The density of the core is about 8 percent smaller than that of pure iron under similar P, T conditions, implying the presence of a substantial amount of light element(s). Sulphur is popularly considered to be the principal light element in the core. If so, the earth accreted about 44 percent of the primordial complement of this element. To accrete sulphur as efficiently as this, and at the same time, to account for the observed depletions by much larger factors of Na, K, Mn, Rb, F, Cs, Zn and Cl, the earth must have accreted in an environment where hydrogen was depleted relative to sulphur by a factor of about 100, compared to the solar nebula. The conditions required are restrictive and encourage evaluation of other light elements as possible components of the core, for example, oxygen. Experimental observations show that the solubility of FeO in liquid iron increases rapidly between 1, 500 and 2, 000°C. Thermodynamic extrapolation of solubility data implies solubility of 40mol.% FeO at 3, 000°C and complete miscibility of liquid Fe and FeO above 3, 500°C. Calculations show that solubility is greatly increased by high pressures and that at 2, 500°C, the liquid metal phase in equilibrium with the probable mineral assemblage in the lower mantle (FeO/(FeO + MgO) = 0.12) would contain more than 50mol.% FeO at a pressure of 300kb, and would be about 10 percent less dense than pure iron. These results imply that FeO is probably a major constituent of the earth's core. Solubility of FeO in metal may be accompanied by a large increase in oxygen fugacity of the core-mantle system relative to the situation where solution of FeO in molten iron does not occur. This effect is enhanced by the pressure-induced partial disproportionation of Fe²⁺ into Fe³⁺ + Fe⁰ in the lower mantle. Accordingly, the distribution of siderophile elements between mantle and core and the occurrence of oxidized species such as H₂O, CO₂ and Fe³⁺ in the mantle could result from attainment of local chemical equilibrium at high pressures between (Fe-FeO) metal and silicate phases in the more oxidizing environment prevailing during core segregation. Models of greater complexity, involving heterogeneous accretion of the earth and chemical disequilibrium between metal and silicate phases may not be necessary. Thus, if FeO indeed enters the core as suggested, rather simple models whereby the earth formed by homogeneous accretion from a mixture consisting of 10% of low-temp. oxidized primordial condensate similar to C1 chondrites (20% H₂O) and 90% of devolatilized, reduced material (mainly metallic iron and magnesium silicates) can provide a satisfactory explanation of the earth's bulk composition.

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Many small particles of barium titanate were discovered in the Allende meteorite. Although the particles are distributed heterogeneously in the meteorite, their presence in matrix is not unusual for Allende. Two types of concentration pattern are observed. One is skeleton-type. Barium titanate particles are distributed in very small inclusions of the meteorite, as if the particles construct a skeleton of the inclusion. Another distribution pattern is spot-type. Aggregates of barium titanate particles are distributed in fine-grained matrix of the meteorite and show no bearing on their surroundings. REE abundances are determined for two skeleton-type barium-titanate rich parts with accompanied high-temperature minerals. Their chondrite-normalized REE patterns have V shape as expected by TANAKA et al. (1976). Based on the data obtained by EPMA, BaO and TiO₂ contents turn out to be 59 and 34%, respectively. Any relation with Ca and Sr which form the other titanates could not be detected in the present investigation. According to the calculation, fundamental barium titanate particulate seems to have the maximum radius of 0.2μm. Observed Ba and Ti contents are explained by the dimensions of X-ray production being wider than the area of aggregate of the fundamental barium titanate particulate. The particles seem to have existed prior to the early condensation stage of high-temperature minerals and some particles played a role of skeleton of small high-temperature minerals. Other particles exempted from such roles, gathered together and formed a large (∼1μm) spot-type Ba-rich cluster. The ultrafine barium titanate particles seem to suggest the particles being free from an early vaporization episode of the nebula.

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The Gocup Granite, in southeastern New South Wales, intrudes low-grade metasediments tentatively assigned to the Ludlovian on fragmentary conodont evidence, and is overlain by a unit rich in volcanic material but containing a good brachiopod fauna of lower to middle Siegenian age. The K-Ar age of four muscovite samples is 409 ± 3m.y.; a Rb-Sr whole-rock isochron on five samples yields a Model 1 age 402 ± 3m.y., initial ⁸⁷Sr/⁸⁶Sr 0.7090 ± 0.0013. Preliminary data by X-ray fluorescence and unspiked strontium mass spectrometry illustrate the effects of some sources of experimental error.

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Using the conformal solution theory of molten salts (REISS et al., 1962; DAVIS and RICE, 1964; BLANDER, 1967), an attempt was made to interpret the patterns of the partition coefficients of trace elements in silicate minerals as a function of ionic radius. It is shown that the partition coefficient is represented to the zeroth order approximation by the quadratic equation of ionic radius in a “simple” homovalent substitution where host and guest cations are of primarily ionic nature. Pressure effects on the partition coefficient of a trace component are qualitatively discussed with emphasis on the interrelationship of melting points between major and minor components.

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An attempt has been made to locate known eucrites within a proposed crust model by estimating the absolute cooling rates from the width of exsolution lamellae of augite in pigeonite. We simplified the model of exsolution phenomena such that the growth of the exsolution lamella will be controlled by the diffusion of Ca atom perpendicular to the lamella. By taking into account temperature dependency of Ca atomic diffusion coefficient in pigeonite and the temperature-time variations at a given depth of the crust, we integrated the equation derived from diffusion equation, with respect to temperature (1, 200-850°C) by the numerical method to match the observed width of lamellae for the bulk Ca content of pigeonite. For a proposed achondrite parent body of 1, 000km in diameter, the depth estimated for Moama is 12km below the surface, Moore County 9km, Juvinas 1.7km and Mt. Padbury 0.5km. The absolute cooling rate for the first two meteorites is about 1°C/10⁴ years. The eucritic crust of the parent body may be thinner than about 15 km.

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Chemical elements in the sediment columns of Pacific pelagic clays have been measured by neutron activation and atomic absorption method. Their vertical variations are discussed on the basis of the idea that the rate of sedimentaiton changed during geological time by the influx of volcanic eruptions.

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A simple and rapid method for the determination of fluoride in the range above 10ppm up to 48.67 wt.% for CaF₂ within a total time of 15 minutes is described. Samples are mixed with PbO₂ in the ratio 1 : 3; and the fluoride is liberated in an induction furnace within ca. 10 minutes. The fluoride is collected in a 0.025 molar sodium-hydroxide solution and after adding 100ml buffer (1M sodium citrate, 1M sodium chloride), the solution is filled up to 250ml with distilled water, and measured by an ion-selective electrode using the technique of standard addition. Analyses of five international reference samples show excellent accuracy from 0.5 to 3% with a standard deviation of less than 4% (e.g., for a fluoride contents of 442ppm in Andesite AGV-1).

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