The architecture of the HP-UHP Dabie massif: New insights from geothermobarometry of eclogites, and implication for the continental exhumation processes

摘要

The establishment of a refined architecture of the South Dabie Domain, which covers more than 90% eclogites in Dabie Massif, is a key to understand the subduction and exhumation processes of high-pressure (HP) and ultra-high-pressure (UHP) rocks. According to field and laboratory works, a large area of HP rocks has been recognized in the central and western part of South Dabie Domain, which was previously considered to be part of the entire UHP unit. Petrological analysis, the determination of the peak P-T conditions for all the eclogites of the South Dabie Domain has been carried out. Three litho-tectonic slices, Units-Ⅰ, Units-Ⅱ and Units-Ⅲ have been defined. The spatial distribution of eclogites throughout the South Dabie Domain allows us to construct a structural-temperature-pressure profile, in which the three temperature and pressure units are well correlated to three lithological-tectonic units. Along this profile, two pressure gaps separate these three units with 0.69 and 0.78 GPa in average, respectively. Compared to the previous work in which the South Dabie Domain has a N-S gradual P-T trend, an abrupt P-T variation observed in the Huanggang-Niutuling area in the central region, and in the Malong-Shima area in the south-eastern part of the South Dabie Domain have been identified. Based on the petrological investigation and structural analysis, a Huanggang klippe with HP metamorphism, and the Malong tectonic window with UHP metamorphism have been revealed in the South Dabie Domain in detail. With these contributions, we suggested that the present P-T pattern in the South Dabie Domain was resulted from the subduction and exhumation of several lithological-tectonic slices in Triassic. The Cretaceous exhumation and succedent uplift of a migmatite dome are the possible cause for the present architecture of the South Dabie Domain.