The areal distribution of Green Tuff district is re-examined, forcusing mainly on the tectonic characters of eastern Hokkaido. Miocene volcanism in eastern Hokkaido began with hornblende-bearing andesite at 14 Ma. The intrusions of ilmenite-series granitoids are slightly earlier than it. Volcanism at 14 Ma, associated with ilmenite-series granitoids, prevails through the outer zone of Southwest Japan. It is proposed that the Miocene igneous belt in eastern Hokkaido extends down to the outer zone of Southwest Japan. Igneous rocks, such as 14 Ma-andesitic basalt at Toyokoro, SE Hokkaido, and 22 Madacitic volcanic conglomerate in Holes 438 and 439, DSDP, and as a heat source for Jyouban hot spring, located off the NE Japan coast, occur between both Miocene igneous belts. On the contrary the Miocene NE volcanic belt, typical of Green Tuff belt, passes through the Oshima Peninsula and attains to the Sea of Japan. There was the zonal arrangement of middle Miocene to Pliocene igneous belts along the Japanese islands from the inner (back-arc) side to outer (trench) one: the arc, monogenic and forearc volcanic belts. The trench during this period was located less than about 100 km far from the forearc volcanic belt, probably through the present Abashiri City area in eastern Hokkaido.

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The Zijinshan copper-gold deposit, Fujian Province, is situated at the margins of an Early Cretaceous volcanic basin, beside a caldera made up of dacitic pyroclastic rocks and subvolcanic (dacite-porphyry) bodies. Silicification and hydrothermal alteration of quartz-dickite, quartz-alunite and quartz-sericite occur as concentric zones around the caldera covering a wider area.
The orebodies occur as filling-veins in a dense fissure zone and as a stockwork fissure system, accompanied by hydrothermal breccias. Native gold, pyrite, digenite, enargite and covellite are the main ore minerals, while gold and copper are the main economic metals. The gold veins occur within the silicified zone in the shallow portions of the deposit. On the other hand, the copper veins lie within the quartz-alunite alteration zone at the 350-900m interval, showing good primary mineralization zoning.
The fluid inclution data suggest that the hydrothermal fluids were characterized by low temperature, low salinity (0.0-5.0 wt% NaCl equivalent) and were in acidic conditions (pH=3.64-3.98). The fluid inclution filling temperatures ranged from 120°C to 140°C for the gold mineralization and from 180°C to 240°C for the copper mineralization. Many fluid inclusions showing evidences of boiling were observed in the quartz-alunite alteration zone. The salinity of these inclusions is higher and ranges from 7.5 to 21.6 wt% NaCl equivalent, while homogenization temperatures show a narrow range.
The δ¹⁸OH₂O values of the hydrothermal fluids range from -3.25 to -4.17‰(SMOW) and the δD values from -60 to -76‰, which coincide with the values to oxygen and hydrogen isotopic compositions of Mesozoic meteoric water in this region. Several evidences suggest that the Zijinshan deposit is a quartz-alunite type epithermal deposit and is the first of its kind to be discovered in the continent of China.

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In the Shandong Province of China, two different granite-greenstone terrains (GGT) are present in east and west sides of the Tancheng-Lujiang fault. In the eastern GGT the greenstone belt (Jiaodong Group) is mainly composed of meta-morphic rock associations belonging to four volcanic cycles of basalt-andesite-dacite-rhyolite. This Group contains komatiite in the lower parts of the stratigraphy and metasediments in the upper parts, and does not show a bimodal character in the chemical composition. These rocks have undergone intense deformation and metamorphism. Geochemical data show that this Group was derived from oceanic sources. This type of greenstone belt is called “O-type”.
In the western GGT, primary and secondary greenstone belts can be identified. Primary greenstones are intruded by tonalitic granites, and occur as enclaves within the granites. The secondary greenstones (Taishan Group) consist of bimodal mafic-felsic volcanic assemblages, and unconformably overlie the tonalitic granites. This bimodal suite is accompanied by a minor ultramafic component near the stratigraphic base, and contains large amounts of metasediments. The Taishan Group is thought to have evolved on sialic continental basement, and is called a“C-type” greenstone belt.

