The Metal Mining Agency of Japan(MMAJ) has developed two high-sensitive SQUID systems for the Time Domain Electromagnetic(TDEM) Survey. The first system had been completed in 2000 for civil engineering survey. MMAJ carried out some TDEM field trials outside magnetic shielding. We could achieve stable long-term operation of all three channels, and obtained good reproducibility of SQUID data and a good correlation between output signals of reference induction coils and the time derivative of SQUID signals in the last field trial on Awaji Island in June, 2001. The result of this trial indicates that the SOUTD magnetometer provides a better sienal-to-noise ratio than an induction coil particularly at late time.
The second system for the mineral exploration has been just developed in February, 2002. The field check to assess performance of the second system also showed a good correlation between the SQUID and coil data at middle time. However, the second system could not take good data at late time because of low slew-rate of the SQUID magnetometer. MMAJ is overcoming this problem on low slew-rate to complete the TDEM system based on SQUID magnetometer for mineral exploration.

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The Yusen No.1 vein group in the Yamada deposit of the Hishikari Mine, a high-grade epithermal Au-bearing quartzadularia vein system, was analyzed based on the structure and ore grade.
Two distinctive ores are recognized at the central part of the vein system, the high Au/Ag (Au/Ag>5, high Au ore) ore and the low Au/Ag ore (Au/Ag<3, low Au ore). Electron microprobe analysis has revealed the difference of electrum composition, 85.6 wt% Au in the high Au ore and 72.1 wt% Au in the low Au ore. Fluid inclusion studies have also delineated the difference of the homogenization temperature and the last melting point of ice between them. Homogenization temperature ranges between 177°C and 215°C in the high Au ore and between 176°C and 211°C in the low Au ore. Last melting point of ice ranges from -2.4°C to 0.0°C and from -0.5°C to 0.0°C, respectively.
Results of analysis imply the difference of physico-chemical condition of the ore torming solutions responsinte for these ores. Drifting exploration shows the structure of these ores, which provides a guideline for subsequent exploration of the lower Dart of the vein system.
Intensely argillized tuff cap layer strictly controls the distribution of the vein at the eastward extension of the Yusen No.1 vein eroun. Tuff can laver may have played an important role responsible for high-grade gold mineralization.
High-grade branching veins have been newly discovered through the interpretation of vein structure resulted from drifting and drilling exploration of the eastward extension of the vein system. Interpretation of vein structure will be important to establish exploration program for additional ore reserves.

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In the Namosi district located 30 km of Suva, the capital of Fiji, there are more than fifteen porphyry Cu-Au prospects (Waisoi; Wainabama; Waivaka Corridor). Of these, however, the Waivaka Corridor area in the center part of the Namosi distirict have not yet been investigated systematically.
We conducted geological, geochemical, and geophysical survey in the Waivaka Corridor area and evaluated the utility of principle features as a survey tool for exploration for porphyry Cu-Au deposits.
Summaries are as follows:
(1) Late Oligocene to Middle Miocene Wainimala formation and Middle Miocene to Pliocene Madurausucu formation distributed in the area, are mainly composed of andesite lava, tuff, and pyroclastic rocks. Late Miocene to Early Pliocene mineralized stocks and dikes, composed mainly of quartzdioritic and dioritic porphyries, are emplaced in those rocks.
(2) The Waivaka corridor, one of the biggest mineralized zones, is situated in an area which is enclosed by two major faults striking ENE-WSW. On the other hands, most quartz and sulfide veins crossing ENE-WSW systems occur along NE-SW to E-W fractures.
(3) The close spatial and temporal relationships between Cu-Au mineralization and hydrothermal alteration accompanied with hypabyssal dikes of Late Miocene age (5.3Ma) suggested a genetic relationship between calc-alkaline magmatism and Cu-Au mineralization.
(4) The Cu contents of soil distributed around dioritic porphyries have commonly more than 250 ppm. In particular, potentially mineralized zones with soil having Cu value of more than 500 ppm are characterized by the presence of the silicified rock and quartz veins.
(5) There are two geochemical features of soil which can be distinguished as a series of erosion. Soil anomalies with Cu-Au-Mo in and around outcropping dioritic porphyries suggest that the porphyry system has suffered erosion. In contrast, soil anomalies with Au-Mo indicate that top of the porphyry system may be still preserved. In both geochemical features, intermediate chargeability zones (14 to 20 mV/V) of IP geophysical survey that may reflect bornite and chalcopyrite, are superimposed beneath these anomalies and it is expected that the presence of promising porphyry Cu-Au system in the underground.

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Horizontal seismic profile method was tested at a tunneling site of the Toyoha mine for exploring the geologic conditions beyond the working face. The conclusions acquired are as follows; (1) it is very difficult to acquire P-wave reflections, (2) walls of cavities are free planes and thus it is difficult to obtain pure P-wave signals, (3) it is easy to obtain S-wave signals by "free walls". In this report we propose that HSP be carried out by using S-waves rather than P-waves.

