内蒙古西部额济纳旗及其邻区磷灰石裂变径迹研究及其油气地质意义

Apatite Fission Track and its Petroleum Geological Significance of the Ejina Area and its Vicinity, Western Inner Mongolia

对额济纳旗及其邻区两条剖面开展磷灰石裂变径迹研究,6个样品年龄介于(90±6)^(113±8)Ma之间,各样品径迹长度分布具有范围较宽、单峰的特征,较为集中地反应了一期冷却年龄,记录了早白垩世末-晚白垩世初期研究区较为缓慢的构造抬升过程。结合野外地质调查与前人资料,认为研究区在早白垩世达到最大埋深,石炭系-二叠系烃源岩开始大规模向油气转化;随后受印度板块向北与青藏高原对接的影响,研究区开始抬升,对油气藏的形成有着重要意义。

The apatite fission track analyses of two profiles in the Ejina area and its adjacent areas were carried out in this study. The fission track ages of the six samples range from（90±6） Ma to（113±8） Ma. The track lengths of these samples are highly varied showing unimodal pattern, indicating a cooling stage and a slow tectonic uplift at the end of the Early Cretaceous- the early stage of Late Cretaceous. Combined with field geological survey and previous works, we suggest that the maximum burial depth of the study area occurred in the Early Cretaceous, when the Carboniferous-Permian source rocks began to generate oil and gas. Then the uplift happened as a result of plate collision between the north of the Indian plate and the Tibetan Plateau, which played an important role in oil-gas accumulation.