鄂尔多斯盆地西缘差异抬升的裂变径迹证据

目的探讨鄂尔多斯盆地西缘从南至北不同地区的差异抬升时期及抬升速率。方法利用磷灰石和锆石裂变径迹年龄的综合分析,研究盆地西缘的构造差异抬升。结果西缘北部汝箕沟地区中生代以来有两次较大的抬升时期,分别为晚白垩世和始新世,抬升速率分别为29.5 m/Ma和46.5 m/Ma。中部石沟驿地区抬升时期较早,为晚侏罗世和晚白垩世,抬升速率分别为40.0m/Ma和21.9 m/Ma。南部的差异抬升最为强烈,最早的抬升时期为晚侏罗世,在炭山地区表现明显;早白垩世末—晚白垩世南部地区发生整体抬升;中新世末期六盘山地区发生快速抬升。罗山、炭山地区相对抬升速率和后期抬升速率为46.3 m/Ma和25 m/Ma,六盘山地区则分别为22.5m/Ma和283.3 m/Ma。结论在鄂尔多斯盆地西部,最早的抬升时期为晚侏罗世,晚三叠世并没有抬升事件,故西部前陆盆地的形态始显现于晚侏罗世。西部的差异抬升导致了不同地区前陆盆地构造发展的不平衡。

Differential uplift in the west margin of Ordos Basin since Mesozoic from the fission track evidence

Aim To discuss the different uplit ages and uplift speed from south to north in the west of Ordos basin. Methods Fission track analysis of apatite and zircon mineral is a useful way to research the structural uplift in orogene or its neighborable basins. Results There happened two major uplit stages in Rujigou area of north part since Mesozoic which were Late Cretaceous and Eocene with uplift speed of 29. 5 m/Ma and 46.5 m/Ma. The uplift stage is earlier in middle part which are Late Jurassic and Late Cretaceous with rate of speed of 40.0 m/Ma and 21.9 m/ Ma respectively. South part has underwent extensive discrepant uplift with ealiest stage of Late Jurassic in Tanshan area. In the late of Early Cretaceous and Late Cretaceous there exists wholely uplit in Luoshan, Tanshan and Liupanshan area. Liupanshan area has experienced quick uplift in late of Miocene. Luoshan and Tanshan has average relative uplift speed and late uplit speed of 46. 3 m/Ma and 25 m/Ma, while in Liupanshan with 22.5 m/Ma, 283.3 m/Ma respectively. Conclusion It shows by fission track data that uplift event happened not in Late Triassic but in Late Jurassic and the foreland basin appears in Late Jurassic.