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LA-ICPMS U-Pb Dating of Zircons from Two Types of Leucosomes in North Dabie Unit: Evidences for Paleoproterozoic Anatexis and Triassic Subduction?

GONG Song-lin1, CHEN Neng-song1, LI Xiao-yan1, LIU Xiao-ming2   

  1. 1. Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China;2. State Key-Lab of Continental Geodynamic, Northwest University, Xi , an 710069, China
  • Received:2007-09-20 Revised:2007-09-20 Online:2007-09-20 Published:2007-09-20

Abstract: 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.