Coherence of the Dabie Shan UHPM terrane investigated by Lu-Hf and 40Ar/39Ar dating of eclogites

The Central China Orogenic Belt (CCOB) is the largest known ultrahigh-pressure metamorphic (UHPM) belt. It extends from Sulu in Eastern China, via the Dabie, Qinling, and North Qaidam mountains to Altyn Tagh some 3000 km to the west. Since the discovery of coesite and diamond-bearing metamorphic rocks in Dabie Shan, the belt has been studied intensively. Some of the results have led to controversy regarding the number of (U)HP metamorphic events and their absolute and relative ages. The prominence of Dabie Shan as part of the largest UHPM belt is reflected by a wealth of published work since the discovery of coesite over 20 years ago. Despite two decades of efforts to decipher its geologic secrets, interpretation of the many reported isotopic ages of the Dabie Shan terrane that aimed to address its metamorphic history is still hampered by the absence of robust thermobarometric data for the same samples. Pre-Triassic metamorphism cannot be traced by Lu-Hf Grt-Cpx geochronology in the main volume of Dabie Shan, which was subjected to Triassic (U)HP metamorphism. The Triassic event erased previous signatures of some, but not all isotopic systems, as is evident from zircon U-Pb ages.