沉积盆地岩浆侵入的热模拟

沉积盆地中岩浆的侵入会导致盆地地温史的变化，影响烃类成熟度，本文对沉积盆地中岩浆侵入过程进行了热模拟，分析了岩浆侵入对沉积盆地温度结构和成油窗的影响，在计算中，既考虑了岩浆凝固过程释放的潜热，又考虑了岩石比热，热导率随温度的变化对热模拟结果的影响，通过计算认识到：沉积盆地中侵入岩浆在垂直方向上的热扩散比水平方向热扩散更快，几公里大小的侵入体其热影响可以在时间上持续数百万年，在空间上扩散至十数公里，

THE THERMAL MODELING OF MAGMA INTRUSION IN SEDIMENTARY BASINS

Thermal evolution of sedimentary basins is critical to oil generation and preservation.In the North China basin, basalt intrusions, although relatively small in volume, arewidespread and buried. However their thermal effects on organic maturation have not beenwell studied. In this study, we used two-dimensiona1 finite element method to solve thepartial differential equation of time-dependent heat transfer and to investigate the thermaleffects of magma intrusion. We use a method of equivalent heat capacity to handle the latent heat effect. Meanwhile, the thermal effect of variable heat conductivity and variablespecific heat with temperature have also been considered in our calculation, and it is foundthat vertical heat transfer is always greater or comparable to horizontal heat transfer. Ac-cording to the parameters of sedimentary basin with magma intrusion in North China, wehave calcu1ated basaltic magma and granite magma models with different background heatflow. To study the effect of magma intrusion on hydrocarbon maturation, the incrementsin Time-Temperature-Index produced by the intrusion are calculated from our model. Variations in temperature created by magma intrusion are calculated, and gcological consequences of such variation are discussed. It is suggested that thermal effect of an intrudedbody several kilometers in size can last a few million years in time and affect tens ofkilometers in space. Such thermal effect can accelerate hydrocarbon maturation and alterthe depths of oil generation window.