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Heterogeneous magnesium isotopic composition of the lower continental crust: A xenolith perspective

文献类型：期刊论文

作者Teng, Fang-Zhen1,2; Yang, Wei2,3; Rudnick, Roberta L.4; Hu, Yan1
刊名GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
出版日期2013-09-01
卷号14期号:9页码:3844-3856
ISSN号1525-2027
关键词magnesium lower crust granulite xenoliths isotope fractionation
DOI10.1002/ggge.20238
文献子类Article
英文摘要We report 26 high-precision whole-rock Mg isotopic analyses for two suites of well-characterized granulite xenoliths from Chudleigh and McBride, North Queensland, Australia, in order to constrain the behavior of Mg isotopes during deep crustal processes and the Mg isotopic composition of the lower continental crust. Previous studies suggest that the Chudleigh granulites are a suite of cogenetic cumulates crystallized from mafic magmas that intruded into and assimilated the preexisting lower crust via combined assimilation and fractional crystallization (AFC). The Mg-26 values of the xenoliths range from -0.31 to -0.21 and correlate with radiogenic isotopes, reflecting mixing of mantle-derived mafic magma (Mg-26=-0.31) with preexisting isotopically heavy crustal materials (Mg-26=approximate to +0.5) through the AFC process. The McBride granulites range compositionally from mafic to felsic, and originated as cumulates, solidified mafic/felsic melts, and restites that formed during basaltic underplating and reworking of preexisting lower crust. Their Mg-26 values vary widely from -0.72 to +0.19 parts per thousand. The large Mg isotopic variation in the McBride xenoliths reflects both distinct source compositions and metamorphic enrichment of garnet, which is isotopically light. Based on these results, the lower continental crust has a heterogeneous Mg isotopic composition, with a weighted average Mg-26 of -0.18 parts per thousand. The bulk continental crust, based on available data, has an average Mg isotopic composition of -0.19 parts per thousand, and is slightly heavier than the mantle. The highly heterogeneous Mg isotopic distribution in the crust indicates that chemical weathering not only modifies the upper crust compositions but also significantly influences lower crust compositions through emplacement of upper crustal materials into the deep crust.
WOS关键词NORTH CHINA CRATON ; PERIDOTITE XENOLITHS ; GRANULITE XENOLITHS ; MANTLE XENOLITHS ; FRACTIONATION ; DIFFUSION ; LITHIUM ; CONSTRAINTS ; CHONDRITES ; QUEENSLAND
WOS研究方向Geochemistry & Geophysics
语种英语
出版者AMER GEOPHYSICAL UNION
WOS记录号WOS:000326247700031
资助机构National Science Foundation(EAR-0838227 ; National Science Foundation(EAR-0838227 ; EAR-1056713 ; EAR-1056713 ; EAR-1340160) ; EAR-1340160) ; National Science Foundation(EAR-0838227 ; National Science Foundation(EAR-0838227 ; EAR-1056713 ; EAR-1056713 ; EAR-1340160) ; EAR-1340160) ; National Science Foundation(EAR-0838227 ; National Science Foundation(EAR-0838227 ; EAR-1056713 ; EAR-1056713 ; EAR-1340160) ; EAR-1340160) ; National Science Foundation(EAR-0838227 ; National Science Foundation(EAR-0838227 ; EAR-1056713 ; EAR-1056713 ; EAR-1340160) ; EAR-1340160)
源URL[http://ir.iggcas.ac.cn/handle/132A11/86808]  
专题中国科学院地质与地球物理研究所
通讯作者Teng, Fang-Zhen
作者单位1.Univ Washington, Dept Earth & Space Sci, Isotope Lab, Seattle, WA 98195 USA
2.Univ Arkansas, Dept Geosci, Isotope Lab, Fayetteville, AR 72701 USA
3.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing, Peoples R China
4.Univ Maryland, Dept Geol, Geochem Lab, College Pk, MD 20742 USA
推荐引用方式
GB/T 7714		 Teng, Fang-Zhen,Yang, Wei,Rudnick, Roberta L.,et al. Heterogeneous magnesium isotopic composition of the lower continental crust: A xenolith perspective[J]. GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS,2013,14(9):3844-3856.
APA Teng, Fang-Zhen,Yang, Wei,Rudnick, Roberta L.,&Hu, Yan.(2013).Heterogeneous magnesium isotopic composition of the lower continental crust: A xenolith perspective.GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS,14(9),3844-3856.
MLA Teng, Fang-Zhen,et al."Heterogeneous magnesium isotopic composition of the lower continental crust: A xenolith perspective".GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS 14.9(2013):3844-3856.

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来源：地质与地球物理研究所

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