The Spontang Ophiolite complex represents the most complete ophiolite sequence amongst the South Ladakh ophiolites and comprises mantle rocks (depleted harzburgites,dunites and minor lherzolites)as well as crustal rocks (basalt,isotropic gabbros,layered gabbros etc.).In the present study,detailed geo-chemistry (whole rock as well as mineral chemistry) and Sr-Nd isotopic analyses of thirty-six ultramafic-mafic samples have been attempted to constraint the evolution and petrogenetic history of the Tethyan oceanic crust.Major,trace-element and REE patterns of the peridotites and their minerals indicate that the lherzolites experienced lower degrees of partial melting resembling abyssal peridotites (at higher temperatures,TRE =～1216 ℃) than the harzburgites (6％-8％ versus 15％-17％).Elevated εNd(t) and vari-able 87Sr/86Sr(t) ratios along with REE patterns suggest that the Spontang mafic rocks display N-MORB affinity with negligible participation of oceanic sediments in their genesis are originated from a depleted upper mantle with little contribution from subduction-related fluids.MORB-type Neotethyan oceanic crust is associated with the earliest phase of subduction (of olderJurassic age) through which a younger intra-oceanic island arc (Spong arc) subsequently developed.Harzburgites REE display typical U-shaped patterns,suggesting that these rocks have been metasomatized by LREE-enriched fluids.On the other side,mafic rocks are characterized by heterogeneous (Nb/La)PM and (Hf/Sm)PM and relatively homoge-neous εNd(t),indicating interaction of subduction-related melts with the upper mantle during the initia-tion of subduction,in Early Cretaceous times.

Mallika K.Jonnalagadda;Mathieu Benoit;Shivani Harshe;Romain Tilhac;Raymond A.Duraiswami;Michel Grégoire;Nitin R.Karmalkar

Interdisciplinary School of Science,Savitribai Phule Pune University,Pune 411007,India;Department of Geology,Savitribai Phule Pune University,Pune 411007,India;Géosciences Environnement Toulouse,CNRS-CNES-IRD-Universiré Paul Sabatier,Observatoire Midi Pyrénées,31400 Toulouse,France;Instituto Andaluz de Ciencias de la Tierra (IACT),CSIC-Universidad de Granada,18100 Armilla,Granada,Spain;Vice-Chancellor's Office,Savitribai Phule Pune University,Pune 411007,India

地学前缘（英文版）

[1]Mallika K.Jonnalagadda;Mathieu Benoit;Shivani Harshe;Romain Tilhac;Raymond A.Duraiswami;Michel Grégoire;Nitin R.Karmalkar-.Geodynamic evolution of the Tethyan lithosphere as recorded in the Spontang Ophiolite,South Ladakh ophiolites (NW Himalaya,India))[J].地学前缘（英文版）,2022(01):326-349

Spontang,Ophiolite,Ladakh,harzburgites,lherzolites,Neotethyan,olderJurassic,Spong,Harzburgites

Geodynamic,evolution,Tethyan,lithosphere,recorded,South,ophiolites,NW,Himalaya,India,complex,represents,most,complete,sequence,amongst,comprises,mantle,rocks,depleted,dunites,minor,well,crustal,basalt,isotropic,gabbros,layered,etc,study,detailed,geo,chemistry,whole,Nd,isotopic,analyses,thirty,six,ultramafic,samples,have,been,attempted,constraint,petrogenetic,history,oceanic,Major,trace,element,patterns,peridotites,their,minerals,indicate,that,experienced,lower,degrees,partial,melting,resembling,abyssal,higher,temperatures,TRE,than,versus,Elevated,vari,able,87Sr,86Sr,ratios,along,display,MORB,affinity,negligible,participation,sediments,genesis,are,originated,from,upper,little,contribution,subduction,related,fluids,type,associated,earliest,phase,age,through,which,younger,intra,island,arc,subsequently,developed,typical,shaped,suggesting,these,metasomatized,LREE,enriched,On,other,side,characterized,heterogeneous,Nb,PM,Hf,Sm,relatively,homoge,indicating,interaction,melts,during,initia,Early,Cretaceous,times

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