地质力学学报2025，Vol.31Issue(4)：557-575,19.DOI:10.12090/j.issn.1006-6616.2025053
藏东金沙江缝合带"三岩地区"榴辉岩的年代学、岩石地球化学特征及构造意义
Chronological,geochemical characteristics and tectonic evolution significance of the Sanyan eclogites in the Jinsha River suture zone,eastern Xizang
摘要
Abstract
[Objective]As a key component of the eastern Tethys tectonic domain,the Jinsha River-Ailao Mountain suture zone is widely recognized as a Paleo-Tethys orogenic belt.However,due to the lack of metamorphic studies on high-pressure/ultra-high-pressure rocks,the subduction-to-closure process of the oceanic crust and the subsequent collisional orogenic evolution remain poorly constrained.[Methods]Systematic field surveys,petrographic observations,zircon U-Pb dating,and whole-rock major and trace element analyses were carried out on the newly discovered eclogites in the Sanyan area of the Jinsha River suture zone in eastern Xizang(Tibet).Based on the degree of retrogressive metamorphism,major mineral assemblages,and textural features,the Sanyan eclogites are classified into four types:garnet-albite-actinolite schist,garnet-actinolite,garnet-amphibolite,and eclogite.[Results]Zircon U-Pb dating of two eclogite samples yields 206Pb/238U ages of 247±2 Ma and 246±1 Ma,respectively.These zircons feature low Th/U ratios,extremely low content of Nb,Ta,and HREE,and no obvious negative Eu anomalies.Therefore,the genesis of the zircons should be eclogite-facies metamorphism,with the～246 Ma age representing the timing of eclogite-facies metamorphism.[Conclusion]The whole-rock major element analysis of 12 samples shows that the protoliths are picritic basalt-basalt,and the trace element characteristics reveal diverse tectonic settings of the protoliths,including ocean island basalt(OIB),normal mid-ocean ridge basalt(N-MORB),and enriched mid-ocean ridge basalt(E-MORB),suggesting that the Sanyan eclogites were mainly formed by subduction of Paleo-Tethys oceanic crust materials(ocean islands and mid-ocean ridge basalts).[Significance]Combining the previously obtained zircon U-Pb ages of eclogites and the Ar-Ar plateau ages of phengites,the complete closure of the Jinsha River Paleo-Tethys Ocean in the early Middle Triassic(T21)is further constrained.关键词
金沙江缝合带/榴辉岩/俯冲作用/古特提斯/青藏高原/地球化学Key words
Jinsha River suture zone/eclogite/subduction/Paleo-Tethys/Qinghai-Tibet Plateau/geochemistry分类
天文与地球科学引用本文复制引用
唐渊,李益多,王冬兵,韩明明,李鑫,罗亮..藏东金沙江缝合带"三岩地区"榴辉岩的年代学、岩石地球化学特征及构造意义[J].地质力学学报,2025,31(4):557-575,19.基金项目
中国地质调查局地质调查项目(DD20240026,DD20190053) （DD20240026,DD20190053）
国家自然科学基金项目(42230311) This research is financially supported by the Geological Survey Projects of the China Geological Survey(Grant Nos.DD20240026 and DD20190053)and the National Natural Science Foundation of China(Grant No.42230311). （42230311）
