石油实验地质2025，Vol.47Issue(5)：1106-1117,12.DOI:10.11781/sysydz2025051106
准噶尔盆地玛湖凹陷风城组黄铁矿硫同位素地球化学特征及其指示意义
Geochemical characteristics and implications of pyrite sulfur isotope in Fengcheng Formation of Mahu Sag,Junggar Basin
摘要
Abstract
The Fengcheng Formation in the Mahu Sag of the Junggar Basin spans the Carboniferous and Permian boundary and represents a typical shale oil reservoir deposited in a marine to continental transitional environment.Comparative studies using scanning electron microscopy(SEM)and the chromium reduction method have revealed that the total sulfur content in this formation is significantly higher than that of the mudstones in the seventh member of the Triassic Yanchang Formation in the Ordos Basin,the Cretaceous Nenjiang Formation in the Songliao Basin,and the Paleogene Lower Ganchaigou Formation in the Qaidam Basin.In addition,pyrite of diverse morphologies develops,including euhedral and framboidal pyrite.However,relevant research on pyrite genesis in this forma-tion is still at an early stage.Based on major element analysis and previous studies,the study concluded that intense volcanic activities and sulfates from the Paleo-Asian Ocean were the main sulfur sources of pyrite in the Fengcheng Formation,and the sulfur-bearing hydrothermal fluids were the secondary source.Riverine input of weathered materials had a relatively minor influence.Meanwhile,based on the characteristics of pyrite sulfur isotope composition(δ34 S),the evolution of the Fengcheng Formation was divided into two stages:Stage 1 extended from the top of the first member(C2f1)to the middle of the second member(C2-P1f2)of the Fengcheng Formation.The variations in sulfate concentrations controlled by the connectivity between the ocean and the lake basin led to significant positive and negative deviations in δ34 S values.Stage 2 extended from the upper part of C2-P1f2 to the third member(P1f3).The fluctuations in δ34 S values were mainly influenced by sedimentation rate.In addition,intense volcanic activities also caused negative deviations in δ34 S values.Studies on factors affecting sulfur isotope fractionation in pyrite of the Fengcheng Formation is beneficial for further understanding the sulfur cycle and reconstructing diagenetic and sedimentary models.Finally,based on the total organic carbon(TOC)content and water environment variations indicated by sulfur isotopes,it is concluded that increased lake basin openness,stratification of high-salinity water caused by strong evaporation,and intense volcanic activities are the key factors influencing the enrichment and preservation of organic matter in the Fengcheng Formation.关键词
黄铁矿/硫来源/硫同位素/有机质富集/风城组/玛湖凹陷/准噶尔盆地Key words
pyrite/sulfur source/sulfur isotope/organic matter enrichment/Fengcheng Formation/Mahu Sag/Junggar Basin分类
能源科技引用本文复制引用
江程舟,王贵文,王松,张益粼,黄玉越..准噶尔盆地玛湖凹陷风城组黄铁矿硫同位素地球化学特征及其指示意义[J].石油实验地质,2025,47(5):1106-1117,12.基金项目
国家自然科学基金(41872133)和中国石油—中国石油大学(北京)战略合作协议(ZLZX2020-01-05-03)联合资助. （41872133）
