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Cu-sulfide mineralogy, texture, and geochemistry in the Tiegelongnan porphyry-epithermal copper system, Tibet, China TEXT SIZE: A A A

The Tiegelongnan porphyry-epithermal deposit (2089 Mt @ 0.53% Cu, 0.08 g/t Au) is host to a large variety of Cu-sulfide minerals, mainly chalcopyrite, bornite, covellite, digenite, enargite, and tennantite. We used LA-ICP-MS to investigate the trace element geochemistry of the Tiegelongnan Cu-sulfides, as well as pyrite, to understand the correlation between sulfides and trace elements, gold in particular, in the porphyry and epithermal systems. Porphyry mineralization consists of stage 1 chalcopyrite-pyrite +/- molybdenite, stage 2 chalcopyrite-bornite, and stage 3 covellite. Epithermal sulfides form stage 4 pyrite-alunite, stage 5 digenite-bornite-chalcopyrite, and stage 6 enargite-tennantite +/- tetrahedrite. Stage 2 chalcopyrite (S2 Ccp, median = 9.7 ppm Au) is the primary porphyry Au host, and stage 6 tennantite in alunite veins (S6 Tnt-s, median = 98.0 ppm Au) is the major epithermal Au host. These Au-rich sulfides formed under higher oxidation conditions, suggesting that a high oxidation state favors the incorporation of Au in Cu-sulfides. Gold contents in coeval chalcopyrite and bornite are positively correlated to temperature, and Au is enriched in chalcopyrite over bornite at low temperatures (< 350 celcius). Positive correlations between Au and As and Te in covellite and chalcopyrite result from the reaction of As3+ + (Au+/Ag+) + Te2- <-> 4Cu(+) + S2-. Epithermal chalcopyrite and bornite contain more As and Pd than that in porphyry stages, and high contents of As, Sn, Cd, Zn, Sb, Te, Au, and Bi in epithermal enargite and tennantite are likely the result of partitioning of these elements in sulfides at low epithermal temperatures. Epithermal overprinting likely leached Cu from earlier porphyry stage sulfides to precipitate high Cu-grade epithermal mineralization. The Cu-sulfides and related trace elements show a spatial distribution, potentially useful for the exploration of overprinted porphyry-epithermal systems.

Publication name

 MINERALIUM DEPOSITA DOI: 10.1007/s00126-021-01075-y Early Access: SEP 2021


 Yang, Chao; Beaudoin, Georges; Tang, Ju-Xing; Song, Yang; Wang, Li-Qiang; Huang, Xiao-Wen

Corresponding author(s) 

 YANG Chao 
 -Chengdu Univ Technol, Coll Earth Sci, Chengdu 610059, Peoples R China
 -Univ Laval, Dept Geol & Genie Geol, Quebec City, PQ G1V 0A6, Canada
 -Ctr Rech Geol & Ingn Ressources Minerales E4m, Quebec City, PQ, Canada

Author(s) from IGCAS   HUANG Xiaowen

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