Ore Deposits In Japan Research Articles

Progress and Future of Resource Geology as Mineral Sciences

Both the history of resource development and the progress of studies of mining and ore deposits in Japan are summarized. Researchers and engineers promoting in studies on ore deposits and resource geology are also reviewed, focusing on Professors Takeo Kato, Takeo Watanabe, Tatsuo Tatsumi, and J. Toshimichi Iiyama as well as other staffs of the Third Professorship, Department of Geology, Faculty of Science, University of Tokyo. Mineralogy, geology and geochemistry are essential for an understanding of resource geology. It is revealed that mineralogy plays an important role in studies on ore deposits and resource geology. Future directions of studies on ore deposits and resource geology are proposed.

On the main antimony ore deposits in Japan and their genetic problems

On the main antimony ore deposits in Japan and their genetic problems

A sulfur isotopic study of alabandites from some manganese ore deposits in Japan

A sulfur isotopic study of alabandites from some manganese ore deposits in Japan

K-Ar ages of some ore deposits in Japan

K-Ar ages of some ore deposits in Japan

Historical Summary of Studies on Ore Deposits in Japan

Historical Summary of Studies on Ore Deposits in Japan

熱水性鉱床に産する緑泥石の化学組成と緑泥石地質温度計の適用性

Compositional and structural properties of clay minerals from hydrothermal systems show highly diverse and systematic variations related to their localities. The chemical compositions of chlorite, one of the most common clay minerals, are thought to have a close relationship with its formational environments such as geological conditions, temperature, chemistry of hydrothermal solution, etc. In this study two chlorite geothermometers were considered by using the chemical composition of chlorites from some hydrothermal ore deposits in Japan. The two chlorite geothermometers are the Cathelineau's thermometer giving an empirical temperature scale of chlorite formation in an active geothermal field, and the Walshe's thermometer giving a thermodynamic temperature scale based on exchange reactions of chlorite solid solutions. On the basis of a comparison of fluid inclusion geothermometry, it is concluded that the two geothermometers can be applied to different compositional types of hydrothermal chlorite. The Cathelineau's thermometer fits well for Mg-chlorite, and the Walshe's thermometer fits for Fe-chlorite, indicating that both two chlorite geothermometers can be used as exploration indicators for geothermal reservoirs and hydrothermal ore deposits. In addition, it must be emphasized that the impurities in the chlorite should be examined in applying the chlorite geothermometers to chlorites.

Re [sbnd]Os dating of molybdenites from ore deposits in Japan: Implication for the closure temperature of the Re [sbnd]Os system for molybdenite and the cooling history of molybdenum ore deposits

Rhenium and Osmium abundances were determined on molybdenites from eighteen ore deposits in Japan; fifteen vein-type, a skarn-type, a greisen-type, and a pegmatite-type deposit. Re Os ages obtained for molybdenites from northeastern, central, and southwestern Japan are 100–130 Ma, 50–75 Ma, and ca. 10 Ma, respectively, reflecting the ages of regional igneous activities in individual areas. For vein-type ore deposits, Re Os ages for molybdenites agree with Rb Sr whole-rock ages of host granitoids, while they are 3–12 Ma older than K Ar mineral ages of the host rocks. On the other hand, Re Os ages of molybdenites from skarn-, pegmatite-, and greisen-type ore deposits agree with K Ar ages of the host rocks. The comparison of Re Os ages for molybdenites with Rb Sr and K Ar ages of host rocks in vein-type deposits suggests that Re Os closure temperature for vein molybdenite is close to whole-rock Rb Sr closure temperature for host granitic rocks, i.e., roughly estimated to be around 500°C, and higher than K Ar closure temperature for host granodiorites, i.e., 230–370°C, if the thermal history of vein molybdenites is essentially equivalent to that of host rocks. One possible explanation for age discrepancies of 3–12 Ma between Re Os ages for molybdenites and K Ar ages for the wall rocks, observed in vein-type molybdenum deposits, is that later thermal events after formation of molybdenum ores may reset K Ar ages. Hydrothermal alteration might have occurred in such a temperature condition as to disturb K Ar mineral systems in wall rocks and made them younger but not the Re Os system in molybdenite. The other explanation might be that the age discrepancies correspond to a cooling interval from ca. 500 to 300°C of host granitoid. On the other hand, the agreement of Re Os ages of molybdenites and K Ar ages of host rocks in skarn-, pegmatite-, and greisen-type deposits in this study indicates no later disturbance for K Ar system in the wall rock or the rapid cooling of the ore and wall rocks after the formation of molybdenite deposits.

