鄂尔多斯盆地黄陵、东胜地区地温场对比

Comparison of Geothermal Fields in the Huangling and Dongsheng Areas,Ordos Basin

鄂尔多斯盆地黄陵、东胜铀矿区分别处于盆地南部渭北隆起的北侧边缘和盆地北部伊盟隆起的东部,赋矿层位都是中侏罗统直罗组。盆地南、北铀矿区在现今地温场及古地温场都存在明显差异,南部现今大地热值及热演化程度明显高于北部。对于下侏罗统延安组和石炭—二叠系煤层,黄陵地区镜质体反射率都高于东胜地区。通过镜质体反射率资料得出同一埋深的一套地层经历的最大古地温和对应的古地温梯度也有南部高于北部的现象。由于早白垩世后期盆地普遍整体抬升使得现今地温相对古地温降低,南部黄陵地区抬升剥蚀量大于北部东胜地区,导致古、今地温差异也大于后者。盆地南部庆阳—富县一带局部构造热运动,导致南部异常地温场的形成,使得南部热演化程度高于北部。

The uranium deposits in the southern and northern parts of the Ordos Basin are located in the northern margin of the southern Weibei uplift and eastern part of the northern Yimeng uplift. Their geological features are similar to each other and uranium is hosted in the Middle Jurassic Zhiluo Formation （J2z）. Both the present and ancient geothermal fields are different in the two areas. The present heat flow contour and the geothermal evolution degree in the southern part of the basin are higher than those in the northern part. Data from the coal-bearing strata of the Lower Jurassic Yan＇an and the Carboniferous- Permian formations show that the vitrinite reflectance in the southern area is higher than that in the northern area. The maximum ancient geothermal temperature experienced, and the corresponding ancient geothermal gradient, both reconstructed from Ro data, also reveal that the southern area are higher than those in the northern basin. The present geothermal is lower than the paleo-geotherreal because of the general uplifting in the Lower Cretaceous period. Because the erosion in the south is more intense than that in the north, the difference between the present and the ancient geothermals in the south is larger than that in the north. It is the tectonic thermal movement in the Qingyang and Fuxian areas in the south of the basin that leads to the formation of the abnormal geothermal fields and the higher geothermal evolution degree in the south.