Mo isotope, one of highly redox-sensitive isotopes, has been shown to be useful tracers of geochemical processes. Many studies for Mo isotope have documented with the help of recently developed analysis tools, but it has not yet been documented in the Korea. In this study, we introduce two-stage column separation method of Mo using column tube (BioRad PolyPrepR column, 10 ml) and anion exchange resin (BioRad Resin AGR 1-X8, 200− 400 mesh). Mo isotope ratios in the solid SRMs (BHVO-2, SDO-1, PACS-2) and liquid SRM (IAPSO) were measured on MC-ICP-MS (Multi-collector Inductively Coupled Plasma Mass Spectrometer) and then compared with reference Mo isotope ratios. Mo isotope ratios in our study overlap with reference Mo isotope ratios within analytical error.

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The Grosmont Formation is a massive, organic-rich carbonate deposit that subdivides into upper (UG) and lower (LG) units. Geochemical analyses of Grosmont carbonate rocks collected from wells 10-12-93-24W4 and 11-33-94-22W4 allowed us to differentiate the depositional and diagenetic conditions for these two units. The UG unit subdivides into three subunits (UG1-UG3) and consists of fine-to coarse-crystalline and subhedral dolomite. The LG unit consists of dolomitic limestone and calcareous dolostone with medium-to coarse-crystalline, euhedral to subhedral dolomite and calcite. These units also include small amounts of quartz, illite, pyrite, K-feldspar and other trace minerals. Petrographic and geochemical analyses indicate that the LG unit formed under influence of clastic sediment input. Isotopic ratios for UG dolomites suggest precipitation within a near surface environment under evaporitic/hypersaline conditions. By contrast, the LG dolomite may have formed in a diagenetic environment at salinities lower than those inferred for UG samples, according to observed isotopic ratios. Both UG and LG carbonates exhibit 87 Sr/ 86 Sr ratios (0.7082 to 0.7086) and δ 18 O values (-4.03 to -6.09‰ PDB) that are consistent with formation from Devonian seawater at temperatures ranging from 44°C to 57°C.

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Upper mantle xenoliths enclosed in Cenozoic alkali basalts in Southwest Japan were found at Kurose Islet. The xenoliths consist primarily of harzburgite and minor lherzolite and exhibit a porphyroclastic texture. Trace element data showing relative depletion in light rare earth elements (REEs) and general spoon‐shaped patterns suggest that xenoliths experienced depletion and slight enrichment processes. Incompatible trace element patterns for the spinel peridotite xenoliths indicate varying degrees of modification by fractional melting (from 6 to 11%). The Kurose spinel peridotites appear to have undergone melt extraction followed by an episode of cryptic mantle metasomatism. A nearby silicate melt may have been the metasomatic agent affecting spinel peridotites. The spinel peridotites originated from depths of 48 to 51 km at equilibrium temperatures ranging from 1030 to 1082 °C.