摘要
黄土岭一带的北大别杂岩发育4类浅色体。其中的第二类浅色体发育在黑云母片麻岩中,为二长花岗质;第三类浅色体发育在长英质麻粒岩的基质中,为钾长花岗质,并与石榴石变斑晶分解有关的含紫苏辉石后成合晶同期。LA-ICPMS测定表明,第二类浅色体中熔体结晶锆石的上下交点年龄分别为:2040±14Ma和242±27Ma;第三类浅色体变质锆石的上下交点年龄分别为:2056+35/-26Ma和244+180/-210Ma。这表明,第二类浅色体和第一类浅色体都是古元古代麻粒岩相变质作用同期深熔产物。古元古代熔体结晶和变质结晶锆石在三叠纪发生了严重的放射性成因铅丢失,可反映长英质麻粒岩和黑云母片麻岩都响应了三叠纪深俯冲事件。
Four types of leucosomes are recognized for the North Dabie complex in Huangtuling area, of which the second type leucosome is adamellitic in the biotite gneisses, and the third type of alkali-feldspar granitic composition developes synchronously with the hypersthene-bearing corona around garnet porphyroblasts in the felsic granulite. LA-ICPMS U-Pb dating yielded upper and lower intercepted ages of 2 040 ± 14 Ma and 242 ±27 Ma for melt-crystallized zircons from the second type leucosome, and 2 056 ±35/-26 Ma and 244 ± 180/-210 Ma for metamorphic zircons from the third type. These results indicate that both the second type leucosome in the biotite gneisses and the first type leucosome were produced synchronously in the Paleoproterozoic granulite-facies metamorphism, and that both the melt-derived and the metamorphic Paleoproterozoic zircons suffered significant lead-loss in the Triaasic, suggesting that both felsic granulite and biotite gneisses be responses to the Triassic deep subduction event.
出处
《高校地质学报》
CAS
CSCD
北大核心
2007年第3期574-580,共7页
Geological Journal of China Universities
基金
国家自然科学基金项目(40272030)
教育部博士学科点基金项目
西北大学大陆动力学国家重点实验室开放基金项目
