Petrogenesis Of The Late Triassic Granite In Western Tanggula Magmatic Belt, Tibet, China

Granite samples from the western Tanggula Mamatic Belt were selected fordetailed studies, containing petrological, mineralogical, geocheimical, zircon U-Pbgeochronological and Hf isotopes studies, to analysis and discuss its scientificsignificance, pertogenesis, features of magma source and tectonic evolution,providing new data constrains on the Longmuco-Shuanghu Paleo-Tyths evolution.The granite contained different type’s intrusives, including granodiorite,monzonite granite and biotite-granite, et al., with marginal-center phase sequentialtransition. All granites belonged to calc-alkalic rock series and strongly peraluminousS-type granitoids. All samples showed typical features of LREE enriched, but HREEdeficit. LILE and HFSE appeared difference that strongly deficited in K, Ti, lightlydeficited in Nb, Ba, Ce and Sr, and enriched in Ta, Pb, which indicting the granite hadbeen suffered a modeate to strong degree of differentiation.By LA-ICPMS U-Pbgeochronological, Zircons from representative samples acquired Trassic ages(oscillatory zones,222.1-231.0Ma), and Meso-Neoproterozoic ages (inheritable core).Hf isotope results could be divided into two groups. Position located inoscillatory zones showed negative Hf isotopic initial ratio and two staged model agesin Proterozoic, all having a smaller variation, which indicted that the protolith of thegranite were formed in Proterozoic and had a homogeneous in Hf isotopiccomposition. Spots located in inheritable core had an unstable feature in Hf isotopicinitial ratio and two staged model ages (all older than Mesoproterozoic), implied acomplicated rock source and basement formation in study area.Geochemical of the Ximari granite indicated that it was strongly peraluminousS-type syncollisional granitoids and typically crust genesis, as the magmatic responseto the Paleo-Tyths’s collision orogenic. Magma source was probably formed under800℃-900℃(T),＜8kbar(P), rich in fluid and partially melt granitic magmadominated by grewacke, what rising and emplacement were controlled by tectonic.