Phosphate minerals, which are ubiquitous in terrestrial and extra-terrestrial rocks, are important carriers of trace elements, including U and Th, which provide chronological information because of their radioactive decay. Abundance and grain sizes of the phosphates are limited in extra-terrestrial materials. Therefore, high resolution and minimally or non-destructive analytical methods must be used for age determination. For this study, we conducted U-Pb dating using a NanoSIMS for three phosphate grains from an old Martian meteorite: ALH 84001. The ²³⁸U-²⁰⁶Pb and ²⁰⁷Pb-²⁰⁶Pb isochron ages were found to be 3850 ± 170 Ma and 4002 ± 52 Ma, respectively, suggesting a concordant signature at approx. 4.0 Ga. A total Pb/U isochron age of 3990 ± 160 Ma is consistent with a previous SHRIMP U-Pb age of 4018 ± 81 Ma (Terada et al., 2003). Moreover, heterogeneous distributions of U are observed in these grains, which might have been preserved since igneous crystallization of the phosphates because the diffusion of U in the mineral is considerably slow.

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To ascertain factors controlling melt production along a typical distal, ‘hotspot-interacting’ mid-ocean ridge, we investigated the extent and distribution of both plume-related and plume-unrelated basalt from the central Indian ridge (CIR) between 15°S and 20°S. Comprehensive geochemical data of fresh-quenched volcanic glasses and basalts were used. Variation of Sr, Nd, and Pb isotopic compositions and Nb/Zr, Ba/Nb, and Ba/La content were interpreted by mixing of three melt end members: the Indian depleted MORB mantle derived melt; radiogenic and enriched melt derived from source mantle for Rodrigues Ridge and the intermediate series of Mauritius Island (RE2, radiogenic enriched component 2); and radiogenic but depleted melt derived from source mantle for Gasitao Ridge (RD, radiogenic depleted component). On the basis of quantitative mantle melting and melt mixing model, results show that sources for RE2 and RD are geochemically distinct from those of the Réunion plume (RE1, radiogenic enriched melt component 1). Moreover, the geochemical variation of MORB of 15°S to 20°S is unrelated to contamination of the upper mantle by the Réunion plume. These results suggest strongly that plume-unrelated heterogeneity is widespread throughout the upper mantle. The chemical characteristics of RE2 are remarkably pronounced in basalt from the central portion of ridge segment 16 around 18°S, suggesting substantial magma production. The influence of RE2 decreases along with decreasing magma production to the north, and is only slightly identifiable in basalt from the northern part of segment 18. Although the influence of RE2 decreases somewhat to the south, basalts with extreme RE2 signature were produced in the center of segment 15 around 19°S, where magma production is high. In contrast to RE2, the geochemical signature of RD in basalt is geographically limited to two localities: the south end of segment 18 and the center of segment 15. However, these observations reveal that both RE2 and RD contribute strongly to magma production on segment 15. Results show that melting of ancient recycled plate materials with a low melting point regulates voluminous magma production along the CIR.

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The ⁸⁷Sr/⁸⁶Sr values in carbonate nodules and ⁸⁷Sr/⁸⁶Sr and εNd values in silicate samples from the valley-fill deposits of the Ganga river have been used to ascertain temporal changes in sediment provenance during the last glacial-interglacial cycle. To understand the changes, a 25 m long core named as the Firozpur core has been sampled for carbonate nodules and sediments. The ⁸⁷Sr/⁸⁶Sr values in carbonate nodules (0.71846 to 0.71965) of the Firozpur core are significantly more radiogenic during Last Glacial Maxima (LGM) and pre-LGM time and suggest that the Ganga river is characterized by higher ⁸⁷Sr/⁸⁶Sr values compared to global average river water (0.7119) at all times in the past and present. Sr and Nd isotopic data in silicate vary significantly with depth, 0.73580 to 0.77894 and -14.3 to -17.6, respectively and falling within the range of silicate rocks of the Higher Himalaya (HH) and the Lesser Himalaya (LH), the two major sediment sources to the Ganga river. The strong anti-correlation between ⁸⁷Sr/⁸⁶Sr and εNd again confirm this hypothesis. Together with the δ¹⁸O values and ⁸⁷Sr/⁸⁶Sr and εNd values of the Firozpur core suggest low precipitation over the HH during LGM caused less sediments supply from it and enhanced sediments supply from the LH. It shows significant influence of climate on erosion in the Himalaya.

