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对华北板块东南缘蚌埠隆起区内凤阳县老山含石榴子石片麻状花岗岩进行了锆石SHRI MP U-Pb定年。阴极发光图像显示所研究样品中锆石通常具有核-幔-边结构。其中,核部年龄为新元古代(一个谐和年龄为673Ma±12Ma)、幔部年龄为三叠纪和具有岩浆结晶环带的边部年龄为159Ma±2Ma。锆石边部明显具有岩浆结晶环带以及高的Th/U比值(一般为0.14~0.45),其年龄代表该岩石的形成时代;幔部具有低的Th/U比值(一般为0.02~0.15),为变质成因;而核部常具有岩浆结晶环带,有时因重结晶等原因而模糊,其年龄应代表源区岩石的形成时代。由于继承锆石的形成时代为新元古代并经过印支期变质作用,这些年龄记录与大别山超高压岩石一致。因此,证明老山含石榴子石片麻状花岗岩为159Ma±2Ma,其为经历了三叠纪多期变质作用改造的华南俯冲陆壳物质发生部分熔融而形成即由华南三叠纪俯冲陆壳物质再循环的结果。而华北板块通东南缘深部存在华南俯冲陆壳岩石,进一步证实在中生代华南板块至少已俯冲至蚌埠地区。
Zircon SHRI MP U-Pb zircon dating was performed on Laoshan pluton-bearing gneissic granite in Fengyang County in the Bengbu uplift, southeast margin of North China Plate. Cathodoluminescence images show that the zircons in the studied samples generally have a core-mantle-edge structure. Among them, the age of the core is the Neoproterozoic (a harmonious age of 673Ma ± 12Ma), the age of the mantle is Triassic and the marginal age of the magmatic crystalline zone is 159Ma ± 2Ma. The zircon margin obviously has magmatic zoning and high Th / U ratio (usually 0.14-0.45), and its age represents the age of the rock formation. The mantle has a low Th / U ratio (usually 0.02-0.15) , Which is the genesis of metamorphism. However, the nuclei often have magmatic zoning, which is sometimes vague due to recrystallization and the age should represent the age of rock formation in the source area. Since the succession of zircon was formed in the Neoproterozoic and after the Indosinian metamorphism, these age records are consistent with the Dabie UHP rocks. Therefore, it is proved that the Laoshan pluton-bearing gneissic granite is 159Ma ± 2Ma, which was formed by the partial melting of the subducted continental crust in South China undergoing Triassic multi-stage metamorphism and formed by the Triassic subduction continental crust The result of material recycling. However, there are deep subducted continental crustal rocks in the southeastern margin of the North China block, further confirming that at least the Mesozoic South China Plate subducted at least to Bengbu.