Geochemistry and trace element behaviors of eclogite during its   exhumation in the Xitieshan terrane, North Qaidam UHP belt, NW China

doi:10.1016/j.jseaes.2012.09.021

CORC > 北京大学 > 地球与空间科学学院

	Geochemistry and trace element behaviors of eclogite during its exhumation in the Xitieshan terrane, North Qaidam UHP belt, NW China
	Zhang, Cong ; Zhang, Lifei ; Bader, Thomas ; Song, Shuguang ; Lou, Yuxing
刊名	journal of asian earth sciences
	2013
关键词	Eclogite protolith Sm-Nd, Rb-Sr isotopic analyses Retrograde metamorphic fluid North Qaidam UHP belt ULTRAHIGH-PRESSURE METAMORPHISM ZIRCON U-PB NOMINALLY ANHYDROUS MINERALS COESITE-BEARING ECLOGITES FLUID-ROCK INTERACTIONS WESTERN GNEISS REGION SUBDUCTION ZONES SM-ND CONTINENTAL COLLISION GARNET-PERIDOTITE
DOI	10.1016/j.jseaes.2012.09.021
英文摘要	The Xitieshan terrane, located in the central part of the North Qaidam ultrahigh pressure (UHP) metamorphic belt, China, is mainly composed of orthogneiss and paragneiss and a few intercalated eclogite layers and boudins. Based on their bulk-rock TiO2-contents, the eclogites can be subdivided into a high-Ti group (TiO2 > 2%) and a low-Ti group (TiO2 < 2%). Whole-rock major and trace element analyses revealed that the protoliths of the low-Ti eclogites are normal-type mid-ocean ridge basalts (N-MORB), whereas those of the high-Ti eclogites are either enriched-type mid-ocean ridge basalts (E-MORB) or near ridge sea-mount basalts, respectively. The Sr-Nd isotopes of eclogites of both groups are similar to those of MORB. Those of the low-Ti eclogites are characterized by positive epsilon(Nd)(T) and restricted I-sr values and therefore provide further evidence for the formation of the protoliths of the eclogites in an oceanic environment. On the other hand, the Sr-Nd isotopes of high-Ti eclogites show mainly positive but also some negative epsilon(Nd)(T) values and relatively broadly distributed I-sr values, indicating minor crustal contamination of the ocean floor basalts. Considering available 750-877 Ma protolith ages preserved in zircon cores, it is inferred that some of the eclogites derived from Neoproterozoic protoliths were emplaced onto the crust far ahead of the Paleozoic deep subduction, while the other eclogites originate from a different oceanic crust, e.g., the Paleo-Qilian ocean, indicating multiple orogenies in the geological history of the Xitieshan terrane, China. Whole-rock and in-situ LA-ICP-MS mineral trace element analyses of eclogites revealed two stages of fluid behavior during retrogression that correspond to the two exhumation stages uncovered by phase equilibrium calculations. The mineral scale trace element distributions and trace element inheritance of newly formed amphibole from its precursors indicate that, at the peak metamorphic stage (M1) and at the earlier (eclogite facies) overprint (M2), the fluid was internally controlled by the rock itself. Within a mafic lens, the amount of water-soluble elements (e.g., Rb, Sr, Ba, U, Pb and LREE), observed in the whole-rock compositions as well as in amphiboles, increases from the core (phengite-bearing eclogite) to the rim (amphibolite) and implies an external fluid source for the amphibolite facies retrogression (M3) which should be helpful for the final exhumation of UHP eclogite. (C) 2012 Elsevier Ltd. All rights reserved.; http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000316155400006&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701 ; Geosciences, Multidisciplinary; SCI(E); 15; ARTICLE; ,SI; 81-97; 63
语种	英语
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/155654]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	Zhang, Cong,Zhang, Lifei,Bader, Thomas,et al. Geochemistry and trace element behaviors of eclogite during its exhumation in the Xitieshan terrane, North Qaidam UHP belt, NW China[J]. journal of asian earth sciences,2013.
APA	Zhang, Cong,Zhang, Lifei,Bader, Thomas,Song, Shuguang,&Lou, Yuxing.(2013).Geochemistry and trace element behaviors of eclogite during its exhumation in the Xitieshan terrane, North Qaidam UHP belt, NW China.journal of asian earth sciences.
MLA	Zhang, Cong,et al."Geochemistry and trace element behaviors of eclogite during its exhumation in the Xitieshan terrane, North Qaidam UHP belt, NW China".journal of asian earth sciences (2013).