Anhydrite occurs as a representative hydrothermal mineral in the upflow zone of the Kakkonda geothermal field, northeast Japan. Gas analysis and microthermometry of fluid inclusions and sulfur isotope measurements were performed for these anhydrites in order to discuss origin of the reservoir fluids and precipitation mechanism of the anhydrite. Fluid inclusions are classified into two-phase, vapor-rich and liquid-rich inclusions, and polyphase inclusions comprising liquid, vapor and solids. The vapor-rich inclusions coexist with the liquid-rich inclusions in most samples, indicating that the fluid inclusions were trapped under boiling conditions. Bulk gas analyses of the liquid-rich inclusions show that the main non-condensable gas component is CO₂ (0.14-2.0 mol %) with subordinate amounts of N₂, CH₄ and Ar. The two-phase liquid-rich inclusions homogenize to liquid phase at temperatures between 222 and 380°C, and have salinities mostly from 0 to 29 wt.% NaCl + CaCl₂ equivalent. The polyphase inclusions homogenize to liquid phase at temperatures between 302 and >480°C after dissolving halite between 104 and 220°C on heating, and have salinities from 28 to 35 wt.% NaCl + CaCl₂ equivalent. In the deep reservoir, the salinities vary over a large range at homogenization temperatures of approximately 320 to 360°C. The δ³⁴S values of anhydrites ranging mostly from +21.6 to +24.2‰ suggest that sulfur in the anhydrite from the Kakkonda field is derived from marine anhydrite. These data indicate that the hypersaline fluid was produced by exsolution from a residual magma at the time of final crystallization of the Kakkonda granite, and moderate to low salinity fluids formed by dilution of the hypersaline fluid with the heated meteoric water and boiling of the dilute fluids. The precipitation of anhydrite might be explained by three mechanisms of a simple cooling of the hypersaline fluid, boiling of the reservoir fluid and pressure drop of the non-boiling reservoir fluid.

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A technique for analyzing stable carbon isotope composition of organic carbon using a Nd-YAG laser microprobe system has been developed. Analyses were performed on graphite rod and silica-graphite discs made from mixtures of silica glass and graphite powders with a weight ratio as SiO₂/C = 3/2. The sample was ablated by the laser and simultaneously combusted by laser ablation with excess O₂ to produce CO₂. Replicate analyses on the two types of standards under O₂-atmospheric condition (8-20 torr) are reproducible to ±0.1 ‰ (1σ) for δ¹³C, which is in agreement with accepted precision by the conventional method. In order to examine the matrix effect by other silicate minerals in natural samples during laser ablation, the silica-graphite disc samples were also combusted by laser ablation without excess O₂ to produce CO₂. In this case, the amounts of CO₂ produced were far smaller (<1%) than those of CO₂ produced with excess O₂ and the δ¹³C values range from -18.9 to -7.5‰. Considering the mass balance, we conclude that the matrix effects of silica or other silicates on the δ¹³C analyses of organic carbon can be ignored because it only result in a little positive shift (<0.2‰) in δ¹³C values. Application of the laser microprobe technique on δ¹³C analyses of organic carbon to five late Archean black shale samples (Jeerinah Formation, Hamersley Basin, Western Australia) gives δ¹³C values that are reproducible to ±0.1-0.3‰, and the mean δ¹³C values range from -37.2 to -39.1‰ which are very close to the δ¹³C values of the kerogens extracted from these shales. The analytical results demonstrate that the laser microprobe technique developed in this study is effective for the in situ isotope analyses of organic carbon in sedimentary rocks with a good precision of ±0.1‰.

