We synthesized carbon products by the Modified Hot Filament Chemical Vapor Deposition (MHFCVD) method in an artificial atmosphere containing noble gases, and measured the noble gas abundances trapped in them. MHFCVD carbon synthesized at high voltage contained large amounts of noble gases enriched in heavy noble gases. The trapping efficiencies of noble gas were the highest among those reported for synthetic samples in laboratory experiments. The elemental abundance patterns are similar to those in Microwave Chemical Vapor Deposition (MWCVD) diamonds, but show severe depletions of Ne. Synthesized (MHFCVD) carbon samples have similar noble gas features to those in diamond-free ureilites. This result suggests that amorphous carbon in diamond-free ureilites was also formed by Chemical Vapor Deposition (CVD), and that noble gases were implanted into amorphous carbon as well as into diamond in ureilites under plasma conditions.

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Metasedimentary and metavolcanic rocks within the Smith River allochthon, southwestern Virginia Piedmont, are present in two units, the Bassett and the Fork Mountain Formations. The younger Fork Mountain Formation contains some metabasalt layers but primarily consists of a biotite gneiss and an overlying high-alumina mica schist; the biotite gneiss is wedge shaped and thins to the northwest. Fourteen major-oxide analyses were performed on samples of metasedimentary rocks from the Fork Mountain Formation. Compositions of both gneisses and schists fall on single linear trends on conventional Harker-type scattergrams, which can be explained by sedimentary mixing lines between pure quartz and a pelitic sedimentary assemblage. In addition, the negative correlation between SiO₂ and K₂O is significant because in igneous rocks these two oxides are normally positively correlated. Thus relatively coarse, quartz-rich sediments apparently became the psammitic rocks that formed the paragneisses, and the finer, clay-rich sediments became the shales that are protoliths to the schists. A simple explanation of these relationships is a relatively fine-grained, deep-water sedimentary facies present in the northwest that transgressed to the southeast through time; the source for these sediments would have been to the southeast. Principal components analysis (PCA), ratio-ratio scattergrams, and t-tests for differences of means, however, indicate that this two-component. mixing is an over-simplification. Some subtle differences in chemistry between the gneisses and schists exist that cannot be explained by linear mixing alone and may imply more than one source region for the sediments. In addition, PCA and simultaneous solution of mass balance equations estimate the following major rock-forming mineralogy for the pelitic sediments, exclusive of quartz: illite - 48%, montmorillonite - 20%, chlorite - 9%, K-feldspar - 20%. This mineral composition is consistent with known patterns of mineral alteration during burial diagenesis. Discriminant function analysis (DFA) was also performed; it suggests that an apparently large compositional gap is present between the gneisses and schists. Conventional bivariate scattergrams and PCA, however, indicate that a compositional continuum exists for most oxides.

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Evaporation experiments using pyrrhotite single crystals (Fe_0.886S) were carried out at temperatures between 500 and 1300°C at 1 atm in an H₂-CO₂ gas flow (0.62-0.64 atm H₂), and at 500 and 900°C under an evacuated condition. Under the H₂-rich condition, spongy metallic iron layer was formed on the sulfide crystal surface at temperatures below the Fe-FeS eutectic point as a result of incongruent evaporation, and developed inward almost conserving its original shape. The thickness of the iron layer increases linearly with time at constant temperatures (linear rate law) due to transportation of evaporated gas species through pores in the spongy iron layers. If incongruent evaporation is controlled by diffusion of element(s) in an evaporation residue layer, a parabolic rate law is expected. The linear rate law shows that FeS evaporates more efficiently than expected based on a parabolic rate law. The linear rate constant obtained at various temperatures obeys the Arrhenius relation: k_FeS = (1.61 ± 0.42) × 10^-3exp(-115 ± 2 [kJ/mol]/RT) [m/sec]. A minor part of metallic iron in the surface layer diffused into the inner sulfide to form stoichiometric FeS (troilite) in the early evaporation stage. Thus, the experiments can be almost regarded as evaporation of troilite. Evaporation coefficients of FeS were obtained by comparing the experimental results with calculated rates using the Hertz-Knudsen equation. They are small (1.4 × 10^-4 ∼ 9.4 × 10^-6) due to slow surface reaction and/or slow escape of S-bearing gas species into the gas flow. Mass-dependent isotopic fractionation of S by the evaporation was not detected within an error of ±3‰ probably due to slow diffusivity of S in the sulfide crystal. In the evacuated experiments, evaporation occurred very slowly due to the absence of H₂ gas, which acts as a reducing agent. Iron residue layer was very thin or sometimes not detected probably because the evaporation rate of S from FeS became comparable to the evaporation rate of metallic iron, which can be neglected under the H₂-rich condition.

