the high δD values suggest meteoric water influence. The Nampala gold deposit likely formed from metamorphic fluids derived from nearby metasedimentary rocks during regional metamorphism, with Au deposition driven by fluid pressure drops and interaction between meteoric and metamorphic fluids with wall rocks. Metamorphism studies indicate greenschist facies, with temperatures ranging from 358 °C to 486 °C (avg. 416 °C ± 50 °C). The gold-enriched fluid at Nampala precipitated gold through metasomatism, driven by interaction with surrounding rocks and decreases in temperature and pressure.
LawrenceDMTreloarPJRankinAH, et al.A fluid inclusion and stable isotope study at the Loulo mining district, Mali, West Africa: implications for multifluid sources in the generation of orogenic gold deposits. Economic Geology.2013; 108: 229–257. https://doi.org/10.2113/econgeo.108.2.229
2.
LawrenceDMTreloarPJRankinAH, et al.The geology and mineralogy of the loulo mining district, Mali, West Africa: evidence for two distinct styles of orogenic gold mineralization. Economic Geology2013; 108: 199–227. https://doi.org/10.2113/econgeo.108.2.199
3.
ZoheirBAQaoudNN. Hydrothermal alteration geochemistry of the betam gold deposit, south eastern desert, Egypt: mass-volume-mineralogical changes and stable isotope systematics. Transactions of the Institutions of Mining and Metallurgy, Section B: Applied Earth Science2008; 117: 55–76. https://doi.org/10.1179/174327508X339828
4.
McfarlaneRMMavrogenesJLentzD, et al.Geology and intrusion-related affinity of the Morila gold mine, Southeast Mali. Economic Geology2011; 106: 727–750. https://doi.org/10.2113/econgeo.106.5.727
5.
SangareA. Geology of Kalana Gold deposit (Southwest Mali), Petrogenesis, Metallogeny and Fluid inclusion study, Doctoral dissertation, University Sidi Mohamed Ben Abdellah, Morroco. 2015.
6.
TraoreDY. Etude Metallogenique du district aurifère de Syama (Mali): Analyse comparative de gisements situés sur une meme structure lithosphériques éburnéenne, (Doctorat de l'Université de Toulouse). 2017.
7.
GabouryD. Parameters for the formation of orogenic gold deposits. Applied Earth Science: Transactions of the Institute of Mining and Metallurgy2019; 128: 124–133. https://doi.org/10.1080/25726838.2019.1583310
8.
Kerr-GillespieFKinnanECarrierA. NI 43-101 Technical Report for the Nampala and Mininko Permits (Mali) and Mineral Resource Estimate for the Nampala Gold Mine. Robex Resources Inc 169p. June. 2018.
9.
KonateSIMBolarinwaATKwayisiD, et al.Provenance and tectonic setting of greywacke and siltstone of the Nampala gold deposit, Southern Mali. 2024; 133(2): 129–147. https://doi.org/10.1177/25726838241263698
10.
KonateBouareBolarinwa , et al.Petrogenesis, geodynamic setting, age of Rhyacian igneous rocks, from Nampala gold deposit: Implications for the crustal growth of the Birimian terrain in southern Mali. Results in Earth Sciences2025. https://doi.org/10.1016/j.rines.2025.100070
11.
CrissREChampionDE. Oxygen isotope study of the fossil hydrothermal system in the Comstock Lode mining district, Nevada. In Stable isotope geochemistry: A tribute to Samuel Epstein. 437–447. 1991.
12.
CrissRETaylor JrHP. Meteoric-hydrothermal systems. Reviews in Mineralogy1996(16): 373–424.
13.
LargeRRBullSWWinefieldPR. Carbon and oxygen isotope halo in carbonates related to the McArthur river (HYC) Zn-Pb-Ag deposit, North Australia: implications for sedimentation, ore genesis, and mineral exploration. Economic Geology2001; 96: 1567–1593. https://doi.org/10.2113/gsecongeo.96.7.1567
14.
