地质学报2025，Vol.99Issue(4)：1120-1133,中插1-中插4,18.DOI:10.19762/j.cnki.dizhixuebao.2023193
滇中盆地石炭纪—中二叠世沉积-古地理特征与富Li黏土岩物源分析
Carboniferous-Middle Permian sedimentary-paleogeographic environment and source of the lithium-rich claystones in the Central Yunnan basin,SW China
摘要
Abstract
The Carboniferous-Middle Permian sedimentary sequences of the Central Yunnan basin,SW China,are rich in bauxite,coal,calcite,limestone,and other types of ore deposits associated with numerous lithium-rich claystones.Understanding the genesis of these ore deposits necessitates a comprehensive analysis of the spatial-temporal evolution of the sedimentary environments and the basin's paleogeography.Systematic field investigations demonstrate that Carboniferous sedimentation in the Central Yunnan basin was dominated by terrigenous clastic and carbonate rocks deposited in a littoral tidal flat-lagoon environment.In contrast,the Lower-Middle Permian sedimentary rocks were mainly deposited in a lagoon-tidal flat-open platform environment.The Lower Carboniferous Datang Formation is characterized by carbonates with muddy shale interlayers,indicating deposition in a tidal flat environment.Lagoon deposition was restricted to areas adjacent to the Niushoushan paleo-uplift.The Middle Carboniferous Weining and Maping formations represent littoral-tidal flat deposits,sporadically exposed around this uplift.The Lower Permian Daoshitou Formation,composed of fine-grained terrigenous clastic rocks with minor limestone lenses,reflects deposition in a tidal flat-lagoon setting.This formation is particularly significant as it hosts the bauxite,coal ore deposits,and lithium-rich claystones.The Middle Permian Qixia and Maokou formations consist of algal clastic limestone,dolomitic leucoblastic bioclastic limestone,and medium-to coarse-grained dolomite,indicating an open-platform depositional environment.A distinct spatial pattern is observed in the thickness of the Datang and Daoshitou formations,with a pronounced thinning trend towards the south.This,coupled with a decrease in the number of coal and bauxite layers southward,suggests a gradual shallowing of seawater depth towards the south,bringing the deposits closer to their source area.Conversely,the Qixia and Maokou formations exhibit a widespread exposure in the north,with their thickness increasing northward.This observation is consistent with the SE-high and NW-low paleogeography of the Central Yunnan basin during the Early-Middle Permian,as evidenced by paleocurrent data.The Niushoushan paleo-uplift,a major source region of the Daoshitou Formation,played a pivotal role in shaping this paleogeographic setting.Geochemical data demonstrate that the Daoshitou Formation is rich in aluminum-and lithium-rich claystones.The concentrations of lithium and bauxite ore(Al2O3)are controlled by weathering processes in the source areas and sedimentary conditions.When Al2O3 content is less than 55％and the Al2O3/SiO2 ratio is less than 3,a positive correlation between lithium content and Al2O3 content is observed.This relationship becomes negative for other variation intervals.Regional geological data analysis demonstrates that the Niushoushan paleo-uplift mainly comprises Precambrian intermediate-mafic volcanic and sedimentary rocks.During the Early-Middle Permian,this region experienced a warm and humid environment.The continuous opening of the Paleo-Tethys during the Early Carboniferous to Middle Permian resulted in regional uplifting and erosion of the Paleo-uplift,exposing Precambrian volcanic rocks and related sedimentary rocks,leading to widespread volcanism.These eroded detritus and volcanic eruptions adjacent to the Niushoushan paleo-uplift are the important sources for the formation of bauxite ore deposits and lithium-rich claystones in the Central Yunnan basin.关键词
石炭纪—中二叠世/沉积-古地理环境/物源分析/富Li黏土岩/牛首山古陆/滇中盆地Key words
Carboniferous-Middle Permian/sedimentary and paleogeographic environment/provenance tracking/lithium-rich claystones/Niushoushan paleo-uplift/Central Yunnan basin引用本文复制引用
张佳慧,闫臻,薛传东,俞良军,魏爱英,付长垒,王维,王宇,周红琳..滇中盆地石炭纪—中二叠世沉积-古地理特征与富Li黏土岩物源分析[J].地质学报,2025,99(4):1120-1133,中插1-中插4,18.基金项目
本文为国家重点研发计划课题(编号2021YFC2901901,2022YFC2903401)和国家自然科学基金项目(编号41922022,42163007,41373049)联合资助的成果. （编号2021YFC2901901,2022YFC2903401）