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The major, trace and REE geochemistry of glauconites (as members of the trioctahedral micas) from the early Cretaceous Kurnub Group of Jordan are discussed. The investigated glauconites, with 7.1 to 9.2% K₂O, are ranked as evolved to highly evolved as defined by Odin and Matter (1981). Al₂O₃ contents show a significant inverse relationship with K₂O and Fe₂O₃. The trace element contents show a broad range of variation in contrast to the major elements and a consistent relationship with major elements is lacking. The studied glauconites show a very wide range in the total amount of REE (ΣREE = 4.5 to 564.5 ppm). Two distinct groups have been differentiated accordingly: I. REE-poor group with ΣREE < 15 ppm and with a weak to moderate LREE/HREE fractionation (1.2 to 8.2); II. REE- rich group with ΣREE up to 565 ppm and with moderately to highly fractionated chondrite-normalized patterns (LREE/HREE ratios 3.5 to 64). The group I glauconites are set in an arenaceous (detrital quartz) dolomitic matrix while group II glauconites are embedded in a mudstone or marlstone or has an argillaceous matrix. The REE abundances are therefore lithologically rather than regionally controlled. When normalized to NASC the investigated glauconites display the distinctive hat-shaped pattern reported for other authigenic minerals of marine origin. The calculated Cc anomaly indicates the formation of glauconites at the boundary between oxic and anoxic environment near the sediment water interface.

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We have studied the mobility of rare earth elements (REE) and yttrium during dolomitization of marine limestone in reaction with MgCl₂ solution at 150°C for 10 and 20 days. On the experiment using the pulverized limestone of 7.5 g and 25 ml of 2 M MgCl₂ solution, 90% of the calcite transformed into dolomite at 150°C within 20 days. The dolomitized products showed that there is no significant change of REE abundances of original marine limestone. This is experimental evidence for the field observation that dolostones sometimes preserve the REE and Y signatures of limestone precursors.

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Fission track (FT) ages of the Omine Acidic Rocks, one of the Tertiary granitic rocks which occurs in the Outer Zone of the Median Tectonic Line, Southwest Japan, are determined in order to assess the timing of intrusion. Nine FT zircon (ZR) ages and one apatite (AP) age are obtained for igneous rocks, and four ZR ages for basement sandstone. Data for each pluton are concordant within a body representing the time of intrusion. The ZR ages from sandstone are concordant with the nearest pluton. The ages of plutons are classified into two groups statistically, suggesting that the Omine Acidic Rocks formed by two intrusive events. The Dorogawa, Tenguyama, Shiratani and Katago-Mukuro Dike are the older group with the weighted mean age of 16.8 ± 0.8 Ma, and the Kose pluton are the younger with an age of 14.2 ± 1.7 Ma.

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Stable carbon-isotope ratios (¹³C/¹²C) and the abundance of carbon, nitrogen and sulfur were measured in flora and soil organic matter from the Sifton Bog and Point Pelee Marsh, which are located in the temperate climatic zone of southwestern, Ontario, Canada. Characteristic bog vegetation contains less N and S than marsh flora; however, invasive species (e.g., Typha) at the Sifton Bog have N and S contents that are similar to vegetation from the Point Pelee Marsh. Flora from both wetlands have δ¹³C values that are similar and characteristic of vegetation possessing the C₃ photosynthetic pathway. The only exception is Utricularia vulgaris L. at the Point Pelee Marsh, which is ¹³C-enriched (average δ¹³C =-18.4‰; range -18.8 to -17.6‰) probably because of CO₂ limitation during growth. Organic matter from peat soils at each wetland exhibits a similar depth distribution of C:N ratios and δ¹³C values. The C:N ratio of soil organic matter decreases with depth, consistent with consumption of labile carbohydrates and fixation of nitrogen by soil microorganisms. Both C:N ratios and δ¹³C values stabilize at a shallow depth in soils at the Point Pelee Marsh, consistent with greater decay efficiency and less recalcitrant vegetation in marsh than in bog environments. Paleovegetational changes associated with a fen to bog succession also may have contributed to the more gradual and larger change in δ¹³C values and C:N ratios observed for soil organic matter at the Sifton Bog.

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