We report on the research and development of a TDEM data acquisition system (SQUITEM) by JOGMEC using a highly sensitive high-temperature SQUID vector magnetometer cooled by liquid nitrogen. SQUITEM meets high requirements for slew rate (6.8 mT/s), dynamic range (100 dB) and bandwidth (DC-100kHz) for metal exploration. It offers deeper penetration of depth than the conventional induction coil system because it can record the step response that decreases with time slower than the impulse response of the induction coil system.
We have conducted field tests several times since 2002 in order to check performance and practicality of SQUITEM. JOGMEC has achieved stable long-term operation of all three channels, obtained good reproducibility of SQUITEM data, and good correlation between the output signals of the reference induction coils and the derivatives of the SQUITEM signals in the field tests. JOGMEC conducted the field test in February, 2005 in Marrakech-Tekna Area, Morocco where JOGMEC carried out metal exploration for the past three years. The SQUITEM data indicated its superiority to the conventional TDEM system (PROTEM) during the field test in Marrakech-Tekna Area in terms of depth of investigation. The reconstructed resistivity sections of SQUITEM data by 1-D inversion code also show good agreement with known geology and apparent resistivities of DC resistivity logging.

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Hyperion is the only spaceborne optical sensor collecting hyperspectral data. This research shows that the spaceborne Hyperion data analysis can detect an alteration zoning related to porphyry copper deposits and is consequently very effective for the mineral exploration. Two study areas are the Yerington Area located in the southwest of Nevada and the Santa Rita Area located in the southwest of New Mexico, USA. Around the Yerington Area, the Yerington porphyry copper mine is located and the alteration zone related to porphyry copper, skarn and epithermal deposits is widely distributed, which were formed by the activity of granodiorite batholith and porphyry dykes. Santa Rita porphyry copper mine is located in the Santa Rita Area. Porphyry copper and skarn deposits related to the activity of granodiorite stock and porphyry dykes are distributed around the area.
As a result of Hyperion data analysis of the two study areas, pyrophyllite, alunite, kaolinite, sericite, chlorite, epidote, calcite, hematite, goethite and jarosite were extracted. Sericite is divided into three compositional structure types of Al-type, normal type and Mg-Fe-type. Kaolinite is divided into two types according to the difference of crystallinity. The mixture of two minerals, pyrophyllite plus sericite and sericite plus chlorite, was also extracted. These mineral distributions are closely related to the geology and mineral deposits. The alteration zoning from the center to the outside, [pyrophyllite, alunite] / [Al-sericite] / [Mg-Fesericite] / [sericite+chlorite] / [chlorite, epidote], was recognized around the advanced argillic alteration in the Yerington Area. The leached, phyllic, argillic and skarn alteration zone were recognized inside the open pit of Santa Rita mine. The leached zone located in the upper wall of the pit is composed of hematite, goethite, jarosite and kaolinite (low crystallinity). Al-sericite is distributed mainly in the granodiorite stock of the west part of the pit and the skarn alteration is distributed mainly around the stock.
As the Hyperion data is noisy, masking the pixels over the noise and selecting proper threshold value are necessary in order to raise the accuracy of the extraction and mapping minerals. Detecting the compositional change and the mixture of minerals based on the alteration and mineral deposits leads to the alteration zoning. These distribution and zoning of alteration minerals provide important geological information and proved that the detection of the minerals by the hyperspectral data is very effective in focusing potential exploration targets. The spaceborne hyperspectral data of optical sensor with high resolution will be a powerful tool for mineral exploration because its global data is easily accessible for end users at low cost.

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An analysis of the geothermal structure and fluid flow in the Ogiri geothermal field was carried out based on the surveys and operational data of the Ogiri Power Station after its commencement.
The results are as follows: (1) Based on the precise seismic reflection survey by NEDO and the electromagnetic sounding method (AMT method) by NKG, it is estimated that the Ginyu-south fault, which runs through the Ora hot spring and forms a geothermal reservoir parallel to the Ginyu fault, exists in the Ogiri field; (2) Based on the hypo-central distribution of microearthquakes and the distribution of self-potential anomalies, geothermal fluid is recharging the Ginyu-fault reservoir from the east or east-southeast side, where the center of Kirishima volcano is located, and most reinjection water is flowing out to the westsouthwest side where it is topographically low; (3) Based on the total production rate of geothermal fluid and changes in pressure of the reservoir, the geothermal fluid recharge rate of the reservoir is estimated to be 1, 100 to 1, 130 tons per hour.
In order to continue stable operations of the Ogiri Geothermal Power Station, we should decline slightly to produce geothermal fluid from the vapor dominate zone of the Ginyu fault reservoir, produce less than 1, 100 tons per hour of geothermal fluid, and extract geothermal fluid from other geothermal reservoirs, such as the Ginyu south fault, for shortage of vapor.

