沉积学报2025，Vol.43Issue(4)：1293-1307,15.DOI:10.14027/j.issn.1000-0550.2024.095
黔西北下三叠统碎屑岩对峨眉山大火成岩省的响应
Response of the Lower Triassic Clastic Rocks in Northwestern Guizhou to the Emeishan Large Igneous Province
摘要
Abstract
[Objective]The Emeishan large igneous province(ELIP),located in southwest China,experienced ex-tensive post-eruption erosion resulting in the accumulation of voluminous volcanic detritus in the adjacent Youjiang Basin during the Late Permian to Early Triassic.These clastic sediments not only record the types and composition characteristics of the denuded volcanic rocks at the top of the ELIP,but also reveal the possible magmatic evolution trend of the denuded volcanic sequence in the ELIP.Therefore,the Lower Triassic clastic rocks in northwest Guizhou are of great significance for the systematic understanding of the denudation sequence and magmatic evolution.[Methods]To further clarify the Early Triassic erosion evolution,we analyzed the provenance of the Lower Triassic Feixianguan Formation in the Weining area,southwestern Guizhou province,and discussed the erosion and magmat-ic process in the late stage of the ELIP.[Results]The mudstones of the Feixianguan Formation are composed of quartz,feldspar,calcite,volcanic lithic fragments,and clay minerals.The structures of volcanic lithic fragments in-dicate a basaltic and felsic volcanic source.The mudstones have high ICV(the Index of Compositional Variability)values,which reflects that the clastic rocks of the Fexianguan Formation in Weining area are derived from the first cy-clic clastic rocks.The mudstone,which of Al2O3/TiO2 ratio are slightly higher than the high-Ti basalt of the ELIP,is characterized by high Fe2O3 and MgO contents.It indicates a dominant source from the Emeishan high-Ti basalt.Detrital zircons from the Fexianguan Formation have an age peak of ca.260 Ma,which support the ELIP as the main provenance.This is consistent with the provenance of the Late Permian clastic sediments in the Youjiang Basin.Compared with the underlying Longtan Formation in the Upper Permian,the Lower Triassic Fexianguan Formation in Weining area,of which～260 Ma zircons have higher Th/Nb and U/Yb ratios,have more zircons with ages of>300 Ma.Such features show a systematic variation in sedimentary sequence.[Conclusions]In the source-sink sedimentary system composed of the Youjiang Basin and ELIP,the zircon geochemical characteristics of detrital sedi-ments preserved in the Late Permian and Early Triassic Induan likely represent the inherent characteristics of the denuded volcanic sequence.Such zircon geochemical characteristics reflect a magmatic evolution process with dimi-nishing crustal assimilation in the late-stage of the ELIP.关键词
贵州/早三叠世/物源分析/峨眉山大火成岩省/岩浆演化Key words
Guizhou/Early Triassic/provenance analysis/Emeishan large igneous province/magma evolution分类
天文与地球科学引用本文复制引用
邓旭升,杨江海,何犇,聂波..黔西北下三叠统碎屑岩对峨眉山大火成岩省的响应[J].沉积学报,2025,43(4):1293-1307,15.基金项目
黔地矿科合(2020-31) （2020-31）
国家自然科学基金项目(42122015)The Research Project of Guizhou Bureau of Geology and Mineral Exploration and Development,No.2020-31 （42122015）
National Natural Science Foundation of China,No.42122015 （）
