In the Namosi district located 30km of Suva, the capital city of Fiji, there are more than fifteen porphyry Cu-Au prospects. The Waisoi is one of the largest prospecting area among them and is composed of two major deposits (Waisoi West ore deposit and Waisoi East ore deposit) which were surveyed by several major exploration companies through in 1970's to 1990's.
We conducted geological survey and geo-structural survey (fracture survey) at the Waisoi area for the exploration of middle to high grade copper ore deposit which can be developed in a current economic circumstance. Summaries are as follows:
(1) Late Oligocene to Middle Miocene Wainimala formation and Middle Miocene to Pliocene Madurausucu formation are distributed in the area and some intrusive rocks (diorite porphyry, quartz diorite porphyry, quartz porphyry) are observed in the area.
(2) Two remarkable silicified and argillized zones with ENE-WSW direction which are recognized from the results of the distribution of strong silicification and argillization zones and direction of fracturing and quartz vein system. The alteration mineral assemblage is mainly sericite-chlorite in these two altered zone.
(3) In the Waisoi West deposit, the directions of quartz veins are mainly NW-SE and ENE-WSW and the shape of ore body is structurally controlled with the same direction as quartz veins. On the other hand, in the Waisoi East deposit, the direction of quartz veins are mainly NE-SW and ENE-WSW, middle to high grade copper mineralization is structurally controlled by the fracture and quartz vein with NE-SW and ENE-WSW direction.
(4) In the Waisoi West deposit, the middle to high grade copper mineralization was thought to be caused by hornblende diorite porphyry intrusion in the early mineralization stage and after this stage, the silicification and quartz veining occurred with the open fracturing of NNW-SSE-NW-SE direction and copper re-enrichment in the Waisoi West ore deposit was thought to be caused by the hydrothermal system in this later stage.
(5) The promising areas of middle to high grade copper mineralization should be qualified by the existence of intrusion of hornblende diorite porphyry and quartz veining with silicification and argillization in the mineralized area which is identified in this survey, and these three promising areas, upper part of Wainitotoyeuyeu, the area from upper part of Wainisovasovatabua to upper part of Wainimasiadamu, upper part of Wainividrausa are extracted on the basis of these qualifications.

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Stream sediment geochemistry is an effective method for identifying areas of mineral potential. In 2002, a stream sediment sampling program was conducted in East Java area of Republic of Indonesia. Minus 166 mesh (<77 micro meter) samples were collected at a density of approximately 0.6 sample/km² and analysed for Au, Ag, Cu and other 46 elements. Comparing the sieving mesh size, it was shown that the minus 166 mesh fraction can reduce the nugget effect more than the minus 80 mesh fraction and therefore be used as more effective mineral exploration tool. In this survey, the relationship between gold grain distribution collecting after panning and Au geochemical anomalies can not be clarified so much. Due to the different geochemical anomalous value resulting from geology, it is necessary to take account of geological background, when you will evaluate the results of geochemical anomalies.

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An exploration and geological investigation program was carried out from fiscal years 2000 to 2002 in Kokpektinskaya area (120km to south of Ust-Kamenogorsk) in order to increase ore reserves and clarify the resource potential ofilmenite placer deposits.
The ilmenite placer deposits in the area are embedded in sandy clay sediment of the Aral Formation of Neogene and hosted within clayey sand above an unconformable surface of weathered basement rocks. They are covered by thick Neogene and Quarternary sediments up to 54m in thickness and totally concealed. The program consists mainly of drilling exploration, petrological and magnetic susceptibility study of source granitoids and paleogeomorphology of the pre-Neogene basement. Japan International Cooperation Agency (JICA) and Metal Mining Agency of Japan (MMAJ) conducted the program under the request of the Kazakhstan Government.
Drilling exploration in the southern extension of the Bektimir No.1 deposit showed that it has a strike length of 2.5km, width up to 2km and average thickness of 4.8m. The calculated ore reserves are 13.3 million m³, average grade is 126.7 kg ilmenite/m³ (cut-off grade: 100 kg ilmenite/m³) and ilmenite contained is 1, 686, 000 tonnes in total.
Investigations of source granitoids concluded that the high ilmenite content rock type is little-differentiated granitoids such as gabbro, diorite and monzonite with low magnetic susceptibility. Paleogeomorphological structure contour maps show that the deposits occupy structural channels, which are interpreted as river valleys of the pre-Neogene basement.
An area east of the Bektimir No.1 deposit was selected as an exploration target, which is corresponds to the above conditions. After the area was selected, drilling survey followed, and intercepts of ilmenite concentration were encountered as a new discovery. The showing has a strike length of 2.5km, width of 200 to 600m and thickness of 0.7 to 4.5m. The calculated potential reserves are 1.05 million m³, average grade is 30.9 kg ilmenite/m³ and ilmenite contained is 32, 500 tonnes (cut-off grade: 20kg ilmenite/m³). Due to the perception that the deposit enlarges and becomes richer toward the downstream, it is a prospective target for further exploration.

