沁水盆地中生代构造热事件发生时期的确定

Determination of Mesozoic tectonic heat event in Qinshui Basin

对沁水盆地构造变动、古地热梯度、古大地热流、裂变径迹年龄、岩浆活动及热液活动等分析资料研究表明,沁水盆地在中生代晚期存在一期强烈的构造热事件,主要发生在距今100～150Ma,主峰值为130～140Ma.沁水盆地石炭系-二叠系煤层热演化程度主要受中生代晚期异常地温场控制,在此基础上,深成变质作用和区域岩浆热变质作用是造成沁水盆地石炭系-二叠系煤层变质程度分带性及差异性的原因.沁水盆地构造热事件的存在及发生时间的确定表明,华北地台中生代以来岩石圈减薄的西界至少可推到沁水盆地以西地区.沁水盆地石炭系-二叠系煤层生烃高峰期受中生代晚期构造热事件控制,煤层生烃高峰期在晚侏罗世-早白垩世,新生代中新世以来发生大规模抬升冷却,地层温度降低,石炭系-二叠系煤层生烃过程停止.

A tectonic heat event happened in Late Mesozoic era in 100-150 Ma ago and the main peak values are 130-140 Ma. The time of the event is revealed by the analyses of tectonic evolution, paleogeothermal gradient, paleogeothermal flux, fission track age, magmatic activity and hydrothermal activity in the Qinshui Basin. Thermal maturation of Permo-Carboniferous coal seams were mainly controlled by geothermal anomaly of Late Mesozoic, on the basis of this geothermal anomaly, different structural units has different metamorphic rank due to plutonic metamorphism and regional magmatic metamorphism. The determination of the existence and timing of the tectonic heat event shows that the Huabei Mass lithosphere had been thinned in Mesozoic, the boundary of thinning might at least extend to the west of Qinshui Basin. Peak generation of hydrocarbon of Permo-Carboniferous coal series in Qinshui Basin happened between Late Jurassic and Early Cretaceous, which was controlled by the tectonic heat event in Late Mesozoic. The large scale uplift in Qinshui Basin happened from Miocene, the stratigraphic temperature dropped down and the hydrocarbon generation of Permo-Carboniferous coal series was stopped.