鄂尔多斯盆地东南缘金锁关地区延长组构造-热演化特征

Tectono-Thermal Evolution of Yanchang Formation in the Jinsuoguan Area of the Southeastern Ordos Basin

采用野外剖面勘测与磷灰石裂变径迹(AFT)分析相结合的研究方法,综合分析了鄂尔多斯盆地东南缘金锁关地区上三叠统延长组的中-新生代构造-热演化特征。金锁关-淌泥河剖面延长组总体呈现为褶皱-冲断构造变形样式,剖面北段的淌泥河处发育较为强烈的斜歪褶皱-冲断构造;该冲断构造属于瑶曲-云梦山冲断构造带的重要组成部分,且中侏罗统卷入了与延长组协同的褶皱变形,并与其上覆的下白垩统呈角度不整合接触关系,表明其构造变形时间主要发生在燕山中期的晚侏罗世。剖面上强、弱变形区段2件延长组砂岩样品的磷灰石裂变径迹(AFT)中值年龄和池年龄非常接近地分布在(105±7)Ma和(93±6)^(94±6)Ma,表明金锁关地区延长组抬升冷却至AFT封闭温度以浅的峰值年龄主要集中在100 Ma左右;砂岩样品AFT热史模拟结果进一步揭示,延长组最晚在早白垩世中期的120 Ma左右已达到最大埋深增温,之后经历了早白垩世晚期120~115 Ma的快速抬升、115~40 Ma的缓慢抬升和40~17 Ma以来的快速隆升剥露过程。

Based on the field survey and apatite fission track （AFT） analysis, thispaper discusses the Meso-zoic-Cenozoic tectonic deformation and thermal evolution of Yanchang Formation in the Jinsuoguan area of the southeast Ordos Basin. The profile of Jingsuoguan-Tangnihe presents a tectonic style composed by fold and fault, and the tectonic deformation developed more stronger in Tangnihe, which belongs to Yaoqu- Yunmengshan Fault. The middle Jurassic formation had participated in the deformation of Yanchang For- mation, which performed an angular unconformity with the overlying formation of the Lower Cretaceous. This means the time of the tectonic deformation during the end of the Middle Jurassic and before the Early Cretaceous. The age recorded by AFT from sandstone samples of central age and pooled age are very close to （105±7）Ma and （934±6）-（94±6）Ma, which means the peak age though the partial annealing zone of Yanchang Formation in Jingsuoguan-Tangnihe is - 100 Ma. Thermal history simulation of AFT reflects that the Yanchang Formation reachedthe maximum depth at least in -120 Ma, then it experienced quick uplift process during 120-115 Ma, slow uplift process during 115-40 Ma and quick uplift-erosive process in the late Early Cretaceous, 40-17 Ma.