The effects of the addition of a small amount of MgCr₂O₄, (0.3 wt.%) to the system Mg₂SiO₄ (forsterite)-CaAl₂Si₂O₈(anorthite)-CaMgSi₂O₆(diopside)-SiO₂ at 1 atm have been studied. The system is an important model to the crystallization and generation of tholeiitic basalt. The primary field of spinel is enlarged compared with that in the Cr-free system at the expense of anorthite primary field, and as a result forsterite and anorthite do not coexist at the liquidus temperatures. Two invariant points have been confirmed : one at about 1298°C shows liquid coexisting with forsterite, protoenstatite, diopside, and spinel, and the other at the temperature below 1265°C shows the assemblage of spinel, protoenstatite, diopside, tridymite, and liquid. The first mineral assemblage corresponds to that of spinel lherzolite. In the Cr-free system this assemblage is not stable at 1 atm and an invariant point having plagioclase lherzolite mineral assemblage is present. It is generally said that the transformation from spinel lherzolite to plagioclase lherzolite takes place at about 8 kbar at 1000°C. The results obtained in the present study indicate that the presence of small amount of Cr in magma significantly reduces this transformation pressure. Another important aspect of the result is that the position of the invariant point is possibly moved by the change of bulk Cr content in the system. If the liquid generated by the partial melting of the spinel lherzolite mantle has the composition of this point, Cr content of the mantle would give significant effect to the composition of magma.

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Molybdenum mineralization is recognized in addition to Pb-Zn skarn mineralization at the Nakatatsu mine. The mineralization consists of: (1) quartz-molybdenite veins; (2) molybdenite films or paints along joints with or without clay minerals; (3) disseminated molybdenite. The ore bodies are hosted in quartz porphyry, plagioclase porphyry, non-calcareous sedimentary rocks and Pb-Zn skarn ore bodies. The host rocks show enrichment in Mo, F, Ca, Mn, Co, Zn, Ag, Sn, W, Pb, Bi and depletion in Na, V, Sr and Ba. Among these elements, F, V and W have correlation with Mo, and Mn, Zn, Sn, W and Pb are correlated with Ca. The non-calcareous country rocks have suffered phyllic alteration. The mode of occurrence of molybdenite, alteration assemblage and geochemical characteristics suggest that the molybdenum mineralization at Nakatatsu is of porphyry type and has some similarities with the Climax-type mineralization.

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Paleozoic-Cenozoic sedimentary rocks from the Chugoku and Shikoku districts contain 1.5-3.5 ppm tin in general (avg. 2.4 ppm, n=179). Those occurring near Paleozoic limestone plateau in the Chugoku district, and containing mafic volcanics are much lower in tin, reflecting their tindepleted source materials. Shales from the chert-dominant strata in Ota-gawa area give highest values for tin (3.8-6.4 ppm) and potassium oxide (3.8-4.9%). Most of the tin may be transported in the form of particulate together with fine sediment fractions during the weathering. Thus, tin is more abundant in the shales and slates than sandstones.
Compared with Recent sediments collected from the lakes and sea areas from the Japanese Islands to Central Pacific, tin contents of sedimentary rocks are more or less similar to those of the lake sediments (2.5 ppm, n=70). The Recent marine sediments have much lower values in tin (1.5 ppm, n=193). Tin is distributed more abundantly in the terrigenous environments than in the oceanic ones.

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Unit cell dimensions have been determined for synthetic pyroenes in the system NaScSi₂O₆-CaNiSi₂O₆ which have been crystallized at 1100-1300°C and atmospheric pressure. The unit cell dimensions show an almost smoth change with composition., The data support the postulate that a complete series of solid solution does eist in the subsolidus region of the binary system.

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Bubble-free thin sections of porous specimens, such as pumices and accretionary lapilli, were made by mean of vacum treatment.

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