Carbon and oxygen isotopic compositions of Tertiary and Permian dolomites in Japan

Abstract

Abstract-Carbon and oxygen isotope abundances were determined for dolomites and calcites in Tertiary (Ogi and Otobe) and Permian (Miyama and Kuzuu) dolostones in Japan. Isotopic ratios of calcites in some of Tertiary and Permian limestones in Japan were also determined for comparison. The isotopic ratios of Tertiary dolomites are extremely low in S 13C values, and depend on localities. Those of Permian dolomites are distributed in narrow ranges from 2 to 6 %o in S 13C PDB and from 23 to 30 %o in in 618 OSMOW. They do not seem to depend on their localities and their mineralogical and geological features.A considerable difference in isotopic ratios between Tertiary and Permian dolo mites suggests that Tertiary dolomites differ from Permian dolomites with respect to the origin. Tertiary dolomites might have been precipitated primarily from sea water in anaerobic environments, possibly owing to rise of PC02 by decarboxylation of organic materials. The isotopic ratios of Permian dolomites cannot be explained by the current theories on the origin of dolomite.

Isotopic studies of graphite in metamorphosed carbonate rocks of central Japan.

“…513C values of calcites are in a narrow range from -0.6 to +4.6%o, except for a few speci mens. These 513C values are close to those of Paleozoic limestones in Japan (OsAKI, 1973). S13C values of scaly graphites vary from -4.3 to +1.6%o, except for one sample (74111701D), and they are obviously lower than those of the coexisting calcites.…”

Carbon-isotope stratigraphy across the Permian–Triassic boundary: A review

“…Unusually high 13 C-enrichments in Permian carbonates were reported in the 1960s and 1970s (e.g., Compston, 1960;Osaki, 1973), marking the highest values of the Phanerozoic (Veizer et al, 1980). Wilgus (1981) proposed a global negative carbon-isotope trend across the P-T transition from her own data (western USA) and from compilation of literature (Compston, 1960;Osaki, 1973;Galimov et al, 1975;Kirkland and Evans, 1976;Veizer and Hoefs, 1976;Magaritz and Schulze, 1980;Veizer et al, 1980), and this was later confirmed by Clemmensen et al (1985), but only from a few data points in the E-Greenland successions. Chen et al (1984) presented the first detailed d 13 C trend for the P-T boundary section at Meishan (South China), the Global Stratotype Section and Point (GSSP) of the Permian-Triassic boundary, showing a decline in excess of 6‰ in the latest Permian, reaching the lowest values at À3‰.…”

Carbon and oxygen isotope studies of graphite bearing carbonates in the Kasuga area, Gifu prefecture, central Japan.

“…and calcite except for 73080406A,B and 73080407, which are nearest the granite contact, and Ka-02, which is farthest from the contact. 3C and 5180 of the dolomite component are distributed from +1.3 to +5.2%o with respect to PDB, and from +25.1 to +30.4°I°0 with respect to SMOW, respectively.The extent of these variations is usual in marble(SHIEH and TAYLOR, 1970) OSAKI (1973). reported carbon and oxygen isotopic compositions of dolomite from Miyama, Gifu Pref., where Permian dolostone and limestone are distributed.…”