Evolution of fluids and melts in deeply subducted continental crust: Insights from an UHP eclogite-vein system in the Dabie terrane, China
文献类型：期刊论文
| 作者 | Tang, Pan1,2; Guo, Shun2,3; Yang, Yueheng2; Chen, Yi2,3; Su, Bin2 |
| 刊名 | LITHOS
 |
| 出版日期 | 2021-10-01 |
| 卷号 | 398页码:24 |
| 关键词 | Metamorphic dehydration Partial melting Eclogite Vein Element transfer Subduction zone |
| ISSN号 | 0024-4937 |
| DOI | 10.1016/j.lithos.2021.106325 |
| 英文摘要 | Both slab-derived high-pressure (HP) or ultrahigh-pressure (UHP) aqueous fluids and hydrous melts are important agents for material cycling in subduction zones. Although numerous studies have investigated the genesis of both fluid phases, the temporal-spatial relationship and the chemical difference between aqueous fluids and hydrous melts during subduction-zone metamorphism remain mysterious. In this study, we present detailed petrological and geochemical studies on the UHP eclogites and enclosed epidote-quartz veins in the Dabie terrane (eastern China) to understand the compositions and behaviors of fluids/melts in subduction zones. The eclogites consist mainly of garnet, omphacite, and hydrous minerals (epidote, phengite, and paragonite). Two stages of epidote, including epidote inclusions in omphacite (Ep-in) and porphyroblastic epidote (Ep-p), are recognized in the eclogites. The obviously higher contents of strontium (Sr) and light rare earth elements (LREEs) in Ep-p than in Ep-in demonstrate the previous coexistence of lawsonite and Ep-in. The combination of petrographic analyses, epidote Sr isotopes, and phase equilibria modeling indicates lawsonite in the eclogite breakdown at -2.2-2.7 GPa and 620-750 degrees C during the initial exhumation, accompanied by the significant release of H2O-rich fluids. This process led to the growth of Ep-p in eclogite and the precipitation of vein omphacite, quartz, and epidote (Ep-v1). On the other hand, many lines of evidence for partial melting in the eclogites are found, including (1) multiphase solid inclusions (MSIs) of Ky + Kfs +/- other phases, which represent the in situ products of phengite partial melting; (2) MSIs of Kfs +/- Pl +/- Qz, which represent the crystallized products of hydrous melts; and (3) veinlets of Kfs +/- Di that crosscut the omphacite. Importantly, the MSIs in texture (1) are exclusively hosted in the Ep-p, which formed by lawsonite breakdown. This distinctive phenomenon indicates that the partial melting of phengite was most likely triggered by the injection of H2O from the lawsonite breakdown (i.e., water-fluxed melting). Phase equilibria modeling suggests that the partial melting of phengite occurred at -1.5-2.0 GPa and 700-750 degrees C during the further exhumation stage of the eclogites. The occurrence of Ep (Epv2) + Pl + Kfs in the veins indicates that melts derived from the eclogites infiltrated the vein system. The compositions of the fluids and melts are quantitatively constrained using the epidote compositions (Ep-v1 and Ep-v2, respectively) and epidote-fluid/melt partition coefficients. The results indicate that the fluids have trace element patterns similar to those of the melts with high contents of large ion lithophile elements (LILEs), Th, U, Pb, and LREEs. Thus, aqueous fluids have the ability to transfer significant amounts of mobile elements from the slab like the hydrous melts, if the appropriate P-T conditions and chemical characteristics of wallrocks can be satisified. Our study reveals multistage metamorphic-fluid/melt evolution in the UHP eclogites, involving metamorphic dehydration and subsequent partial melting during the exhumation of subducted continental crust. We provide petrological evidence linking fluid liberation to the occurrence of partial melting in eclogites. Moreover, this study indicates that the development of vein systems in HP-UHP rocks may provide high-permeability channels that allow the flow and escape of melts formed during later-stage process. We propose that the occurrence of early-stage dehydration events in deeply subducted slabs facilitates the generation of hydrous melts and their transport in subduction zones. |
