鄂尔多斯盆地能源矿产氯仿沥青Sm-Nd同位素研究

Sm-Nd isotope study of chloroform bitumen in various energy minerals of the Ordos basin

对鄂尔多斯盆地石油、煤、含铀砂岩及其围岩的氯仿沥青进行了Sm-Nd同位素研究。结果表明,盆地流体(包括深部流体)活动具有多期性,且后期的流体活动对铀矿床的形成具有重要作用;赋存于同一套地层中的含铀砂岩沥青、煤沥青及石油沥青,虽然均具有富集地幔特征,但并非同期活动的产物;东胜矿区侏罗系直罗组煤沥青和盆地西南部陈家山矿区侏罗系延安组的煤沥青,源区时代上存在较大差异,伴生沥青并非全部由煤的热演化形成,可能还存在外来流体的加入,且东胜直罗组煤的伴生沥青较延安组煤的伴生沥青来源深度更大;盆地内马岭油田的直罗组石油沥青、陈家山延安组煤层石油沥青及其煤沥青在源区特征上具有内在联系。

Sm-Nd isotope study has been performed on chloroform bitumen in oil, coal, uranium-bearing sandstone and its country rocks in the Ordos basin. The results indicate that the activity of fluids （including deep fluids） in the basin shows the multi-stage character, and that the late-stage fluid activity played a significant role in the formation of uranium deposits. Uranium-bearing sandstone bitumen, oil bitumen and coal bitumen in the same sequence of strata have the enriched mantle features, but they are not products of the same stage. A comparison between the coal bitumen in the Jurassic Zhiluo Formation of the Dongsheng field and that in the Jurassic Yan＇an Formation of the Chengjiashan field in the southwest of the basin indicates that： there is appreciable difference in ages of the bitumen sources; the associated bitumen did not all form by thermal evolution of coals but might contain exotic fluids, and the associated bitumen in coals of the Zhiluo Formation was derived from an even deeper source than that in coals of the Yan＇an Formation in the Dongsheng field. There is some internal genetic relation between the oil bitumen of the Zhiluo Formation in the Maling oilfield and the coal bitumen and oil bitumen in the coal bed of the Ya＇nan Formation of Chengjiashan in the Ordos basin.