Mixing diagrams for hydrothermal solutions: Applications to interpretation of fluid inclusion data of hydrothermal ore deposits in Japan.

Temperature-chloride mixing diagrams at 500 and 1000 bars, and at vapor-saturated pressures, are calculated in order to demonstrate the mixing behavior of saline (up to 40 NaCl wt%) high-temperature solutions with 1 wt% low-temperature solutions, with the results applied to interpreting fluid inclusion data. The temperature of the initial saline solutions is 450°C at 500 bars, 600°C at 1000 bars, or 300°C at vapor-saturated pressures. The temperature of the diluent is 100° or 300°C at 500 and 1000 bars, and 100°C at the vapor-saturated pressure. Mixing diagrams at 500 and 1000 bars are recast onto the relation between homogenization temperature and chloride concentration of fluid inclusion using densities of NaCl solutions. Temperature-chloride mixing diagrams indicate that mixing of 40 wt% fluids with dilute solutions at 1000 bars is not linear, but shows a greater decrease in temperature with up to 3 wt% NaCl deviation. The deviations are larger (up to 9 wt%) with respect to homogenization temperature versus concentration relations. In contrast, mixing lines for 30 to 10 wt% initial fluids at 1000 bars and those for 40 to 10 wt% fluids at 500 bars are nearly linear with respect to temperature (or homogenization temperature) and NaCl concentration, within ±3 wt% deviations. At vapor-saturated pressures, 300°C and 25 to 5 wt% initial solutions show nearly linear mixing relationships under the condition that vapor/liquid volume ratios are less than 1. Potassium chloride solutions show almost identical temperature-chloride relations with sodium chloride solutions, up to 325°C, 500 bars, and 6 mole/kg, when the molalities of saline and dilute solutions are same for both solutes. The relations between homogenization temperature and concentration for KCl solutions show slightly smaller slopes than those for NaCl solutions. Application of these results to fluid inclusion data of the Ohe, Toyoha, and Fujigatani-Kiwada deposits in Japan indicates that high temperature and high salinity fluids (335°C and 6.3 wt% for the Ohe deposit; 325°C and 4.6 wt% for the Toyoha deposit; 360°C and 7.4 wt% for the Fujigatani-Kiwada deposits) mixed with low temperature and low salinity solutions (221°C and 1.6 wt% for the Ohe deposit; 209°C and 0.0 wt% for the Toyoha deposit; 250°C and 1.9 wt% for the Fujigatani-Kiwada deposits).

Strontium isotope systematics and metallogenesis of skarn deposits in Japan

In order to understand skarn petrogenesis, we determined the strontium isotope compositions of 168 skarns and 43 host or surrounding rocks in Japan. Most skarns have low Rb/Sr ratios (<0.1) and formation ages younger than 120 Ma, indicating negligible contents of 87 Sr due to a decay of 87 Rb. Multiple analyses of skarns from three representative base metal deposits demonstrate that their 87 Sr/ 86 Sr ratios vary only slightly (<0.001) within single mines, irrespective of time and position, indicating that even a single skarn sample can give a representative 87 Sr/ 86 Sr ratio on a single mine scale. On the other hand, skarns from 78 ore deposits in Japan reveal regional variations in the 87 Sr/ 86 Sr ratio ranging from 0.705 to 0.726. The variations are best classified by the ore metal type; skarns of the copper-iron type are rich, whereas those of the lead-zinc type are deficient, in Sr derived from the intrusions responsible for skarn formation. In many cases, Sr was derived from the original carbonate and aluminous rocks replaced by the skarns. Given that host limestones have relatively uniform 87 Sr/ 86 Sr ratios (0.7081 + or - 0.0007), the variability in the strontium isotope composition of skarns may be attributed to the difference and/or the amount of the involved aluminous rocks which have a wider range in the 87 Sr/ 86 Sr ratio. This is consistent as a whole with the occurrence of skarn deposits; copper-iron deposits form in geologic settings dominated by and often in contact with cogenetic large plutonic batholiths, whereas most lead-zinc deposits occur where sedimentary or igneous rocks with higher amounts of 87 Sr are common and form nearer and often distant from smaller hypabyssal dike or stock intrusions. An Sr isotope signature derived from the associated magmatic fluid is perceptible only in some skarns of the copper-iron type. The original magmatic fluid may have been modified isotopically when it encountered aluminous rocks and limestones and leached Sr from them.

