We present an overview of the internal structure of the ophiolite massifs along the Yarlung Zangbo suture zone(YZSZ)in southern Tibet with a focus on the geochemical character and tectonic evolution of the Ocean Islan...We present an overview of the internal structure of the ophiolite massifs along the Yarlung Zangbo suture zone(YZSZ)in southern Tibet with a focus on the geochemical character and tectonic evolution of the Ocean Island Basalt(OIB)and mafic alkaline rock assemblages associated with these ophiolites.The Jurassic–early Cretaceous lavas,massive diabase and gabbroic rocks are either tectonically intercalated with the early Cretaceous,subduction-influenced ophiolitic units,or occur as thrust sheets or blocks with an early Cretaceous mélange and in a Jurassic-Cretaceous flysch unit structurally beneath these ophiolites.They display uniform chondrite-normalized REE patterns with light rare earth element(LREE)enrichment and heavy rare earth element(HREE)depletion,no obvious Eu anomalies or negative Nb,Ta and Ti anomalies,and primitive mantle normalized trace element patterns with significant large-ion lithophile element(LILE)enrichment,similar to those of modern OIB and the Hawaiian alkaline basalts.These mafic alkaline rock assemblages represent OIB-and Plume-type(P-type)oceanic crustal rocks(with no subduction influence)that formed from magmas produced by partial melting of plume–metasomatized asthenospheric mantle source during the early stages of the opening of a Neotethyan seaway between Proto-India and Eurasia.展开更多
基金supported by the National Nature Science Foundation of China(41303027)Special Fund for Basic Scientific Research of Central Colleges,Chang’an University(310827153506,310827153407)to G.-X.Yang.Y.Dilek’s research in Tibet and on the Yarlung-Zangbo suture zone ophiolites has been funded by the Chinese Academy of Geological Sciences(Beijing,China).
文摘We present an overview of the internal structure of the ophiolite massifs along the Yarlung Zangbo suture zone(YZSZ)in southern Tibet with a focus on the geochemical character and tectonic evolution of the Ocean Island Basalt(OIB)and mafic alkaline rock assemblages associated with these ophiolites.The Jurassic–early Cretaceous lavas,massive diabase and gabbroic rocks are either tectonically intercalated with the early Cretaceous,subduction-influenced ophiolitic units,or occur as thrust sheets or blocks with an early Cretaceous mélange and in a Jurassic-Cretaceous flysch unit structurally beneath these ophiolites.They display uniform chondrite-normalized REE patterns with light rare earth element(LREE)enrichment and heavy rare earth element(HREE)depletion,no obvious Eu anomalies or negative Nb,Ta and Ti anomalies,and primitive mantle normalized trace element patterns with significant large-ion lithophile element(LILE)enrichment,similar to those of modern OIB and the Hawaiian alkaline basalts.These mafic alkaline rock assemblages represent OIB-and Plume-type(P-type)oceanic crustal rocks(with no subduction influence)that formed from magmas produced by partial melting of plume–metasomatized asthenospheric mantle source during the early stages of the opening of a Neotethyan seaway between Proto-India and Eurasia.
