Rare peak and ubiquitous post-peak zircon in eclogite: Constraints for the timing of UHP and HP metamorphism in Erzgebirge, Germany

doi:10.1016/j.lithos.2018.10.017

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

	Rare peak and ubiquitous post-peak zircon in eclogite: Constraints for the timing of UHP and HP metamorphism in Erzgebirge, Germany
	Schmaedicke, Esther 1; Will, Thomas M.2; Ling, Xiaoxiao 3; Li, Xian-Hua 3; Li, Qiu-Li 3
刊名	LITHOS
	2018-12-01
卷号	322 页码:250-267
关键词	Eclogite Erzgebirge Exhumation Symplectite UHP metamorphism U-Pb dating
ISSN号	0024-4937
DOI	10.1016/j.lithos.2018.10.017
英文摘要	Erzgebirge eclogite occurs in three high-pressure (HP) units, including one UHP unit (Unit 1). Each sample investigated contains either magmatic or metamorphic zircon but never both. This is in contrast to many literature examples of eclogite with more than one generation of zircon. We infer that metamorphic zircon formed at the expense of a magmatic precursor, and that the process either went to completion (consuming all magmatic zircon) or did not occur at all. Metamorphic zircon is only present in UHP eclogite and one HP eclogite from Unit 2. Another sample from Unit 2 and one from Unit 3, which experienced the lowest metamorphic PT conditions of all samples, contain only magmatic zircon. The U-Pb SIMS age of c. 540 Ma of igneous zircon, being somewhat younger than average Hf model ages (i.e., 567 and 591 Ma), is attributed to crystallization in the basaltic or gabbroic precursor that formed from a juvenile mantle source. The time of peak metamorphism is recorded by only two zircons from UHP eclogite giving ages of 360.5 +/- 5.4 Ma and 359.7 +/- 5.3 Ma that well agree with a previous three-point Sm-Nd isochron of 360 +/- 7 Ma. All other grains gave younger ages, mainly between 340 and 330 Ma but covering a range of c. 350-315 Ma, which is attributed to retrogression at amphibolite-facies conditions. We infer (i) that this post-eclogitic zircon replaced peak-metamorphic grains (only in UHP eclogite) as well as magmatic zircon and (ii) that peak-metamorphic zircon did not form in non-UHP eclogite. Growth of peak and post-peak zircon was governed by fluid and/or melt. The latter is related to decompressional melting in felsic host rocks (and possibly also to late-orogenic granitic magmatism). Fluid is either of external origin (melt-derived or from dehydration reactions in subducting foot-wall units) or due to decompressional release of internal fluid (molecular water from fluid inclusions or structural water in omphacite and garnet). The new and former age data can best be reconciled with a two-stage exhumation process. Initial, buoyancy-driven exhumation was fast and terminated as the HP/UHP slices reached lower crustal levels where the rocks presumably rested for 10-20 million years, followed by slow exhumation associated with gravitational collapse of the Variscan orogen. The majority of metamorphic zircon (with ages of 340-330 Ma) grew at lower crustal levels, where the rocks presumably rested for 10-20 million years, and other grains (younger than 330 Ma) during the final, slow exhumation that partly overlapped with the time of granitic magmatism. (C) 2018 Elsevier B.V. All rights reserved.
资助项目	National Natural Science Foundation of China[41303042] ; Chinese National Key Research and Development Plan, China Ministry of Science and Technology[2016YFE0203000] ; Chinese Academy of Sciences
WOS关键词	HIGH-PRESSURE METAMORPHISM ; BEARING ULTRAMAFIC ROCKS ; U-PB ; FACIES ROCKS ; SAXONIAN ERZGEBIRGE ; WORKING REFERENCE ; CORE COMPLEX ; DEEP FLUIDS ; SM-ND ; HF
WOS研究方向	Geochemistry & Geophysics ; Mineralogy
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000452817700016
资助机构	National Natural Science Foundation of China ; National Natural Science Foundation of China ; Chinese National Key Research and Development Plan, China Ministry of Science and Technology ; Chinese National Key Research and Development Plan, China Ministry of Science and Technology ; Chinese Academy of Sciences ; Chinese Academy of Sciences ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Chinese National Key Research and Development Plan, China Ministry of Science and Technology ; Chinese National Key Research and Development Plan, China Ministry of Science and Technology ; Chinese Academy of Sciences ; Chinese Academy of Sciences ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Chinese National Key Research and Development Plan, China Ministry of Science and Technology ; Chinese National Key Research and Development Plan, China Ministry of Science and Technology ; Chinese Academy of Sciences ; Chinese Academy of Sciences ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Chinese National Key Research and Development Plan, China Ministry of Science and Technology ; Chinese National Key Research and Development Plan, China Ministry of Science and Technology ; Chinese Academy of Sciences ; Chinese Academy of Sciences
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/90283]
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	Schmaedicke, Esther
作者单位	1.Univ Erlangen Nurnberg, Geozentrum Nordbayem, Schlossgarten 5a, D-91054 Erlangen, Germany 2.Univ Wurzburg, Inst Geog & Geol, D-97074 Wurzburg, Germany 3.Chinese Acad Sci, State Key Lab Lithospher Evolut, Inst Geol & Geophys, Beijing 100029, Peoples R China
推荐引用方式 GB/T 7714	Schmaedicke, Esther,Will, Thomas M.,Ling, Xiaoxiao,et al. Rare peak and ubiquitous post-peak zircon in eclogite: Constraints for the timing of UHP and HP metamorphism in Erzgebirge, Germany[J]. LITHOS,2018,322:250-267.
APA	Schmaedicke, Esther,Will, Thomas M.,Ling, Xiaoxiao,Li, Xian-Hua,&Li, Qiu-Li.(2018).Rare peak and ubiquitous post-peak zircon in eclogite: Constraints for the timing of UHP and HP metamorphism in Erzgebirge, Germany.LITHOS,322,250-267.
MLA	Schmaedicke, Esther,et al."Rare peak and ubiquitous post-peak zircon in eclogite: Constraints for the timing of UHP and HP metamorphism in Erzgebirge, Germany".LITHOS 322(2018):250-267.