首页|准噶尔盆地玛湖凹陷风城组有机质多元富集机制

准噶尔盆地玛湖凹陷风城组有机质多元富集机制

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基于岩心和薄片资料,对准噶尔盆地玛湖凹陷风城组烃源岩开展了锆石SIMS U-Pb年代学、有机碳同位素组成、主/微量元素含量和岩矿分析等测试工作.在风城组一段获得2个锆石U-Pb年龄分别为(306.0±5.2)Ma和(303.5±3.7)Ma,结合碳同位素地层学数据,推断风城组的沉积年代约为距今297～306 Ma,跨越石炭纪—二叠纪界线,对应古气候划分的冰期事件C4和P1之间的间冰期.在风城组识别出多个Hg/TOC高值段,同时在页岩中普遍发现了蚀变的火山灰,表明在其沉积期发生多期火山活动.在风城组二段中部出现B/Ga高值段,与蒸发岩矿物及硅硼钠石的出现密切相关,表明水体高盐度与热液活动有关.综合分析表明,风城组沉积期温暖湿润的气候既有助于湖泊中藻类及细菌等生烃母质的发育又可加速大陆风化,促进营养元素输入;火山活动给湖泊提供了大量营养物质,提高了初级生产力;温暖的气候和较高的盐度有助于水体分层并导致缺氧,进而促进有机质的保存.以上多种因素相互作用,共同控制了玛湖凹陷风城组有机质的富集.
Multiple enrichment mechanisms of organic matter in the Fengcheng Formation of Mahu Sag,Junggar Basin,NW China
Based on core and thin section data,the source rock samples from the Fengcheng Formation in the Mahu Sag of the Junggar Basin were analyzed in terms of zircon SIMS U-Pb geochronology,organic carbon isotopic composition,major and trace element contents,as well as petrology.Two zircon U-Pb ages of(306.0±5.2)Ma and(303.5±3.7)Ma were obtained from the first member of Fengcheng Formation.Combined with carbon isotopic stratigraphy,it is inferred that the depositional age of the Fengcheng Formation is about 297-306 Ma,spanning the Carboniferous-Permian boundary and corresponding to the interglacial period between C4 and P1 glacial events.Multiple increases in Hg/TOC ratios and altered volcanic ash were found in the shale rocks of the Fengcheng Formation,indicating that multiple phases of volcanic activity occurred during its deposition.An interval with a high B/Ga ratio was found in the middle of the second member of Fengcheng Formation associated with the occurrence of evaporite minerals and reedmergnerite,indicating that the high salinity of the water mass was related to hydrothermal activity.Comprehensive analysis suggests that the warm and humid climate during the deposition of Fengcheng Formation is conducive to the growth of organic matter such as algae and bacteria in the lake,and accelerates the continental weathering,driving the input of nutrients.Volcanic activities supply a large amount of nutrients and stimulate primary productivity.The warm climate and high salinity is conducive to water stratification,leading to water anoxia that benefits organic matter preservation.The above factors interact with each other and control the enrichment of organic matters jointly in the Fengcheng Formation of Mahu Sag.

Junggar BasinMahu SagFengcheng Formationorganic matterinterglacial periodvolcanismpaleo-salinitypaleo-environmental evolution

龚德瑜、刘泽阳、何文军、周川闽、秦志军、卫延召、杨春

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中国石油勘探开发研究院,北京 100083

油气藏地质及开发工程全国重点实验室(成都理工大学),成都 610059

中国石油新疆油田公司勘探开发研究院,新疆克拉玛依 834000

准噶尔盆地 玛湖凹陷 风城组 有机质 间冰期 火山活动 古盐度 古环境演化

国家自然科学基金国家自然科学基金国家自然科学基金中国石油前瞻性基础性技术攻关项目中国石油前瞻性基础性技术攻关项目中国石油直属院所基础科学研究和战略储备技术研究基金四川省自然科学基金

4180217742272188423030562021DJ02062022DJ05072020D-5008-0423NSFSC5461

2024

10.11698/PED.20230673

石油勘探与开发
中国石油天然气股份有限公司勘探开发研究院 中国石油集团科学技术研究院

石油勘探与开发

CSTPCD北大核心
影响因子：4.977
ISSN：1000-0747
年,卷(期)：2024.51(2)
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