摘要
为研究黔北地区下寒武统牛蹄塘组烃源岩母质来源和沉积环境,开展了生物标志化合物分析,结果表明:①正构烷烃OEP接近1.0,无明显奇偶优势,受轻微生物降解影响,正构烷烃多表现为双峰型(C18/C25),(nC21+nC22)/(nC28+nC29)值为0.54～1.01,显示重烃组分占绝对优势;Pr/Ph值范围在0.51～0.82之间,具有植烷优势。②烃源岩样品组成相对丰度五环三萜烷>三环萜烷>四环萜烷,三环萜烷中C21、C23、C24呈倒V字形分布,Ts/(Tm+Ts)为0.45～0.50。③C27规则甾烷/C29规则甾烷略小于1或者接近1,芳烃化合物DBT/P为0.05～0.09。根据这些特征并结合干酪根同位素及正构烷烃同位素组成和变化规律,认为该区域下寒武统牛蹄塘组烃源岩形成于浅海还原环境,且有机质主要来源于细菌、藻类等低等水生生物,有机质热演化程度较高。根据常量、微量元素指标并结合有机地化指标刻划出从灯影组到牛蹄塘组和明心寺组沉积时期的水体环境,将牛蹄塘组烃源岩的形成分为3个阶段,第一阶段为早寒武世初始快速海侵阶段,第二阶段为深水还原高有机质产力阶段,第三阶段为海水缓慢变浅高有机质产力阶段,而到了明心寺组沉积时期为浅水氧化非烃源岩阶段。
In order to investigate source material and sedimentary environment of Lower Cambrian Niutitang Formation source rock in northern Guizhou, the authors studied the biomarkers. The results show that they have the following characteristics： （1） OEP values of the n-alkanes are close to 1.0, showing no odd-even carbon dominance; N-alkanes mostly have bimodal performance（C18/C22）, and the ratios of （nC21＋nC22/（nC28＋nC29）are 0.54-1.01, indicating a dominant role of heavy hydrocarbon components; the average ratios of Pr/Ph vary from 0.51 to 0.82, showing phytane dominance.（2） According to the relative abundance, tricycfic terpane〉pentacyclic triterpane〉quart- cyclic terpane. The tricyclic terpane contents ofC21, C23 and C24 show inverted V-shaped distribution, and the ratios of Ts/ （Tm＋Ts） are between 0.45 and 0.50. （3） The average ratio of C27 and C29 of the sterane is slightly smaller than or close to 1. Aromatic compounds DBT/P are between 0.05 and 0.09. Based on these features combined with the isotope of kerogen and the isotope of the monomer hydrocar- bon composition and variation, the authors believe that the black rock of Niutitang Formation was formed in a reduction environment in shallow water in the Early Cambrian, with high degree of thermal evolution of organic matter, and the main sources were the bacte- ria, algae and other aquatic organisms. The constant index of MnO/TiO2, the trace indicators ofBa, Sr/Ba, U/Th, V/（V＋Ni）, and the combination oforgailic geochemical indicators depict the aquatic environment from Upper Sinian Dengying Formation to Lower Cam- brian Niutitang Formation and Mingxinsi Formation, and the source rocks of Niutitang Formation hydrocarbon are divided into three stages, the first stage being the initial rapid transgression stage in Early Cambrian, the second stage being a stage of deep-water reducing environment with high organic matter productivity, and the third stage being a stage of shallow waters with high organic matter productivity.
出处
《地质通报》
CAS
CSCD
北大核心
2012年第11期1910-1921,共12页
Geological Bulletin of China
基金
中国地质调查局地质调查项目<雪峰山西侧地区海相油气地质调查>(编号:1212010782003)
国家自然科学基金项目<黔东新元古代中期沉积盆地演化与地层划分对比研究>(批准号:41072088)
关键词
牛蹄塘组
烃源岩
生物标志物
有机碳同位素
微量元素
黔北
Niutitang Formation
source rocks
biomarker
organic carbon isotope
trace elements
northern Guizhou
