摘要
采用粘土矿物学、成岩变质矿物组合、镜质体反射率及流体包裹体数据等指标，综合讨论了准噶尔盆地西北缘晚古生代地层成岩极低级变质作用的特征和油气勘探意义。变质指示矿物和古地温梯度研究确认，西北缘玛湖坳陷北段下二叠统火山岩存在极低级变质作用，具水热变质特征，变质相为葡萄石阳起石相，温度为２２０～３２０℃，压力ｐ＜２００ＭＰａ，表明极低级变质事件发生于早二叠世，未对上二叠统地层产生影响；下二叠统风城组和上二叠统地层于侏罗纪（１５０Ｍａ）达到最大古地温，为１３０～１８０℃，压力ｐ为１００～２００ＭＰａ，处于晚成岩Ａ，Ｂ期。与西准噶尔界山上古生界相比，盆地西北缘变质程度较低。因此，盆地深部上古生界仍是寻找油气。
Based on clay mineralogy, diagenetic metamorphic minera l association, vitrinite reflectance and fluid inclusion, the characteristics of diagenesis and very low grade metamorphism of the Upper Paleozoic strata and their significance for oil gas exploration in the northwestern margin of the Junggar Basin are comprehensively discussed. Very low grade metamorphism related to hydrothermal metamorphism was recognized in volcanic rocks of the Lower Permian strata at north of the Ma Lake Sag by index mineral and higher geothermal gradient, its metamorphic facies attained to the prehnite actinolite facies. The p T field of this facies ranges from about 220 to 320℃ below 200MPa. It is shown that the very low grade metamorphic event occurred in Early Permian, and had very little effect on the Upper Permian strata. The diagenesis in the Upper Paleozoic strata belonged to the A and B stage of the late diagenesis, and the peak diagenetic event occurred about 150Ma in Jurassic, and the diagenetic temperature is about 130～180 ℃. In comparison with that in the boundary hill of the Western Junggar, th e metamorphic grade of the Upper Paleozoic strata in the northwestern margin of Junggar Basin is lower apparently. Therefor, there are still potential regions for oil gas exploration, particularly for gas exploration in the Upper Paleozoic strata.
出处
《地学前缘》
EI
CAS
CSCD
1999年第2期251-258,共8页
Earth Science Frontiers
基金
地质行业科技发展基金
关键词
上古生界
成岩
极低级变质作用
油气勘探
盆地
northwestern margin of Junggar Basin, Upper Paleozoic, diagenesis and very low grade metamorphism, oil gas exploration
