Abstract

The Dabie Mountains represent a fault-bounded, coesite-bearing eclogite gneissic terrane within the collisional belt between the Sino-Korean and Yangtze cratons. The following geologic evidence indicates that this terrane has been subjected to regional ultrahigh-pressure metamorphism. (1) The country rocks have a metamorphic pressure-temperature evolution compatible with that of the eclogites, on the basis of the occurrence of quartz pseudomorphs after coesite, calcite pseudomorphs after aragonite, relict high-pressure assemblages in different rock types of the country rocks, and consistent, comparable compositional zonations of garnets in both country rocks and eclogites. (2) Peak metamorphic pressure-temperature conditions consistently decrease both from east to west in the collisional belt and from north to south in the Dabie Mountains, and clockwise pressure-temperature paths are common for eclogites over the region. (3) Layered eclogites interbedded with gneisses and amphibolites contain omphacite, kyanite, and garnet, indicating a minimum pressure of 20 kbar at 600 °C for formation of these rocks.

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