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Ultrahigh Pressure Metamorphism and Tectonic Evolution of Southwestern Tianshan Orogenic Belt, China: A Comprehensive Review
Author(s) -
ZHANG Lifei,
WANG Yang,
ZHANG Lijuan,
LÜ Zeng
Publication year - 2020
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.14487
Subject(s) - geology , metamorphism , eclogite , geochemistry , phengite , metamorphic facies , metamorphic rock , blueschist , zircon , coesite , glaucophane , greenschist , protolith , petrology , subduction , facies , geomorphology , seismology , tectonics , structural basin
Recently, a huge ultrahigh‐pressure (UHP) metamorphic belt of oceanic‐type has been recognized in southwestern (SW) Tianshan, China. Petrological studies show that the UHP metamorphic rocks of SW Tianshan orogenic belt include mafic eclogites and blueschists, pelitic garnet phengite schists, marbles and serpentinites. The well‐preserved coesite inclusions were commonly found in eclogites, garnet phengite schists and marbles. Ti‐clinohumite and Ti‐chondrodite have been identified in UHP metamorphic serpentinites. Based on the PT pseudosection calculation and combined U‐Pb zircon dating, the P‐T‐t path has been outlined as four stages: cold subduction to UHP conditions before∼320 Ma whose peak ultrahigh pressure is about 30 kbar at 500 °C, heating decompression from the P max to the T max stage before 305 Ma whose peak temperature is about 600 °C at 22 kbar, then the early cold exhumation from amphibolite eclogite facies to epidote‐amphibolite facies metamorphism before 220 Ma and the last tectonic exhumation from epidote amphibolite facies to greenschist facies metamorphism. Combining with the syn‐subduction arc‐like 333‐326 Ma granitic rocks and 280‐260 Ma S‐type granites in the coeval low‐pressure and high‐temperature (LP‐HT) metamorphic belt, the tectonic evolution of Tianshan UHP metamorphic belt during late Cambrian to early Triassic has been proposed in this paper.