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Since 2001, Nittetsu Mining Co., Ltd. has conducted ASTER Image Analysis for mineral exploration targeting porphyry copper-type deposit in Northern Chile. In Oga Area, which is located about 200km southeast of Antofagasta, Region II, Chile, a promising phyllic alteration zone was extracted by ASTER Image Analysis. In 2002 and 2003, surface geological mapping and geochemical survey, including total 89 points of pit survey, were carried out covering the extracted alteration zone. Cu-Mo geochemical anomaly, suggesting possibility of porphyry copper deposit, was confirmed, and quartzhematite-limonite veinlet networking and acid leaching were observed in this area. Therefore, the company has conducted 12 holes, total 3, 068m, of RC drilling in 2004, however, no significant copper mineralization was observed. Low initial copper content in ore-related magma and not enough development of hydrothermal circulation system were considered as the principal reason of such weak copper concentration in this area.
On the other hand, the drilling result confirmed significant epithermal Au mineralization. Au anomaly of more than 100ppb was observed in total interval of 240m, which is about 8% of total drilled length, and maximum Au content was 1, 300 ppb from 2m interval. The distribution of Au anomaly is not related with the degree of alteration, but probably is controlled by NW-SE trending fault system. Therefore, Au potential could be new regional exploration target around this area. Further exploration works for gold target, including trench survey and diamond core drilling, are required in Oga Area.

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A remote sensing study was conducted in a sparse vegetation area of Kalgoorlie, west Australia, aiming at effective utilization of polarimetric synthetic aperture radar (SAR) data for lithofacies discrimination. The study includes data processing, image interpretation, ground truth and evaluation of the results.
Three lithofacies discrimination methods, namely contrast enhancement method between two geologic units, simple scatters decomposition method and maximum likelihood method, were applied to L-band polarimetric SAR data of JPL/AIRSAR after reducing the influence of backscatter by vegetation. The contrast enhancement image between two geologic units and simple scatter components image had the same effectiveness to ASTER image for discriminating lithofacies, however, these two images were superior to ASTER and multi-band polarimetric SAR images in the discrimination of the specific lithofacies.

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The mining sector in the Islamic Republic of Mauritania was the backbone of the country's economy in the 1960s when Mauritania gained independence from France. However, mineral exploration has been limited due to several factors including the limited availability of geological information, poor legal and fiscal framework and lack of mining sector promotion measures as well as the vast scale of the country, severe climate and lack of infrastructure.
In response to the request of the Mauritanian Government, Japan International Cooperation Agency conducted "the Study on the Strategic Plan of Mineral Resource Development". A geological survey was implemented from November 2003 to March 2005 in the areas of mineral potential in Mauritania with the purpose of promoting domestic and foreign private investments in the exploration of mineral resources.
Mauritania comprises five geological provinces. These are the Reguibat Shield, Taoudeni Sedimentary Basin, Tindouf Sedimentary Basin, Mauritanides and Atlantic-Coastal Sedimentary Basin. Major metal ore deposits are distributed within both the Reguibat Shield and the Mauritanides.
In the central area of the Reguibat Shield, magnetite formations occur in the Archean groups and large-scale highgrade hematite banded-iron formations occur in the lower Proterozoic groups. These deposits are the sources of iron ores that support Mauritania economy. In the southwestern area of the shield, epithermal; and mesothermal gold-bearing quartz network and disseminated deposits (e.g.Tasiast gold deposit) occur in banded iron formations (BIFs) of the Archean greenstone belt. Moreover, gold-bearing quartz vein deposits (e.g.Tijirit Ator gold deposit) occur in the basalt and ophicalcite units.
The Mauritanides is most significant in copper and gold mineralization among the five geological provinces. These comprise a carbonate replacement magnetite-bearing copper and gold deposits and prospects (e.g.Guelb Moghrein deposit), copper and gold-bearing quartz veins in mafic schist and carbonate (e.g.Tabrinkout prospect), copper (and gold)-bearing quartz veins in andesitic to basaltic volcanic rocks (e.g.Indice 78 and Oudelemguil prospects) and disseminated copper deposits (e.g.Kadiar). The other important deposit type is orthomagmatic PGE-bearing chromite deposits in serpentinite (e.g.Guidimaka).
In the future, it is desirable that exploration and development focus on gold deposits in the Reguibat Shield, and copper and gold deposits and platinum-bearing chromite deposits in the Mauritanides.

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A review on primary and supergene copper minerals was made for principal Chilean porphyry copper deposits in Cretaceous to Pliocene ages, with the objective to estimate their formational enrvironments. The primary copper mineralization is characterized by disseminated sulfide minerals, such as chalcopyrite, bornite, digenite, enargite, and tetrahedrite-tennantite, locally with primary covellite and nukundamite. This association indicates "high sulfidation" conditions at temperatures below 500°C. The supergene enrichment zone developed extensively in upper parts of the deposits, which is attributed principally to the Miocene Andean orogeny and to the associated climate change, is divided into the oxidized subzone of chrysocolla, atacamite, antlerite, brochantite and tenorite with lesser amounts of malachite and azurite, and the sulfurized subzone of chalcocite, covellite, native copper and cuprite. The sulfurized subzone is inferred to have been generated under reduced conditions below underground water level, in contrast to the oxidized subzone formed under moderately acidic to neutral oxidized conditions.

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