NaitoKFukahoriYPeimingH, et al.Oxygen and carbon isotope zonations of wall rocks around the Kamioka PbZn skarn deposits, central Japan: application to prospecting. Journal of Geochemical Exploration1995; 54: 199–211. https://doi.org/10.1016/0375-6742(95)00044-5
15.
BeinlichABarkerSLLDippleGM, et al.Large-scale stable isotope alteration around the hydrothermal carbonate-replacement cinco de mayo zn-ag deposit, Mexico. Economic Geology2019; 114(2): 375–396. doi:https://doi.org/10.5382/econgeo.2019.4635
16.
FouillacAMDommangetAMilesiJP. A carbon, oxygen, hydrogen and sulfur isotopic study of the gold mineralization at Loulo, Mali. Chemical Geology1993; 106: 47–62. https://doi.org/10.1016/0009-2541(93)90165-F
17.
Lambert-SmithJSLawrenceDMVargasCA, et al.The Gounkoto Au deposit, West Africa: constraints on ore genesis and volatile sources from petrological, fluid inclusion and stable isotope data. Ore Geology Reviews2016: 606–622. https://doi.org/10.1016/j.oregeorev.2015.10.025
18.
Lambert-SmithJSRochollATreloarP, et al.Discriminating fluid source regions in orogenic gold deposits using B-isotopes. Geochimica et Cosmochimica Acta2016: 57–76. doi:https://doi.org/10.1016/j.gca.2016.08.025
19.
Grandjean da CostaFLuizKEHarrisC, et al.Fluid inclusion and stable isotope (O, H, C) constraints on the genesis of the Pedra Branca gold deposit, Troia Massif, Borborema Province, NE Brazil: an example of hypozonal orogenic gold mineralization. Ore Geology Reviews2019; 107: 476–500. https://doi.org/10.1016/j.oregeorev.2019.03.007
20.
McFallKRobertsSTeagleD, et al.The origin and distribution of critical metals (Pd, Pt, Te and Se) within the Skouries Cu–Au porphyry deposit. Greece. Applied Earth Science2016; 125: 100–101. https://doi.org/10.1080/03717453.2016.1166651
21.
ChisambiJVon Der HeydenB. The origin and evolution of the ore-forming fluids at the Manondo-Choma gold prospect, Kirk range, southern Malawi. Open Geosciences2023; 15(1): 1–14. https://doi.org/10.1515/geo-2022-0494.
22.
TraoreDYSanogoSKoneAY, et al.Geochemistry of Magmatic Rocks of the Syama Belt, Southern Mali, West Africa Craton. 2022: 250–272. https://doi.org/10.4236/ojg.2022.123014
23.
KUSNIRIDIALLOM. Résultats des travaux de prospection. Projet MLI/82/007. Unpublished report, UNDP/DNGM, Bamako, 159 pp. 1986.
24.
LiégeoisJPClaessensWCamaraD, et al.Short-lived eburnian orogeni in southern Mali. Geology, tectonics, U–Pb and Rb–Sr geochronology. Precambrian Research1991: 111–136. doi:https://doi.org/10.1016/0301-9268(91)90050-K
25.
WaneO. Etude géologique du Birimien de la région de Massigui (Paléoprotérozoïque du Mali méridional): la zone de cisaillement du Banifing, structure majeure du craton ouest africain. These, Université de Lille 1. 2010.
BarinkovIPNovikovAG. Rapport sur le levé aéromagnétique dans la partie sud du Mali. DNGM, 1966.
30.
CabyRDelorCAgohO. Lithologie, structure et métamorphisme des formations birimiennes dans la région d'Odienné (côte d'Ivoire): rôle majeur du diapirisme des plutons et des décrochements en bordure du craton de man. Journal of African Earth Sciences2000; 30(2): 351–374.
31.
BeyssacOGofféBChopinC, et al.Raman spectra of carbonaceous material in metasediments: a new geothermometer. Journal of Metamorphic Geology2002; 20: 859–871. https://doi.org/10.1046/j.1525-1314.2002.00408.x
32.
