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Formation process of dunites and chromitites in Orhaneli and Harmancik ophiolites (NW Turkey): Evidence from in-situ Li isotopes and trace elements in olivine

文献类型：期刊论文

作者Chen, Chen5,6,7; De Hoog, Jan C. M.4; Su, Ben-Xun3,5,7; Wang, Jing3,5,7; Uysal, Ibrahim2; Xiao, Yan1,5
刊名LITHOS
出版日期2020-12-01
卷号376页码:12
关键词Olivine Trace element Li isotopes Ophiolite Chromitite Mantle-crust transition zone
ISSN号0024-4937
DOI10.1016/j.lithos.2020.105773
英文摘要Trace elements and Li isotopic compositions of olivine from the mantle-crust transition zone of the Bursa ophiolites (including Orhaneli ophiolite and Harmancik ophiolite) in NW Turkey were measured to constrain the genesis of these dunites and chromitites. A cumulate origin for dunite can be ruled out due to the depletion of incompatible trace elements (Zr, Ti, and heavy rare earth elements) in olivine, instead the chemical signatures point to a replacive origin via melt-rock interaction. The olivine grains in the dunites have lower MnO (0.06-0.15 wt%), Co (106-137 ppm), and higher NiO (0.23-0.44 wt%) concentrations than olivine phenocrysts in MORB, suggesting these transition-zone dunites have equilibrated with extremely depleted melts. Additionally, the relatively small delta Li-7 variations of olivine (average delta Li-7 +4.8 to +8.7 parts per thousand) of the Orhaneli suite indicate the Li isotopic compositions of melts percolating through these dunites are relatively homogeneous. However, the large delta Li-7 variations of olivine (-2.5 to +20.3 parts per thousand) in Harmancik dunites can be explained by incomplete diffusive equilibration with melts percolating through these dunites, suggesting infiltration happened not long before obduction of the ophiolite. Olivine in chromitites has higher Fo (92.6-94.7) than coexisting dunites, likely induced by subsolidus Mg-Fe exchange between olivine and chromite. The higher chromite contents of the chromitites can also explain the lower concentrations of Sc, V, Co and Zn in coexisting olivine grains. Mixing of depleted mantle-derived melts and boninitic magmas is suggested to induce a compositional shift from the olivine-chromite cotectic line to the liquidus field of chromite, causing the precipitation of chromite and formation of chromitite layers in the dunites. The heavy Li isotopic compositions (+6 to +11 parts per thousand) of olivine in chromitites compared to MORB, together with the estimated compositions of parental magmas (Al2O3: 9.8-11.4 wt%; TiO2: 0.22-0.38 wt%) for the chromitites, indicate an arc-like geochemical affinity, hence a subduction-related setting in which these mantle-crust transition zones formed (C) 2020 Elsevier B.V. All rights reserved.
WOS关键词MELT-ROCK INTERACTION ; SUBDUCTION INITIATION ; OMAN OPHIOLITE ; PODIFORM CHROMITITE ; ORTHO-PYROXENE ; GEOCHEMICAL CONSTRAINTS ; TECTONIC SIGNIFICANCE ; MANTLE CHROMITITES ; LUOBUSA OPHIOLITE ; ULTRAMAFIC ROCKS
资助项目National Natural Science Foundation of China[91755205] ; National Natural Science Foundation of China[41772055] ; United Kingdom National Environment Research Council `Deep Volatiles' program[NE/M000427/1]
WOS研究方向Geochemistry & Geophysics ; Mineralogy
语种英语
WOS记录号WOS:000580897000037
出版者ELSEVIER
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 ; United Kingdom National Environment Research Council `Deep Volatiles' program ; United Kingdom National Environment Research Council `Deep Volatiles' program ; United Kingdom National Environment Research Council `Deep Volatiles' program ; United Kingdom National Environment Research Council `Deep Volatiles' program ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; United Kingdom National Environment Research Council `Deep Volatiles' program ; United Kingdom National Environment Research Council `Deep Volatiles' program ; United Kingdom National Environment Research Council `Deep Volatiles' program ; United Kingdom National Environment Research Council `Deep Volatiles' program ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; United Kingdom National Environment Research Council `Deep Volatiles' program ; United Kingdom National Environment Research Council `Deep Volatiles' program ; United Kingdom National Environment Research Council `Deep Volatiles' program ; United Kingdom National Environment Research Council `Deep Volatiles' program ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; United Kingdom National Environment Research Council `Deep Volatiles' program ; United Kingdom National Environment Research Council `Deep Volatiles' program ; United Kingdom National Environment Research Council `Deep Volatiles' program ; United Kingdom National Environment Research Council `Deep Volatiles' program
源URL[http://ir.iggcas.ac.cn/handle/132A11/98720]  
专题地质与地球物理研究所_中国科学院矿产资源研究重点实验室
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Chen, Chen; De Hoog, Jan C. M.
作者单位1.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China
2.Karadeniz Tech Univ, Dept Geol Engn, TR-61080 Trabzon, Turkey
3.Univ Chinese Acad Sci, Beijing 100049, Peoples R China
4.Univ Edinburgh, Sch GeoSci, Grant Inst, Edinburgh EH9 3FE, Midlothian, Scotland
5.Chinese Acad Sci, Innovat Acad Earth Sci, Beijing 100029, Peoples R China
6.Chinese Acad Sci, Guangzhou Inst Geochem, Key Lab Mineral & Metallogeny, Guangzhou 510460, Peoples R China
7.Chinese Acad Sci, Inst Geol & Geophys, Key Lab Mineral Resources, Beijing 100029, Peoples R China
推荐引用方式
GB/T 7714		 Chen, Chen,De Hoog, Jan C. M.,Su, Ben-Xun,et al. Formation process of dunites and chromitites in Orhaneli and Harmancik ophiolites (NW Turkey): Evidence from in-situ Li isotopes and trace elements in olivine[J]. LITHOS,2020,376:12.
APA Chen, Chen,De Hoog, Jan C. M.,Su, Ben-Xun,Wang, Jing,Uysal, Ibrahim,&Xiao, Yan.(2020).Formation process of dunites and chromitites in Orhaneli and Harmancik ophiolites (NW Turkey): Evidence from in-situ Li isotopes and trace elements in olivine.LITHOS,376,12.
MLA Chen, Chen,et al."Formation process of dunites and chromitites in Orhaneli and Harmancik ophiolites (NW Turkey): Evidence from in-situ Li isotopes and trace elements in olivine".LITHOS 376(2020):12.

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来源：地质与地球物理研究所

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