Tectonothermal Evolution of the Eastern Tibetan Plateau Foreland: Fission-Track Thermochronology of the Southern Dabashan Fold-Thrust Belt  

作　　者：张增宝 沈传波 邵春 刘昭茜 

机构地区：[1]Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education, China University of Geosciences [2]Faculty of Earth Resources, China University of Geosciences

出　　处：《Journal of Earth Science》2013年第4期479-490,共12页地球科学学刊（英文版）

基　　金：supported by the National Natural Science Foundation of China (No. 40902038);the Petro China Innova-tion Foundation (No. 2009D-5006-01-08);the Project of China Geological Survey (No. 12120113094200)

摘　　要：Apatite fission-track dating and thermal-history modeling were carried out on samples from the Dabashan （大巴山）, a fold-thrust belt, northeast of the Sichuan （四川） Basin and east of the Tibetan Plateau. A first cooling event in the Late Cretaceous is followed by a prolonged period of ther- mal stability with exhumation rates of 〈0.025 mm/a, as determined from age vs. elevation relationships. The preservation of age vs. elevations relationships and the lack of distinct age changes across tectonic structures indicate that the Dabashan fold-thrust belt formed prior to the Late Cretaceous, consistent with the current view of Triassic-Early Cretaceous shortening. Relatively short mean track lengths （-12 μm） indicate that the samples remained in the partial annealing zone for a prolonged time. The knick points in the best-fitting temperature-time models suggest that the onset of late-stage accelerated cooling commenced at 〈11 Ma. Related exhumation rates are 0.3-0.2 mm/a assuming geothermal gra- dients of 20 and 30 ℃/km. We speculate that this late-stage event results from eastward growth of the Tibetan Plateau and overstepping of the Sichuan Basin, it is likely responsible for the youthful mor- phology of the Dabashan.Apatite fission-track dating and thermal-history modeling were carried out on samples from the Dabashan （大巴山）, a fold-thrust belt, northeast of the Sichuan （四川） Basin and east of the Tibetan Plateau. A first cooling event in the Late Cretaceous is followed by a prolonged period of ther- mal stability with exhumation rates of 〈0.025 mm/a, as determined from age vs. elevation relationships. The preservation of age vs. elevations relationships and the lack of distinct age changes across tectonic structures indicate that the Dabashan fold-thrust belt formed prior to the Late Cretaceous, consistent with the current view of Triassic-Early Cretaceous shortening. Relatively short mean track lengths （-12 μm） indicate that the samples remained in the partial annealing zone for a prolonged time. The knick points in the best-fitting temperature-time models suggest that the onset of late-stage accelerated cooling commenced at 〈11 Ma. Related exhumation rates are 0.3-0.2 mm/a assuming geothermal gra- dients of 20 and 30 ℃/km. We speculate that this late-stage event results from eastward growth of the Tibetan Plateau and overstepping of the Sichuan Basin, it is likely responsible for the youthful mor- phology of the Dabashan.

关 键 词：FISSION-TRACK fold-thrust belt Dabashan tectonothermal evolution eastern Tibetan Plateau. 

分 类 号：P618.31[天文地球—矿床学]