Minor and trace element variations in chromite from the Songshugou dunites, North Qinling Orogen: Evidence for amphibolite-facies metamorphism

doi:10.1016/j.lithos.2019.01.009

CORC > 地质与地球物理研究所 > 中国科学院地质与地球物理研究所 > 岩石圈演化国家重点实验室

	Minor and trace element variations in chromite from the Songshugou dunites, North Qinling Orogen: Evidence for amphibolite-facies metamorphism
	Yu, Hong 1,3; Zhang, Hong-Fu 1,2; Zou, Hai-Bo 2,3; Yang, Yue-Heng 1
刊名	LITHOS
	2019-03-01
卷号	328 页码:146-158
关键词	Chromite Minor and trace elements Metamorphism Dunite Songshugou Ophiolites
ISSN号	0024-4937
DOI	10.1016/j.lithos.2019.01.009
英文摘要	The Songshugou dunites are part of the ultramafic sequence of the Songshugou ophiolite within the Qjnling Group metamorphic rocks, which are distributed in the northern part of the Shang-Dan Suture Zone (SDSZ) in central China. The dunites include lenses of coarse- and medium-grained dunite set in a fine-grained dunite host. Disseminated chromite within these dunites can be classified into three microstructural types: (1) partly altered chromite with primary cores surrounded by porous chromite rims; (2) porous chromite with abundant pores that are filled with chlorite; and (3) homogeneous chromite. The primary magmatic cores of the partly altered chromite (Chr) is depleted in Cr and enriched in Al and Mg. Porous chromite includes Cr-rich Chr and ferritchromite (Fe-Chr) that is enriched in Fe2+ but depleted in Al. Homogeneous chromite is mainly Cr-magnetite (Cr-Mag) that is enriched in Fe3+ and extremely depleted in Al. The primary Cr-poor chromite was gradually transformed to porous Cr-rich Chr and/or by Fe-Chr during metamorphism. Reaction of Cr-poor Chr with olivine (Ol) produces chlorite (Chl) and secondary Chr enriched in Cr and Fe2+. Mg and Al diffuse away from primary Chr, leaving a residual Al- and Mg-depleted, Cr-rich Chr and Fe-Chr. Porous Chr is enriched in Zn, Co, Mn, but depleted in Ga, Ni, and Sc, due to the fluid-assisted formation of Chl within the pores of porous chromite. Zn, Co, and Mn from the metamorphic fluids diffuse toward the cores of chromite. The elements Sc, Ti, V, and Ni diffuse from Cr-poor Chr core to Cr-mag rim with increasing Fe3+/(Fe3+ + Fe2+). Late precipitation of Cr-mag occurred under oxidizing and hydrous conditions. The infiltration of fluid produced non-porous Fe3+-rich Chr or Cr-mag along grain boundaries or fractures within chromite. These fluids further promoted the reordering of octahedral sites, enhancing higher mobilization and enrichment of Ga, Ni, Sc, V, and Ti. The infiltration of high oxygen fugacity fluids promoted diffusion of Ga, Ni, Sc, and Ti toward the rims, and diffusion of Zn, Co, and Mn toward the cores. All chromite grains from the Songshugou dunites have low Mg-# [molar 100 x Mg/(Mg + Fe2+)] values, and high Cr-# [molar 100 x Cr/(Cr + Al)] and Fe3+/(Cr + Al + Fe3+), similar to metamorphic chromite formed under amphibolite-facies conditions. The observed positive Zn-Co-Mn anomalies and negative Ga-Ni-Sc anomalies in chromite, and the crystallization of Chl, are fingerprints of amphibolite-facies metamorphism. The compositions of chromite, the inferred mineral assemblage in which it occurs, and mineral equilibria modeling of the assemblage all suggest amphibolite-facies metamorphic temperatures ranging from 600 degrees C to 700 degrees C. (C) 2019 Elsevier B.V. All rights reserved.
资助项目	National Natural Science Foundation of China[41603037] ; National Natural Science Foundation of China[41688103] ; National Natural Science Foundation of China[41525012]
WOS关键词	CENTRAL CHINA ; PETROGENETIC INDICATOR ; TECTONIC EVOLUTION ; OMAN OPHIOLITE ; GROUP MINERALS ; SPINEL ; INSIGHTS ; ORIGIN ; MANTLE ; ROCKS
WOS研究方向	Geochemistry & Geophysics ; Mineralogy
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000463308800011
资助机构	National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/91300]
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	Yu, Hong
作者单位	1.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, POB 9825, Beijing 100029, Peoples R China 2.Northwest Univ, State Key Lab Continental Dynam, Dept Geol, Xian 710069, Shaanxi, Peoples R China 3.Auburn Univ, Dept Geosci, Auburn, AL 36849 USA
推荐引用方式 GB/T 7714	Yu, Hong,Zhang, Hong-Fu,Zou, Hai-Bo,et al. Minor and trace element variations in chromite from the Songshugou dunites, North Qinling Orogen: Evidence for amphibolite-facies metamorphism[J]. LITHOS,2019,328:146-158.
APA	Yu, Hong,Zhang, Hong-Fu,Zou, Hai-Bo,&Yang, Yue-Heng.(2019).Minor and trace element variations in chromite from the Songshugou dunites, North Qinling Orogen: Evidence for amphibolite-facies metamorphism.LITHOS,328,146-158.
MLA	Yu, Hong,et al."Minor and trace element variations in chromite from the Songshugou dunites, North Qinling Orogen: Evidence for amphibolite-facies metamorphism".LITHOS 328(2019):146-158.