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The Metal Mining Agency of Japan has conducted research towards the utilization of ASTER data in mineral exploration since 1996. To promote utilization of ASTER data, spectral data base and indices for discriminating for rocks and alteration minerals were established, and case studies were carried out. Case studies shows ASTER improves abilities to identify rocks and alteration minerals for mineral exploration.

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The Hishikari deposit, which is located in the northern part of Kagoshima Prefecture, Kyushu island, Japan, is an epithermal Au-bearing quartz vein-type deposit about 1 Ma old. The purpose of this study was to clarify the relation between concentrations of Au and trace elements such as rare earth elements (REEs) in Au-bearing quartz veins based on mineralization sequence, mineral assemblage and analytical data obtained by INAA and LA-ICP-MS and to determine the framework of the hydrothermal system forming the Au-bearing quartz veins.
The investigation was carried out using samples of extremely Au-enriched ores, 2, 130 and 3, 700 g/t Au, from Ryosen. No. 1 and Ryosen No. 5 veins in the Hishikari Lower Andesitic rocks, respectively, and typical Au ores of 200 g/t Au from Hosen No. 5 vein in alternation of shale and sandstone of the Shimanto Supergroup. The Au contents in the ores of Ryosen No. 1 and Ryosen No. 5 veins as determined by INAA decreased with the progress of mineralization, from 30, 300 ppm to 1.59 ppm and from 11, 500 ppm to 56.5 ppm, respectively. On the other hand, the Au content in the ores of Hosen No. 5 vein have increased from 5.7 ppm in the early stage to 57.1 ppm in the later stage.
The REE concentrations of quartz in the Au-bearing quartz veins were measured by LA-ICP-MS. The REE concentrations in quartz in the early stage of mineralization of Ryosen No. 5 vein were high and decreased gradually with the progress of mineralization. On the other hand, the REE concentrations in Hosen No. 5 vein were low in the early mineralization stage, which is characterized by a low Au concentration, and high in the later mineralization stage, which is characterized by a high Au concentration. A positive correlation was found between Au content and REE contents of these Au-bearing quartz veins. REE in these quartz veins would have been included in impurities of quartz crystals and/or clay minerals among grain boundaries of quartz crystals.
The estimated REE concentrations of the Hishikari hydrothermal solutions forming the Au-bearing quartz veins are 0.85 ppb for La, 2.18 ppb for Ce, 3.44 ppb for Nd, 0.76 ppb for Sm, 0.03 ppb for Eu, 0.24 ppb for Tb, 0.12 ppb for Yb and 0.05 ppb for Lu. These estimated concentrations of REE are different from those of REE in magmatic water and similar to those of REE in hot spring water, ground water and river water, which are of meteoric origin, in the area in which granitic rocks are distributed. REE in Au-bearing quartz veins of the Hishikari deposit were thought to have been extracted by water/rock interaction between hydrothermal solution and country. Quartz immediately after opening of veins has high Au and REE concentrations, and the concentrations of these elements gradually decrease with the progress of precipitation of quartz in the veins. These facts suggest that the water/rock ratio changed from low to high and that hydrothermal solutions related to later Au mineralization were interacted with country rocks depleted in these elements, that were depleted as a result of interaction between country rocks and hydrothermal solutions related to earlier Au mineralization.

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The Hakone volcano is the triple caldera on the base rocks called Yugashima formation belonging to the lower Miocene (Fig. 1). The river Hayakawa(barranco)erodes down to the Yugashima formation in the caldera.
At Ohwakudani (Fig. 1), there exists explosion crater where the vapor H₂O-CO₂-H₂S is gushing out (Table 2). Around this area, acidic hot springs containing H₂S and HSO₄^-, with a little or no NaCl are distributed. They are condensed vapor, and diluted by the ground water accompanied by oxidation of H₂S to HSO₄. (A) Ohwakudani, (B) Yunohanazawa, (C) Ubako and (D) Gora in Fig. 1 are exaples of this type (Table 4A, B, C, D). The CO₂ in the vapor is separated from the acidic hot water.
The reservoir of original magmatic fluid exists in the Yugashima formation just below the central cone.
The vapor composed of H₂O - CO₂-H₂S boils and is separated from the hot liquid (differentiation of the magmatic emanation).
The residual liquid flows along the fissures in the Yugashima formation. The liquid is composed of nearly neutral hot water, containing NaCl, SO₄^2- and HCO₃^-. The hot springs of this type occur in the Yugashima formation or just above the formation. (F) Sokokura, (G) Miyanoshita and (H) Yumoto in Fig. 1 are the examples (Table 4F, G and H).
The differentiaiton of high - temperatured hot spring(magmatic emanation) corresponds to the formation of acid - sulfate type and adularia - sericite type in the epithermal deposits.

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