High-temperature inter-mineral magnesium isotope fractionation in mantle xenoliths from the North China craton

doi:10.1016/j.epsl.2011.05.047

	High-temperature inter-mineral magnesium isotope fractionation in mantle xenoliths from the North China craton
	Liu, Sheng-Ao 1,2,3; Teng, Fang-Zhen 2,3; Yang, Wei 2,3,4; Wu, Fu-Yuan 4
刊名	EARTH AND PLANETARY SCIENCE LETTERS
	2011-08-01
卷号	308 期号:1-2 页码:131-140
关键词	magnesium isotopes inter-mineral isotope fractionation spinel olivine pyroxene peridotite xenolith
ISSN号	0012-821X
DOI	10.1016/j.epsl.2011.05.047
文献子类	Article
英文摘要	To investigate the magnitude and mechanism of inter-mineral Mg isotope fractionation at mantle temperatures, we measured Mg isotopic compositions of coexisting olivine (Ol), orthopyroxene (Opx), clinopyroxene (Cpx), phlogopite (Phl) and spinet (Spl) from harzburgite, Iherzolite and clinopyroxenite xenoliths in the North China craton. These xenoliths are well-characterized and formed over a wide temperature range from similar to 800 to 1150 degrees C. The coexisting Opx and Ol have constant and indistinguishable Mg isotopic compositions, with delta(26)Mg ranging from -0.29 to -0.22%. in Ol and from -0.28 to -0.22 parts per thousand in Opx (Delta(26)Mg(Opx-Ol) = delta(26)Mg(Opx) - delta(26)Mg(Ol) = -0.04 to +0.04%.; n = 11). By contrast, Mg isotopic compositions of Cpx and Phl are variable and slightly heavier than coexisting Ol (Delta 26Mg(Cpx-Ol) = 0 to +0.13 parts per thousand. n = 13; Delta(26)Mg(Phl-Ol) = +0.11 to +0.20%, n = 3). Isotope fractionations between coexisting Cpx and 01 are correlated with temperatures, implying equilibrium isotope fractionation. The degree and direction of isotope fractionations among these mantle silicates agree with theoretical predictions, suggesting that inter-mineral Mg isotope fractionation is primarily controlled by the Mg-O bond strength, with stronger bonds favoring heavier Mg isotopes. Cpx and Phl have shorter and thus stronger Mg-O bonds, and hence are isotopically heavier than coexisting 01. Compared with coexisting silicates, delta(26)Mg values of spinets are more variable and much heavier, ranging from +0.03 to +0.28%. The Delta(26)Mg(Opx-Ol) values vary significantly from +0.25 to +0.55% (n = 10) and show an excellent, positive, linear correlation with 10(6)/T(2)(K) [Delta(26)Mg(Spl-Ol) = 0.63 (+/- 0.12) x 10(6)/T(2)(K)-0.03(+/- 0.08)], indicating equilibrium Spl-Ol isotope fractionation. The absence of intra-mineral isotopic variation and quantitative diffusion calculations further confirm isotope exchange equilibrium between coexisting Spl and Ol. Our results demonstrate the existence of measurable Mg isotope fractionation between mantle minerals and suggest that the large high-temperature equilibrium Delta(26)Mg(Opx-Ol) Mg isotope fractionation in peridotite xenoliths can potentially be used as a geothermometer in mantle geochemistry. (C) 2011 Elsevier B.V. All rights reserved.
WOS关键词	SPINEL ; DIFFUSION ; OLIVINE ; GEOTHERMOMETRY ; METASOMATISM ; PERIDOTITES ; LITHIUM ; CRUST ; MG
WOS研究方向	Geochemistry & Geophysics
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000293486100014
资助机构	National Science Foundation(EAR-0838227 ; National Science Foundation(EAR-0838227 ; Arkansas Space Grant Consortium(SW19002) ; Arkansas Space Grant Consortium(SW19002) ; National Natural Science Foundation of China(40973016) ; National Natural Science Foundation of China(40973016) ; China Scholarship Council ; China Scholarship Council ; EAR-1056713) ; EAR-1056713) ; National Science Foundation(EAR-0838227 ; National Science Foundation(EAR-0838227 ; Arkansas Space Grant Consortium(SW19002) ; Arkansas Space Grant Consortium(SW19002) ; National Natural Science Foundation of China(40973016) ; National Natural Science Foundation of China(40973016) ; China Scholarship Council ; China Scholarship Council ; EAR-1056713) ; EAR-1056713) ; National Science Foundation(EAR-0838227 ; National Science Foundation(EAR-0838227 ; Arkansas Space Grant Consortium(SW19002) ; Arkansas Space Grant Consortium(SW19002) ; National Natural Science Foundation of China(40973016) ; National Natural Science Foundation of China(40973016) ; China Scholarship Council ; China Scholarship Council ; EAR-1056713) ; EAR-1056713) ; National Science Foundation(EAR-0838227 ; National Science Foundation(EAR-0838227 ; Arkansas Space Grant Consortium(SW19002) ; Arkansas Space Grant Consortium(SW19002) ; National Natural Science Foundation of China(40973016) ; National Natural Science Foundation of China(40973016) ; China Scholarship Council ; China Scholarship Council ; EAR-1056713) ; EAR-1056713)
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/74668]
专题	中国科学院地质与地球物理研究所
通讯作者	Liu, Sheng-Ao
作者单位	1.Univ Sci & Technol China, Sch Earth & Space Sci, CAS Key Lab Crust Mantle Mat & Environm, Hefei 230026, Anhui, Peoples R China 2.Univ Arkansas, Dept Geosci, Isotope Lab, Fayetteville, AR 72701 USA 3.Univ Arkansas, Arkansas Ctr Space & Planetary Sci, Fayetteville, AR 72701 USA 4.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 10029, Peoples R China
推荐引用方式 GB/T 7714	Liu, Sheng-Ao,Teng, Fang-Zhen,Yang, Wei,et al. High-temperature inter-mineral magnesium isotope fractionation in mantle xenoliths from the North China craton[J]. EARTH AND PLANETARY SCIENCE LETTERS,2011,308(1-2):131-140.
APA	Liu, Sheng-Ao,Teng, Fang-Zhen,Yang, Wei,&Wu, Fu-Yuan.(2011).High-temperature inter-mineral magnesium isotope fractionation in mantle xenoliths from the North China craton.EARTH AND PLANETARY SCIENCE LETTERS,308(1-2),131-140.
MLA	Liu, Sheng-Ao,et al."High-temperature inter-mineral magnesium isotope fractionation in mantle xenoliths from the North China craton".EARTH AND PLANETARY SCIENCE LETTERS 308.1-2(2011):131-140.