Zircon U-Pb Geochronology Of The Hinterland Central Dabie Eclogites

The hinterland of the central Dabie (HCD) has not been concerned by geologistsfor a long time, no any datum of metamorphic grade and age can not be available.In this study, the field investigation, petrological analysis, P-T estimates and ZirconU-Pb age for eclogites have been carried out in order to probe the components andmetamorphic age of the HCD. The study indicate that the HCD can be divided intoNiutuling and Malong terranes. The Niutuling terrane underwent high-pressuremetamorphism, three metamorphic mineral assemblages can be defined: theprograde metamorphism,the peak-metamorphism and retrograde-metamorphism,the peak P-T conditions are T=605±58oC and P=2.36±0.20GPa; However,Malongterrane underwent ultrahigh-pressure metamorphism, three metamorphic mineralassemblages can be defined as well, the peak P-T conditions are T=679±33oC andP=2.88±0.16GPa。Seven eclogitic samples has been chose for zircon U-Pb dating. Meanwhile, theRaman spectroscopy for inclusions in zircons have been finished, and its aim is todistinguish ages of metamorphic level. The ages from Niutuling terrane show twotypes of ages:(1)the age of peak metamorphism is235.2±4.2Ma confirmed bygarnet, rutile and omphacite；(2) the age of amphibolite-facies metamorphism is217.3±3.5Ma confirmed by amphibole and feldspar； Meanwhile,the ages fromMalong terrane show two of ages as well:(1)the age of peak metamorphism is226.4±2.6Ma confirmed by coesite；(2) the age of retrograde metamorphism is219.2±1.5Ma confirmed by garnet and rutile,.Combined with previous researches, we find that the age of peak metamorphismof Niutuling terrane is consistent with the age of peak metamorphism of southDabie terrane,while the age of peak metamorphism of Malong terrane is consistentwith the age of peak metamorphism of central Dabie terrane.Combined withpetrological analysis, P-T estimates and zircon U-Pb geochronology, Niutulingterrane should be belong to lower-temperature and high-pressure unit，similar to thesouth Dabie Terrane. However， Malong terrane should be belong to middle-temperature and ultralhigh-pressure unit， underwent UHP metamorphis mtogether wi th the central Dabie terrane.