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Mineralization of an intra-oceanic arc in an accretionary orogen; insights from the Early Silurian Honghai volcanogenic massive sulfide Cu-Zn deposit and associated adakites of the eastern Tianshan (NW China)

Mao Qigui, Wang Jingbing, Xiao Wenjiao, Brian F. Windley, Karel Schulmann, Yu Mingjie, Fang Tonghui and Li Yuechen
Mineralization of an intra-oceanic arc in an accretionary orogen; insights from the Early Silurian Honghai volcanogenic massive sulfide Cu-Zn deposit and associated adakites of the eastern Tianshan (NW China)
Geological Society of America Bulletin (November 2018) 131 (5-6): 803-830

Abstract

The Honghai volcanogenic massive sulfide (VMS) deposit occurs in the Kalatage inlier of the Dananhu-Haerlik arc, Eastern Tianshan, in the southern Altaids. The deformed deposit, hosted in a suite of early Paleozoic basic to intermediate volcanic, volcaniclastic, and sedimentary rocks, consists of lenticular massive to semimassive, and sulfide-silicate stockwork orebodies. The orebodies are characterized by zoning of metallogenic elements and sulfide minerals outward from a central stockwork zone as follows: (Fe + or - Cu), (Fe + Cu + Zn + Au + Ag; Cu > Zn), (Fe + Zn + Cu + Au + Ag; Zn > Cu), and (Fe + or - [Cu/Zn]). A typical VMS hydrothermal alteration zone that formed around the foot of the massive orebodies is several times larger than the lenticular massive orebody. The hydrothermally altered rocks contain sericite, chlorite, and epidote zones from the core outward. Re-Os and argon dating of pyrite and sericite shows that the Honghai VMS deposit formed in the Early Silurian (436 + or - 2 Ma) and was deformed in the Early Devonian (410 + or - 4 Ma). This is the first documented early Paleozoic VMS deposit in the Eastern Tianshan. Our multidisciplinary data indicate that the Honghai Cu-Zn deposit formed in an immature/nascent island arc, where early tholeiitic lavas evolved into transitional basic-andesitic volcanic rocks and calc-alkaline intrusions with relatively high epsilon Nd(t) values (+6.2-+8.4) and low ( (super 87) Sr/ (super 86) Sr) (sub i) ratios (0.70412-0.70541). The Sr-Nd-Pb-S isotopic and geochemical data suggest that the ore-forming melts started in mantle-derived volcanic rocks and deep subvolcanic intrusions, and some alteration was influenced by seawater. The deposit formed in a high-level subvolcanic intrusion driven by sub-seafloor CO (sub 2) -rich, NaCl-CaCl (sub 2) -H (sub 2) O hydrothermal fluids (temperatures: 99-377 degrees C, salinities: 6%-18% NaCl equivalent) circulating in active extensional faults in a submarine caldera. Extension of the immature (nascent) intra-oceanic arc was one of the important factors that controlled the development and preservation of the VMS deposit. Future work will benefit from this improved understanding of the VMS deposits formed in immature (nascent) intra-oceanic arcs, especially in early Paleozoic island arcs in the Eastern Tianshan in the southern Altaids.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 131
Serial Issue: 5-6
Title: Mineralization of an intra-oceanic arc in an accretionary orogen; insights from the Early Silurian Honghai volcanogenic massive sulfide Cu-Zn deposit and associated adakites of the eastern Tianshan (NW China)
Affiliation: Beijing Institute of Geology for Mineral Resources, Beijing, China
Pages: 803-830
Published: 20181128
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 163
Accession Number: 2019-007059
Categories: Economic geology, geology of ore depositsGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 9 tables, geol. sketch maps
N41°00'00" - N44°00'00", E87°00'00" - E96°00'00"
Secondary Affiliation: Chinese Academy of Sciences, Xinjiang Institute of Ecology and Geography, CHN, ChinaUniversity of Leicester, GBR, United KingdomUniversity of Strasbourg, FRA, France
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201906
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