地质学报2011，Vol.85Issue(7)：1116-1127,12.DOI:11-1951/P.20110715.0858.009
喜马拉雅东构造结地区雅鲁藏布江蛇绿岩地质年代学研究
Geochronological Study of the Yarlung Tsangpo Ophiolite in the Region of the Eastern Himalayan Syntaxis
摘要
Abstract
The Yarlung Tsangpo suture forms a bended ophiolitic melange in the eastern syntaxis area. Its geochemistry and genesis has been studied previously, but the chronology study is very poor. This paper reports the results of geochronology study of the ophiolite. Two types of zircon were selected from metamorphosed basalt and gabbro. One type of zircon is cylindrical-shaped double cone, with clear rhythm concentric rings, that yields a weighted mean age at 185. 8±1. 7 Ma (MSWD = 0. 64, n=11) and high Th/U ratios (mainly 0. 63-2. 79) by SHRIMP II analyses. Another three such zircon grains give 207±29 Ma(MSWD=6. 5) and 209 ± 20Ma (MSWD = 3. 0) ages by SHRIMP II and LA-ICP-MS analyses respectively. Another type of zircon grains are semi-euhedral columns to short cylindrical double cones, with weak internal zoning and lower Th / U ratios (mainly 0. 005~0. 033) and yield a weighted mean age at 32. 74±0. 65 Ma(MSWD = 0. 92,n=11). There are also some metamorphosed zircon grains that give ages ranging from 82. 8 Ma to 70. 8 Ma. Geochronological dating suggests that the ophiolite formed in early Jurassic and locally in late Triassic. We argue that the Neo-Tethys began northward subduction in the Early Jurassic to Late Triassic time and closed in the Late Cretaceous time, thus causing ophiolite tectonic emplacement.关键词
喜马拉雅东构造结/雅鲁藏布江蛇绿岩/锆石U-Pb定年/新特提斯/构造演化Key words
The eastern Himalayan syntaxis/ Yarlung Tsangpo ophiolite/ Zircon U/Pb dating/ Neo-Tethys/ Tectonic evolution引用本文复制引用
耿全如,彭智敏,张璋..喜马拉雅东构造结地区雅鲁藏布江蛇绿岩地质年代学研究[J].地质学报,2011,85(7):1116-1127,12.基金项目
本文为国家自然科学基金项目(编号40773001)资助的成果. （编号40773001）
