地质科学2025，Vol.60Issue(4)：1075-1097,23.DOI:10.12017/dzkx.2025.070
四川盆地晚二叠世高Ti玄武岩成因:对峨眉山地幔柱深部活动规律的地质意义
Petrogenesis of Late Permian high-Ti basalts in the Sichuan Basin:Geological significance for deep Emeishan mantle plume activity
摘要
Abstract
The Emeishan Large Igneous Province(ELIP)is considered to be product of the Permian mantle plume activity,which is divided into three zones:the inner,intermediate and outer zones.Both high-Ti(TiO2＞2.5％,and Ti/Y＞500)and low-Ti(TiO2＜2.5％,and Ti/Y＜500)basalts are present in the ELIP.At present,the research on the basalts is mainly concentrated in the inner and intermediate zones,whereas studies of basalts in the outer zone are rare and the petrogenesis is controversial,which causes the lack of a comprehensive understanding of mantle plumes.The Sichuan Basin is located in the outer zone region,and the Permian volcanic rocks developed in the basin can provide the key constraints for indicating the outer zone magmatism process of the mantle plume.In this study,petrology,major and trace elements,Sr-Nd-Pb isotopes of Permian volcanic rocks from outcrops and drilled cores in the Sichuan Basin were tested and analyzed to clarify the magmatic origin and genetic mechanism of basalts in the Sichuan Basin.Based on the results of previous studies on the chronology and geochemistry of basalts in the inner and intermediate zones,regional variations of high-Ti basalts in the whole ELIP area are discussed.The results show that the basalts in Sichuan Basin are high-Ti alkaline basalts with TiO2 contents ranging from 3.79％to 4.42％and Ti/Y ratio ranging from 603.93 to 751.33,with EMII-like OIB characteristics.The high-Ti basalts have not experienced obvious crustal mixing,have a high degree of partial melting,and the fractional crystallization is dominated by clinopyroxene,which originated from the Emeishan mantle plume modified by the subducted materials of the Paleotethys Ocean.The formation time of high-Ti basalts in Sichuan Basin is consistent with that of ELIP.The basalts in the basin are part of the outer zone of the large igneous province.From the inner zone to the outer zone in the ELIP,high-Ti basalts exhibit thinning in thickness,the melting degree of magma source increases,the melting pressure decreases,the melting depth decreases,and the melting ratio of garnet phase decreases.Comprehensive studies show that the Emeishan mantle plume underplated the lithosphere in the Middle to Late Permian.In the inner zone with high temperature,continental lithosphere mantle first melted and formed the low-Ti basalts.Subsequently,the Emeishan mantle plume was decompressed and melted,and the overflow high-Ti basalts were formed and widely distributed in ELIP area.关键词
峨眉山大火成岩省/四川盆地/二叠纪高Ti玄武岩/地幔柱/玄武岩成因Key words
Emeishan Large Igneous Province/Sichuan Basin/Permian high-Ti basalts/Mantle plume/Basalt petrogenesis分类
天文与地球科学引用本文复制引用
王尉,彭思桥,田雨露,秦丽媛,孟凡超,陈骁,张玺华,刘冉,李亚,白晓亮..四川盆地晚二叠世高Ti玄武岩成因:对峨眉山地幔柱深部活动规律的地质意义[J].地质科学,2025,60(4):1075-1097,23.基金项目
国家自然科学基金面上项目(编号:42272225)、山东省自然科学基金面上项目(编号:ZR2021MD083)和崂山实验室科技创新项目(编号:LSKJ202203401)资助 （编号:42272225）
