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Redox state of the Baogutu reduced porphyry Cu deposit in the Central Asian Orogenic belt
Zhu, Bin1,2; Zhang, Hong-Fu1; Shen, Ping1; Su, Ben-Xun1; Xiao, Yan1; He, Yong-Sheng3
2018-10-01
Source PublicationORE GEOLOGY REVIEWS
ISSN0169-1368
Volume101Pages:803-818
AbstractReduced porphyry Cu deposits are scarce and their origins remain enigmatic. The Late Carboniferous Baogutu reduced porphyry Cu deposit in the western Junggar Terrane, NW China, provides an opportunity to address this issue. In this study, we conducted systematic analyses in terms of petrography, mineral chemistry, major elements, trace elements and Fe isotopes to investigate the redox state of its primary magma and further constrain the origin of Baogutu copper deposit. Based on the petrological observation and mineral chemistry, two magmatic stages have been recognized during the formation of ore-forming diorite. The early stage is characterized by the crystallization of magnetite and high Mg-# [Mg/(Mg + Fe2+)1 hornblende under oxidized condition (Delta NNO > 2.36, calculated by the equation given by Scaillet and Evans (1999). The late stage is characterized by the crystallization of ilmenite and low Mg-# biotite under reduced condition (Delta NNO < -0.6). The large decrease of oxygen fugacity (log fO(2), more than 3 units) between the two stages may result from the contamination of organic carbon during the emplacement of magma. In addition, major and trace element compositions of the Baogutu ore-forming diorites show the affinity of arc magmas which are like those that host oxidized porphyry Cu deposits. In this study, we first report the Fe isotopic compositions of reduced porphyry copper deposit and discuss its application for the origin of ore deposit. The delta Fe-56 values of less altered diorites and granodiorites (+ 0.083%o and +0.054%o) fall into the field of arc magmas, consistent with their major and trace elements results. The delta Fe-56 values of sulfides (chalcopyrite and pyrite) show a large span (0.228 to + 0.614%o) and the early formed disseminated sulfides are enriched in light Fe isotopes relative to the late formed vein-hosted sulfides, which indicates that hydrothermal fluid evolves toward heavy Fe isotope enrichment. The average delta Fe-56 of all hydrothermal sulfides (chalcopyrite and pyrite) is much higher than that of Baogutu silicate rocks, which demonstrates that the hydrothermal fluid are Fe isotopically heavy and it well explains the positive correlations between delta Fe-56 and indices of hydrothermal alteration for altered plutonic rocks and wall rocks. In summary, major elements, trace elements and Fe isotopes of the Baogutu porphyries show the affinity of arc magmas, same as the typical oxidized porphyry Cu deposits. Both petrological observations and Fe isotope features of the Baogutu porphyry Cu deposit indicate that the primary magma of Baogutu porphyries is oxidized and its reduced features are secondary.
KeywordBaogutu reduced porphyry Cu deposit Redox condition Primary magma Fe isotope Ore-forming fluid
DOI10.1016/j.oregeorev.2018.08.024
Funding OrganizationNational Natural Science Foundation of China, China ; National Natural Science Foundation of China, China ; National Natural Science Foundation of China, China ; National Natural Science Foundation of China, China ; National Natural Science Foundation of China, China ; National Natural Science Foundation of China, China ; National Natural Science Foundation of China, China ; National Natural Science Foundation of China, China
WOS KeywordIRON ISOTOPE FRACTIONATION ; MO-AU DEPOSIT ; NW-CHINA ; WEST JUNGGAR ; TECTONIC EVOLUTION ; OXIDIZED MAGMAS ; OXYGEN-FUGACITY ; MOSSBAUER-SPECTROSCOPY ; CHALCOPHILE ELEMENTS ; NORTHERN XINJIANG
Language英语
Funding ProjectNational Natural Science Foundation of China, China[91014007] ; National Natural Science Foundation of China, China[91214203] ; National Natural Science Foundation of China, China[U1303293] ; National Natural Science Foundation of China, China[41390442]
Funding OrganizationNational Natural Science Foundation of China, China ; National Natural Science Foundation of China, China ; National Natural Science Foundation of China, China ; National Natural Science Foundation of China, China ; National Natural Science Foundation of China, China ; National Natural Science Foundation of China, China ; National Natural Science Foundation of China, China ; National Natural Science Foundation of China, China
WOS Research AreaGeology ; Mineralogy ; Mining & Mineral Processing
WOS SubjectGeology ; Mineralogy ; Mining & Mineral Processing
WOS IDWOS:000448092400043
PublisherELSEVIER SCIENCE BV
Citation statistics
Cited Times:1[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Identifierhttp://ir.iggcas.ac.cn/handle/132A11/89151
Collection岩石圈演化国家重点实验室
Corresponding AuthorZhu, Bin
Affiliation1.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China
2.Beijing Res Inst Uranium Geol, Beijing 100029, Peoples R China
3.China Univ Geosci, State Key Lab Geol Proc & Mineral Resources, Beijing 100083, Peoples R China
Recommended Citation
GB/T 7714
Zhu, Bin,Zhang, Hong-Fu,Shen, Ping,et al. Redox state of the Baogutu reduced porphyry Cu deposit in the Central Asian Orogenic belt[J]. ORE GEOLOGY REVIEWS,2018,101:803-818.
APA Zhu, Bin,Zhang, Hong-Fu,Shen, Ping,Su, Ben-Xun,Xiao, Yan,&He, Yong-Sheng.(2018).Redox state of the Baogutu reduced porphyry Cu deposit in the Central Asian Orogenic belt.ORE GEOLOGY REVIEWS,101,803-818.
MLA Zhu, Bin,et al."Redox state of the Baogutu reduced porphyry Cu deposit in the Central Asian Orogenic belt".ORE GEOLOGY REVIEWS 101(2018):803-818.
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