Abstract: The lithological features, the types of organic matter and its occurrence and carbon and oxygen isotopic value were clarified by combining core observation, thin slice authentication, X ray diffraction analysis, kerogen type identification and carbon and oxygen isotope analysis. The characteristic of strata, the distribution of volcanoes of Junggar Basin were also taken into consideration. A comprehensive analysis was conducted to evaluate environmental response of volcanism in Lucaogou formation in Jimsar sag. The results show that rocks is a mixed sedimentation of effusive rock and carbonate rocks, volcanic materials is widely developed in Lucaogou formation and origins from the edge of sag or distant source volcano activity. Organic matter is predominantly unstructural algae and asphaltene. The carbon isotopic value of carbonates ranges between 6.8‰ and 9.7‰ with an average of 8.3‰, featured in high positive excursions, while oxygen isotopic value varies from -11.9‰ to -4.3‰ with an average of -6.2‰. During the period of volcanic activity, the volcanic material released high amounts of nutrient to the lake basin, which is beneficial to the algae and other organic organisms. In the poor oxygen and calm water environments, the organic matter is distributed in the laminar algal and the carbon isotope value is high positive drift. During the intermittent period of volcanic activity, the lake level decreased and the lake bottom water changed to the oxygen-enriched environments. The organic matter is locally enriched or dispersed in local layers, and the carbon isotope values decreased slightly. The frequent volcanic activity promoted the organism boom, which lead carbon isotope value to have high positive characteristics and change trends.

Key words: carbon isotope, volcanism, environmental response, Lucaogou formation, Jimsar sag

摘要： 通过岩心、薄片观察、X射线衍射分析、干酪根鉴定和碳氧同位素测试等技术方法，明确了岩石学特征、有机质组分类型及赋存状态、碳氧同位素值特征，结合准噶尔盆地二叠纪地层特征及火山机构分布，对吉木萨尔凹陷芦草沟组沉积时期火山活动的环境响应进行研究。结果表明：吉木萨尔凹陷芦草沟组岩性为火山物质与碳酸盐岩的混合沉积，火山物质为凹陷周缘或远源火山活动输入。有机质组分以降解藻和沥青质体为主，来源于遭受降解作用的低等水生藻类。剖面碳酸盐岩碳同位素介于6.8‰~9.7‰，平均值为8.3‰，具有向正高值漂移的特征，氧同位素介于-11.9‰~-4.3‰，平均值为-6.2‰。通过对准噶尔盆地二叠纪地层特征及火山机构分布调查的结果表明，该时期盆地范围内火山活动规模大，范围广。凹陷内部火山活动较弱，受其周缘火山活动的影响强烈。火山活动期间，飘落湖盆中的火山物质释放出大量营养元素有利于藻类等有机生物生长，在安静还原的水体环境中，有机质呈藻纹层分布，碳同位素具有正高值特征。火山活动间歇期，湖平面下降，湖泊底部水体向氧化环境转变，有机质遭到降解，以局部顺层富集或分散状分布，碳同位素值降低。凹陷周缘及盆地范围内长期、频繁的火山活动促使藻类等低等生物繁盛是碳同位素具有正高值特征及规律变化的根本原因。

关键词: 碳同位素, 火山作用, 环境响应, 芦草沟组, 吉木萨尔凹陷