Study on fluid inclusions and features of ore-forming fluids of Diakha gold deposit,Mali, West Africa |
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| Authors: | 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 structural-ly 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 aque-ous-carbonic CO2-rich ( LCO2 +VCO2 ±H2O) in stage I.The exclusively aqueous H2O+NaCl ±CO2 fluid in-clusions ( 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 sa-linity (<6 wt ％NaCl equiv), indicating an estimated trapping pressure for the deposit between 610 to 800 bars. |
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