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Studies of mineral assemblages, homogenization temperatures and salinities of fluid inclusions, and hydrogen and oxygen isotopic ratios for the pyrophyllite mineralization of the Nishiyama-higashi deposit, Southwestern Japan, were combined to determine the environment of formation and the origin of the hydrothermal solution responsible for this miner-alization.
Six mineralogic zones were formed in the deposit by a hydrothermal solution passing through an E-W fissure in Cretaceous dacitic volcanic rocks. The constituent minerals of the zones are: Weakly altered zone: quartz ≥ plagioclase, K-feldspar, chlorite, muscovite and pyrite; Zone I: quartz and muscovite ≥ pyrophyllite and hematite; Zone IIa: pyrophyllite and quartz ≥ hematite; Zone IIb: pyrophyllite, kaolinite and quartz ≥ dickite and hematite; Zone III: alunite and quartz ≥ pyrophyllite and kaolinite ≥ muscovite, diaspore and corundum; Zone IV: pyrophyllite, kaolinite and quartz ≥ diaspore; Zone V: corundum, diaspore, quartz, pyrophyllite and kaolinite. The paragenetic sequence of the formation of the deposit from early to late stage is: formation of corundum-diaspore (around 370°C)→formation of diaspore-pyrophyllite (325-280°C)→formation of pyrophyllite-hematite (335-260°C)→formation of kaolinite-dickite-alunite-quartz-hematite (about 190°C). The formation of kaolinite-dickite-alunite-quartz-hematite is associated with boiling of the hydrothermal solution at around 190°C. The salinities of the hydrothermal solution associated with the formation of the Nishiyama-higashi deposit range mainly from 0.0 to 1.1 wt% NaCl equivalent. Si0₂ concentration of the hydrothermal solution was less than 10^-2.3 moles/kg H₂O for the formation of corundum-diaspore, 10^-2.04-10^-1.96 moles/kg H₂O for the formation of diaspore-pyro-phyllite, 10^-2.08 -10^-1.90moles/kg H₂O for the formation of pyrophyllite-hematite, and less than 10^-2.08 moles/kg H₂O for the formation of kaolinite-dickite-alunite-quartz-hematite. The pHs of the hydrothermal solution forming the Weakly al-tered zone, Zone IIb and Zone III were 4.6 - 6.8, 1.6 - 4.5 and 1.6, respectively. The hydrothermal solution forming Zones IIb and III was very acidic. The range of total sulfur concentration of the hydrothermal solution was 10^-2 - 10^-5moles/kg H₂O and the major sulfur species in the solution was HSO₄.
On the basis of the data on hydrogen and oxygen isotopic ratios of pyrophyllite, dickite and quartz, the hydrogen and oxygen isotopic ratios of the hydrothermal solution responsible for the formation of pyrophyllite-hematite are -60‰ and 0‰, respectively. On the other hand, the hydrogen and oxygen isotopic ratios of the hydrothermal solution responsible for the formation of kaolinite-dickite-alunite-quartz-hematite range from -70 to -50‰ and from -7 to -4‰, respectively. The hydrothermal solution for the Nishiyama-higashi pyrophyllite deposit originated from meteoric water in a volcanic environ-ment. As hydrothermal activity progressed, the water/rock ratio and the ratio of meteoric water in the hydrothermal solution increased. The hydrothermal system of the Nishiyama-higashi pyrophyllite deposit was a paleogeothermal system in Creta-ceous time.

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In South Korea granitic rocks are mainly Jurassic and Cretaceous, but some are Paleogene. A new geobarometer based on aluminum in amphibole and a new amphibole-plagioclase geothermometer have been proposed by several articles. Amphibole and plagioclase analyses have been carried out for ten samples of Jurassic and Cretaceous granitic rocks utilizing an electron dispersive X-ray analyzer. The amphibole geobarometer of JOHNSON and RUTHERFORD (1989) indicates that Jurassic granitic rocks range 2.5-6.3 kbar and Cretaceous ones range 2-4.2 kbar. The equilibration temperature of amphiboleplagioclase (BLUNDY and HOLLAND, 1990) for Jurassic granitic rocks range 700-790°C and Cretaceous ones range 680-770°C. Therefore, it is suggested that the Jurassic granitic rocks are exposed the lower level of batholiths compared with Cretaceous plutons at the present erosional level.

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Some sea-floor hydrothermal ore deposits have been identified on the mid-oceanic ridge and in the back-arc basin. This time at the top of a seamount on the volcanic front in Izu-Ogasawara Arc we have discovered the modem occurrence of hydrothermal activity. The active hydrothermal field with the occurrences of sulfide mineralization has been discovered by the JAMSTEC 'Sinkai 2000' in the caldera at the top of Suiyo Seamount in Sitiyo Seamounts.
The volcanic rocks sampled at the top and the foot of the caldera wall are the calc-alkaline rock series dacites, and the low potassium andesites. This is in contrast to the tholeiitic basalts from some seamounts around Suiyo Seamount.
The sulfides of the vent chimneys from this hydrothermal field is characterized by the enrichment in Cu. The Cu contents of many ores exceed 10wt%, suggesting that the temperature of these hydrothermal fluids is enough high to dissolve copper in them. The highest Au content of sulfide samples is 71 ppm, whose average of 12 samples is 25 ppm. The highest Ag content is 337.1 ppm, whose average of 12 sumples is 176 ppm. The average Au/Ag ratio is 0.142. This ratio is very high, compared with the sulfides from some sea-floor hydrothermal ore deposits.
The high Au content of hydrothermal ore deposits at the Suiyo Seamount is worthy to note because the geological setting resembles that of the hydrothermal system at Osore-zan that was discovered in recent year in the most northern part of Japan.

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