山西含煤地层中的岩浆岩及其对煤层的影响

Magmatic Rocks and the Influence on Coal Strata in Coal-bearing Layers in Shanxi Province

含煤地层中岩浆岩侵入在山西含煤盆地分布广泛,对煤层破坏和影响较大。运用煤田地质学和煤岩学的观点,分析研究了山西含煤地层岩浆岩的岩性特征和侵入规律。认为山西含煤地层岩浆岩主要是三叠纪晚期的煌斑岩体和白垩纪早期的碱性—偏碱性岩。前者产生于伸展构造背景下,受区域深大断裂控制。后者是华北克拉通东部早白垩纪岩石圈减薄大规模岩浆活动的结果。岩浆岩的大规模侵入破坏了含煤地层的稳定性和连续型,造成无煤区,但提高了地层古地温梯度,使侵入区煤层产生大规模区域热变质和小规模的接触变质;促进了煤层的二次生烃,提高了煤的渗透率;影响了煤中部分微量元素的分布。

The intrusion of magmatic rocks in coal bearing formations is widely distributed in coal bearing basins in Shanxi province. It has a great impact on coal strata. By using geology and coal petrology in coalfields, the lithology characteristics and intrusion rules of magmatic rocks in coal bearing strata in Shanxi province have been analyzed. It is concluded that magmatic rocks in coal bearing strata are mainly lamprophyre rocks in late Triassic and the alkaline—alkaline rocks in early Cretaceous period. The former occurrs under the background of extensional tectonics. It is controlled by the deep faults in the area. The latter is the result of the early Cretaceous lithospheric thinning and magmatic activity in the eastern part of North China Craton. Large scale intrusion has destroyed the stability and continuity of coal bearing strata. Thus, the area without coal has been fomred, but increased the paleo geothermal gradient. Large scale regional thermal metamorphism and small scale contact metamorphism in the invaded area have been formed. It has promoted secondary hydrocarbon generation in coal strata, and improved coal permeability. The intrusion of magmatic rocks has affected the distribution of some trace elements in coal.