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40 Ar‐ 39 Ar Geochronology and Tectonic Implications of the Blueschist from Northwestern Qiangtang, Northern Tibet, Western China
Author(s) -
Xianchun TANG,
Kaijun ZHANG
Publication year - 2012
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 - 10.1111/1755-6724.12015
Subject(s) - blueschist , glaucophane , geology , geochemistry , geochronology , lawsonite , terrane , metamorphic rock , subduction , craton , tectonics , paleontology , eclogite
Blueschist exposed in the northwestern Qiangtang terrane, northern Tibet, western China (∼84°30′ E, 34°24′ N), provides new constraints on the tectonic evolution of Qiangtang as well as northern Tibet. The blueschist represented by lawsonite‐ and glaucophane‐bearing assemblages equilibrated at 375–400 °C and ∼11 kbar. 40 Ar‐ 39 Ar analysis on mineral separate from one blueschist sample yielded a well‐defined plateau age of ∼242 Ma. Geochemical studies show the blueschist is metamorphosed within‐plate basalts. The high pressure‐low temperature blueschist indicates a Triassic event of lithosphere subduction, and clearly represents an extension of the central Qiangtang metamorphic belt, and defines an in situ suture between eastern and western Qiangtang.