Geochemical constraints on the protoliths of eclogites and blueschists from North Qilian, northern Tibet
文献类型：期刊论文
| 作者 | Zhang, Long1; Chen, Ren-Xu1; Zheng, Yong-Fei1; Hu, Zhaochu2; Yang, Yueheng3; Xu, Lijuan4 |
| 刊名 | CHEMICAL GEOLOGY
 |
| 出版日期 | 2016-02-10 |
| 卷号 | 421页码:26-43 |
| 关键词 | Subduction zone Eclogite and blueschist Backarc basin Basalt geochemistry Metamorphic zirconology North Qilian |
| DOI | 10.1016/j.chemgeo.2015.11.026 |
| 文献子类 | Article |
| 英文摘要 | An integrated study of whole-rock geochemistry, mineral O isotope geochemistry and zirconology was carried out for low-temperature eclogites and blueschists from the North Qilian orogen in northern Tibet. The results demonstrate that these oceanic-type eclogites and blueschists were produced by metamorphism of backarc basin basalts rather than mid-ocean ridge basalts as commonly thought. These high pressure metabasites show significant heterogeneity in their major and trace element compositions, varying from island arc basalts-like, mid-ocean ridge basalts-like to oceanic island basalts-like, respectively, in trace element distribution diagrams. Such variable compositions are comparable with those of backarc basin basalts at different stages. Whole-rock Nd isotope analyses indicate that the compositional difference between the metabasite protoliths can be ascribed to involvement of different amounts of subducted sediment-derived melts in the backarc mantle. Oxygen isotope fractionations between coexisting minerals are not at equilibrium; garnet O isotope analyses indicate that whole-rock delta O-18 values are either higher or lower than normal mantle value, which is attributable to seawater-hydrothermal alteration during seafloor spreading to open the backarc basin. Relict magmatic zircon domains show oscillatory zoning, high Th and U contents, high Th/U ratios, and steep HREE patterns, with protolith U-Pb ages of 486-496 Ma. Metamorphic zircon domains exhibit lowered Th, U and HREE contents and Th/U ratios than the relict magmatic domains and contain mineral inclusions of omphacite, rutile and phengite, giving concordant U-Pb ages of 463 +/- 10 Ma for eclogite-facies metamorphism. Zircons have markedly depleted Hf isotope compositions with Hf model ages slightly or significantly older than the protolith ages, suggesting incorporation of crustal components into the magma sources of these metabasite protoliths. Most zircons have delta O-18 values different from normal mantle values, and the distinct zircon O isotopes in different samples are in accordance with garnet delta O-18 values for the same sample, pointing to a localized fluid source for the metamorphism. Therefore, the different metabasites with different compositions were metamorphosed from different basaltic rocks generated in a backarc basin in the early Paleozoic. Their occurrence in the same region indicates that a backarc basin was transformed to an oceanic subduction zone where eclogite-facies metamorphism occurred. (C) 2015 Elsevier B.V. All rights reserved. |
| WOS关键词 | ULTRAHIGH-PRESSURE METAMORPHISM ; OXYGEN-ISOTOPE FRACTIONATION ; SUBDUCTION-ZONE FLUIDS ; ABLATION-MC-ICPMS ; DABIE-SULU OROGEN ; HUWAN SHEAR ZONE ; P-T PATH ; TRACE-ELEMENT ; NW CHINA ; U-PB |
| WOS研究方向 | Geochemistry & Geophysics |
| 语种 | 英语 |
| WOS记录号 | WOS:000367525700003 |
| 资助机构 | Chinese Ministry of Science and Technology(2015CB856106) ; Chinese Ministry of Science and Technology(2015CB856106) ; Natural Science Foundation of China(41422301 ; Natural Science Foundation of China(41422301 ; Foundation for the Author of National Excellent Doctoral Dissertation of China(201229) ; Foundation for the Author of National Excellent Doctoral Dissertation of China(201229) ; Program for New Century Excellent Talents in University(NCET-11-0875) ; Program for New Century Excellent Talents in University(NCET-11-0875) ; 41372073 ; 41372073 ; 41173013) ; 41173013) ; Chinese Ministry of Science and Technology(2015CB856106) ; Chinese Ministry of Science and Technology(2015CB856106) ; Natural Science Foundation of China(41422301 ; Natural Science Foundation of China(41422301 ; Foundation for the Author of National Excellent Doctoral Dissertation of China(201229) ; Foundation for the Author of National Excellent Doctoral Dissertation of China(201229) ; Program for New Century Excellent Talents in University(NCET-11-0875) ; Program for New Century Excellent Talents in University(NCET-11-0875) ; 41372073 ; 41372073 ; 41173013) ; 41173013) |
| 源URL | [http://ir.iggcas.ac.cn/handle/132A11/62104]  |
| 专题 | 地质与地球物理研究所_岩石圈演化国家重点实验室 |
| 作者单位 | 1.Univ Sci & Technol China, Sch Earth & Space Sci, CAS Key Lab Crust Mantle Mat & Environm, Hefei 230026, Peoples R China 2.China Univ Geosci, Fac Earth Sci, State Key Lab Geol Proc & Mineral Resources, Wuhan 430074, Peoples R China 3.Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China 4.China Univ Geosci, State Key Lab Geol Proc & Mineral Resources, Beijing 100083, Peoples R China |
| 推荐引用方式 GB/T 7714 | Zhang, Long,Chen, Ren-Xu,Zheng, Yong-Fei,et al. Geochemical constraints on the protoliths of eclogites and blueschists from North Qilian, northern Tibet[J]. CHEMICAL GEOLOGY,2016,421:26-43. |
| APA | Zhang, Long,Chen, Ren-Xu,Zheng, Yong-Fei,Hu, Zhaochu,Yang, Yueheng,&Xu, Lijuan.(2016).Geochemical constraints on the protoliths of eclogites and blueschists from North Qilian, northern Tibet.CHEMICAL GEOLOGY,421,26-43. |
| MLA | Zhang, Long,et al."Geochemical constraints on the protoliths of eclogites and blueschists from North Qilian, northern Tibet".CHEMICAL GEOLOGY 421(2016):26-43. |
入库方式： OAI收割
来源：地质与地球物理研究所
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