Magnetic Structure of the Dengfeng-Lushan Crustal Cross-Section,Henan

摘要

Magnetic parameters for rocks from a crustal cross-section exposed in the Dengfeng-Lushan area,Henan Province are systematically determined.The results,along with their mineralogy,chemical composition,density and P-wave velocity,indicate that there is a general increase in susceptibilityK,natural remanent magnetization J.and saturation isothermal remanence Jr with increasing metamorphicgrade （apparent crustal depth） from the Early Proterozoic Angou Group （greenschist facies） through theLate Archean Dengfeng Group （amphibolite facies） to the Taihua Group （high-amphibolite to granulitefacies）.Metasedimentary rocks of the Angou and Dengfeng Groups show a clear paramagnetic nature,whileother rock types are dominantly ferrimagnetism.The Taihua Group reflects the magnetic distribution of thelower crust of the cross-section and has average K,Jn and Jr values of 6680×10-6 SI,0.166 A/m and 71.78A/m,respectively,which are in good agreement with those of other exposed high-grade metamorphic ter-rains in the world.