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以英国北威尔士和我国黔东湘西、新疆乌尔禾和塔里木的沥青为例,讨论了沥青的 Pb、Sr、Nd 同位素地球化学特征。结果表明:(1)沥青(前身物石油)的形成可能有多种途径,如壳源有机物生成(北威尔士、黔东湘西)和深源无机合成,后者的地质环境为地幔俯冲带(乌尔禾沥青)或下地壳麻粒岩相(塔里木);(2)沥青生成的时代比习惯认为的要古老得多。Pb、Sr、Nd 同位素还可给出原油运移、沥青沉淀的年龄。深入研究沥青的成因,对油气资源评价、勘探目标选择有重要意义。
Taking the North Wales of UK and the bitumen of Qiangdong, Xiangdong, Wuerhe and Tarim in Xinjiang as an example, the Pb, Sr and Nd isotopic geochemical characteristics of bitumen were discussed. The results show that: (1) There are many possible ways for the formation of bitumen (formerly petroleum), such as the formation of shell-derived organic matter (North Wales, East Qiangdong and West) and deep-source inorganic synthesis. The latter is characterized by the mantle subduction zone Erhe bitumen) or lower crust granulite facies (Tarim); (2) bitumen is generated much older than it is used to. Pb, Sr, Nd isotopes can also give the migration of crude oil, asphalt precipitation age. In-depth study of the cause of bitumen, oil and gas resources evaluation, exploration of the target selection is of great significance.