地质通报2025，Vol.44Issue(2)：424-440,17.DOI:10.12097/gbc.2024.01.015
南天山造山带东段变流纹岩原岩的喷发时代与构造背景:来自锆石U-Pb年龄和微量元素的约束
The eruptive age and tectonic setting of the protolith of the meta-rhyolite in the eastern segment of the South Tianshan Orogenic Belt:Constraints from zircon U-Pb age and trace elements
摘要
Abstract
[Objective]The composition and age of metamorphic rocks provide a crucial window into understanding the nature,formation,and evolution of orogenic belt basements.Based on an analysis of zircon age and trace elements from the Xingeer Formation in the eastern part of the South Tianshan Orogenic Belt,this paper explores the age of meta-rhyolite and its significance for the tectonic evolution of the Southern Tianshan orogenic belt.[Methods]The lithology,LA-ICP-MS zircon U-Pb dating,and zircon trace element analysis of the meta-rhyolite in the Xingeer Formation,located in the eastern part of the South Tianshan Orogenic Belt,have been systematically conducted.The data have been comprehensively analyzed in conjunction with regional research findings.[Results]LA-ICP-MS zircon U-Pb dating results indicate that the protolith was formed in the Early Devonian(418～412 Ma).The zircon exhibits a relative depletion in light rare earth elements(LREE)and enrichment in heavy rare earth elements(HREE),characterized by a negative Eu anomaly and a positive Ce anomaly.Trace element analysis reveals positive anomalies of U and Hf,along with negative anomalies of Nb,La,Pr,and Ti.Based on zircon trace element analysis,it is inferred that the crustal thickness at the time of rhyolite eruption was less than 35 km,with evidence of plagioclase fractionation and crystallization in the magmatic source region.The zircon Ti thermometer indicates a high magmatic crystallization temperature(>800℃),suggesting a high-temperature magmatic origin.This implies that the rhyolite's development may be associated with continental rifting.[Conclusions]Based on previous studies,it is inferred that the South Tianshan Orogenic Belt may have been part of the Tarim Craton during the Early Paleozoic,with its northern margin representing an active continental margin.Influenced by subduction and retreat along the northern margin,the South Tianshan region experienced significant back-arc extension during the Late Silurian to Early Devonian.The meta-rhyolite identified in this study is likely to have formed within the tectonic setting of Early Devonian back-arc extensional rifting.关键词
南天山造山带/变流纹岩/锆石U-Pb年龄/泥盆纪/高温岩浆作用/弧后伸展Key words
South Tianshan Orogenic Belt/meta-rhyolite/zircon U-Pb age/Devonian/high temperature magmatism/back-arc extension分类
地质学引用本文复制引用
黄少英,陈守文,袁文芳,罗彩明,段云江,亢茜,章凤奇..南天山造山带东段变流纹岩原岩的喷发时代与构造背景:来自锆石U-Pb年龄和微量元素的约束[J].地质通报,2025,44(2):424-440,17.基金项目
国家自然科学基金面上项目《塔里木板块西南部青白口纪晚期盆地属性与转换过程及其对超大陆聚合的制约》(批准号:42372244) （批准号:42372244）
