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Recent micro-analytical studies have revealed large amplitude variations in Sr/Ca and oxygen isotopic composition in coral skeletons; variations that cannot be ascribed to changes in SST or in salinity. They show the great potential for determining chemical variations at length scales of direct relevance to the biomineralization process. For example, it is now possible to measure geochemical variations within the two basic micrometer-sized building blocks of the coral skeleton. Such micro- and nano-meter scale observations, in combination with controlled laboratory culturing of corals, hold the promise of yielding important new insights into the various biomineralization processes, which may affect the chemical and isotopic composition of the skeletons.

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Previously we reported (Omata et al., 2005, GCA, v 69, p3007-3016) that annual fluctuation in skeletal carbon stable isotope is result of the mixture of two isotopic disequilibrium processes as kinetic and metabolic isotope effects. To examine these effects, we conducted in vitro culture experiments to examine effects of light intensities on carbon and oxygen isotope variations in Porites spp.
At the result of analysis, compositional changes in carbon and oxygen isotope ratios showed simultaneous transitions, caused by the kinetic fraction due to lack of metabolic fraction. It may represent that metabolic isotope effects increased with increasing light intensity, and the kinetic isotope effects with increasing the growth rate.

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The skeletal oxygen isotope ratio of Porites corals, together with the carbon isotope ratio, is the most frequently used proxy of past seawater temperature and composition for tropical oceans. We conducted tank experiments in which we grew Porites spp. colonies in thermostated seawater at five temperature settings between 21 and 29 degree C. We also examined oxygen and carbon isotope ratios of Porites corals collected from Sekisei Reef of southern Ryukyu Islands, Japan. Growth-rate-related kinetic isotope effects found in both the cultured corals and the deep slower-growing corals may be, at least partly, attributed to low light condition.

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The effect of changes in aragonite saturation state of seawater on coral calcification was studied using colonial coral (Porites) and solitary coral (Fungia) in the laboratory conditions at 25 degree. The increase in seawater aragonite saturation state from 1.56 to 5.18 caused an increase in coral calcification rates. The calcification rates of the samples and the saturation states were observed to be a linear ralationship. If atmospheric carbon dioxide increase in future as predicted, seawater saturation state will decrease and the coral calcification may decrease.

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We measured noble gas isotopic ratios of olivine xenocrysts in an alkali-basalt sampled from a northwest Pacific seamount. The xenocrysts are reported to be derived from upper-mantle from major element compositions. By applying both vacuum crushing and stepwise heating extraction of the noble gases, uncontaminated 3He/4He ratios range between 7.2 and 7.7 RA and 40Ar/36Ar ratios are up to 5000 in the xenocrysts. These observations demonstrate that the upper mantle beneath the oceanward slope of the Japan Trench has a similar isotopic composition to the MORB source, suggesting a uniform MORB source is largely distributed in the upper mantle.

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In this paper we report a diopside (CaMgSi2O6) crystal growth from the melt by the Czochralski pulling method. We confirmed the single crystal of diopside on the basis of X-ray diffraction measurement and chemical analysis by SEM-EDS.

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Feldspar minerals are wellknown to be widspreadly distributed in nature. Additionally, feldspars have highly sensitive property to radiation-induced luminescence, so that avalavility to chronology of burnt archaeological materials has been expected. However, there exists intinsic drowback owing to anomalous fading effects of the feldspars. In this presentation, some feldspar minerals were thermally treated under oxidatave or reductive conditions, followed to the stability examination of luminescent centers as a function of the storage periods. Blue thermoluminescence and far-red one were utilized and the experimental results were discussed from aspects of fading causes.

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West Philippine Basin (WPB) is inactive and the oldest back-arc basin occupying western half of the Philippine Sea Plate. Geochemical and petrological characeristics of basement rocks from the western part of WPB are reported with implications for its spreading tectonics.

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Petrographic characteristics and whole-rock major trace element contents and isotopic data are presented for basaltic rocks from the Bure area, NW Ethiopia.

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Heated quartz emits light whose intensity is proportional to its equivalent dose. This light is called thermoluminescence (TL). Because of such response, TL from quartz is applied to dating of archeological materials and geological sediments. If the equivalent doses of quartz grains in gouges are reset due to heating during a fault movement, TL could be utilized to dating of fault movements. However, many researchers doubt such assumption. Here, we measure TL from milled quartz grains and inspect quantitavely the reduction of TL sources based on the diameter dependence of TL intensity. Moreover, considering surface disordered layers on milled grains, we discuss the mechanisms of the reduction. Finally, we comment on TL dating of fault movements.

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Here we present U-Pb ages and trace element (U, Th, REEs, Y, and Hf) compositions of a zircon micro-vein and host granite zircons as well as their internal textural features used to understand the mode of their formation and subsequent fluid-influenced alteration and recrystallization.

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Granitic rock fragments found in the Ulleungdo volcanic island, South Korea, show very young Rb-Sr mineral isochron and K-Ar ages. The granitic rocks suggest that the granitic magma was cogenetically evolved from the Stage 3 Ulleungdo alkali basaltic magma formed at the back arc basin during the opening of the East Sea and Sea of Japan.