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Dissolved and particulate forms of rare earth elements (REE) in the surface seawater of coastal area were separately determined with Inductively Coupled Plasma ion source Mass Spectrometry (ICP-MS) in order to discuss the REE partitioning between them. Two different samples were prepared on the occasion of each sampling: one sample was acidified before it was filtrated (AF) and another sample was acidified after filtrated (FA). On the two samples (AF and FA) we measured the REE abundances of the filtrate and the collected matter on the filter separately. In either sample, the filtrate showed a “W type tetrad effect”-like variation in the chondrite normalized REE pattern. The partitioning pattern of sample FA shows a clearer “W type tetrad effect”-like variation than that of sample AF, indicating that “labile” showed a “M type tetrad effect”-like variation. Besides Ce anomaly, anomalous behavior of Tb has been observed in the filtrate of the sample FA. Th in the collected shows rather capricious behavior.

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Stable carbon isotopic compositions were determined for diploptene in the sediment core KH-79-3, L-3 (core length: 235 cm) taken from the Oki Ridge in the southern part of the Japan Sea. Two major groups of diploptene with different δ¹³C values were recognized. The first group appears in the 0-130 cm section (present to 10 kyr B.P.) of the core, the δ¹³C values being -25.0 ± 0.7‰ on average. Diploptene in this section should have originated from cyanobacteria. The second group which is strongly depleted in ¹³C (-53.1 ± 5.3‰ on average), is observed in the 145-204 cm section (12-21 kyr B.P.). Diploptene in this section might have originated from methanotrophic bacteria. This indicates that an anoxic bottom water condition was developed during 12-21 kyr B.P. (the last glacial period), which was perhaps caused by the development of seawater stratification in the Japan Sea.

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Geochemical and Sm-Nd isotopic data are presented for basaltic volcanic rocks from the Longsheng Ophiolite, which were crystallized at 977 ± 10 Ma and tectonically emplaced into the Danzhou Group (Banxi equivalent) along the southern margin of the Yangtze Block, SE China during the Neoproterozoic. The volcanic rocks have undergone low-grade alteration and metamorphism, displaying high Na₂O contents (>5%) and a large variation of mobile elements, but a relatively small range of immobile elements. With enrichment of Th and LREEs, relatively low high-field-strength elements and other REEs, and the Ta-Nb-Ti negative anomaly, the volcanic rocks are geochemically similar to basalts forming in subduction-related environments, typical of the “supra-subduction zone” ophiolites. Nd isotopes of the volcanic rocks preclude a MORB-like depleted mantle source for the Longsheng Ophiolite, though their Sm-Nd isotopic systems have been rehomogenized during the late Neoproterozoic alteration. The Longsheng volcanic rocks, therefore, are interpreted to have been generated either by extension and thinning of a continental arc, or at a backarc side of continental arc during the early stage of the backarc spreading.

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Sixteen aliquots of JB-1 with different weights were studied by instrumental neutron activation analysis. It is observed that concentrations of Na, Fe, Sc, U, Th and rare earth elements are reproducible for JB-1 with the sample size of mg level. However, concentrations of Mo, W and Ta show a significant scatter even at 50 mg level. It is, therefore, suggested that chemical standards be used for Mo, W and Ta determination for geological samples, otherwise the rock reference sample, if used as a standard, be checked for the reproducibility of concentrations of these three elements.

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