羌塘中部早志留世斜长岩岩石成因及其对古特提斯洋早期俯冲的制约OA

The subduction timing of the Longmu Co-Shuanghu-Lancang Ocean has not been well constrained due to the lack of critical evidence,restricting our understanding of the evolutionary history of the Paleo-Tethys Ocean.This study focuses on the anorthosites intruded into the early Paleozoic ophiolite in the Taoxinghu area of central Qiangtang,northern Tibet,and conducts zircon U-Pb dating,whole-rock geochemical analysis,and zircon Lu-Hf isotopic analysis.This study reveals that the anorthosites yield a zircon U-Pb age of(435±5)Ma,indicating that their formation age is the Early Silurian.Geochemical characteristics show that the anorthosites possess adakitic rock affinities,being enriched in light rare earth elements(LREEs)and large ion lithophile elements(LILEs),and displaying significant positive Eu anomalies.The anorthosites are rich in sodium and poor in potassium(Na2O/K2O＞2).Lu-Hf isotopic analysis exhibits a distinct mantle-derived signature,suggesting their derivation from the partial melting of subducted oceanic crust with contamination by mantle wedge material.This study suggests that the anorthosites formed in a tectonic setting associated with the subduction of the Paleo-Tethys Ocean during the Early Silurian,providing a new constraint on the timing of the early subduction of the Longmu Co-Shuanghu-Lancang Ocean.