The peak metamorphic conditions of eclogites in the Taihu area of Dabie mountains and its implication for tectonics.

The Taihu area in the Dabie Mountains had been identified as the conjugate area between the 'cold' and 'hot' eclogites, we have carried on geological mapping in the Tailm area of the Dabie Mountains, and investigated on petrography characterists, variance of mineral composition, K-D-value and the peak metamorphic P-T conditions of the eclogites in detail. This study has shown that the eclogites in Taihu area can be divided into three types from south to north: 1 Zhujiachong-type eclogite; 2 Daba-type eclogtie; 3 Jinheqiao-type eclogite. An obvious gap of the peak metamorphic P-T conditions appears between the Zhujiachong and Jinheqiao-types, with the average values of P-T conditions of the Zhujiachong-type eclogite being P = 2.14GPa and T = 563degreesC, and that of the Jinheqiao-type eclogite being P = 3.76GPa and T = 791degreesC. The Daba-type eclogties are distributed around quartz/coesite phase transition in P-T conditions, which, tectonically, is equal to high-ultrahigh pressure transition belt. The Zhujiachong and Daba-type eclogties correspond to the 'cold' and 'hot' eclogites separately. They show a good continuity in the respect of the peak metamorphic conditions and no obvious pressure gap. Hence, we consider that the boundary line of the 'cold' and 'hot' eclogites does not exist.