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Magmatic sulfide formation and oxidative dissolution in the SW Okinawa Trough: A precursor to metal-bearing magmatic fluid
Li, Zhenggang1,2,3; Chu, Fengyou1,2; Zhu, Jihao1,2; Ding, Yi1,2; Zhu, Zhimin1,2; Liu, Jiqiang1,2; Wang, Hao1,2; Li, Xiaohu1,2; Dong, Yanhui1,2; Zhao, Dineng1,2
2019-08-01
Source PublicationGEOCHIMICA ET COSMOCHIMICA ACTA
ISSN0016-7037
Volume258Pages:138-155
Corresponding AuthorLi, Zhenggang(lizg@sio.org.cn) ; Chu, Fengyou(Chu@sio.org.cn)
AbstractMagmatic sulfide formation and oxidative dissolution are effective in metal pre-enrichment and remobilization during magmatic processes, and are considered to be a prerequisite for the formation of magmatic-hydrothermal ore deposits in subduction zones. However, this sequential process and sulfide oxidation mechanism are poorly understood. In this study, we report fine-grained sulfides with variable degrees of oxidation distributed within mafic cumulates, brought into felsic magma as mafic magma intrusions in the southwestern Okinawa Trough. Thermodynamic modeling suggests that the oxygen fugacity (fO(2)) of primitive mafic magma is similar to FMQ + 2.5, reducing to similar to FMQ + 1 in evolved mafic magma and to similar to FMQ + 0.5 in felsic magma. This variation results from the continuous assimilation of reduced country rocks, as reflected by negative delta S-34(VCTD) values (-0.62% +/- 0.23%) of magmatic sulfides and highly radiogenic Sr-Nd isotopic compositions of host dacite. Magmatic reduction and addition of crust-derived sulfur result in early formation of crystalline sulfides, dominantly pyrrhotite, enriched in Cu (0.93 +/- 0.38 wt.%). A new injection of oxidized mafic magma triggers partial to complete oxidation of the earlier magmatic sulfides, ultimately transforming them into hematite-magnetite (HM) intergrowths. This means that sulfide oxidation is not directly associated with the mafic magma itself, but more likely with high-fO(2) magmatic fluid exsolved from the primitive mafic magma. The oxidative dissolution process releases >90% of Cu from the primary sulfides, with this Cu preferentially moving into magmatic fluid. This indicates that metal remobilization and transfer is very efficient under HM buffer conditions, in which trisulfur S-3(-) ions with high affinities for Au and Cu are probably the dominant sulfur species. We suggest that the periodic injection of oxidized mafic magma into continental crust containing reduced lithologies is essential for the sequential process of early sulfide formation and later oxidative dissolution in the Okinawa Trough and in other subduction zone settings with similar tectono-magmatic conditions. This process could be a precursor to the generation of metal-bearing magmatic fluid, contributing to mineralization in subduction zones. (C) 2019 Elsevier Ltd. All rights reserved.
KeywordMagmatic sulfide saturation Sulfide oxidation Hematite-magnetite intergrowth Metal remobilization Okinawa Trough
DOI10.1016/j.gca.2019.05.024
Indexed BySCI
Language英语
Funding ProjectScientific Research Fund of the Second Institute of Oceanography ; MNR of China[JG1605] ; MNR of China[JT1504] ; Open Fund of the Key Laboratory of Marine Geology and Environment, Chinese Academy of Sciences[MGE2016KG04] ; Zhejiang Provincial Natural Science Foundation[LQ17D060005] ; Zhejiang Provincial Natural Science Foundation[LZ16D060001] ; Natural Science Foundation of China[41830540] ; 13th FiveYear Plan for Resources and Environment Projects of China Ocean Mineral RD Association[DY135-E2-2-01]
WOS Research AreaGeochemistry & Geophysics
WOS SubjectGeochemistry & Geophysics
WOS IDWOS:000472708700009
PublisherPERGAMON-ELSEVIER SCIENCE LTD
Citation statistics
Document Type期刊论文
Identifierhttp://ir.qdio.ac.cn/handle/337002/161765
Collection海洋地质与环境重点实验室
Corresponding AuthorLi, Zhenggang; Chu, Fengyou
Affiliation1.State Ocean Adm, Key Lab Submarine Geosci, Hangzhou 310012, Zhejiang, Peoples R China
2.Minist Nat Resources, Inst Oceanog 2, Hangzhou 310012, Zhejiang, Peoples R China
3.Chinese Acad Sci, Inst Oceanol, Key Lab Marine Geol & Environm, Qingdao 266071, Shandong, Peoples R China
First Author AffilicationInstitute of Oceanology, Chinese Academy of Sciences
Corresponding Author AffilicationInstitute of Oceanology, Chinese Academy of Sciences
Recommended Citation
GB/T 7714
Li, Zhenggang,Chu, Fengyou,Zhu, Jihao,et al. Magmatic sulfide formation and oxidative dissolution in the SW Okinawa Trough: A precursor to metal-bearing magmatic fluid[J]. GEOCHIMICA ET COSMOCHIMICA ACTA,2019,258:138-155.
APA Li, Zhenggang.,Chu, Fengyou.,Zhu, Jihao.,Ding, Yi.,Zhu, Zhimin.,...&Zhao, Dineng.(2019).Magmatic sulfide formation and oxidative dissolution in the SW Okinawa Trough: A precursor to metal-bearing magmatic fluid.GEOCHIMICA ET COSMOCHIMICA ACTA,258,138-155.
MLA Li, Zhenggang,et al."Magmatic sulfide formation and oxidative dissolution in the SW Okinawa Trough: A precursor to metal-bearing magmatic fluid".GEOCHIMICA ET COSMOCHIMICA ACTA 258(2019):138-155.
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