Comparative study of the wallrock and ore and ore forming mechanisms at the Nibao gold deposit, Guizhou, China |
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The majority of the orebodies at the Nibao gold deposit are controlled by a reverse fault and an unconformity between the Middle Permian and Upper Permian stratigraphic units. In this paper, based on petrographic study, X-ray diffraction (XRD) analysis and microprobe analysis (EMPA) were integrated to identify and quantify the altered minerals and gold bearing arsenian pyrite, make a comparative study of the characteristics between the wallrock and the ore. Major and trace element analyses were used to determine the element fluxes during mineralization. The main objective of this paper is to understand the relationship between altered minerals and the ore forming, and the ore-forming mechanisms at the Nibao gold deposit. The results indicate that pyrite shows a negative correlation with quartz and a positive correlation with illite. Ore samples have undergone decarbonation, and pyrite in the ore samples generally shows core-rim texture. A part of wallrock samples also have undergone decarbonation, but pyrite in the wallrock samples does not show core-rim texture. Au was added to the ore, while CaO, MgO, S, Ba and Be were removed from the wallrock in the uncomformity. In the reverse fault, Au, Sc, As and Fe2O3 were added to the ore while SiO2, CaO, Sr, W and Be show the characteristics of being removed from the wallrock. The integrated results suggest that decarbonation and sulfidation are the main ore forming mechanisms at the Nibao gold deposit. Before mineralization, decarbonation provides favor environment for ore forming. During the ore forming process, minerlization through sulfidation to form gold bearing arsenian rims on pyrite. Publication name | ACTA PETROLOGICA SINICA, 32 (11):3343-U337; 2016 | Author(s) | Wei DongTian; Xia Yong; Tan QinPing; Xie ZhuoJun; Yan Juno; Guo HaiYan; Liu JianZhong | Corresponding author | XIA Yong xiayong@vip.gyig.ac.cn Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, Guiyang 550002, Peoples R China. | View here for the details
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