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采用单颗粒锆石铅蒸发法及高精度离子探针对建平变质杂岩中的表壳岩磁铁石英岩进行了同位素年代学研究 .结果表明 :建平杂岩中磁铁石英岩形成年龄约 2 5 2 0～ 2 5 5 2Ma ;该区的麻粒岩相变质作用约于 2 487Ma达到高峰 ;约 ( 1 80 6± 1 6 )Ma ,即中元古代 ,本区又发生了一次变质事件 ,但其强度相对较弱 .推测建平变质杂岩可能形成于陆块形成后不久即发生大陆碰撞和地壳加厚的晚太古活动大陆边缘的环境中
The single-particle zircon lead evaporation method and high-precision ion probe were used to study the isotopic chronology of caseinite magnetite quartzite in Jianping metamorphic complex.The results show that the age of magnetite quartzite in Jianping Complex is about 2 5 2 0 ~ 2 5 5 2Ma. The granulite-facies metamorphism in this area peaked at about 2 487Ma; about 1880 ± 16 Ma, ie, a metamorphic event took place in this area during the Mesoproterozoic, But its intensity is relatively weak.It is presumed that the Jianping metamorphic complex may be formed in the environment of the Late Permian continent continental margin shortly after the formation of the continental block and the occurrence of the continental collision and thickening of the crust