Mineralogical Constraints on the Magma Mixing Beneath the Iheya Graben, an Active Back-Arc Spreading Centre of the Okinawa Trough

doi:10.1093/petrology/egaa098

IOCAS-IR > 海洋地质与环境重点实验室

	Mineralogical Constraints on the Magma Mixing Beneath the Iheya Graben, an Active Back-Arc Spreading Centre of the Okinawa Trough
	Zhang, Yu-Xiang 1,2,3,4; Zeng, Zhi-Gang 1,2,4; Gaetani, Glenn 3; Zhang, Le 5; Lai, Zhi-Qing 6
	2020-09-01
发表期刊	JOURNAL OF PETROLOGY
ISSN	0022-3530
卷号	61 期号:9 页码:23
通讯作者	Zeng, Zhi-Gang([email protected])
摘要	The Iheya Graben is a back-arc spreading centre in the middle part of the Okinawa Trough. It is also located in the centre of an anomalous volcanic zone (volcanic arc migration phenomenon, or VAMP) and is characterized by bimodal volcanism, unusually high heat flow and active hydrothermal circulation. The subvolcanic magma plumbing system and the magmatic processes related to the formation of rare erupted intermediate lavas in this area remain uncertain. In this study, we conducted systematic mineralogical analyses (in situ major element, trace element and Sr isotopes) and whole rock geochemical analyses (major element, trace element and Sr-Nd isotopes) on an andesite (T5-2; type C andesite) and a rhyolite (C11; type 2 rhyolite), and present evidence for magma mixing in the origins of these lavas. Andesite T5-2 contains a mafic mineral assemblage and a silicic mineral assemblage, which are derived from a basaltic melt and a type 2 rhyolitic melt, respectively. A 4:6 mixture of basalt and type 2 rhyolite from the Iheya Graben reproduces the whole-rock major element, trace element, and Sr-Nd isotope compositions of T5-2. Rhyolite C11 contains a group of disequilibrium minerals that crystallized from a less evolved rhyolitic melt with relatively more enriched Sr-Nd isotope compositions, suggesting mixing of this melt with a more evolved and isotopically more depleted rhyolitic melt. This mixing process could produce a series of rhyolitic melts with a negative correlation between SiO2 concentrations and Sr-87/Sr-86 ratios (or a positive correlation for Nd-143/Nd-144 ratios), which are recorded by the whole group of type 2 rhyolites. The results from mineral-based thermobarometers suggest that the premixing storage temperatures of the basaltic and rhyolitic melts are similar to 1100 degrees C and 870-900 degrees C, respectively. The hybrid andesitic melt has temperatures of similar to 950 to similar to 980 degrees C. The magma storage pressures are not well constrained, ranging from similar to 400 MPa to similar to 100 MPa. We show that magma mixing plays a significant role in the origins of diverse volcanism in the middle Okinawa Trough; more specifically, two of the three types of andesites (types B and C) and one of the two types of rhyolites (type 2) are associated with magma mixing. We thus propose a complex magma plumbing system with multichamber magma storage and frequent magma mixing beneath the Iheya Graben.
关键词	magma mixing magma plumbing system Okinawa Trough pre-eruptive storage conditions
DOI	10.1093/petrology/egaa098
收录类别	SCI
语种	英语
资助项目	National Natural Science Foundation of China[91958213]; Open Fund of the Key Laboratory of Marine Geology and Environment, Chinese Academy of Sciences[MGE2020KG07]; Strategic Priority Research Program of the Chinese Academy of Sciences[XDB42020402]; China Postdoctoral Science Foundation[2019M662454]; International Partnership Program of the Chinese Academy of Sciences[133137KYSB20170003]; National Program on Global Change and Air-Sea Interaction[GASI-GEOGE-02]; Special Fund for the Taishan Scholar Program of Shandong Province[ts201511061]
WOS研究方向	Geochemistry & Geophysics
WOS类目	Geochemistry & Geophysics
WOS记录号	WOS:000634894800008
出版者	OXFORD UNIV PRESS
引用统计	被引频次：13[WOS] [WOS记录] [WOS相关记录]
文献类型	期刊论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/170634
专题	海洋地质与环境重点实验室
通讯作者	Zeng, Zhi-Gang
作者单位	1.Chinese Acad Sci, Inst Oceanol, Key Lab Marine Geol & Environm, Qingdao 266071, Shandong, Peoples R China 2.Qingdao Natl Lab Marine Sci & Technol, Lab Marine Mineral Resources, Qingdao 266071, Shandong, Peoples R China 3.Woods Hole Oceanog Inst, Dept Geol & Geophys, Woods Hole, MA 02543 USA 4.Chinese Acad Sci, Ctr Ocean Megasci, Qingdao 266071, Shandong, Peoples R China 5.Chinese Acad Sci, Guangzhou Inst Geochem, State Key Lab Isotope Geochem, Guangzhou 510640, Guangdong, Peoples R China 6.Ocean Univ China, Coll Marine Geosci, Qingdao 266100, Shandong, Peoples R China
第一作者单位	中国科学院海洋研究所; 中国科学院海洋大科学研究中心
通讯作者单位	中国科学院海洋研究所; 中国科学院海洋大科学研究中心
推荐引用方式 GB/T 7714	Zhang, Yu-Xiang,Zeng, Zhi-Gang,Gaetani, Glenn,et al. Mineralogical Constraints on the Magma Mixing Beneath the Iheya Graben, an Active Back-Arc Spreading Centre of the Okinawa Trough[J]. JOURNAL OF PETROLOGY,2020,61(9):23.
APA	Zhang, Yu-Xiang,Zeng, Zhi-Gang,Gaetani, Glenn,Zhang, Le,&Lai, Zhi-Qing.(2020).Mineralogical Constraints on the Magma Mixing Beneath the Iheya Graben, an Active Back-Arc Spreading Centre of the Okinawa Trough.JOURNAL OF PETROLOGY,61(9),23.
MLA	Zhang, Yu-Xiang,et al."Mineralogical Constraints on the Magma Mixing Beneath the Iheya Graben, an Active Back-Arc Spreading Centre of the Okinawa Trough".JOURNAL OF PETROLOGY 61.9(2020):23.

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