Magmatic sulfide formation and oxidative dissolution in the SW Okinawa Trough: A precursor to metal-bearing magmatic fluid

doi:10.1016/j.gca.2019.05.024

CORC > 海洋研究所 > 中国科学院海洋研究所 > 海洋地质与环境重点实验室

	Magmatic sulfide formation and oxidative dissolution in the SW Okinawa Trough: A precursor to metal-bearing magmatic fluid
	Li, Zhenggang 1,2,3; Chu, Fengyou 1,2; Zhu, Jihao 1,2; Ding, Yi 1,2; Zhu, Zhimin 1,2; Liu, Jiqiang 1,2; Wang, Hao 1,2; Li, Xiaohu 1,2; Dong, Yanhui 1,2; Zhao, Dineng 1,2
刊名	GEOCHIMICA ET COSMOCHIMICA ACTA
	2019-08-01
卷号	258 页码:138-155
关键词	Magmatic sulfide saturation Sulfide oxidation Hematite-magnetite intergrowth Metal remobilization Okinawa Trough
ISSN号	0016-7037
DOI	10.1016/j.gca.2019.05.024
通讯作者	Li, Zhenggang(lizg@sio.org.cn) ; Chu, Fengyou(Chu@sio.org.cn)
英文摘要	Magmatic 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.
资助项目	Scientific 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研究方向	Geochemistry & Geophysics
语种	英语
出版者	PERGAMON-ELSEVIER SCIENCE LTD
WOS记录号	WOS:000472708700009
内容类型	期刊论文
源URL	[http://ir.qdio.ac.cn/handle/337002/161764]
专题	海洋研究所_海洋地质与环境重点实验室
通讯作者	Li, Zhenggang; Chu, Fengyou
作者单位	1.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
推荐引用方式 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.