In this paper, physicochemical environments during burial metamorphism of the Dales Gorge Member in the Witterioom area were estimated based on the geotectonic history in the Hamersley area (MIYANO, 1976a) and mineral assemblages in banded iron formation (MIYANO, 1976b) as follows;
Rock pressure (Ps): 700-1300 bars
Temperature
Maximum: 230±20°C (within 1000±300 bars)
Minimum: 100±20°C (within 1000±300 bars)
Dominant range: 80-160°C
Partial pressures of fluids
Po₂ (=fo₂): 10^-58.5-10^-42.8 bars
Dominant range: 10^-55.8-10^-42.8 bars
Ps₂ (=fs₂): 10^-27.1-10^-15.2 bars
Dominant range: 10^-22.0-10^-15.2 bars
PCO₂: about 1-55 bars (within 120±40°C)
The phase equilibria of banded iron formation were discussed in terms of the systems of Fe-Si-O-H and Fe-Si-C-O-H. In the Fe-Si-O-H system, pure minnesotaite does not coexist with hematite. Considering, however, impurities in minnesotaite, the assemblage of two minerals can be associated. Pure greenalite seem to be unstable at higher temperatures by taking into account the effect of error in the Gibbs free energy, ΔG°_{f, 298.15}, of minnesotaite. In the Fe-Si-C-O-H system, four phases of hematite, magnetite, siderite, and minnesotaite (impure phase) can coexist together in the absence of graphite. Considering common impurities in greenalite, it is predicted that five phases, hematite, magnetite, siderite, greenalite, and minnesotaite, can coexist together(Fig. 12(C)). But greenalite is extremely rare in the Hamersley area. Then it is likely that greenalite is unstable under the CO₂ pressure estimated above (Fig. 12 (D)).
From analysis of T-XCO₂ diagram, burial metamorphism of the Dales Gorge Member seem to have taken place within one phase region of H₂O and CO₂, where XCO₂ gives 0.001 to 0.05 within the estimated temperature at PCO₂+PO₂H=1000 bars.

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About 850 granitoids from various localities, mostly from the Japanese Islands are analyzed for arsenic by an arsine-generated atomic absorption method. The range varies from 0.1 to 87 ppm in fresh rocks, but generally from 0.2 to 6 ppm. Foliated granitoids of the high T/P type metamorphic belts have the lowest range and the average is 0.7 ppm. Massive granitoids of the nonmetamorphic belts are 2.1 ppm in their average; the Sierra Nevada batholith falls within the same category (avg. 2.1 ppm).
Miocene granitods in the southwestern Outer belt, which is a tin belt, have the widest range as 0.1-87.0 ppm and the highest average as 5.9 ppm. Tin granitoids in other regions, such as the Erzgebirge (avg. 17.3 ppm), Malay Peninsula (avg. 5.0) and Mt. McKinley, Alaska (avg. 19.2 ppm), are also high. Thus arsenic in granitoids becomes to be enriched in the following order: deeply sheeted concordant type, common discordant type, and discordant type tin granite. Generalized average in the previous papers, 2 ppm, corresponds to the average of the common discordant type batholith and stock.
Small granitoid stocks associated with arsenic and tin (plus Cu+Pb+Zn) mineralizations have generally higher contents of arsenic than those unrelated. Pervasively altered granitoids in base metal mining areas are enriched in arsenic. The element may be useful in geochemical exploration.

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