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C and O isotopic composition of carbonatites ranges of d13C -5.89 to -6.94%o, -5.53 to -6.08%o and 9.51 to 10.9%o, 9.46 to 10.4%o for d18O respectively. The d13C data in this study for OL lavas and Siilinjarvi carbonates coincide with previous studies. The d18O data fall on the heavier side of the primary igneous carbonatites range in contrast to the data of OL 1988 eruption. This enrichment can be explained on the basis of liquid immiscibility between coexisting carbonatites and silicate melts. The carbonates are generally heavier in 18O than the typical mantle minerals therefore such enrichment in d18O is in agreement with the mantle geochemistry.

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Lakes Nyos and Monoun experienced a "limnic eruption" in 1980s due to excessive accumulation of magmatic CO2. The lakes are being recharged with the CO2 at a rate of ca. 120 mega moles per year. The total pressures of dissolved gases reached 73% of saturation at Lake Nyos (206m, 2001) and 97% at Lake Monoun (56m, 2003), suggesting a possibility of the near future recurrence of the limnic eruption. A degassing pipe was installed at each lake in 2001 and 2003 to make the lakes safe. Recent observation indicates that the gas contents have been reduced by 12-14% compared to the pre-degassing level. We need to increase the number of the pipes for acceleration of the degassing efficiency. We also need to set up a device to avert accumulation of magmatic CO2 in the lake.

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The chemical changes in oceanic crustal rocks during hydrothermal alteration were investigated through the Oman and Troodos ophiolite in order to evaluate seawater-rock interaction through the oceanic crust including Layer 3. Based upon the depth-profile and the correlation among 20 elements analyzed in this study, elements were classified into 6 groups: Group 1 (Ca, P, Al), Group 2 (Mg, Ni, Co, Cr), Group 3 (Fe, Ti, Na, Mn, Zn, Y), Group 4 (K, Rb, Ba), Group 5 (Li, Cd) and Group 6 (other elements such as Sr, Cu). Each profile reflects original rock composition and its modification during high and low temperature alteration. The degree of alteration was assessed by 87Sr/86Sr ratios of rocks and the abundance of secondary minerals. Heavy metals were leached from the lower oceanic crust.

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50 hotspring waters in Osaka Prefecture were studied on the geochemical characterization and those origins. The groundwaters can be classified into 3 groups based on the major element chemistry. 1: Dilute and cold calcium-bicarbonate water, occasionally contains carbon-dioxide, issued mostly from the fracture of basement rocks and shallow Quaternary sediments. 2: Dilute sodium-bicarbonate water taken from the lower fresh water formation of Quaternary Osaka Group. 3: Saline water, occasionally associating with carbon-dioxide, taken from the lowermost part of the Osaka Group formation and underlying basement granitic rocks. The latter groundwater are grouped into fossil seawater and Arima-type brine, which shows oxygen shift.

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Forty-five hot spring samples in Japan with various hot spring types were measured their del37Cl values. Del37Cl values ranges from -1.62 to 0.97 permil. Hot spring with magmatic origin has higher positive del37Cl value (0.5-0.9) and that of fossil seawater has negative value. Matsushiro hot spring, which is typical magmatic origin, shows "oxygen-shift" on delD vs del18O diagram and can be extrapolated to the range of andesite magmatic water. Del37Cl also shows the correlation with del18O. From this relation, del37Cl value of andesite magmatic water was estimated to be 1.5 to 1.9 permil. This del37Cl value suggests that Cl in andesie magmatic water is mixture of mantle Cl (4.2_-_7.0 permil) and subducted seawater.

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Arsenic, antimony and mercury are an element of special interrest in connection with volcanic activity, as the element and its compounds can be good indicators of the activity because of their volatility. Therefore, it can have the interrest for the chemical form and the behavior. This study reports arsenic, antimony and mercury concentrations , chemical forms and its behaviors in geothermal waters mainly Southern Kyushu, Japan.

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It is widely believed that groundwater As contamination in Bangladesh is likely to be caused by naturally occuring source. Thus, geochemical approaches play a key role to clarify the formation mechanism. We have investigated some geochemical and hydrological characteristics of As contaminated groundwater in Sonargaon area since 2003. Additionally, detailed geologic structures are clarified by recent drilling survey. In this presentation, a model of formation process is reviewed on the basis of our current research.

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Relationships between climate factors and d¹⁸O values of tree rings in two species with different root systems were investigated in the northern Hokkaido Island. In spruce (Picea jezoensis with a shallow root type, the d¹⁸O values are negatively correlated with precipitation in July and August. Thus the d¹⁸O value in spruce must be valuable as a proxy of summer precipitation in this area. On the other hand, d¹⁸O value in oak (Quercus crispula) with deeper root than spruce, is not very sensitive to summer precipitation but negatively correlated mainly with relative humidity in July and August. Thus the d¹⁸O value in oak must become a proxy of summer relative humidity in this area.

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