岩石矿物学杂志2025，Vol.44Issue(4)：803-822,20.DOI:10.20086/j.cnki.yskw.2025.4092
川东地区龙潭组泥页岩地球化学特征及沉积环境
Geochemical characteristics and sedimentary environment of the Longtan Formation shale in eastern Sichuan Basin:An example of Huayingshan section
摘要
Abstract
In order to investigate the sedimentary environment,controlling factors and formation pattern of the shale of Longtan Formation of the Upper Permian in eastern Sichuan Basin,systematic tests of organic petrology,organic geochemistry and elemental geochemistry were conducted on the shale samples from Huayingshan profile as the research object.The results indicated that the source rock of the Longtan Formation shale in the studied area is complex.Diagrams of Co/Th-La/Sc,La/Yb-ΣREE and TiO2-Al2O3/TiO2 suggested that the source rocks of the Longtan Formation shales are mainly Emeishan basalt with high Ti content and intermediate acidic volcanic rocks.The trigonometric diagrams of Th-Sc-Zr,Th-Co-Zr and La-Th-Sc showed that the source rocks were mainly formed in the tectonic background of passive continental margin environment.The average chemical alteration index(CIA)of the Longtan Formation shale was 80.64,indicating moderate to high intensity weathering;the Sr/Cu val-ues ranged from 0.48 to 8.08,with an average of 2.22,and the MgO/CaO values ranged from 0.62 to 52.58,with an average of 14.36,reflecting warm and humid climate condition during the sedimentation period of the Long-tan Formation overall.The Sr/Ba values ranged from 0.37 to 1.86 and 100 MgO/Al2O3 values ranged from 3.27 to 5.45,indicating a semi-saline transitional sedimentary environment.The mean value of Zr/Al was 7.97×10-3 and that of 100 Mn/Fe was 0.68,indicating that the sedimentary water in the Longtan period of the Huayingshan area was relatively shallow and was also consistent with the geological background of shallow continental shelf reported by previous studies.The V/(V+Ni)values ranged from 0.62 to 0.98,averaged 0.89,Ni/Co values ranged from 0.47 to 13.81,averaged 5.49,and Ceanom values had averaged value of 0.03,suggesting that the sedimentary wa-ter of the Longtan Formation was mainly in a weakly reductive to reductive environment.In terms of sedimentary environment,organic matter characteristics and geological background,it could be inferred that the organic-rich shale of the Longtan Formation was formed in a warm and humid climate environment.In the background of strong weathering,after the death,the higher plants entered the water body accompanied with the numerous input of ter-restrial debris formed by basalt and intermediate acidic volcanic rocks,and high plants rapidly deposited,buried,and effectively preserved under the background of the condition of rapid deposition,and finally that high-quantity source rock with inclined kerogen type was formed.关键词
龙潭组/元素地球化学/沉积环境/形成模式/川东地区Key words
Longtan Formation/elemental geochemistry/sedimentary environment/sedimentary model/eastern Sichuan分类
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游水凤,柳汉丰,庞新龙,蔡娉婷,曹涛涛..川东地区龙潭组泥页岩地球化学特征及沉积环境[J].岩石矿物学杂志,2025,44(4):803-822,20.基金项目
国家自然科学基金项目(42472208) （42472208）
湖南省自然科学基金项目(2024JJ5145) （2024JJ5145）
江西省教育厅教改课题(JXJG-21-52-6) （JXJG-21-52-6）
湖南省自然资源厅科研项目(20230149DZ) National Natural Science Foundation of China(42472208) （20230149DZ）
Natural Science Foundation of Hunan Province(2024JJ5145) （2024JJ5145）
Education Reform Project of Jiangxi Provincial Department of Education(JXJG-21-52-6) （JXJG-21-52-6）
Research Project of Hunan Provincial Department of Natural Resources(20230149DZ) （20230149DZ）
