Petrogenesis of tholeiite associations in the Kudi ophiolite(western Kunlun Mountains,northwestern China):implication for evolution of back-arc basins
会议名称：《中国科学院地质与地球物理研究所2002学术年会》
会议日期：2002年
学科分类：0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学]
关 键 词：tholeiite associations Kudi ophiolite back-arc basin western Kunlun
摘 要：The Kudi ophiolite in the western Kunlun Mountains comprises harzburgites,dunites, cumulate dunites,cumulate pyroxenites and gabbros,diabase dikes,and pillow and massive lavas, and are fragments of a supra-subduction zone(SSZ) ophiolite of early *** extrusive rocks can be classified into three groups of tholeiites,i.e.,back-arc basin(BAB) tholeiites,low-Ti island arc tholeiites(IAT) and LREE-enriched IAT,as shown by their distinctive geochemical *** SSZ-type mantle peridotites,cumulate complex with arc tholeiite affinity,and BABB-type diabase dikes and basalts constitute an upper mantle and crustal section of a back-arc basin formed by coupling of MORB-type mantle upwelling with fluid efflux from slab *** low-Ti IAT are characterized by low Ti and HFSE,and slightly U-shaped or LREE-depleted chondrite-normalized REE patterns,and represent melts derived from a depleted mantle source region(extraction of BABB magma) modified compositionally by fluids and/or melts from the subducting lithospheric slab during propagation and extension of the back-arc *** interpret the LREE-enriched IAT as products of closure of the back-arc basin,since an interaction between the parental magma of this IAT and the mantle peridotites(formerly the upper mantle of the basin) in a newly formed mantle wedge had occurred.