3D model of Svecofennian Accretionary Orogen and Karelia Craton based on geology,reflection seismics,magnetotellurics and density modelling:Geodynamic speculations  

作　　者：Michael V.Mints Victor N.Glaznev Olga M.Muravina Elena Yu Sokolova 

机构地区：[1]Geological Institute,RAS,Moscow,Russia [2]Voronezh State University,Voronezh,Russia [3]Schmidt Institute of Physics of the Earth,RAS,Moscow,Russia [4]All-Russian Research Geological Oil Institute,Moscow,Russia

出　　处：《Geoscience Frontiers》2020年第3期999-1023,共25页地学前缘（英文版）

基　　金：the RF state project(No.0135-2019-0036);partly supported by the project(No.0135-20180039)of the Program of the Presidium of the RAS“Fundamental problems of geological and geophysical study of lithospheric processes”;the Russian Foundation for Basic Research for supporting project(No.19-05-00336)。

摘　　要：A 3D model of deep crustal structure of the Archaean Karelia Craton and late Palaeoproterozoic Svecofennian Accretionary Orogen including the boundary zone is presented.The model is based on the combination of data from geological mapping and reflection seismic studies,along profiles 1-EU,4 B,FIRE-1-2 a-2 and FIRE-3-3 a,and uses results of magnetotelluric soundings in southern Finland and northern Karelia.A seismogeological model of the crust and crust-mantle boundary is compared with a model of subhorizontal velocity-density layering of the crust.The TTG-type crust of the Palaeoarchaean and Mesoarchaean microcontinents within the Karelia Craton and the Belomorian Province are separated by gently dipping greenstone belts,at least some of which are palaeosutures.The structure of the crust was determined mainly by Palaeoproterozoic tectonism in the intracontinental settings modified by a strong collisional compression at the end of the Palaeoproterozoic.New insights into structure,origin and evolution of the Svecofennian Orogen are provided.The accretionary complex is characterized by inclined tectonic layering:the tectonic sheets,~15 km thick,are composed of volcanic-sedimentary rocks,including electro-conductive graphite-bearing sedimentary rocks,and electro-resistive granitoids,which plunge monotonously and consecutively eastward.Upon reaching the level of the lower crust,the tectonic sheets of the accretionary complex lose their distinct outlines.In the seismic reflection pattern they are replaced by a uniform acoustically translucent medium,where separate sheets can only be traced fragmentarily.The crust-mantle boundary bears a diffuse character:the transition from crust to mantle is recorded by the disappearance of the vaguely drawn boundaries of the tectonic sheets and in the gradual transition of acoustically homogeneous and translucent lower crust into transparent mantle.Under the effect of endogenic heat flow,the accretionary complex underwent high-temperature metamorphism and partial melting.Blurring of

关 键 词：Reflection SEISMICS MAGNETOTELLURICS SVECOFENNIAN ACCRETIONARY Orogen SVECOFENNIAN Ocean 3D crustal model Velocity-density layering 

分 类 号：P542[天文地球—构造地质学] P631[天文地球—地质学]