Petrology and Sr-Nd Isotopic Disequilibrium of the Xiaohaizi Intrusion, NW China: Genesis of Layered Intrusions in the Tarim Large Igneous Province

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	Petrology and Sr-Nd Isotopic Disequilibrium of the Xiaohaizi Intrusion, NW China: Genesis of Layered Intrusions in the Tarim Large Igneous Province
	Wei, Xun 1,2,3; Xu, Yi-Gang 1; Zhang, Chuan-Lin 4; Zhao, Jian-Xin 5; Feng, Yue-Xing 5
刊名	JOURNAL OF PETROLOGY
	2014-12-01
卷号	55 期号:12 页码:2567-2597
关键词	Xiaohaizi intrusion isotopic disequilibrium assimilation and fractional crystallization layered mafic intrusions Tarim LIP
通讯作者	Xu, YG (reprint author), Chinese Acad Sci, Guangzhou Inst Geochem, State Key Lab Isotope Geochem, Guangzhou 510640, Guangdong, Peoples R China.
英文摘要	Layered mafic intrusions (LMI) are sporadically distributed in the Early Permian Tarim large igneous province (LIP), NW China, and are crosscut by numerous contemporaneous dykes. The Xiaohaizi wehrlite intrusion is composed mainly of olivine (Fo69-75), clinopyroxene (Mg# = 75-84), intercumulus plagioclase (An53-86) and Fe-Ti oxides. Both petrography and mineral compositions suggest that olivine and clinopyroxene crystallized earlier than plagioclase and Fe-Ti oxides. The dykes are of alkali basalt to trachyandesite with low Mg# (35-39). The least-contaminated dykes display strong rare earth element (REE) fractionation, enrichment of Nb and Ta, and depletion of Pb relative to other similarly incompatible elements, bearing strong similarity to ocean island basalts (OIB). This, together with their positive epsilon Nd-i values (4.3-4.8), is consistent with derivation from an enriched asthenospheric mantle source. Clinopyroxenes in the wehrlites display convex-upward chondrite-normalized REE patterns. The melts in equilibrium with these clinopyroxenes have very similar trace element compositions to those of the crosscutting dykes, suggesting a similar mantle source shared by the Xiaohaizi wehrlite intrusion and dykes. The Xiaohaizi wehrlite intrusion is characterized by Sr-Nd isotopic disequilibrium between clinopyroxene and plagioclase separates: Sr-87/(86)Sri (0.7038-0.7041) and epsilon Nd-i (1.0-1.9) of clinopyroxene are lower and higher than the respective ratios of intercumulus plagioclase (Sr-87/Sr-86(i) = 0.7042-0.7043, epsilon Nd-i = 0.4-1.0). The Sr-87/(86)Sri and epsilon Nd-i of clinopyroxene separates correlate positively and negatively with Zr/ Nb, respectively, implying variable degrees of crustal contamination during the formation of the Xiaohaizi wehrlite intrusion. Sr-87/(86)Sri increases and epsilon Nd-i decreases with increasing Ca content of plagioclase, indicating that higher An plagioclases experienced higher degrees of contamination. This can be explained by assimilation of continental crust through a turbulent magma ascent (ATA) process. However, this ATA model fails to account for the positive correlation between the Mg# and epsilon Nd-i of clinopyroxene separates. The isotopic disequilibrium in the Xiaohaizi LMI is more probably generated during an assimilation and fractional crystallization process involving Archean-Neoproterozoic basement and carbonates as contaminants.
学科主题	Geochemistry & Geophysics
收录类别	SCI
语种	英语
WOS记录号	WOS:000348056300010
内容类型	期刊论文
源URL	[http://ir.qdio.ac.cn/handle/337002/23832]
专题	海洋研究所_海洋地质与环境重点实验室
作者单位	1.Chinese Acad Sci, Guangzhou Inst Geochem, State Key Lab Isotope Geochem, Guangzhou 510640, Guangdong, Peoples R China 2.Chinese Acad Sci, Inst Oceanol, Key Lab Marine Geol & Environm, Qingdao 266071, Peoples R China 3.Univ Chinese Acad Sci, Beijing 100049, Peoples R China 4.CGS, Nanjing Inst Geol & Mineral Resources, Nanjing 210016, Peoples R China 5.Univ Queensland, Radiogen Isotope Facil, Sch Earth Sci, Brisbane, Qld 4072, Australia
推荐引用方式 GB/T 7714	Wei, Xun,Xu, Yi-Gang,Zhang, Chuan-Lin,et al. Petrology and Sr-Nd Isotopic Disequilibrium of the Xiaohaizi Intrusion, NW China: Genesis of Layered Intrusions in the Tarim Large Igneous Province[J]. JOURNAL OF PETROLOGY,2014,55(12):2567-2597.
APA	Wei, Xun,Xu, Yi-Gang,Zhang, Chuan-Lin,Zhao, Jian-Xin,&Feng, Yue-Xing.(2014).Petrology and Sr-Nd Isotopic Disequilibrium of the Xiaohaizi Intrusion, NW China: Genesis of Layered Intrusions in the Tarim Large Igneous Province.JOURNAL OF PETROLOGY,55(12),2567-2597.
MLA	Wei, Xun,et al."Petrology and Sr-Nd Isotopic Disequilibrium of the Xiaohaizi Intrusion, NW China: Genesis of Layered Intrusions in the Tarim Large Igneous Province".JOURNAL OF PETROLOGY 55.12(2014):2567-2597.