Bulk compositions of intimate intergrowths of chalcopyrite and sphalerite and their genetic implications

To determine the bulk chemical compositions of chalcopyrite containing starlike sphalerite and sphalerite including dotlike chalcopyrite, specimens from various types of ore deposits in Japan were used for modal and electron microprobe analyses. According to the analytical results, most of the measured zinc contents in chalcopyrite containing starlike sphalerite are less than 0.8 at%, corresponding to the maximum solubility of zinc in chalcopyrite as determined experimentally at 400°C. However, specimens from the Maruyama deposit in the Tsumo mine contain 1.2–1.4 at% Zn, which are within the solubility limit of an intermediate solid solution (ISS) above 400°C. It is therefore concluded that starlike sphalerite in chalcopyrite are exsolution products derived from primary chalcopyrite solid solution and/or zincic ISS. Measured copper contents in sphalerite including dotlike chalcopyrite yield considerably higher values, i.e., 1.5–6.0 at%, which exceed the solubility limits of copper in sphalerite solid solution as determined experimentally. This result suggests that not all the chalcopyrite dots were exsolved from sphalerite, but that most of them are the product of some other mechanisms.

二，三のマンガン鉱床産の共存する角せん石類について

Coexisting amphiboles in samples from three manganese ore deposits in Japan have been investigated by an electron probe microanalysis and an X-ray powder diffraction method. The coexistences of manganoan actinolite and tirodite (from the Fukadaniguchi mine and the Fukumaki mine), actinolitic hornblende and tschermakitic hornblende (from the Fukumaki mine), manganoan ferri-winchite, manganoan magnesio-riebeckite, and manganoan actinolite (from the Nodatamagawa mine) are newlydescribed. Assemblages of amphiboles from manganese ore deposits in Japan, were classified according to their occurrences and their associated minerals.

本邦産マンガン硼酸塩鉱物

Four manganese borate minerals, jimboite, wiserite, sussexite, and Mineral X of Epprecht et al. (1959) have been found in seventeen bedded manganese ore deposits in Japan. Their principal mineralogical properties and mineral associations are given to present their diagnostic features and the characteristics of manganese ores comprising them. The manganese borates occur as layers conformable with bedded textures of ores, minute veinlets cutting them, or minor interstitial bodies among associated minerals. Ore minerals associated with them include rhodochrosite, jacobsite, sonolite (or alleghanyite), alabandite, jacobsite, galaxite, hausmannite, tephroite and gageite, these being characteristic in low silica and higher grade manganese ores. The occurrences suggest the simultaneous concentration of boron with manganese, these elements being considered to have been released from basic magma after the reaction with sea water.

Unilateral isotopic variation of Miocene ore leads from Japan

Lead isotope ratios of Miocene ore deposits in Japan are examined in reference to their positions relative to the geological structure of the island arcs. A detailed inspection of the data indicates that in northeast Japan the ore lead becomes slightly less radiogenic from the Pacific Ocean side to the Japan Sea side, suggesting some coherence between ore and volcanic rock leads along zones parallel to the magmatic front. Also, in southwest Japan a slight but systematic difference in isotopic composition appears to exist in the Miocene ore leads which might be correlated with the positions of individual deposits relative to assumed magmatic front lines.