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The rare earth element (REE) partition coefficients between calcite and aqueous solution were obtained experimentally under the conditions of pH, ionic strength and REE concentration level in the parent solution which were relatively close to those in seawater environment. Two different concentration levels of the REE dopant solutions were used in the experiments. The obtained partition coefficients for Sm, which have relatively high values, range from 20.8 to 116, and those for Lu, which show relatively low values, range from 10.9 to 79.1. The mutual fractionations among REEs are relatively small. On the partition coefficient versus ionic radius diagram, the patterns show weak convex upward shape having a vague maximum in the light REE, but these curves are not likely to be parabolic as expected from the trace element partitioning studies for the phenocryst-magma pairs. Therefore, it was considered that the REE partitioning between calcite and aqueous solution is not mainly controlled by the crystal structure-ionic radius effect. As for the factors on the REE partitioning experiments, crystal growth rate, REE concentration level and dominant REE species in the solutions were examined, but any clear relationships were not found, although the REE concentration level might be operative. Because the experimental condition in the present study are relatively close to the natural ones, the REE partition coefficients obtained in the present study would be useful for examining the REEs abundances in natural CaCO₃ materials.

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The atmospheric concentrations of nonsea-salt (nss) SO₄^2- and trace elements (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, Se, V, and Zn) were measured for aerosol samples collected concurrently at ten sites across Japan during winter (December to February in 2004-2006), when the contribution of Asian outflow to their concentrations would have been maximized. The sulfur isotope ratio (δ³⁴S) of nss SO₄^2- was also measured and used to identify the sources of nss SO₄^2- in the aerosols. Sites in urban and industrial areas tended to have high concentrations of nss SO₄^2- and trace elements. In other sites, however, the concentrations of nss SO₄^2- and trace elements decreased with increasing longitude. On the basis of the δ³⁴S values of nss SO₄^2- and the results of air trajectory analysis, it is likely that the regional variations in the concentrations of nss SO₄^2- and trace elements are strongly related to their emissions in the regions over which the air mass passed, particularly in the 30-40°N region, which has the highest emissions in China. To evaluate the relative contribution of Asian outflow to the concentrations of nss SO₄^2- and trace elements at each site, for convenience we assumed that the fraction dominated by Asian outflow (referred to as the Asian outflow fraction) corresponds to the concentrations expected from an exponential concentration-longitude relationship among three sites that are far from major emission areas in Japan. For nss SO₄^2- and As, much higher contributions of the Asian outflow fraction (93% and 83% on average, respectively, at 10 sites) were observed, whereas for the other trace elements, only average contributions were observed at all the sites, i.e., within 50-67%. The high contributions of Asian outflow to the concentrations of nss SO₄^2- and As are attributable to a marked difference in their emissions from coal combustion between China and Japan.

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Mesoproterozoic Pipe 2 kimberlite intruding granitic gneisses in the Wajrakarur kimberlite field (WKF) of Eastern Dharwar craton, southern India, is one of the first discovered pipes from this field. The two different intrusions belonging to coherent facies are observed in this kimberlite which are texturally distinct i.e., macrocrystic (with abundant macrocrysts) as well as aphanitic (devoid of or very fewer macrocrysts). Petrographic observations give evidence of presence of veined metasomatic mantle in the source region. Distinct geochemical variation is observed between macrocrystic (Mg# 75.4-76.6, SiO₂: 34.3-35.4 wt%, MgO: 18.7-20.4 wt%) and aphanitic samples (Mg# 74.7-75.5, SiO₂: 30.4-31.8 wt%, MgO: ∼21 wt%), furthermore aphanitic samples are relatively more enriched in trace and rare earth elements. Geochemical studies point out that aphanitic and macrocrystic varieties of Pipe 2 kimberlite to be products of the same mantle source but have experienced different evolutionary histories. The inferred primary magma of Pipe 2 kimberlite (for both aphanitic and macrocrystic) is suggested to have a composition of ∼33 wt% SiO₂, Mg# ∼ 75.6 and ∼460 ppm Ni. Pipe 2 primary magma can be derived by using forward melting model assuming ∼1% partial melting of a source enriched in light REE by a factor of ∼11 x chondrite and almost chondritic heavy REE with 2% residual garnet. Differences between aphanitic and macrocrystic varieties in their chondrite normalized REE abundance patterns can be explained by about 5% crystal fractionation of primary magma and not by variations in the degree of partial melting. The primitive mantle normalized trace element patterns exhibit significant negative K, Sr, P, Ti and Hf anomalies that are interpreted to be characteristic of the primary magma. Combined petrology and whole rock geochemistry including compatible and incompatible element abundances and their ratios confirm that Pipe 2 kimberlite intrusions are archetypal Group I kimberlites similar to other kimberlites of EDC and not lamproites.

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