峨眉山玄武岩与茅口组灰岩的接触关系：对峨眉山地幔柱动力学模型的指示意义  

Contact Between the Emeishan Basalt and Maokou Formation:Implication for the Geodynamic Model of the Emeishan Mantle Plume

作　　者：李宏博[1,2] 朱江[1] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [2]中国地质博物馆,北京100034

出　　处：《大地构造与成矿学》2013年第4期571-579,共9页Geotectonica et Metallogenia

基　　金：国家自然科学基金(批准号:40925006);中国地质大学(北京)地质过程与矿产资源国家重点实验室开放课题基金项目(编号:GPMR2011)联合资助

摘　　要：本文较为系统地整理、归纳了峨眉山大火成岩省(Emeishan large igneous province,ELIP)的区域地质调查资料,证实了峨眉山玄武岩与茅口组灰岩之间广泛发育平行不整合(喷发不整合)接触界面,说明总体上两者之间并非断层接触关系。峨眉山玄武岩与茅口组灰岩的平行不整合接触关系是由于峨眉山地幔柱作用导致地壳大幅抬升成陆,茅口组灰岩顶部遭受剥蚀后被溢流玄武岩所覆盖的结果。不整合界面上普遍发育的角砾状灰岩、底砾岩、红土(古土壤)层、黏土岩等就是这一地质事实的遗迹。隆升之后的快速沉降以及地幔柱与岩石圈作用的复杂性,可能在局部地区存在海相沉积和连续的生物地层的现象,但不足以否定峨眉山玄武岩喷发前地壳曾经整体抬升。因此,峨眉山玄武岩与茅口组灰岩之间的平行不整合接触关系支持了峨眉山地幔柱动力学模型。It is still controversial about the lithospheric uplift prior to the Emeishan mantle plume, among which the key issue is the contact relationship between the Emeishan basalt and the underlying Maokou Formation. Therefore, it is crucial to re-examine the contact relationship. Based on the data of regional geological survey in the Emeishan large igneous province （ELIP）, the contact between the Emeishan basalt and the Maokou Formation is unconformity （eruption unconformities）, rather than faulted contacts. There are brecciola, basal conglomerate, paleosol, clay in the boundary, which resulted from the geological events in the end of the Late Permian. All these suggest that the Maokou Formation may have been uplifted over the sea level by the Emeishan mantle plume and then denudated differentially. Hydromagmatic deposits, submarine basaltic extrusions and local preservation of complete biostratigraphic zone can be attributed to the rapid subsidence followed the plume-induced domal uplift, as well as the complexity of plume-crust interaction. Therefore, the unconformity between the Emeishan basalts and the Maokou Formation is confirmed, which provides evidence for the geodynamic model of the Emeishan mantle plume.

关 键 词：峨眉山大火成岩省 峨眉山玄武岩 茅口组灰岩 接触关系 地幔柱 地壳抬升 

分 类 号：P542[天文地球—构造地质学]