松辽盆地基底浅变质岩的有机地球化学特征

Organic geochemistry of epimetamorphic rock in basement of the Songliao Basin

松辽盆地基底石炭-二叠系地层处于浅变质阶段。岩石有机地球化学分析表明,有机碳含量0.05%～2.08%,氯仿沥青“A”含量0.0003%～0.0029%,MAB抽提物含量0.0012%～0.0028%,H/C摩尔比0.10～0.52,Ro范围2.98%～4.16%。随成熟度的增加,可溶有机质含量以及干酪根H/C摩尔比降低。按岩石抽提物的正构烷烃分布和生物标志化合物的分布可把样品分为两类,第一类样品中正构烷烃分布呈偶碳优势,伽马蜡烷丰度高、C28甾烷丰度高,反映高盐度环境菌、藻有机质的贡献;第二类样品中正构烷烃分布呈奇碳优势,伽马蜡烷丰度低、C29甾烷丰度高,反映陆源植物为主要生源的沉积特征。

Permo-Carboniferous in the Songliao Basin underwent epimetamorphi sm . The results of rock organic geochemical analyses show that the rocks have tota l hydrocarbon content of 0.05%～2.08%, chloroform bitumen “A”0.000 3%～0.00 2 9%, MAB extraction content 0.001 2%～0.002 8%, H/C mole ratio 0.10～0.52, a nd with vitrinite reflectance (Ro) of 2.98%～4.16%. The organic matter content s and H/C ratios decrease with increasing maturity. According to the distributio n of n-alkanes and biomarkers of extraction from the rocks, the samples could b e divided into two types. The first type of samples is characterized by even car bon number predominance in distribution of n-alkanes, with high gammacerane and C28 sterane contents, indicating the contribution of bacterium and alga in hype rsaline environment. The second type of samples by odd carbon number predominanc e in distribution of n-alkanes, with low gammacerane content and high C29 stera ne content, showing the sedimentary characteristics of major input of terrestria l plant.