First elastic pressure constraints on an eclogitic diamond from the Mengyin kimberlite: evidence for deep subduction beneath the eastern North China Craton

Eclogitic minerals enclosed in diamonds from Paleozoic kimberlites provide the only direct record of ancient subducted material beneath the eastern North China Craton (NCC). However, the scarcity of suitable mineral pairs has long prevented robust pressure estimates, leaving the entrapment conditions of these diamonds poorly constrained. Here, we apply coesite-in-diamond elastic barometry to a primary eclogitic diamond (SD-234) from the Mengyin kimberlite. The method does not require coexisting minerals and is therefore well suited to inclusion-poor eclogitic diamonds. Coesite inclusions in SD-234 yield entrapment pressures of up to 5.9 ± 0.1 GPa at 1210–1260 °C, corresponding to a depth of ∼183 km. The entrapment depth lies well within the Paleozoic NCC lithospheric root and overlaps the deeper levels sampled by peridotitic diamonds and mantle xenoliths, indicating that subduction-related crustal material reached cratonic-root depths. This is the first direct elastic pressure constraint on eclogitic diamond from the Paleozoic kimberlites of the eastern NCC. This finding provides new insight into the deep-subduction processes that preceded lithospheric destruction beneath the NCC and demonstrates the broader potential of elastic barometry for reconstructing deep subduction histories in diamond suites worldwide.