摘要
Abstract
The Central Asian Orogenic Belt(CAOB)is a continental orogenic belt with the most significant continental crustal accretion and modification since the Phanerozoic.The Xing'an-Mongolian Orogenic Belt,located in the eastern part of the CAOB,hosts abundant products of tectonic-magmatic activities,serving as a natural window for studying the evolution and transformation of the Paleo-Asian Ocean tectonic setting.The authors sampled granite porphyry from the Boketu area in the eastern segment of the Xing'an-Mongolian orogenic belt.LA-ICP-MS U-Pb dating results reveal emplacement ages of 206±4 Ma and 202±3 Ma for these rocks.Petrological and geochemical characteristics indicate that the late-Triassic granite porphyry is enriched in Si,K,and FeOT,with high FeOT/(FeOT+MgO)and(Na₂O+K2O)/Al2O₃ ratios,low Sr,and high Yb contents.These rocks exhibit peraluminous to strongly peraluminous features,depletion in Nb and Ta,low La/Yb,Zr/Hf,and Nb/Ta ratios,and a strong negative Eu anomaly,consistent with typical A-type granite characteristics.They are interpreted as products of partial melting of felsic crust under low-pressure conditions,with mantle-derived material metasomatism and contamination during their formation.The granite porphyry in the study area belongs to the A2-type granite,which indicates a post-orogenic setting.Tectonic discrimination diagrams further reveal that all samples fall within the intraplate tectonic field,suggesting that the study area was in an extensional setting during the transition from the late orogenic stage to a stable intraplate setting in the Late-Triassic.This result further indicates that the influence of the Paleo-Asian ocean tectonic setting was approaching cessation.关键词
兴蒙造山带/晚三叠世/花岗斑岩/构造域Key words
Xing'an-Mongolia orogenic belt/Late Triassic/Granite porphyry/Tectonic setting分类
天文与地球科学
