地质力学学报2026，Vol.32Issue(1)：84-106,23.DOI:10.12090/j.issn.1006-6616.2025146
玛南地区风城组富有机质页岩成因机制——来自有机岩石学、生物标志物及同位素的证据
Genesis of organic-rich shales in the Fengcheng Formation,southern Mahu Sag:Evidence from organic petrology,biomarkers,and isotopes
摘要
Abstract
[Objective]The Mahu Sag,a pivotal,hydrocarbon-rich depression within the Junggar Basin,hosts the Permian Fengcheng Formation,a primary source rock interval widely regarded as a key"sweet spot"target for shale oil exploration.Unlike the well-studied depocenter and northern slope of the Mahu Sag,the Southern Mahu Sag represents a marginal lacustrine facies.Although possessing distinct source rock quality,organic matter(OM)occurrence,and paleo-environmental evolution,the underlying genetic mechanisms remain poorly constrained.[Methods]To address this,this study integrates organic petrology,molecular geochemistry,and stable carbon isotope analyses on 33 mudstone and shale samples from 12 wells in the Southern Mahu Sag.Systematic tests were conducted to comprehensively evaluate the geochemical characteristics and hydrocarbon generation potential.These included determination of the total organic carbon(TOC)and total sulfur(TS)content,Rock-Eval pyrolysis,measurement of vitrinite reflectance(Ro),chloroform bitumen"A"extraction,gas chromatography–mass spectrometry(GC–MS)of saturated and aromatic hydrocarbons,and analysis of the carbon isotope compositions of extracts and fractions.[Results]The results indicate that the OM abundance of the Fengcheng Formation source rocks in the Southern Mahu area generally reaches"good"to"excellent"levels.However,affected by the dilution of terrigenous detritus and transport effects,the OM is predominantly mixed Type II–III kerogen,contrasting significantly with the Type I–II OM typically found in the Northern Mahu area.The samples are generally within the peak oil-generation window(Ro>0.8%).[Conclusions]After rigorously assessing and calibrating the thermal maturity effects on source-related parameters(e.g.,Pr/Ph,β-carotane,and ETR),multi-proxy analysis confirms that the OM mainly originates from lower aquatic organisms,such as algae and bacteria,with limited input from higher terrestrial plants.Regarding the depositional environment,the study area primarily evolved in a saline lacustrine slope setting,characterized by dual control of endogenous chemical precipitation and exogenous terrigenous detrital input.The water column exhibited weak reducing and high-salinity conditions.[Significance]This study(i)elucidates the material basis of the Fengcheng Formation source rocks as a"saline mixed sedimentary"shale oil enrichment zone in a marginal facies,(ii)reveals the depositional heterogeneity compared to the sag center and northern slope,and(iii)provides a theoretical foundation for expanding shale oil exploration in the Junggar Basin.关键词
准噶尔盆地/玛南地区/风城组/烃源岩评价/生物标志物Key words
Junggar Basin/Southern Mahu Sag/Fengcheng Formation/source rock evaluation/biomarker分类
天文与地球科学引用本文复制引用
陈山河,齐洪岩,王伟,王振林,李杨虎,汤富康,郭守鑫,傅正航..玛南地区风城组富有机质页岩成因机制——来自有机岩石学、生物标志物及同位素的证据[J].地质力学学报,2026,32(1):84-106,23.基金项目
国家科技重大专项(2025ZD1405001) （2025ZD1405001）
新疆天山英才计划青年拔尖人才项目(2022TSYCJC0027) This research was financially supported by the National Science and Technology Major Project(Grant No.2025ZD1405001)and the Tianshan Talents Program(Outstanding Young Talents Project)(Grant No.2022TSYCJC0027). （2022TSYCJC0027）
