岩石矿物学杂志2026，Vol.45Issue(1)：1-18,18.DOI:10.20086/j.cnki.yskw.2026.5041
藏东同卡微陆块泥质高压麻粒岩的变质作用及地质意义
Metamorphism and geological significance of pelitic high-pressure granulites in the Tongka microcontinent block,eastern Xizang
摘要
Abstract
The Tongka microcontinent block,situated in the eastern segment of the Bangong-Nujiang suture zone in the central Tibetan Plateau,preserves key evidence of the Early Jurassic tectonic evolution of the Tethyan Ocean through its metamorphic and magmatic records.Pelitic high-pressure granulites occur as interlayers within dominant felsic gneisses and are accompanied by leucosomes of varying scales.These granulites are primarily composed of garnet,kyanite,biotite,K-feldspar,quartz,with minor accounts of plagioclase,muscovite,sillimanite,and ru-tile.Integrated analyses—petrography,mineral chemistry,geochronology,and phase equilibrium modeling—reveal a clockwise metamorphic p-T-t path that can be divided into three distinct stages:① Near-isobaric heating prograde metamorphic stage:this stage is characterized by prograde conditions of 0.70～0.88 GPa and 655～680℃,constrained by the compositions of garnet cores and associated biotite inclusions;② Peak metamorphic stage:the peak mineral assemblage—garnet+kyanite+biotite+K-feldspar+quartz+rutile+melt±plagioclase—formed under condi-tions of 0.98～1.06 GPa and 770～790℃,as indicated by phase stability fields and the compositions of garnet mantles and matrix biotite.Zircon U-Pb dating yields a metamorphic age of 175 Ma,representing the timing of high-pressure granulite-facies metamorphism;③ Cooling and decompression retrograde stage:The retrograde as-semblage of biotite+plagioclase+sillimanite+muscovite reflects post-peak conditions of 0.32～0.68 GPa and 600～725℃.This clockwise p-T-t path reflects crustal thickening associated with the collision between the Tongka mi-crocontinent block and the Qiangtang terrane.The near-isobaric heating stage likely records prolonged thermal input from upwelling asthenosphere into the thickened lower crust of the microcontinent.关键词
高压麻粒岩/微陆块/同卡/班公湖-怒江缝合带Key words
high-pressure granulite/microcontinent block/Tongka/Bangong-Nujiang suture zone分类
天文与地球科学引用本文复制引用
田作林,张泽明,陈言飞,董昕..藏东同卡微陆块泥质高压麻粒岩的变质作用及地质意义[J].岩石矿物学杂志,2026,45(1):1-18,18.基金项目
中国地质调查局地质调查项目(DD20240100702,DD20221630) （DD20240100702,DD20221630）
国家自然科学基金项目(U2244203,41872069) （U2244203,41872069）
中国地质科学院基本科研业务费(JKYQN202315) China Geological Survey Project(DD20240100702,DD20221630) （JKYQN202315）
National Natural Science Foundation of China(U2244203,41872069) （U2244203,41872069）
Basic Scientific Research Operating Fund of the Chinese Academy of Geological Sciences(JKYQN202315) （JKYQN202315）
