Petrogenesis and tectonic implications of gabbro and plagiogranite intrusions in mantle peridotites of the Myitkyina ophiolite, Myanmar

doi:10.1016/j.lithos.2017.04.014

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	Petrogenesis and tectonic implications of gabbro and plagiogranite intrusions in mantle peridotites of the Myitkyina ophiolite, Myanmar
	Xu, Yang 1,2; Liu, Chuan-Zhou 1,3; Chen, Yi 1,3; Guo, Shun 1,3; Wang, Jian-Gang 1; Sein, Kyaing 4
刊名	LITHOS
	2017-07-01
卷号	284 页码:180-193
关键词	Plagiogranites Gabbros Supra-subduction zone (SSZ) Myitkyina ophiolite Myanmar
ISSN号	0024-4937
DOI	10.1016/j.lithos.2017.04.014
文献子类	Article
英文摘要	Centimeter-size intrusions of gabbros and plagiogranites occur in mantle peridotites of the Myitkyina ophiolite, Myanmar. The gabbros mainly consist of plagioclase and clinopyroxene, whereas orthopyroxene occasionally occurs. The plagiogranites are mainly composed of plagioclase, quartz and amphibole, with small amount of accessory minerals, such as zircon, apatite and rutile. Plagioclase in the gabbros varies from andesine to anorthite (An(37-91)), whereas plagioclase in the plagiogranites is less calcic (An(1-40)). Clinopyroxene in the gabbros is pervasively altered to hornblende. The gabbros contain 42.97-52.88 wt% SiO2, which show negative correlations with Al2O3, CaO and MgO, but positive correlations with Na2O, P2O5 and TiO2. Microtextural relations reveal the crystallization of clinopyroxene prior to plagioclase in the Myitkyina gabbros. This suggests that the gabbros were crystallized from hydrous melts, which is also supported by the occurrence of orthopyroxene and anorthitic plagioclase in some gabbros. The gabbros have slightly enriched Sr-Nd isotopes, with initial Sr-87/Sr-86 ratios of 0.703938-0.706609 and epsilon(Nd(t)) values of +2.4-+7.2, and relatively variable Hf isotopes, with epsilon(Hf)(t) values of +13.4-+24.9. A subduction component is required to explain the decoupled Nd-Hf isotopes of the gabbros. Binary mixing suggests that addition of ca 2% subducted sediments to a depleted mantle can account for the Nd-Hf decoupling. Therefore, both petrological and geochemical data of the gabbros support that the Myitkyina ophiolite was originated in a supra-subduction zone setting. The plagiogranites have compositions of tonalites and trondhjemites, containing 56.93-77.93 wt% SiO2, 1.27-10.79 wt% Na2O and 0.05-0.71 wt% K2O. They are slightly enriched in LREE over HREE and display positive anomalies in Eu, Zr, Hf but negative Nb anomalies. Very low TiO2 contents (0.03-0.2 wt%) of the plagiogranites suggest that they were not products of fractional crystallization of MORB but were generated by hydrous melting of gabbros. This process is also supported by the nearly constant contents of both La and Yb with increasing SiO2 of the plagiogranites. The Sr-Nd-Hf isotopes of the plagiogranites indicate the involvement of crustal component in their genesis. We proposed that the Myitkyina plagiogranites were generated by partial melting of the mafic protoliths in the subducted slab. (C) 2017 Elsevier B.V. All rights reserved.
WOS关键词	SR-87/SR-86 ISOTOPE RATIO ; HIGH-AN PLAGIOCLASE ; OCEANIC-CRUST ; MASS SPECTROMETRY ; PHASE-EQUILIBRIA ; SPREADING RIDGE ; INDIAN RIDGE ; MARIANA ARC ; LU-HF ; BASALT
WOS研究方向	Geochemistry & Geophysics ; Mineralogy
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000405252300013
资助机构	National Natural Science Foundation of China(41673038) ; National Natural Science Foundation of China(41673038) ; CAS(QYZDB-SSW-DQC032) ; CAS(QYZDB-SSW-DQC032) ; Chinese Academy of Sciences(XDB03010201) ; Chinese Academy of Sciences(XDB03010201) ; National Natural Science Foundation of China(41673038) ; National Natural Science Foundation of China(41673038) ; CAS(QYZDB-SSW-DQC032) ; CAS(QYZDB-SSW-DQC032) ; Chinese Academy of Sciences(XDB03010201) ; Chinese Academy of Sciences(XDB03010201) ; National Natural Science Foundation of China(41673038) ; National Natural Science Foundation of China(41673038) ; CAS(QYZDB-SSW-DQC032) ; CAS(QYZDB-SSW-DQC032) ; Chinese Academy of Sciences(XDB03010201) ; Chinese Academy of Sciences(XDB03010201) ; National Natural Science Foundation of China(41673038) ; National Natural Science Foundation of China(41673038) ; CAS(QYZDB-SSW-DQC032) ; CAS(QYZDB-SSW-DQC032) ; Chinese Academy of Sciences(XDB03010201) ; Chinese Academy of Sciences(XDB03010201)
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/42774]
专题	地质与地球物理研究所_岩石圈演化国家重点实验室
通讯作者	Liu, Chuan-Zhou
作者单位	1.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China 2.Univ Chinese Acad Sci, Beijing 100049, Peoples R China 3.CAS Ctr Excellence Tibetan Plateau Earth Sci, Beijing 100101, Peoples R China 4.Myanmar Geosci Soc, Yangon, Myanmar
推荐引用方式 GB/T 7714	Xu, Yang,Liu, Chuan-Zhou,Chen, Yi,et al. Petrogenesis and tectonic implications of gabbro and plagiogranite intrusions in mantle peridotites of the Myitkyina ophiolite, Myanmar[J]. LITHOS,2017,284:180-193.
APA	Xu, Yang,Liu, Chuan-Zhou,Chen, Yi,Guo, Shun,Wang, Jian-Gang,&Sein, Kyaing.(2017).Petrogenesis and tectonic implications of gabbro and plagiogranite intrusions in mantle peridotites of the Myitkyina ophiolite, Myanmar.LITHOS,284,180-193.
MLA	Xu, Yang,et al."Petrogenesis and tectonic implications of gabbro and plagiogranite intrusions in mantle peridotites of the Myitkyina ophiolite, Myanmar".LITHOS 284(2017):180-193.