摘要
用TSQ70GC－MS－MS仪器分析我国珠江口盆地、北部湾盆地下第三系烃源岩的大量样品中，均检测出丰富的40甲基甾烷。通过质谱鉴定确定化合物的构型，在成熟岩样中多为4α－甲基甾烷，在未成熟生油岩中又鉴定出丰富的4β－甲基甾烷（包括C28－C30），其质谱特征以M／Z123为基峰。4β－甲基甾烷的热稳定性差，随着热成熟度的增加，很快向4α－甲基构型转化，直至消失，4β－甲基甾烷是未成熟烃源岩的重要标志，在我国近海陆架盆地多发现于下第三系淡水半深水－深水湖相沉积岩中，有一定的普遍意义。
Large quantites of samples of Palaeogene hydrocarbon source rocks in the Pearl River Mouth Basin and the Beibu Gulf Basin offshore China were analysed by using TSQ 70 GC-MS-MS-DS and abundant 4-methylsteranes were detected.The structure types of com- pounds were identified by mass spectra.4α-methylsteranes are mostly found in mature sam- pies,while 4β-methylsteranes (C_(28)—C_(30)) are in immature samples whosde mass spectra is characterized by m/z 123 base peak.4β-methylsteranes have bad thermal stability and rapidily converted to 4α-isomers until 4β-isomers disappeared with the maturity increase. 4β-methylsteranes usually found in paleogene semideep water lacustrine sediments offshore Chi- na are important biomarkers of immature source rocks.
出处
《中国海上油气（地质）》
1993年第1期19-25,共7页
China Offshore Oil and Gas(Geology)
