Tectonic-sedimentary constrains for hydrocarbon generating organism assemblage in the Lower Cambrian argillaceous source rocks,Tarim Basin
Tectonic-sedimentary constrains for hydrocarbon generating organism assemblage in the Lower Cambrian argillaceous source rocks,Tarim Basin
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Sinopec Exploration
生烃生物是烃源岩研究的重要对象。目前的研究主要是通过模拟实验研究生烃潜力，而对影响生烃生物发育和分布的地质背景关注较少。而生烃生物的发育与分布对预测烃源岩和指导油气勘探具有重要意义。本研究选取了库鲁克塔格地区亚尔当山南段下寒武统西山布拉克组和柯坪地区东尔沟剖面下寒武统玉尔图斯组。两个组的研究表明，西山布拉克组的生烃生物以底栖藻类为主，并含有一定量的浮游藻类;而乌尔图斯组的生烃生物则以底栖藻类为主。两组硅质岩的Ce、Eu元素异常及稀土元素配分模式表明，两段均受到热液流体的影响，其中南雅尔当山段的影响大于东尔沟段。泥岩的常量和微量元素分析表明，早寒武世西山布拉克组还原水较少，库鲁克塔格地区火山活动较多，可能是该地区地形起伏较大的原因。结合现存藻类的分布，认为构造活动、水深和古地形的差异可能是造成雅尔当山南段西山布拉克组与东尔沟剖面玉尔图斯组生烃生物组合差异的主要原因。
Hydrocarbon generating organism is an important object for the source rock research. The studies,so far,were focused on their hydrocarbon-generation potential via simulation experiments,and less attention was paid to the geological settings that affect development and distribution of hydrocarbon generating organisms. However,the development and distribution of hydrocarbon generating organisms is very important for predicting source rocks and guiding petroleum exploration. In this study,the Lower Cambrian Xishanbulake and Yuertus formations were selected from the Southern Yaerdangshan and Dongergou sections in Kuluketage and Keping districts,respectively. Researches on two formations demonstrate that the hydrocarbon generating organisms in the Xishanbulake Formation are dominated by benthic algae,and include some planktonic algae; whereas hydrocarbon generating organisms in the Yuertusi Formation are benthic algae. Anomaly of elements Ce and Eu and REE patterns of cherts in the two formations imply that the two sections were affected by hydrothermal fluid,and that the influence in the Southern Yaerdangshan section was stronger than that in the Dongergou section. Major and trace elements analyses of mudstones indicate that the Xishanbulake Formation have less reduction water,and more active volcano in the Kuluketage district which might be resulted in more undulating terrain than that in the Keping district during the Early Cambrian. Correlated with distribution of extant algae,it could be concluded that the difference in tectonic activity,water depth,and paleo-terrian may be the major cause for the difference in hydrocarbon generating organism assemblages between the Xishanbulake Formation in the Southern Yaerdangshan section and the Yuertus Formation the Dongergou section.