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Extraction of promising mineralized area, application of mining property and ground truth were carried out using satellite image analysis technique in northern Chile.
We have developed and prepared analysis techniques for extraction of promising mineralized area using ASTER data in joint researches with ERSDAC. After public release of ASTER data, we immediately started to gather ASTER data and analyzed over 120 scenes of ASTER data, and we have picked up more than 120 promising areas. Considering regional geol-ogy, metallogenic belt and existing mining properties, we have limited to 15 areas (ca. 770km²) of high priority from the ini-tial promising areas. From Oct. 2001, application of mining property and ground truth of 15 promising areas were started. In the acquired mining properties, geological survey is progressing continuously and some drilling survey caught some of good mineralizations. We will shift to detail survey in those promising areas.
On the other hand, drastically we can reduce time and costs for analysis of geology, structure and alteration zone in such vast area as northern Chile by application of satellite image analysis using ASTER data. Results of ground truth have revealed high efficiency of analysis techniques for extraction of the prospects using ASTER data.

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The Tizapa deposit is a strata-bound volcanogenic massive sulfide deposit, situated in Mexico State, Mexico. The deposit consists of several ore bodies, generally occur between Jurassic to Cretaceous meta volcanic rocks of green schist as footwall and meta sedimentary rocks of graphitic schist as hangingwall. The formation of several ore bodies is considered as the results of structural deformation due to folding and faulting. Drillings and underground drifts have traced the ore bodies over an area of approximately 1, 000 by 1, 200 meters. The sulfide ore bodies vary in thickness up to 20 meters, and they have north-northwest down dips with 30-40 degrees. The results of ore grade distribution analysis and patterns of metal zoning within the Tizapa ore bodies show continuity of ore bodies across the area studied when effects of deformation are removed, and the hypothesis that there was originally a single continuos ore body in the Tizapa deposit was supported. There are several areas enriched in Cu relative to other metals, that correspond with intensely altered footwall zones (Alteration index >90). These areas may be feeders to the metals. The higher Cu grade zone and strong alteration were also detected in the northeast of the ore deposit, that suggests there is high possibility that the ore deposit extends further to the north of the zone.

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Clay veins have been found by uranium exploration drilling around the Black Rock uranium prospect in the northern part of the Alligator Rivers Uranium Field (ARUF), northern Australia. The mineralogical and chemical features are described to clarify relations with uranium mineralization, because it is not accompanied by uranium mineralization.
X-ray diffraction and chemical analysis for major elements indicate that the clay vein consists mainly of chlorite (clinochlore to ferroan clinochlore) and lesser mica clay mineral (t-1M dominant).
The clay vein is compared with the clay alteration zone around the uranium deposits in ARUF in terms of mode of occurrence, mineral and chemical compositions. Mineral composition of the clay vein is only in accordance with that of the inner alteration halo of the clay alteration zone. It is, however, different from mineral composition of the outer alteration halo in terms of lack of Fe chlorite in the clay vein. Chemical composition of the clay vein is similar to that of the clay alteration zone, except for lack in the vein of high iron content which is observed in some samples of the alteration zone. As a whole, the feature of the clay vein corresponds to the inner alteration zone around the uranium deposit in ARUF.
The mode of occurrence of the clay vein is very different from that of the clay alteration zone. Mode of occurrence, and mineral and chemical compositions of the clay vein resemble a chlorite vein in the Lower to Middle Proterozoic sandstone above the Jabiluka deposit, one of major uranium deposit in the ARUF. Because of the similarity between the clay and the chlorite veins, the clay vein is regarded as marginal facies of an alteration zone. The fluid that formed the clay vein is estimated to have been oxidized, because of the existence of hematite and ubiquitous Mg chlorite. This nature is in accordance with the mineralizing fluid that formed the inner alteration zone in the Nabarlek deposit. In conclusion, the vein-forming fluid was possibly related to the uranium mineralization, judging from similarity of mineral and chemical compositions between the clay vein and the inner clay alteration zone, and of nature of vein-and ore-forming fluids.
In the uranium deposits in ARUF, ferrous iron in Fe chlorite and mafic mineral such as amphibole have acted as an important reductant against oxidized ore-forming fluid. No uranium mineralization in the clay vein is estimated to have resulted due to the lack of Fe chlorite. Therefore, alteration accompanying Fe chlorite needs to be confirmed to find a uranium mineralization. In the Jabiluka deposit, a general spatial correlation between the intensity of chlorite in the sandstone and the close proximity to ore below has been suggested. Because the mode of occurrence, mineral and chemical compositions of the clay vein resemble those of the chlorite vein, deeper parts of the distributed area of the clay vein are most prospective as an exploration target.
Conclusively, confirmation of following points should be important in any future exploration to reach uranium ore; more frequent occurrence of the clay vein, a strongly altered zone below the clay vein and an alteration zone accompanying Fe chlorite.

