The high-dT/dP-type Hidaka Metamorphic Belt in Hokkaido, northern Japan, represents a tilted crustal section of a magmatic arc of Tertiary age. The highest metamorphic grades reached are granulite facies, and the syn-metamorphic granitic rocks are widely distributed in this metamorphic terrane. The granitic rocks are mainly tonalitic and granodioritic in composition, and are classified into peraluminous (S-type) and metaluminous (I-type) granitoids. A large amount of pyroxene-bearing S-type tonalites (garnet-orthopyroxene tonalite) is distributed in the Niikappu river region in the northern part of the Hidaka Metamorphic Belt. Pyroxene-bearing I-type tonalite (two-pyroxene hornblende tonalite) bodies are also distributed in this area.The pyroxene-bearing tonalites are classified into several sub-types on the basis of their field occurrence, texture, mineral assemblage and geochemical features. Homogeneous IH- and SH-type tonalite are thought to represent original magmas, i.e. those which have been generated by partial melting of mafic metamorphic rocks and pelitic-psammitic metamorphic rocks, respectively. Model calculations assuming batch partial melting indicate that possible restites are garnet-two-pyroxene mafic granulite for IH-type and garnet-orthopyroxene aluminous granulite for SH-type. The unexposed lowermost crust of the ‘Hidaka crust’ is thought to be composed of garnet-two-pyroxene mafic granulite, garnet-orthopyroxene aluminous granulite and metagabbros.

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Garnet bearing granite (Grt granite) and high grade pelitic gneisses occur in the Kannak Complex, southern Kontum Massif, central Vietnam. Electron microprobe (EMP) dating of monazite in Grt granite and garnet orthopyroxene gneiss (Grt Opx gneiss) gave ages of ca. 260 Ma from cores and ca. 230 Ma from thin rims. Since most monazite grains are predominately of core composition, the ca. 260 Ma age indicates the timing of high temperature metamorphism and the formation of Grt granite. Grt granite is locally accompanied by coeval intrusions of fine grained gabbro, which is a candidate for the heat source leading to high grade metamorphism and partial melting of the crust during the Late Permian.

A series of arsenic remediation tests were conducted using a washing method with biodegradable organic acids, including oxalic, citric and ascorbic acids. Approximately 80% of the arsenic in one sample was removed under the effect of the ascorbic and oxalic acid combination, which was roughly twice higher than the effectiveness of the ascorbic and citric acid combination under the same conditions. The soils treated using biodegradable acids had low remaining concentrations of arsenic that are primarily contained in the crystalline iron oxides and organic matter fractions. The close correlation between extracted arsenic and extracted iron/aluminum suggested that arsenic was removed via the dissolution of Fe/Al oxides in soils. The fractionation of arsenic in four contaminated soils was investigated using a modified sequential extraction method. Regarding fractionation, we found that most of the soil contained high proportions of arsenic (As) in exchangeable fractions with phosphorus, amorphous oxides, and crystalline iron oxides, while a small amount of the arsenic fraction was organic matter-bound. This study indicated that biodegradable organic acids can be considered as a means for arsenic-contaminated soil remediation.

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