U-Pb zircon dating of the glaucophane eclogites from the Southern Dabie Mountains, North Hubei Province

Abstract

Using the single zircon U-Pb technique, two typical glaucophane eclogites which provide the age information of HP/LT (high pressure/low ternperature) metamorphism and their archean protolith have been geochronologically investigated, sampling at Gaojiao, Hangan County, and at Chenjiahe, Machen Countv. north Hubei Province. .. The zircons extracted from the two glaucophane eclogites are similar, being light yellow-colourless with shapes ranging from oval to prismatic. 7 analyses of the Gaojiao eclogite and 5 analyses of the Chenjiahe eclogite give the lower intercept ages of 1138 f 39, 1127 + 234Na and upper intercepts of 2872 + 40, 2674 + 249Ma, MSWD= 1.5 , and 3'. 7, respectively. No correlaction between the U-Pb ages and morphology of zircons was observed. The data -points on the concordia diagrams. Close to the lower intercepts of the two eclogites are. We interpret the lower interceptioxi ages as the time of the HP/LT metamorphism and the upper interception ages of 2647-2827 reflecting the archean protolith of there eclogites . The present work confirms the occurrence af later mesoprotozoic HP/LT metamorphism in the Southern Dabie Orogen. We conclude a multistage history of high pressure metamorphism in the Dabie Mountians, comparing to the Caledonian HP-UHP eclogites of the central area and the Indosian eclogites which associated with ultramafic rocks in the north Dabie terrane.