柴西新生代沉积源区及盆地热历史的磷灰石裂变径迹分析

Apatite Fission Track Analyses of Cenozoic Sedimentary Source and Basin Thermal History in West Qaidam Basin

通过对柴达木盆地西部干柴沟地区西岔沟剖面10件新生代砂岩样品磷灰石裂变径迹年龄的分析和年龄一温度热演化史的模拟，研究了柴西新生代碎屑沉积岩源区及盆地的热历史。磷灰石样品大多未退火，来自不同的物源区。裂变径迹颗粒年龄分组显示，盆地经历了23．5，29．6，35．8Ma3次构造热事件；沉积物源区在42．0～40．5，39．0～37．5，14．0～11．5，6．0～4．5Ma发生了明显的构造活动，源区发生了较明显的变化，特别是12Ma左右的构造活动，导致下油砂山组顶部物源发生了很大的改变；40．5～39．0，16-14，11．5～6．0Ma沉积物的源区发生了明显的升降运动，导致剥蚀速率加快；平均围限径迹长度为9．4～11．7μm，总体来看，干柴沟地区及周缘山系在37-15Ma近22Ma的地质时期内一直比较稳定，30Ma左右的热事件在盆地或周缘山系都有较明显的反映。

The Cenozoic sediments provenance and basin thermal history ot： the west Qaidam Basin is studied by the analysis of the age of apatite fission track and inversion of time-temperature evolutionary history of 10 sandstone samples from Xichagou section of Ganchaigou region. Most of apatites are unannealed and from different sources. The fission track grain age distribution shows three times of tectonic heat events. 23.5, 29.6, 35.8 Ma. In the sedimentary source obvious tectonic movements and changes occurred during 42.0--40. 5,39.0--37.5,14.0--11. 5, 6.0--4.5 Ma. In particular, the tectonic movements in 12 Ma caused the great changes of sedimentary sources at the top of Youshashan Group and the obvious lifting movement caused denudation rate increased during 40.5--39.0, 16.0--14.0,11.5--6.0 Ma; The mean trace lengths are 9.4--11.7μm. In general,the construct was stable during 37--15 Ma at Ganchaigou region and periphery mountain system, and the obvious thermal event in 30 Ma was reflected in basin and periphery mountain system.