Two-stage exhumation of deeply subducted continental crust: Insight from zircon, titanite, and apatite petrochronology, Sulu belt of eastern China

Abstract The rates and mechanisms by which deeply subducted continental crust was exhumed back to the surface are not well understood, but can be better characterized using multimineral petrochronology. Here, we combine zircon, titanite, apatite U-Pb ages from leucogranite phengite gneiss with a pressure–temperature (P–T) path eclogite provide robust quantitative constraints on cooling exhumation of Sulu belt, large ultrahigh-pressure metamorphic terrane in eastern China. leucogranite, formed during exhumation, is enriched light rare earth elements (REE) relative heavy REE ion lithophile high field strength elements, similar hydrous crustal melts. Whole-rock Sr-Nd isotope compositions indicate that directly derived host gneiss, more likely sourced deeper exhuming crust. For mantles inherited zircon yield an age 230 ± 2 Ma temperature 802 36 °C based minimum pressure 2.9 GPa, records timing P–T initial decompression. Overgrowths constrain crystallization 224 1 Ma, coeval growth rims at 764 42 within quartzeclogite facies. Titanite define single populations lower concordia intercept 222 3 198 7 temperatures 720 30 ∼450 100 °C, respectively, recording passage through quartz-eclogite amphibolite facies then transition upper greenschist Although data nearly constant rate 10.9−3.6+4.5 °C/m.y., completed two stages. first stage coesiteeclogite ∼1.2 corresponding depth Moho, occurred 7.5−2.6+5.8 km/m.y. Thereafter, into mid-crust much slower 0.87−0.71+0.86 faster accompanied migration melt along foliation would have decreased average density weakened crust, enhancing return flow.