In the Jokoku-Katsuraoka mining area, southwestern Hokkaido, Japan, there occur different types of ore deposits, such as bedded manganese deposits associated with bedded chert of the Paleozoic-Mesozoic age; magnetite skarn deposits, manganese polymetallic veins and replacement deposits genetically related to the Neogene shallow acidic intrusives (Fig.1). In this paper, the manganese, lead, zinc and silver polymetallic mineralizations in the Jokoku-Katsuraoka mining area are summarized, emphasis being placed on mineralizations of the Katsuraoka skarn deposit, and those of the Matahachi deposit of the Jokoku mine, one of the representative polymetallic veins in the area.
Based on the macrostructures of single ore body, four mineralization stages are distinguished by the major tectonic breaks at the Katsuraoka deposit and the Matahachi deposit of the Jokoku mine (Fig.3). The sequence of mineralization in the Jokoku-Katsuraoka mining area is established as shown in Fig. 9.
Variations of CdS and MnS contents of sphalerites and those of filling temperatures and salinity ranges of fluid inclusions in minerals, such as quartz, sphalerite, rhodochrosite and others, are examined in reference to modes of occurrence of the minerals from the skarn and the veins in the area (Figs.5, 6 and 7).

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Miocene granitic stocks intruding into Mesozoic sedimentary rocks and having available outcrop from 700 to 1400 meters above sea level show various vertical variations. The texture is hollocrystalline granitic in the deeper part but porphyritic in the shallower part, and many ore deposits are located in the shallower part. The magnetic susceptibility and arsenic content are lowest in the deeper part and increase generally upward. Pyrrhotite is seen only in the deeper part, while pyrite prevails in most other parts. Iron oxides indicate that oxygen fugacity of the granitoids is lowestin the deeper part and becomes higher in the shallower part. The total sulfur content is higher in the deeper part but is lower in the shallower part, and is highest in the top of the altered stock and also in the ore deposits.
It is suggested that quartz diorite-tonalitic I-type magma of the Green Tuff activity intruded forcibly into Mesozoic sandstone and shale, and received sedimentary sulfur and carbon into the magma chamber from the wall rocks as fluid phase by hydrothermal convection around the intrusive bodies. This unique mechanism of the crustal contamination would be the main cause for the hetrogeneous distribution of magnetic susceptibility and variety of iron oxides and sulfides assemblages in the granitoids and ore deposits. Evolutional trends of two representative ore deposits are shown in Figure 10. Intensive mineralizations around the Chichibu mine stocks could be explained by addition of ore-forming components to the ore deposits from the sedimentary wall rocks.

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This study is concerned in determination of the type of red-pink granite masses that are most favourable, as a host rock for uranium mineralizations in any form either as vein type or as filling fractures. The different characteristic features of well known fertile granite are used as a parameter to pinpoint the unknown red-pink granite masses scattered elsewhere in the Eastern Desert of Egypt.
This study revealed that the most probably favourable red-pink granites for uranium occurrences possess high silica content, enriched in sodium and potassium, besides impoverished in the ferromagnesium elements and calcium. In addition, the structural patterns that govern the uranium mineralization are subsidiary faults or fractures parallel to major structures and/or along the downwall of uplifting. None of the uranium deposits stray very far away from the edge of the granite bodies.

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Changes in solute concentration of a fluid phase percolating in rocks are simulated using a mass balance equation. Fluid having given solute concentration is constantly injected into a rock column and flows through it with constant velocity (v). A mono-component system is considered and parameters such as temperature, pressure, porosity, fluid density (ρ), surface area (A) and diffusion coefficient are assumed to be constant. The first order rate constant (k) is used to simulate the rock-fluid interaction. The fluid reacts with the rock, and changes its solute concentration in the reaction zone until the equilibrium is achieved. The concentration profile of the fluid phase does not change in a "steady state", but it advances after the rock is completely reacted at the inlet. The reaction zone, where unreacted mineral remains, corresponds to a "partially altered zone" in nature. The characteristic width of the reaction zone is represented by ρv/Ak. The estimated range of ρv/Ak at 250°C is wide; 10⁴ to 10¹² [cm] for veins, 10^-1 to 10⁷ [cm] for geothermal reservoirs and 10^-4 to 10⁴ [cm] for metamorphic environments. The width of the partially altered zone determined by field observations permits to estimate by means of model calculations.

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