大别山东南麓宿松群铷—锶年龄及其构造意义的探讨

本文根据对宿松群变质岩的宏观地质调查,结合室内岩石与矿物的镜下鉴定,测定全岩及单矿物Rb-Sr等时线年龄数据,认为该变质岩系曾经过二次变质与变形作用。第一次是加里东期褶皱及变质作用,形成绿帘角闪岩相,其时限为470～448Ma;第二次是印支期,表现为岩石片理化、塑性变形、推复构造及退变质作用,形成低绿片岩相,其时限为231～211Ma。

THE Rb-Sr AGES OF METAMORPHIC SERIES OF THE SUSONG GROUP AT THE SOUTHEASTERN FOOT OF THE DABIE MOUNTAINS,ANHUI PROVINCE,AND THEIR TECTONIC SIGNIFICANCE

Isotopic age determination on the Susong Group metamorphic rocks yields Rb-Sr whole-rock isochron ages of 448 Ma and 470 Ma,a Rb-Sr whole rock- mineral isochron age of 231 Ma and a phengite K-Ar age of 210 Ma. The results show that for the Susong Group folding and metamorphism occurred in the Caledonian movement and that compresso-shear took place in the Indosinian Cycle. The rocks exhibit well-developed schistosity and gravels in fractures are plastically deformed to assume a "S" shape,so the rocks appear to be both ductile and brittle. Petrological and isotope chronological studies show that the nappe structure of the Susong Group were formed during the Indosinian period.