The Huanzala mine in Peruvian Andes is producing silver-lead-zinc ore. Its ore bodies are bedded or lenticular in shape, replacing a limestone formation of Cretaceous age.
Since 1964, systematic exploration and development for the Huanzala mine had been promoted intensively on the Huanzala north deposits located in the north side of the Torres river, some of whose ore bodies are exposed on the surface.
On the other hand, by the exploration in 1974 and 1975 in the Huanzala south district, located on the south side of the Torres river, neither outcrop of orebody nor well anomaly of IP survey has been found out except few outcrops of weak gossan. Consequently, the exploration on this district was suspended in 1976.
Through the development on the Huanzala North deposits, following facts were revealed by geological study.
(1) The mineralization is closely related to faults, and ore deposits are formed near to north-northeast faults with a steep dip and northwest thrust with a dip of 40°-60°.
(2) Also the mineralization is closely related to quartz porphyry sheets. Most of ore deposits are germinated near to these sheets. However, in a limestone formation some ore deposits appear about 500 m distant from the sheet intruded zone.
(3) Even weak anomaly of metal factor of IP survey indicates existence of ore deposit.
Applying these knowledge to the Huanzala south district, exploration was done again with core boring and tunnel excavation from 1981 to 1988. And in weak metal factor anomaly zones, the Huanzala south deposits were discovered, which are located near to the above mentioned faults in a limestone formation, maximum 300 m distant from quartz porphyry sheet. These are estimated a million tons of the ore reserves with ore grade of 0.01% Cu, 5.8% Pb, 12.2% Zn and 2.8 oz/st Ag.

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The Tengumori copper deposit of the Kamaishi mine exists along an unconformity between a Permian limestone and a Cretaceous sandstone. The post-mineralization Tengumori Fault has displaced this deposit into two major ore bodies. A vertical zonation of calc-silicate minerals is recognized as follows, from the hanging-wall sandstone to the footwall limestone: the weakly skarnized sandstone, the upper garnet-clinopyroxene zone, the clinopyroxene zone, the lower garnet-clinopyroxene zone and the unmineralized limestone. Copper ores are developed mainly in the clinopyroxene zone.
The mineral paragenesis at the Tengumori deposit suggests that the hydrothermal processes may be divided into three stages: 1) calc-silicate, 2) ore mineralization and 3) calcite stages. Clinopyroxene and two types of garnet were formed during the talc-silicate stage. Garnet-1 (earlier type) dominates in the hanging-wall side of the deposit, especially in the upper garnet-clinopyroxene zone, and possesses an intermediate chemical composition (And _40-60). Garnet-2 (later type) occurs mostly in the lower garnet-clinopyroxene zone and its chemical composition is almost pure andradite. The ore mineralization stage is characterized by sulfide and minor quartz mineralization replacing clinopyroxene. The major sulfide minerals are chalcopyrite, hexagonal and monoclinic pyrrhotite, cubanite, and pyrite. There exists a lateral zoning of the Fe and Cu sulfide minerals concentric from the Tengumori Fault: the later sulfur-rich sulfide minerals tend to occur near the fault, while the earlier sulfides at the margin. The Fe content of hexagonal pyrrhotite appears to increase with distance away from the fault. The paragenesis, the vertical zoning of the calc-silicate minerals, and the lateral zoning of the sufide minerals strongly suggest that the hydrothermal solutions ascended along the Tengumori Fault and spread laterally to the marginal parts of the deposit.
Fluid inclusion data show that the formation of the calc-silicate stage involved hydrothermal solutions with higher temperatures and salinities than those of the ore mineralization stage. Fugacities of H ₂ and H₂S in the hydrothermal fluids for the calc-silicate and the ore mineralization stages were calculated. The results show that the sulfide minerals were formed under higher H₂S conditions than the calc-silicate minerals. When sulfide minerals crystallized, considerable proportions of the ferrous iron came from clinopyroxene, and H₂S from ore-forming fluids. This is supported by the fact that the chemical compositions of clinopyroxene relicts in sulfides are Fe-poor relative to those of the unaltered clinopyroxene.

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Cleavages and minor folds are developed in the Devonian and Carboniferous strata of the Iberian Pyrite Belt. We used these minor structures to analyze fold structures, and recognized three stages of folding. The first stage folds (F₁) are generally tight overfolds with associated slaty cleavages or schistosities (S ₁). The second stage folds (F₂) are commonly open to gentle folds with associated crenulation cleavages (S ₂). The third stage folds (F₃) are recognized only in a limited area, with an additional associated crenulation cleavage (S ₃). The lithological successions of the Tharsis mine (Filon Norte), the Aznalcollar mine, and the Pomarao area are folded by the first stage folding, which form slaty cleavages (S₁). In the Vulcano mine (Tharsis area), the Sotiel mining area, and the Corte do Pinto area the first stage folds (F₁) are refolded by the second stage folding which form crenulation cleavages (S ₂).

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In the Northern Kitakami Massif, bedded manganese deposits are deposited as strata-bound in the Pre-Miyakoan sedimentary rocks. They have been considered to be concentrated in the Permian beds in the "Northern Kitakami Belt" and in the Triassic to Jurassic beds in the "Iwaizumi Belt". But the detailed geological age of bedded manganese deposits remains unknown.
The geological age and setting of bedded manganese deposits of the Otaniyama mine area, located in the southeastern part of the "Northern Kitakami Belt", are studied from a micropaleontologic viewpoint.
Conclusively, the geological age of the chert with interbeds of the manganese ore bodies is considered to be the Triassic from occurrence of conodont fossils. The chert beds are considered to be included as the exotic sheets or blocks in the clastic rocks (Jurassic to Lower Cretaceous?). The Lower Permian limestone beds and their accompanied basic volcanoclastic rocks in the lower part are also interpreted as in the case of the chert beds.
The depositional age of the manganese ore bodies is clarified to be restricted to Late Triassic (Carnian-Norian) from the conodont fossils yielded from the underlying and overlying chert.
The geology of the Otaniyama mine area can be interpreted as an accretionary body which was formed from the Jurassic to Early Cretaceous (?). The depositional environment of the source materials of the manganese ores is thought to be an oceanic basin far from the land area and is deeper than the CCD.

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Toyoha deposit, the most productive Ag-Pb-Zn vein-type deposit in Japan, is closely situated to the junction between the Northeast Honshu Arc and Kuril Arc.
Studies on stratigraphy, mineralization, geochronology, geological structure and vein pattern of the deposit indicate that the deposit is composed of east-west trending dextral strike-slip shear veins together with northwest-southeast extensional veins. These veins make rhomb-shaped structures, which are defined as "pull-apart vein system". The vein system was formed by a dextral strike-slip shear movement in east-west trend during the Pliocene. This movement is related to the westward dislocation of the frontal Kuril Arc since the latest Miocene.
The deposit is found at the west-southwest extension of the maximum displaced zone within the dextral shear belt along the Kuril Arc. The magnificent potentiality of the deposit may be ascribed to such intense shear movement caused by the oblique subduction of the Pacific Plate.

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Au ₁₀Ag₉₀ alloy was placed in 5.2 molal aqueous NaHS solution at a temperature of 150°C for 120 days in order to observe the change of the texture of the material. Very fine-grained electrum (<1μm) coexisting with argentite was synthesised. The texture of the synthesised material was very similar to so called "chalcopyrite disease" (BARTON and BETHKE, 1987).

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