Assuming a hypothetical mean ocean water to represent the "parental ore solution", possible effects of such chemical variables as pH, metal concentration, and salinity on the resultant ore-forming processes were examined on the basis of available thermochemical data of related hydrothermal systems. On this basis, a variety of geochemical processes responsible for the differentiation of ore types in nature was discussed.
Applications of the results to the Kuroko ores of Miocene age in Japan and Recent submarine sulfide ores on the Red Sea floor suggest the prevalence of slightly alkaline hydrothermal process and/or some insigni-ficant metal-leaching process for the former type of mineralization and the less alkaline hydrothermal process and/or some significant salt-leaching process for the latter type of mineralization.

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Lead contents of barite coexisting with galena from the Senzai vein, Oe mine, Hokkai-do, lie in a comparatively narrow range from 120 to 290 ppm (or 9×10^-5 to 2×10^-4 mole fraction) in PbSO₄ content. Combining these data with fluid inclusion studies and phase equilibrium studies, the possible physicochemical conditions of the Senzai mineralization were estimated.
The results are as follows:
(1) Formation temperature: 180°-230°C
(2) Oxygen fugacity: 10^-40.3-10^-35.7 atm
(3) Sulfur fugacity: 10^-13.8-10^-11.6 atm
(4) Carbon dioxide fugacity: 10^-1.5-10^-0.4 atm

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Volumetric variations of opaque minerals in the diabase sheets in which the Shimokawa bedded cupriferous iron sulphide deposits occur are studied.
Essential minerals of the tholeiitic diabase are clinopyroxene, amphiboles after clino-pyroxene and plagioclase. Mafic minerals are more predominant in the diabse sheets above the ore-horizon than the sheets below it. And also these minerals are more concentrated in the upper part of each diabase sheet. These trends of volumetric variations of mafic minerals are concordant with the assay results of MgO and some trace transition elements such as Ni, Co and Cr.
Titanium minerals such as ilmenite, titanite, rutile and some titaniferous silicate mineral are more enriched in the diabase sheets below the ore-horizon than in the sheets above it, con-trary to the above results. As for the each sheet, these titanium minerals are more enriched in the middle and lower part of it. These distribution trends of titanium minerals coincide with the trend of chemical abundances of TiO₂ and V.
Chromite seems more abundant in the sheets above the ore horizon than the sheets below it. This trend is roughly reflected upon the Cr contents of the rocks.
Sulphide minerals in the diabase are pyrrhotite, pyrite, chalcopyrite and sphalerite. Distribution of these minerals is at randum and this feature corresponds to the irregularity of assay results of chalcophile elements such as Ag, Cu, Mo, Pb and Zn.
In conclusion, variations of chemical composition as well as mineral composition in the Shimokawa diabase sheets are controlled by the degree of magmatic differentiation indicated by the value of solidification index or (Total Fe as FeO)/MgO ratio.
Another interesting phenomenon about the alteration has been revealed. That is to say, abundance of relict pyroxene which remains against amphibolitization is coinside with the abundance of ilmenite which remains against leucoxenization. This suggests that these two kinds of alterations progressed simultaneously and were caused by the same factor.

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Trace elements in beryl from Homret Mukpid pegmatite, Egypt, were determined by laser microprobe spectroscopy (JOEL JLM-200) and ion microprobe mass analysis (HITACHI IMA-2). The beryl shows growth zoning which is parallel to {1010}. Analyzed points in the beryl crystal correspond to five zones indicated in Fig.1. Point 1 is almost colorless, points 2 and 4 are light blue, and points 3 and 5 show bulish tint.
Eight elements (Si, Ti, Al, Fe, Be, Mn, Mg and Ca) were detected by both analytical methods, and six more elements (Zr, Cr, Na, K, Li and Cs) by the latter (Table 2 and Fig. 2). The following is the results by microprobe analyses (Table 1 and Fig. 2): (i) the composition of the beryl scarcely differs from its ideal formula, (ii) especially, that of the central zone (point 1) is almost ideal, (iii) a part of Al is replaced by Fe³⁺, (iv) the deeper colored zones (points 2 and 4) are rich in Ti, Mn, Mg, Ca, Na and K, as compared with the pale parts, (v) Zr and Cr con-centrate in the central and marginal zones (points 1 and 5), and (vi) the content of Li is high in the center, while Cs in the margin.
These results indicate that laser and ion microprobe analyses are very useful for the determination of trace elements in small areas. The writers believe that both apparatuses would contribute to the mineral exploration as well as mineralogy, geology and geochemistry.

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Iron-copper deposits of the Sampo mine, Okayama Prefecture are of contact-metaso-matic type, and the iron-oxide(magnetite)ores have been known to contain tin with up to 0.5 percent by weight. In these ores, tin appears to occur as minute grains of cassiterite, varying in size up to 100μ across, and they are embedded in calcite immediately adjacent to magnetite.
In this paper, malayaite from clinopyroxene skarn lying between crystalline limestone and leucocratic biotite-granite through magnetite ore on the Yoshiki 9th adit-level of the mine is examined by use of electron-probe X-ray microanalyzer and micro-beam X-ray diffractometer.
The present malayaite occurs as a microvolume mineral up to 300μ across, euhedral to subhedral in form, and is developed sparsely in the mosaic aggregates of clinopyroxene, actinolitic hornblende and fluorspar. The chemical analyses of Grain#(A)by electron microprobe method gave the following chemical composition on the average; SiO₂ 22.22, TiO₂ 0.60, SnO₂ 56.72, Fe₂O₃ 0.05, CaO 20.61, Total 100.20 (all in weight percent). From this, the chemical formula on the basis of five oxygen atoms may be calculated as, Ca_0.98(Sn_1.00Fe3+0.00Ti_0.02)_1.02O₁Si_0.99O₄, which corresponds closely to CaSnOSiO₄, the stoichiometric composition of malayaite. The principal reflections appearing on the X-ray diffraction patterns are, 5.03Å(35)(011), 3.29Å(20)(200), 3.06Å(35)(002), 2.668Å(>100)(122, 031)and 2.415Å(25)(211).
As far as the present malayaite is concerned, it might be formed by the reaction of calcium, tin and silica at the frontal zone of skarnization, where tin and other volatile constituents might have been concentrated(TAKENOUCHI and SHOJI, 1969; TAKENOUCHI, 1971).

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