摘要
榴辉岩研究对深入认识超高压变质带构造演化过程具重要意义。绿梁山地区榴辉岩以透镜体形式出露于花岗片麻岩中,岩相学和温压计算结果显示,绿梁山榴辉岩经历了一个顺时针的P-T演化轨迹:①峰期榴辉岩相阶段。以石榴子石+绿辉石+金红石为特征,温压条件为P>25.5 kPa、T>840℃;②高压麻粒岩相阶段。以绿辉石退变为透辉石和斜长石为特征,形成的温压条件P=17.1~18.7 kPa、T=814℃~896℃;③角闪岩相阶段。以透辉石退变为角闪石和斜长石、金红石退变为钛铁矿为特征,形成的P-T条件为P=4.5~6.5 kPa、T=581℃~665℃。结合前人研究成果,提出一个多阶段构造演化模型:绿梁山榴辉岩的原岩在新元古代时期位于大陆地壳中,由于大洋地壳俯冲牵引作用,伴随大陆地壳一起被拖拽至俯冲通道内,于深度至少75 km处发生变质作用;随后进行了一个相对较慢的折返过程之后出露于地表。
The study of eclogite is of great significance for the further understanding of the structural evolution process of UHP metamorphic belt.In this paper,a series of studies have been carried out on the newly discovered eclogites in the Luliangshan to explore the subduction exhumation process and the mechanism of structural evolution.The Luliangshan eclogites surrounded by granitic gneiss or paragneiss as lens.Petrology and P–T calculation shows that the eclogites have experienced a metamorphic process clockwise path.①The peak eclogite-facies metamorphic stage,is characterized by the peak mineral assemblages of garnet+omphacite+rutile+quartz at T>840℃and P>25.5 kbar.②The HP granulite-facies,is characterized by the retrogradation of omphacite to diopside and plagioclase,with P–T condition of 814-896°C and 17.1-18.7 kbar.③The subsequent amphibolite-facies stage,is characterized by amphibole+plagioclase symplectitic around the clinopyroxene and the retrogradation of rutile to ilmenite,with the metamorphic condition of 674℃~686℃and 6.4-6.9 kbar.Meanwhile,combined with previous studies,a multi-stage tectonic evolution model is proposed that protolith of the Luliangshan eclogite was emplaced into continental crust during the Neoproterozoic,which was dragged into the subduction channel together with the continental crust due to the subduction traction of the oceanic crust,and metamorphosed at a depth of at least 75 km.Afterwards,it emerged to the surface with a relatively slow exhumation process.
作者
李卓凡
于胜尧
侯可军
纪文涛
彭银彪
姚勇
Li Zhuofan;Yu Shengyao;Hou Kejun;Ji Wentao;Peng Yingbiao;Yao Yong(Key Laboratory of Submarine Geosciences and Prospecting Techniques,MOE,Institute for Advanced Ocean Study,College of Marine Geosciences,Ocean University of China,Qingdao,Shandong,266100,China;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao,Shandong,266237,China;MNR key Laboratory of Metallogency and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Science,Beijing,100037,China)
出处
《新疆地质》
CAS
CSCD
北大核心
2020年第3期325-331,共7页
Xinjiang Geology
基金
国家自然科学基金41572053资助。
