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Evolution of multistage hydrothermal fluids in the Luoboling porphyry Cu-Mo deposit, Zijinshan ore field, Fujian Province, China; insights from LA-ICP-MS analyses of fluid inclusions

Zhao Xiaoyu, Zhong Hong, Hu Ruizhong, Mao Wei, Bai Zhongjie, Lan Tingguang and Xue Kai
Evolution of multistage hydrothermal fluids in the Luoboling porphyry Cu-Mo deposit, Zijinshan ore field, Fujian Province, China; insights from LA-ICP-MS analyses of fluid inclusions
Economic Geology and the Bulletin of the Society of Economic Geologists (December 2020) Pre-Issue-Publication

Abstract

The Luoboling Cu-Mo deposit, with 1.4 million tons (Mt) Cu and 0.11 Mt Mo, is the largest porphyry deposit in the Zijinshan district of southeast China. Mineralization at Luoboling is divided into premineralization, synmineralization, and late-mineralization stages. Consistent Cs/(Na + K) ratios in fluid inclusions suggest that the mineralizing fluids originated from a common source-the Luoboling granodiorite porphyry. The absence of initial supercritical fluid inclusions and abundant coexisting vapor and brine fluid inclusions imply that the fluids exsolved at low-pressure two-phase conditions, with temperatures of 250 degrees to 600egrees C and salinities of 30 to 60 wt % NaCl equiv (brines) and <10 wt % NaCl equiv (vapors). The deposit formed at approximately 120 to 800 bar, corresponding to the depths of approximately 1.2 to 3.2 km (assuming a transition from lithostatic to hydrostatic load). Metals such as Mo (up to 77 ppm), Pb (up to 8,800 ppm), Zn (up to 13,000 ppm), and Ag (up to 130 ppm) migrated mainly in brines. Although vapor inclusions have high concentrations of Cu (up to 20,000 ppm), hypersaline fluid was the major medium for Cu transport and precipitation. The successive precipitation of Mo and Cu occurred when fluids cooled to approximately 500 degrees C and approximately 350 degrees to 450 degrees C, respectively. The late-stage quartz-pyrite veins with phyllic alteration were formed by Cu-rich magmatic hydrothermal fluids. The Zijinshan epithermal Cu-Au deposit and the Luoboling porphyry Cu-Mo deposit originated from independent hydrothermal systems. Nonetheless, the increasing trends of Pb, Zn, and Ag concentrations in different stage inclusions from Luoboling imply potential for distal Pb-Zn-Ag mineralization.


ISSN: 0361-0128
EISSN: 1554-0774
Coden: ECGLAL
Serial Title: Economic Geology and the Bulletin of the Society of Economic Geologists
Serial Volume: Pre-Issue-Publication
Title: Evolution of multistage hydrothermal fluids in the Luoboling porphyry Cu-Mo deposit, Zijinshan ore field, Fujian Province, China; insights from LA-ICP-MS analyses of fluid inclusions
Affiliation: Chinese Academy of Sciences, Institute of Geochemistry, State Key Laboratory of Ore Deposit Geochemistry, Guiyang, China
Published: 20201218
Text Language: English
Publisher: Economic Geology Publishing Company, Lancaster, PA, United States
Number of pages: 26
References: 84
Accession Number: 2021-011648
Categories: Economic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 plates, 6 tables, geol. sketch maps
N25°07'60" - N25°13'60", E116°19'00" - E116°27'30"
N24°00'00" - N27°00'00", E115°45'00" - E119°00'00"
Secondary Affiliation: Zijin Mining Group Company, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2021, American Geosciences Institute.
Update Code: 2021
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