摘要
Hydrogen and oxygen isotope studies were carried out on mineral separates from high to ultrahigh pressure metamorphic rocks at Huangzhen and Shuanghe in the eastern Dabie Mountains, East China. The δ18O values of eclogites cover a wide range of ?5‰ to+9‰, but the δD values of micas fall within a narrow range of ?85% to ?70‰. Both equilibrium and disequilibrium oxygen isotope fractionations were observed between quartz and the other minerals, with reversed fractionations between omphacite and garnet in some eclogite samples. The δ18 O values of ?5‰ to ?1‰ for some of the eclogites represent the oxygen isotope compositions of their protoliths which underwent meteoric water-rock interaction prior to plate subduction. The preservation of oxygen isotope heterogeneity in the eclogites implies a channelized flow of fluids during progressive metamorphism caused by rapid subduction. Retrograde metamorphism has caused oxygen and hydrogen isotope disequilibria between some of the minerals, but the fluid for retrograde reactions was internally buffered in the stable isotope compositions.
Hydrogen and oxygen isotope studies were carried out on mineral separates from high to ultrahigh pressure metamorphic rocks at Huangzhen and Shuanghe in the eastern Dabie Mountains, East China. The δ <sup>18</sup>O values of eelogites cover a wide range of-5‰ to+9‰, but the δD values of micas fall within a narrow range of -85‰ to -70‰. Both equilibrium and disequilibrium oxygen isotope fractionations were observed between quartz and the other minerals, with reversed fractionations between omphacite and garnet in some eclogite samples. The δ <sup>18</sup>O values of -5‰ to -1‰ for some of the eclogites represent the oxygen isotope compositions of their protoliths which underwent meteoric water-rock interaction prior to plate subduction. The preservation of oxygen isotope heterogeneity in the eclogites implies a channelized flow of fluids during progressive metamorphism caused by rapid subduetion. Retrograde metamorphism has caused oxygen and hydrogen isotope disequilibria between some of the minerals, but the
基金
Project supported by the Chinese Ministry of Science and Technology (Grant No. 95-Pre-39)
the National Natural Science Foundation of China (Grant Nos. 49794042, 49473173 and 49453003)
the Chinese Academy of Sciences (Grant No. KZ951-A1-401-5).
