大别山南部宿松杂岩的U-Pb锆石和Ar-Ar角闪石年龄及其地质意义

U-Pb zircon and Ar-Ar hornblende ages of the Susong complex of the southern Dabie orogen and their geological implication.

大别造山带南部宿松杂岩中花岗片麻岩和斜长角闪岩的U-Pb锆石年龄和Ar/Ar角闪石年龄测定结果表明,二长花岗片麻岩的形成年龄为2018±73Ma和2010±38Ma,白云斜长片麻岩的形成年龄为741±7Ma,宿松杂岩经过228Ma左右的变质作用。这些结果表明大别山南缘存在较大规模的古元古代花岗质结晶基底,广泛分布在宿松杂岩中的花岗片麻岩和由花岗片麻岩强烈剪切变形而成的白云斜长片麻岩、白云钠长石英片岩形成于新元古代,不整合覆于二长花岗片麻岩之上并被新元古代花岗片麻岩侵入的变质沉积岩形成于中元古代晚期-新元古代早期。由此得出,宿松杂岩主要由古元古代二长花岗片麻岩、中新元古代变质沉积岩和新元古代变质花岗岩和变质基性岩组成,因而也是扬子板块的俯冲陆壳基底的一部分。

U-Pb zircon and hornblede Ar-Ar ages of granitic gneiss and amphibolite from the Susong Complex of the southern Dabie Orogen constrain the protolith of the monzogneiss at 2018 +/- 73 Ma [Sic] 2010 +/- 38 Ma, the protolith of the muscovite plagioclase gneiss was formed at 741 +/- 7 Ma, and metamorphism of the Susong Complex around 228 Ma. These results indicate that the Paleoproterozoic granitic crystalline basement is distrubuted over a large area in the southern margin of the Dabie Mountains. The granitic gneiss, muscovite plagioclase gneiss and muscovite-plagioclase quartz schist formed by strongly shearing from the granitic gneiss broadly distributed in the Susong Complex were formed in Neoproterozoic, while the meta-sedimentary rocks, unconformity above the monzogneiss and intruded by the Neoproterozoic granitic gneiss, were formed in Meso-Neoproterozoic. It is concluded that the Susong Complex is composed of the Paleoproterozoic monzogneiss, the Meso-Neoproterozoic meta-sendimentary rocks, and the Neoproterozoic granitic gneiss and meta-basic rocks, therefore, it was a part of the subducted basement of the Yangtze block.