GarbaI. Origin of pan-African mesothermal gold mineralisation at Bin Yauri, Nigeria. Journal of African Earth Sciences2000; 31(2): 433–449. https://doi.org/10.1016/S0899-5362(00)00098-1
33.
LiuKYangRChenW, et al.Trace element and REE geochemistry of the Zhewang gold deposit, southeastern Guizhou Province, China. Chinese Journal of Geochemistry2014; 33: 109–118. https//doi:10.1007/s11631-014-0665-3
HammondNQShimazakiH. Geology and geochemical aspects of ore formation at the Prestea mesothermal vein gold deposit in the Birimian system of Ghana. International Geology Review1994; 36: 715–731.
36.
KazapoeRWOkunlolaOArhinE, et al.Geology and isotope systematics of gold deposits in Abansuoso area of Sefwi Belt, Southwestern Ghana. Geology, Ecology, and Landscapes2024; 8(3): 423–444.
37.
KerrichR (1987) Stable isotope geochemistry of au-ag vein deposits in metamorphic rocks. In: KyserT.K. (Ed.). Stable isotope geochemistry of low temperature fluids. Mineralogical association of Canada short course. (13): 287–336.
38.
AldertonDHMSerafimovskiT. The geology and genesis of the Plavica copper-gold deposit, Macedonia. Transactions of the Institutions of Mining and Metallurgy, Section B: Applied Earth Science2007; 116: 94–105. https://doi.org/10.1179/174327507X167073
39.
TreloarPJLawrenceDMSenghorD, et al.The Massawa gold deposit, eastern Senegal, West Africa: an orogenic gold deposit sourced from magmatically derived fluids?Geological Society Special Publication2014: 135–160. https://doi.org/10.1144/SP393.12
40.
Lambert-SmithJSLawrenceDMMüllerW, et al.Palaeotectonic setting of the south-eastern Kédougou-Kéniéba Inlier, West Africa: new insights from igneous trace element geochemistry and U-Pb zircon ages. Precambrian Research2016; 274: 110–135. https://doi.org/10.1016/j.precamres.2015.10.013
41.
McCuaigTCKerrichR. P-T-t-deformation-fluid characteristics of lode gold deposits: evidence from alteration systematics. Ore Geology Reviews1998; 12(6): 381–454.
TiceMMBostickBCLoweDR. Thermal history of the 3. 5–3 . 2 Ga Onverwacht and Fig Tree Group, Barberton greenstone belt, South Africa, inferred by Raman microspectroscopy of carbonaceous material. May 2014. 2004. doi:https://doi.org/10.1130/G19915.1.
44.
Van ZuilenMAChaussidonMRollion-BardC, et al.Carbonaceous cherts of the Barberton Greenstone Belt, South Africa: isotopic, chemical and structural characteristics of individual microstructures. Geochimica et Cosmochimica Acta2007; 71: 655–669. https://doi.org/10.1016/j.gca.2006.09.029
45.
MarshallCPLoveGDSnapeCE, et al.Structural characterization of kerogen in 3.4 Ga Archaean cherts from the Pilbara Craton, Western Australia. Precambrian Research2007; 155: 1–23. https://doi.org/10.1016/j.precamres.2006.12.014
46.
SfornaMCVan ZuilenMAPhilippotP. Structural characterization by Raman hyperspectral mapping of organic carbon in the 3.46 billion-year-old apex chert, western Australia. Geochimica et Cosmochimica Acta2014; 124(4): 18–33. https://doi.org/10.1016/j.gca.2013.09.031
47.
LahfidABeyssacODevilleNF, et al.Evolution of the Raman spectrum of carbonaceous material in low-grade metasediments of the Glarus Alps (Switzerland). Terra Nova2010; 22: 354–360. https://doi.org/10.1111/j.1365-3121.2010.00956.x
48.
KonateSIMBolarinwaATKazapoeRW, et al.A review of the current state of knowledge on gold mineralization in Mali, western Africa. Geology, Ecology, and Landscapes2024: 1–25. https://doi.org/10.1080/24749508.2024.2441514
Supplementary Material
Please find the following supplemental material available below.
For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.
For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.