Syntheses of stannoidite and mawsonite and their genesis in ore deposits

Mawsonite and stannoidite characteristically occur with bornite and chalcopyrite in xenothermal ore deposits in Japan. The two minerals are not found in hypothermal ore deposits in which stannite occurs. Data on the thermal stability and phase diagrams of the system Cu-Fe-Sn-S including mawsonite and stannoidite are limited. Therefore, synthetic and experimental studies, especially of mawsonite and stannoidite, were carried out to obtain information on the genesis of the two minerals in nature. Phase diagrams of a part of the system Cu-Fe-Sn-S have been constructed at 700 degrees , 500 degrees , and 300 degrees C from the results of dry, flux, and hydrothermal syntheses. Differential thermal analyses and heating experiments were also carried out. The results indicate that mawsonite is stable at temperatures below 390 degrees C and that it decomposes to stannoidite, bornite, and chalcopyrite above this temperature. Mawsonite coexists with stannoidite, bornite, and chalcopyrite in the synthetic products as well as in the natural occurrence. Although mawsonite does not contain appreciable amounts of zinc, natural stannoidite generally contains some zinc. According to the results of heating experiments, natural stannoidite containing 3 weight percent of zinc decomposes to bornite, stannite, and chalcopyrite at about 500 degrees C, while zinc-free synthetic stannoidite is stable up to 800 degrees C. The temperature range of stability of zincian stannoidite may vary greatly with the zinc content. The sulfur fugacity determination by the electrum tarnish method indicates that the univariant assemblage of mawsonite, stannoidite, bornite, and chalcopyrite requires a higher sulfur fugacity than that of stannoidite, stannite, bornite, and chalcopyrite. It is also concluded from the results of experiments and observation of natural ores which carry mawsonite and stannoidite that mawsonite could have been formed by replacing stannoidite at temperatures lower than 390 degrees C and at a higher sulfur fugacity than the assemblage of stannoidite, bornite, and chalcopyrite.

Role of temperature and CO 2 pressure in the formation of skarn and its bearing on mineralization

Based on the mode of occurrence of the skarn-type ore deposits in Japan, ore-bearing skarn is, with a few exceptions, defined by the presence of grandite garnet and the lack of wollastonite, kilchoanite, vesuvianite, xonotlite, hydrogrossular, and bucchulite. The condition of formation of ore-bearing skarn is given by conditions under which grandite garnet is always formed, and where wollastonite and xonotlite are unstable.(1) According to phase relations in the system CaO-Al 2 O 3 -SiO 2 -H 2 O, the kilchoanite-bearing skarn of Kilchoan (Scotland) formed under a temperature of range of 550 degrees C and 600 degrees C. The barren skarn at Fuka (Japan), which is similar in many respects to that of Kilchoan, is inferred to have formed at relatively higher temperatures. The vesuvianite-bearing skarn of the Mitate mine (Japan) formed at a lower temperature compared to that of Broadford (Skye), which is presumed to be formed below 600 degrees C. The vesuvianite-bearing skarn of the Chichibu mine (Japan) is presumed to have formed at a still lower temperature but above 400 degrees C, according to the stability relations of vesuvianite and wollastonite.(2) Xonotlite is stable in hydrothermal fluids containing less than 0.7 mole percent CO 2 and decomposes to calcite and quartz under higher CO 2 pressures. Although the stability relations of hydrogrossular and bicchulite have not yet been studied in fluids containing carbon dioxide, the synthesis results and the texture of skarn seem to suggest that they are formed under low CO 2 pressures similar to xonotlite. On the other hand, grandite garnet is unstable in fluids containing more than 2 mole percent CO 2 at 400 degrees C. Therefore, ore-bearing skarns seem to be formed under intermediate CO 2 pressures. Accordingly, fractures associated with the skarn-type ore deposits act not only as channelways for the ore-forming fluids but also as a way to release excess CO 2 pressure.(3) Some ore-bearing skarns include wollastonite, vesuvianite, clinozoisite, and prehnite which are almost free from iron. However, the majority of ore-bearing skarns consist of garnet and/or clinopyroxene with measurable iron. It is considered that the presence of iron in the ore-forming fluids plays a major role in the formation of orebearing skarn.The favorable condition of formation of ore-bearing skarns is presumed to be as follows: (1) temperature is generally below 400 degrees C, (2) CO 2 pressure has upper and lower limits determined by the stability of grandite garnet and the instability of xonotlite, hydrogrossular, and others, respectively, and (3) availability of iron in the ore-forming fluids.

