Study on fluid inclusions and features of ore-forming fluids of Diakha gold deposit, Mali, West Africa

doi:10.3969/j.issn.1673-9736.2018.01.01

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Global Geology ›› 2018, Vol. 21 ›› Issue (1) : 1-13. DOI: 10.3969/j.issn.1673-9736.2018.01.01

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Study on fluid inclusions and features of ore-forming fluids of Diakha gold deposit, Mali, West Africa

Yassa Konare, WANG Keyong, WANG Zhigao

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Abstract

The Diakha gold deposit is located in the southeastern margin of the highly prospective/productive Paleoproterozoic (Birimian) Kédougou-Kéniéba Inlier. Gold mineralization is closely associated with a narrow, sub-vertical, NE-trending shear corridor. The corridor is to the east of a sinistrally reactivated D1 west-dipping fault, which emanated from SMSZ (D2 reverse-sinistral regional structure). The mineralization is hosted by fine-grained sandstone and breccias units associated with a moderate to strong hydrothermal alteration, which is dominated by albitization, carbonization, silicification, hematization, and chloritization. Diakha field data and laboratory analysis suggest the existence of two main stages of hydrothermal mineralization, namely stage I and stage Ⅱ. Stage I is of a breccias type of mineralization and represents the major gold bearing stage. It isassociated with hematite+calcite+ankerite/dolomite and quartz pervasive alteration, controlled by the predominantly brittle-ductile NNE to NE-shearing structures of the main deformation event D2. Stage Ⅱ is represented by the second minor hydrothermal episode, showing local quartz-tourmaline and tremolite alteration which is structurally controlled by the dipping S3 cleavage formed during D3 deformation. Petrographic and microthermometric studies of fluid inclusions from quartz veins reveal the presence of early dominant carbonic CO₂-pure and aqueous-carbonic CO₂-rich (LCO₂+VCO₂±H₂O) in stage I. The exclusively aqueous H₂O+NaCl±CO₂ fluid inclusions (L-type) are observed in stage Ⅱ. Interpretation shows that the ore-forming fluids originated from a homogeneous H₂O-CO₂ fluid during phase separation, with trapping temperatures of 250℃ to 280℃ and low salinity (<6 wt% NaCl equiv), indicating an estimated trapping pressure for the deposit between 610 to 800 bars.

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Kédougou-Kéniéba Inlier / Diakha deposit / hydrothermal alteration / Au-mineralization / fluid inclusions

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Yassa Konare, WANG Keyong, WANG Zhigao. Study on fluid inclusions and features of ore-forming fluids of Diakha gold deposit, Mali, West Africa[J]. Global Geology. 2018, 21(1): 1-13 https://doi.org/10.3969/j.issn.1673-9736.2018.01.01

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