| WOS关键词 | ULTRAHIGH-PRESSURE ECLOGITE ; MULTIPHASE SOLID INCLUSIONS ; METAMORPHIC ROCKS ; ELEMENT MOBILIZATION ; MINERAL INCLUSIONS ; TRACE-ELEMENTS ; COUNTRY ROCKS ; MASS-TRANSFER ; EXHUMATION ; DEHYDRATION |
| 资助项目 | National Science Foun-dation of China[41922013] ; National Science Foun-dation of China[41672059] ; National key R&D Program of China[2018YFA0702700] ; Youth Innovation Promotion Association CAS[2017090] |
| WOS研究方向 | Geochemistry & Geophysics ; Mineralogy |
| 语种 | 英语 |
| WOS记录号 | WOS:000683549000005 |
| 出版者 | ELSEVIER |
| 资助机构 | National Science Foun-dation of China ; National Science Foun-dation of China ; National Science Foun-dation of China ; National Science Foun-dation of China ; National key R&D Program of China ; National key R&D Program of China ; National key R&D Program of China ; National key R&D Program of China ; Youth Innovation Promotion Association CAS ; Youth Innovation Promotion Association CAS ; Youth Innovation Promotion Association CAS ; Youth Innovation Promotion Association CAS ; National Science Foun-dation of China ; National Science Foun-dation of China ; National Science Foun-dation of China ; National Science Foun-dation of China ; National key R&D Program of China ; National key R&D Program of China ; National key R&D Program of China ; National key R&D Program of China ; Youth Innovation Promotion Association CAS ; Youth Innovation Promotion Association CAS ; Youth Innovation Promotion Association CAS ; Youth Innovation Promotion Association CAS ; National Science Foun-dation of China ; National Science Foun-dation of China ; National Science Foun-dation of China ; National Science Foun-dation of China ; National key R&D Program of China ; National key R&D Program of China ; National key R&D Program of China ; National key R&D Program of China ; Youth Innovation Promotion Association CAS ; Youth Innovation Promotion Association CAS ; Youth Innovation Promotion Association CAS ; Youth Innovation Promotion Association CAS ; National Science Foun-dation of China ; National Science Foun-dation of China ; National Science Foun-dation of China ; National Science Foun-dation of China ; National key R&D Program of China ; National key R&D Program of China ; National key R&D Program of China ; National key R&D Program of China ; Youth Innovation Promotion Association CAS ; Youth Innovation Promotion Association CAS ; Youth Innovation Promotion Association CAS ; Youth Innovation Promotion Association CAS |
| 源URL | [http://ir.iggcas.ac.cn/handle/132A11/101900]  |
| 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 | Guo, Shun |
| 作者单位 | 1.Univ Chinese Acad Sci, Beijing 100049, Peoples R China 2.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, POB 9825, Beijing 100029, Peoples R China 3.CAS Ctr Excellence Tibetan Plateau Earth Sci, Beijing 100101, Peoples R China |
| 推荐引用方式 GB/T 7714 | Tang, Pan,Guo, Shun,Yang, Yueheng,et al. Evolution of fluids and melts in deeply subducted continental crust: Insights from an UHP eclogite-vein system in the Dabie terrane, China[J]. LITHOS,2021,398:24. |
| APA | Tang, Pan,Guo, Shun,Yang, Yueheng,Chen, Yi,&Su, Bin.(2021).Evolution of fluids and melts in deeply subducted continental crust: Insights from an UHP eclogite-vein system in the Dabie terrane, China.LITHOS,398,24. |
| MLA | Tang, Pan,et al."Evolution of fluids and melts in deeply subducted continental crust: Insights from an UHP eclogite-vein system in the Dabie terrane, China".LITHOS 398(2021):24. |
入库方式： OAI收割
来源：地质与地球物理研究所
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