拉萨地块北部孔马地区早白垩世花岗闪长岩地球化学、锆石U-Pb年代学及其构造意义OA

Cretaceous magmatic rocks are widely distributed in the northern the Lhasa Terrane,and the recorded magmatic-metamorphic events are of great significance for studying the petrogenesis and tectonic setting of Creta-ceous magmatic rocks in the Lhasa Terrane.This paper reports the petrology,geochemical results and zircon U-Pb age of the Early Cretaceous granodiorite exposed in the Kongma area located in the northern Lhasa Terrane.The re-sults show that the LA-ICP-MS zircon U-Pb age of granodiorite in the study area is 113.2±1.3 Ma,which belong to the late Early Cretaceous magmatism.These rocks are belong to the high potassium calc-alkaline series,with alu-minum saturation index(A/CNK=1.05～1.12)and medium negative Eu anomaly,relatively enriched large ion lithophile elements Rb,Th,U,K,and deficient high field strength elements Ti,P,Ta,which is a peraluminous S-type granite.Geochemical characteristics of the rocks shows that they were originated from the partial melting of the ancient crust with the mixing of mantle materials.Combined with the regional data,it is believed that the gran-odiorite in the Kongma area was formed in the tectonic environment of the southward subduction collision of the Bangonghu-Nujiang oceanic crust in the late Early Cretaceous,which may be related to the asthenosphere material upsurge caused by the slab break-off under gravity drag.