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Alteration and paragenesis of the basalt-hosted Au deposits, southwestern Guizhou Province, China: Implications for ore genesis and exploration TEXT SIZE: A A A
Carlin-type Au deposits are dominantly hosted in sedimentary rocks. Recent exploration has identified two deposits (Jiadi and Damaidi) hosted in the Emeishan basalt in southwestern Guizhou Province, China, that contain Carlin-type mineralization. In this study, ore and alteration minerals from the two deposits were examined, mineral parageneses were established through detailed petrography, whole-rock chemistry and mineralogical studies, and results were compared with the sediment-hosted Carlin-type Au deposits. In both deposits, pre-ore stage minerals are mainly igneous minerals in basalt, including orthopyroxene, clinopyroxene, plagioclase, magnetite, and minor ilmenite and apatite. These minerals formed during the eruption and formation of the Emeishan Large Igneous Province. The Au ore-stage mineral assemblage consists of arsenian pyrite, arsenopyrite, illite, jasperoid quartz, (Fe)-dolomite (locally Ca-Mg-siderite), rutile, and apatite. This transition indicates that pre-ore basalt was altered to minerals that characterize Carlin-type ore. Electron probe microanalysis and laser ablation-inductively coupled plasma-mass spectrometry analyses show that the arsenian pyrite and arsenopyrite contain -457 ppm and -556 ppm Au, respectively, and are enriched in As, Cu, Sb, Hg, and Tl. Gold is ionically bound in the disseminated arsenian pyrite and arsenopyrite which formed during sulfidation. During the late-ore stage, open space-filling realgar, calcite, quartz, stibnite, and orpiment precipitated as the hydrothermal system cooled and collapsed. Post-ore stage minerals include hematite and chlorite, reflecting post-ore oxidation. Comparison studies indicate the two deposits share remarkable similarities to the Guizhou sediment-hosted Carlin-type Au deposits. The basalt-hosted and sediment-hosted Au deposits in Dian-Qian-Gui area formed in response to the same widespread metallogenic event. This study confirms that basalt can host Carlin-type Au mineralization. Future exploration for Carlin-type Au deposits in Dian-Qian-Gui area can be expanded into regions dominated by basalt, especially the anticlines above the unconformity between the Maokou limestone and Emeishan basalt.
 

Publication name

 ORE GEOLOGY REVIEWS Volume: 131 Article Number: 104034 DOI: 10.1016/j.oregeorev.2021.104034 Published: APR 2021

Author(s)

 Li, Junhai; Wu, Pan; Xie, Zhuojun; Liu, Jianzhong; Zhang, Shuangju; Song, Weifang; Zhang, Bingqiang; Li, Songtao; Xu, Liangyi; Zheng, Lulin

Corresponding author(s) 

 XIE Zhuojun 
 xiezhuojun@mail.gyig.ac.cn   
 Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, Guiyang 550081, Peoples R China.

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