Relation Between Tectonics and Metallogenesis in Peripheral Sea-Island-Arc Complex of Japan and Vicinity: ABSRACT

Several attempts have been made to discover the genetic relation between the tectonic development and metal concentration in this area. A brief synthesis of the relations in the following four geologic periods and their respective major ore deposits in Japan and vicinity indicates: (1) Quaternary-recent, sulfur deposits; (2) Miocene, Kuroko deposits; (3) end of Mesozoic, Mo-W and base-metal deposits; and (4) end of Paleozoic, standard massive sulfide deposits. The distribution of these mineral deposits is related to the tectonic development of the area. Although more revisions and refinements are needed, the following conclusions may be of practical use. 1. The theory of plate consumption at the subduction zone is compatible with the distribution of mineral deposits in general. 2. Large scale distribution patterns of certain mineral deposits are influenced closely by the tectonic development of large geologic units, such as island arcs. 3. Localization of richly mineralized areas is controlled by the deep structural features of the subducting plate and magmatic activities most probably initiated at or above the upper friction surface of these plates. 4. The hypothesis of the oceanward migration of arcs leaving peripheral seas behind near Japan is compatible with the ore distribution. A prevailing tension environment in the rear, and the resulting tension breaks or basins, could produce favorable locations for metal concentration. 5. Amount of erosion after the final emplacement of the ore deposits is another controlling factor of ore distribution at the presently feasible depth. End_of_Article - Last_Page 1452------------

黒鉱鉱床の物理探鉱

黒鉱鉱床の物理探鉱

Stratigraphic Horizon of the Miocene Bedded Manganese Ore Deposits in Japan

Stratigraphic Horizon of the Miocene Bedded Manganese Ore Deposits in Japan

Mineralogical Problems of Intermediate Clay Minerals

AbstractOn the basis of mineralogical studies on many kinds of clay minerals found in Japan, the writers attach great importance to subtle variations in clay minerals and discuss them in the light of the concept of intermediate minerals. An intermediate mineral behaves partly as one mineral (say A) with certain treatments, and as mineral B under other conditions. There are two types of intermediate minerals: the deviation type and the mixed-layer type. The deviation type is homogeneous enough in its structure that we can describe it as composed of a combination of clearly different layer groups. The mixed-layer type has an interstratified structure of two or more kinds of layers. Furthermore it is suggested that each component layer of the mixed-layer type, in general, shows the properties of the deviation type. As an example of a mineral that can be discussed in light of the intermediate mineral concept, the writers describe the properties of very complex mixed-layer minerals related to mica clay minerals associated with epithermal ore deposits in Japan. Normally the mixed-layer minerals are found where there has been successive attack under different conditions of chemical environment or in an area that is transitional between two different chemical environments.Intermediate minerals in general are considered to be a mineral state (mineral configuration) modified in various degrees from an original mineral in response to successive changes of environmental conditions. The above viewpoints are supported by study of many clay specimens collected from alteration zones of epithermal ore deposits in Japan.It is considered that formation of intermediate minerals may be originated because of a latent defect structure in the original mineral. Polar character that is due to unequal distribution or ratio of the tetrahedral cations in a silicate layer may be favorable for the formation of the regular mixed-layer structure. Finally, intermediate minerals may be arranged according to the following scheme: Mineral A—deviation type of mineral A—mixed-layer mineral A-B—deviation type of mineral B—mineral B.

Mg-Enrichment around Some Ore-Deposits in Japan : Particularly with Reference to Hydrothermal Gypsum and Silica Deposits

It is suggested by the present writer that Mg-enrichment is very common in the altered halos of some hydrothermal ore-deposits in Japan -with particular reference to gypsum deposits in Tertiary formations as well as to silica deposits in the bedded chert of the Chichibu Palaeozoic formation., Stoichiometric studies reveal that some of the Mg-enrichment is due to the supply of magnesium from ascending solutions, while others merely to local concentration of that component in the rocks., Magnesian-chlorite (including leuchtenbergite) is characteristic to the products of magnesium enrichment, and associated with extremely variable amount of either sericite or montmorillonite, giving rise to clayey zones in the altered aureoles., From these mineral associations, the oreforming temperatures can be estimated as having not exceeded about 450°C., The elucidation of variation in crystallinity of those minerals, however, seems to be neccesary for a more detailed temperature estimation., Attention is given to the petrochemical characteristics of the green tuff of Miocene age of regional development in Japan., These rocks are enriched in magnesium relative to other components particularly to iron, and are impoverished in SiO2, probably due to submarine alteration.,