湖相碳酸盐岩有机质热演化产物及其碳同位素组成特征

Thermolysis Production of Lake Carbonatite Organic Matter and its Carbon Isotopic Composition Characteristic

通过泌阳凹陷第三系核桃园组核三段湖相碳酸盐岩的热模拟实验 ,对有机质热演化特征、释放气体组分及含碳气体碳同位素组成特征获得了以下认识 :(1 )释放气体主要以二氧化碳和烷烃类气为主 ,含有少量烯烃气体 ,在 30 0～ 40 0℃时达到气体释放峰 ,随温度的升高 ,C4～ C6 较重烷烃气含量增加 .二氧化碳随温度的升高释放量增大 ,主要为碳酸盐分解贡献 ;(2 )含碳气体碳同位素随温度的升高增重 ,在气体释放峰温度段 350℃左右时发生明显“转折”,碳同位素组成明显变重 ,结果造成在不同的热演化阶段碳同位素值有较大范围的变化 .

In this paper, lake carbonatite in Hei 3 section of Tertiary Heitaoyuan Formation of Biyang depression has been pyrolysised and the thermal evolution of organic matter,gas component releasing and carbon isotopic composition of carbon bearing gas is better comprehended. We understand that (1) releasing gases are mainly made up of CO 2 and alkane gases, and have a little ethylenic gases. There is a gas releasing peak at the temperature of 300～400℃ and the content of C 4～C 6 increases with temperature rise. The content of CO 2 increases too, with temperature rising and comes mainly from carbonatite; (2) The higher the temperature increases, the higher weight the carbon isotopic composition of carbon bearing gas is. At the gas releasing peak of temperature about 350℃ the carbon isotopic composition apparently“changes greatly” and becomes weight. Hence the carbon isotopic composition changes in a large range at different pyrolysis stages.