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In order to recognize the chronological transition of the volcanism related to the formation of Kuroko deposits, authors examined the variation of major chemical compositions on the felsic and basaltic volcanic rocks that belonged to pre-/post-Kuroko mineralization at the Hokuroku district in northern Japan. The felsic volcanics are classified, based on field observation, into D1 dacite, D2 dacite, and footwall dacite group. The footwall dacite group is further subdivided into Green dacite, Shako dacite, White rhyolite (D3 dacite) and definite footwall dacite(D4 dacite) in descending order of the stratigraphy.
By the preliminary examination on AL₂O₃-(CaO+Na₂O)-K₂O and K₂O-Na₂O-CaO diagrams, it was suggested that about a half of specimens in the footwall dacite group (35/72) could be reliable to discuss the primary difference in chemical compositions without considering the influence of alteration, and that the various dacite in the footwall dacite group could have different origins from the petrological viewpoint.
Post-Kuroko dacite (Green dacite and D2 dacite) and the dacite (Shako dacite and White rhyolite) formed contemporaneously with Kuroko deposits are clearly separated by the AL₂O₃-SiO₂ diagram; the former is plotted in the low Al and slightly high Si domain, and the latter is plotted in the opposite side. On the other hand, D4 dacite (pre-Kuroko activity) and D1 dacite (later in the post-Kuroko volcanism) are dispersed between former two domains. However, they can be clearly separated by CaO-TiO₂ diagram; the D1 group dacite is represented in the high CaO and high TiO₂ domain.
Authors investigated the chronological transition in mean values of major elements by rock type. Data in pre-Kuroko dacite show constant AL₂O₃ and SiO₂ contents. However, the contemporaneous dacite (White rhyolite, except for Shako dacite) is characterized by low MgO/(MgO+FeO^*) and high Na₂O+K₂O value. On the contrary, post-Kuroko dacite (Green dacite and D2 dacite) is characterized by high SiO₂ and low AL₂O₃ contents and high MgO/(MgO+FeO^*) value. Felsic volcanic rocks in the hanging-wall, such as T2 tuff, Porphyry, Granitoid and D1 dacite, show constant AL₂O₃ value with slightly ascending SiO₂ value and slightly descending MgO/(MgO+FeO^*) value from bottom to top stratigraphically. Those indicate that there were two volcanic cycles, and that the Kuroko mineralization took place related to more differentiated magma at the end of the first volcanic cycle, and then another felsic volcanism commenced immediately after Kuroko mineralization.
Basaltic rocks are called B3 (pre-Kuroko), B2-b (just above Kuroko horizon), B2-a (early in the hanging-wall rock units) and B1 (later in the units) basalt respectively in ascending order. It is recognized that TiO₂ contents gradually decrease from B3 (high Ti contents) via B2-b(middle Ti) to B2-a basalts (low Ti), and that TiO₂ contents become high in B1 (high Ti) again on the TiO₂ -SiO₂ diagram. This suggests that B3 basalt would be deeper origin and that the magma chamber would have gradually become shallower until the period of post-Kuroko activity.
Both felsic and basaltic volcanic rocks indicate that the magma chamber changed from deeper level at the pre-Kuroko stage to shallower level at the post-Kuroko volcanism. It appears from the above that the Kuroko mineralization was caused at the transitional period of volcanism that had changed from deeper to shallower origin.

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The Shimokawa greenstone-argillaceous sediment complex, which occurs as a tectonic slab in the Hidaka belt, central Hokkaido, northern Japan, consists of diabase/basalt sills and dikes, basaltic pillowed sills with minor amounts of pillow lavas, greenstone breccias and intercalated fine-grained terrigenous sediments.
Basaltic magma is thought to have injected into unconsolidated sediments and formed sills of diabase and basalt. In the case where magma ascended into unconsolidated wet sediments near the seafloor under the condition of Pm (magma pressure)-σz (lithostatic pressure of sediment) ≥τ₀ (shear strength of sediment), the magma became quenched and predominantly formed pillow structures. On the contrary, where magma ascended into less wet sediments, it formed sills under the condition of P_m-σ_z>τ₀.
Greenstone breccia is made up of lithic components derived from the diabase/basalt sill and dike, pillowed sill and lava, and is characterized by chaotic aggregate of disrupted angular clasts with subordinate pulverized greenstone and argillaceous matrix. Pillowed sills and greenstone breccias occur at three different horizons and constitute key beds. The existence of greenstone breccia stratum at different horizons in the complex implies that they were formed during the interval of basaltic magmatism and sedimentation of terrigineous sediments. A favored interpretation to account for the greenstone breccia is that they originated from the steep and unstable escarpment, transported to the lower level of the basin as mass movement in the form of debris flows and rock falls triggered by collapse of slopes, and settled during volcanism and sedimentation. Volcanogenic massive sulfide deposits occupy the lower most horizon of the complex and are hosted in either sediments or greenstones.
Volcanism and hydrothermal activity are assumed to have occurred where fine-grained terrigineous sediments were supplied continuously. Syn-volcanic and syn-sedimentary faults are also thought to provide pathways for discharging hydrothermal solutions, from which sulfide minerals precipitated and formed the Shimokawa volcanogenic massive sulfide deposits.
These phenomena support that the Shimokawa greenstone-argillaceous sediment complex was a part of sedimented spreading center located close to the continent.

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