Gold fineness and pyrite geochemistry: Evidences for physico-chemical conditions and genesis of ore-bearing fluids at Me Xi Au Deposit, Quang Tri, Vietnam

https://tapchi.humg.edu.vn/en/archives?article=307
  • Affiliations:

    1 Trường Đại học Mỏ - Địa chất Hà Nội;
    2 Trung tâm nghiên cứu Địa chất - Mỏ, CODES, Đại học Tasmania, Australia

  • Received: 11st-Mar-2015
  • Revised: 11st-Apr-2015
  • Accepted: 30th-Apr-2015
  • Online: 30th-Apr-2015
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Abstract:

The paper present gold and pyrite study result at the Me Xi gold deposit in Vinh Linh, Quang Tri, central Vietnam. Electron microprobe analysis of gold grains from ore Stage 2 sample yielded high gold fineness values (~845), implying that the transport of Au in ore fluids takes place as chloride complexes rather than bisulphite complexes and the gold transport occurred in high temperature (>300 oC). However, the wide range of the inferred gold fineness (IGF) values (268-953 with a mode of 850-953) calculated from the fire assay analysis may suggest various physico-chemical conditions of Au-bearing fluid. The low-moderate IGF may reflect the low-moderate temperature (<300 oC) of gold deposition and gold is transported by bisulphite complexes. The LA ICP-MS trace element investigation of pyrite shows very poor Au content (mostly <1 ppm) and no inclusion of free Au in all selected pyrite. However, it shows a positive correlation between the concentrations of Au and Ag, Cu, Sb, Tl, Pb, Bi, As, Ni and Co in pyrite 2B. The Stage 2 pyrite exhibit Ni-As-Ag-Sb-Pb-Cu-Bi rims as the concentrations of those metals in the rim of the late sub-stage pyrite 2B. The high concentrations those metals in Stage 2 may be partially leached from the organic-rich host sequence of shale and black shale by hydrothermal fluids with the convection of meteoric water.

How to Cite
Le, T.Xuan, Tran, H.Thanh, Nguyen, L.Quang, Khin, Z. and Abhisit, S. 2015. Gold fineness and pyrite geochemistry: Evidences for physico-chemical conditions and genesis of ore-bearing fluids at Me Xi Au Deposit, Quang Tri, Vietnam (in Vietnamese). Journal of Mining and Earth Sciences. 50 (Apr, 2015).