The volcanism in the Hishikari Au mining area, southern Kyushu, Japan, is characterized by continued bimodal mode (andesite and dacite). The mineralization stage overlaps with the dacite eruptions. The magma erupted these dacites (especially Kurozonsan Dacites) are characterized by high fO₂, high Cl content, rather low crystallization temperature and emplacement at shallow depth. The features are similar to those of I type granitic rocks associated with mineralization.
In such high fO₂ and Cl rich magma, S should form an oxidized species such as SO₂, and Cl should bind with Au to form AuCl₂^-. In the country rock, the accretionary Shimanto Supergroup, the AuCl₂^- discharged from magma becomes unstable with decreasing fO₂ and temperature. As the Shimanto Supergroup has abundant organic matter, the oxidized S species from magma is converted to H₂S and/or HS^-. The Au decomposed from AuCl₂^- would react with HS^- to form Au(HS)₂^-. The Au(HS)₂^- would be transported upward through the thick Shimanto Supergroup. Near the surface, the mixing with oxic groundwater, as well as cooling and boiling, decomposes the Au(HS)₂^-. Hence, the conversion from chloro-complex to bisulfide-complex might play an important role in forming the large reserve, the high grade and the high precious/base metal ratio of the Hishikari epithermal gold deposits.

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This study evaluates the potential of scandium resources in lateritic bauxite deposits and lateritic Ni-Co deposits derived from mafic parent rocks. Mafic rocks generally contain more Sc than felsic rocks because Sc replaces iron and manganese in pyroxene and amphibole. Pyroxenite and hornblendite are most enriched in Sc whereas peridotite is poor in Sc. Chemical weathering causes rocks to be enriched in Sc, which behaves as an immobile element, because mobile elements are leached from the rocks. Scandium contents of bauxite depend on those of parent rocks and they are estimated to be ~40 ppm in Indochina Peninsula. Red mud, Fe-rich residue in the process of refinery of bauxite, contains high concentration of Sc. Scandium-bearing lateritic Ni-Co deposits contain higher grades of Sc ores than bauxite and recently have been explored in Australia. As Sc contents of the laterite is controlled by those of parent rocks, pyroxenite-derived laterite may form high-grade Sc deposits (>100 ppm). However, Ni and Co grades tend to decrease in the high-grade deposits in Australia. Large amounts of resources and developed techniques in Sc recovery as a by-product indicate that bauxite deposits and lateritic Ni-Co deposits are prospective Sc resources in the near future.

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Feeding ores and tailing slime from representative Pb-Zn deposits hosted in Paleozoic carbonates-rich sedimentary rocks and Triassic rhyolites were studied chemically by ICP/MS. The Pb-Zn ores from the Cho Dien sedimentary area, called Cho Dien type, are rich in chalcophile elements such as Cd, In, As, Ag, and also Fe. Recovery rates of the flotation are high in the Zn (58%) and thus Cd (64%), and also lead (92%). Arsenic and iron are high in both the feeding ores and tailing slime, implying these are contained as arsenopyrite and transported to the tailing ponds. The Pb-Zn ores from the Lang Hich sedimentary area, Lang Hich type, have high Zn/Pb and Cd/Zn ratios, but are poor in chalcophile elements, and Fe and Mn. About 87 % Zn and 88 % Cd of the ores are recovered by the flotation. Arsenic and Fe are originally low with averages of 185 ppm As and 1.15 wt.% Fe; all moved to the tailing pond. The rhyolite-hosted ores at Na Son mine are rich in Pb (Pb/Zn=4.1), and also rich in some lithophile components (e.g., REE) and such chalcophile elements as Cd, In, Cu, Co, Ni, Bi, Ag, Sb and Se, but very low in As. Important pollutants of Pb, Cd and As are well decreased in the tailing slime.

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Surface soil and stream sediments of 36 samples were analyzed in the Na Bop mining area for the major and minor elements by ICP/MS and total C and S by infrared methods. Important ore metals for the environment, such as arsenic, base metals and cadmium, are high in surface soils and stream sediments. Arsenic is positively correlated with iron and cadmium is also well correlated with zinc, implying that the arsenic and cadmium originated in the ore minerals of arsenoppyrite and sphalerite in the ores; then the minerals were moved into the surface materials.
Some of the ore components are enriched in soil and stream sediments below the Bac Can tailing pond along the NE-trending small valley (e.g., As & Pb, Figs. 4 & 5), but are low along the N-S trending main valley where sulfide orebodies cropping out. Soils are higher in the total C contents relative to stream sediments at the same sampling point, but no such tendencies are observed on the total S and As. The pollution is much smaller in scale relative to large copper mining area of the Hitachi mine, Japan, and the Karabash mine of Ural, Russia, where all the mining equipments including mineral separation and smelting plants were located. This study should further be extended much down stream side including agriculture lands and products.

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