Oxygen and carbon isotope composition from the UHP Shuanghe marbles, Dabie Mountains, China

<正> Investigations on the oxygen and carbon isotope compositions from the ultrahigh-pressure （UHP）-metamorphosed Shuanghe marbles, that occur as a member of a UHP slab, show that the δ18O values range from +11.1‰ to+20.5‰ SMOW, and δ13C from+1.0‰ to+5.7‰ PDB, respectively. The variations in isotope compositions show a centimeter scale of homogeneity and a heterogeneity of regional scale larger than 1 meter. In contrast to the eclogite marbles from Norway, the Shuanghe marbles have inherited the carbon isotope compositions from their sedimentary precursor. The δ13C shows positive correlation to the content of dolomite. The depletion in 18O, compared with the protolithic carbonate strata, might result from three possible geological processes: 1) exchanging oxygen isotope with meteoric water before the UHP metamorphism, 2) decarbonation during the UHP metamorphism, and 3) exchanging oxygen isotope with country gneiss at local scale during retrograde metamorphism. It seems that the adveetion