Geochemistry of eclogites of the Tso Morari complex, Ladakh, NW Himalayas:Insights into trace element behavior during subduction and exhumation

作     者：Mallika K.Jonnalagadda Nitin R.Karmalkar Raymond A.Duraiswami 

作者机构：Department of Geology Savitribai Phule Pune University 

出 版 物：《Geoscience Frontiers》 (地学前缘（英文版）)

年 卷 期：2019年第10卷第3期

页      面：811-826页

核心收录：

学科分类：07[理学] 0708[理学-地球物理学] 0704[理学-天文学] 

基　　金：financial support received from CSIR, New Delhi by means of SRF (9/137/(0499)/2011-EMR-I) BCUD, Savitribai Phule Pune University, Pune for financial support received through BCUD research project grants 

主　　题：Trace elements UHP metamorphism Protolith Eclogites Tso Morari Ladakh 

摘      要：Whole rock major and trace element compositions of seven eclogites from the Tso Morari ultra-high pressure(UHP) complex, Ladakh were determined with the aim of constraining the protolith origins of the subducted crust. The eclogites have major element compositions corresponding to sub-alkaline basalts. Trace element characteristics of the samples show enrichment in LILE s over HFSEs(Rb, Th, K except Ba) with LREE enrichments((La/Lu)n = 1.28-5.96). Absence of Eu anomaly on the Primitive Mantle normalized diagram suggests the absence of plagioclase fractionation. Positive correlation between Mg# with Ni and Cr suggests olivine fractionation of mantle melts. Narrow range of(La/Yb)n(2.1-9.4) and Ce/Yb(6.2-16.2) along with Ti/Y(435-735) ratios calculated for the Tso Morari samples is consistent with generation of melts by partial melting of a garnet free mantle source within the spinel peridotite field. Ternary diagrams(viz. Ti-Zr-Y and Nb-Zr-Y) using immobile and incompatible elements show that the samples range from depleted to enriched and span from within plate basalts(WPB)to enriched MORB(E-MORB) indicating that the eclogite protoliths originated from basaltic *** Mantle normalized multi element plots showing significant Th and LREE enrichment marked by negative Nb anomalies are characteristic of continental flood basalts. Positive Pb, negative Nb, high Th/Ta, a narrow range of Nb/La and the observed wide variation for Ti/Y indicate that the Tso Morari samples have undergone some level of crustal contamination. Observed geochemical characteristics of the Tso Morari samples indicate tholeiitic compositions originated from enriched MORB(E-MORB) type magmas which underwent a limited magmatic evolution through the process of fractional crystallization and probably more by crustal contamination. Observed geochemical similarities(viz. Zr, Nb, La/Yb, La/Gd,La/Nb, Th/Ta ratios and REE) between Tso Morari eclogites and the Group I Panjal Traps make the trap basa