R8: Metamorphic rocks and tectonics

[R8-03] Excess Argon behavior in Dora Maila

*Tetsumaru Itaya¹, Hironobu Hyodo², Takeshi Imayama² (1. HIGC, 2. IFST, Okayama Univ. of Sci.)

Keywords:Dora-Maira, UHP unit, Excess argon behavior,, Muscovite & K-feldspar Ar-Ar ages

Biotites in the undeformed meta-granites from UHP unit of Dora-Maira record “Excess Argon Wave” (EAW) derived from the deformed white micas in the eclogite and the blueschist units during the exhumation. White micas and K-feldspar in the granite give 70~150 Ma and 20~50 Ma of Ar-Ar age fractions, respectively. These data suggest that white micas, biotites and K-feldspar have trapped successively the EAW during the exhumation of the UHP unit. We will propose a model of the EAW behavior.