饶河杂岩中枕状玄武岩的锆石U-Pb年代学、地球化学及其地质意义

    ZIRCON U-Pb CHRONOLOGY AND GEOCHEMISTRY OF THE PILLOW BASALTS FROM RAOHE COMPLEX: Geological Implications

    • 摘要: 那丹哈达增生杂岩为中国东部古太平洋板块俯冲最为可靠的地质记录之一,对限定古大洋板块的西向俯冲具有重要的理论意义.饶河杂岩位于那丹哈达增生杂岩的核心位置,发育典型的增生杂岩组合,其中玄武岩类多呈构造透镜体状产出于超镁铁质-镁铁质杂岩带,变形轻微,没有遭受变质.对饶河杂岩中枕状玄武岩样品进行的同位素年代学和地球化学研究结果表明:饶河杂岩中枕状玄武岩锆石LA-ICP-MS U-Pb年龄为中侏罗世(168±2 Ma),枕状玄武岩大离子亲石元素Rb、Sr亏损,高场强元素Nb、Ta富集,Th元素丰度较高,形成于洋岛(OIB型)环境.饶河杂岩中枕状玄武岩的形成时代和成因环境,对于该区侏罗纪时期构造动力学背景研究具有意义.

       

      Abstract: As one of the most reliable geological records of paleo-Pacific Plate subduction in eastern China, the Nadanhada accretionary complex is of great importance to define the westward subduction of paleo-oceanic plate. The Raohe Complex is located in the core of the complex, developed with typical accretionary complex association, among which the basaltoids, mostly in structural lenticles, are occurred in the ultramafic-mafic complex zone with slight deformation but no metamorphism. Study on the isotopic chronology and geochemistry of the pillow basalt samples from Raohe Complex shows that the LA-ICP-MS zircon U-Pb age is Middle Jurassic(168±2 Ma), with depletion of LILEs (Rb and Sr), enrichment of HFSEs(Nb and Ta) and high-abundant Th, which was formed in the ocean island environment (OIB). Its formation age and genetic environment is significant to study the tectonic dynamic background of the area during the Jurassic period.

       

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