四川盆地东北部须家河组海陆过渡相沉积环境演化——来自元素地球化学的证据  

Sedimentary environment evolution of marine-continental transitional facies in Xujiahe Formation,northeastern Sichuan Basin:Evidence from element geochemistry

作　　者：薄尚尚 田继先[3] 王晔桐 付爽 谌恒池 孙国强 BO Shangshang;TIAN Jixian;WANG Yetong;FU Shuang;SHENHengchi;SUN Guoqiang(Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China;University of Chinese Academy of Sciences,Beijing 100049,China;Research Institute of Petroleum Exploration and Development,Langfang 065007,China;Northeastern Sichuan Gas Mine of PetroChina Southwest Oil&Gasfield Company,Dazhou 635000,China)

机构地区：[1]中国科学院西北生态环境资源研究院,甘肃兰州730000 [2]中国科学院大学,北京100049 [3]中国石油勘探开发研究院,河北廊坊065007 [4]中国石油西南油气田分公司川东北气矿,四川达州635000

出　　处：《天然气地球科学》2024年第4期645-660,共16页Natural Gas Geoscience

基　　金：中国石油天然气股份有限公司前瞻性与基础性重大科技项目“不同类型大气田(区)成藏主控因素及领域评价”(编号:2021DJ0605)资助。

摘　　要：须家河组海陆过渡相沉积物有效记录了四川盆地晚三叠世古气候—环境变迁的信息,分析沉积环境对于探索有机质富集和油气成藏机理具有重要意义。通过对四川盆地东北部(川东北)不同位置上三叠统须家河组地质剖面进行野外观察和描述、对各层段样品开展岩石学和元素地球化学分析,结合区域构造背景,对川东北须家河组碎屑岩的沉积环境进行了探讨。结果表明:川东北须家河组碎屑组分主要为岩屑和石英,砂岩类型以中粒岩屑砂岩和中粒长石岩屑砂岩为主。CIA、CIW、PIA等参数和ICV—CIA、WIP—CIA等相关性判别图指示须家河组遭受了中等程度的化学风化,须四段和须六段化学风化最强,经历了弱的沉积再旋回;Mo/Al、Mo/Mo*、V/Cr等值和V/Al—U/Al、V/Al—Mo/Al等交会图反映须家河组沉积期为氧化环境,且须四段和须六段的氧化程度更高。受陆源输入、湖侵/海侵事件和气候变化的联合影响,须家河组沉积时期气候有由温暖潮湿向炎热潮湿转变的趋势,水体咸—淡交替,盐度变化大,水平面波动较为频繁,须四段和须六段沉积期水深最浅,湖盆的古生产力水平中等偏低,呈现出先升高、再降低、再升高的趋势,水体的陆源输入是古生产力的主控因素。须家河组沉积时期的环境演化、地层旋回与湖盆经历的2次收缩(T3x4和T3x6水退)和1次扩张(T3x5水进)存在明显的联动性。The marine and continental transitional sediments of Xujiahe Formation effectively record the information of the Late Triassic paleoclimate-environment changes in the Sichuan Basin.The analysis of sedimentary environment is of great significance for exploring the mechanism of organic matter enrichment and hydrocarbon accumulation.Based on field observation and description of the geological profiles of the Upper Triassic Xujiahe Formation in different locations in the northeast Sichuan Basin,petrology and element geochemical analysis of the samples in each section,combined with the regional tectonic setting,the depositional environment of the clastic rocks in the Xujiahe Formation in the northeastern Sichuan Basin is discussed.The results show that the clastic components of Xujiahe Formation in northeastern Sichuan Basin are mainly cuttings and quartz,and the types of sandstone are mainly medium-grained lithic sandstone and medium-grained arkose lithic sandstone.The parameters of CIA,CIW,PIA,and the correlation discrimination maps of ICV-CIA and WIP-CIA indicate that the Xujiahe Formation has suffered a moderate degree of chemical weathering,and the chemical weathering of the fourth(T3 x 4)and sixth(T3 x 6)members of Xujiahe Formation is the strongest and has undergone a slight sedimentary recycle.The ratios of Mo/Al,Mo/Mo*,V/Cr and the cross plot of V/Al-U/Al and V/Al-Mo/Al indicate that the sedimentary period of Xujiahe Formation was an oxidizing environment,and the oxidation degree of the fourth and sixth members of Xujiahe Formation was higher.Affected by the combination of terrestrial source input,lake intrusion/sea intrusion events and climate change,the climate of the Xujiahe Formation sedimentary period has a trend of changing from warm and humid to hot and humid,the water body is salty-light alternate,the salinity changes greatly,the horizontal fluctuation is more frequent,the water depth of the fourth and sixth members of Xujiahe Formation is the shallower,the paleoproductivity level of the lake basin is

关 键 词：元素地球化学 沉积环境 古气候 须家河组 川东北 

分 类 号：TE122.113[石油与天然气工程—油气勘探]