Collision Event during 177-135 Ma on the Eastern Margin of the Qinghai-Tibet Plateau: Evidence from 40Ar/ 39Ar Dating for Basalts on the Western Margin of the Yangtze Platform

• Published in: Acta geologica Sinica (Beijing) Vol. 76; no. 2; pp. 194 - 204
• Main Authors: Zengqian, HOU, Wen, CHEN, Jiren, LU
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.06.2002
• Subjects: 40Ar/39Ar; 40Ar/39Ar age; age; basalts; basalts in the Emei LIP; collisional; collisional orogeny; Emei; LIP; orogeny; plateau; Qinghai-Tibet; Qinghai-Tibet plateau; the
• ISSN: 1000-9515; 1755-6724
• DOI: 10.1111/j.1755-6724.2002.tb00085.x

Geochronology of continental flood basalts sampled from the Emei large igneous province (LIP) on the western margin of the Yangtze platform was investigated by the laser microprobe 40Ar/39Ar dating technique. These basalts yield a fairly wide range of 40Ar/39Ar ages, varying from 259 to 135 Ma. One basalt sample, at least altered, recorded the oldest 40Ar/39Ar age of about 259 Ma, corresponding to a peak eruption age of the Emei LIP continental flood basalts. Most of the samples yield much younger ages from 135 to 177 Ma, which are consistent with the K-Ar ages for the same samples (122.8-172.1 Ma). The dating data suggest that these Permian basalts had been widely affected by the regional tectonothermal event at 177-135 Ma. The event was probably caused by the convergence and collision among the Laurasia, Yangtze and Qiangtang-Qamdo continental blocks on the eastern margin of the Qinghai-Tibet plateau after the late Triassic. The age of the event reflects the timing of the peak collisional orogeny.