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Chemical composition and mode of occurrences of (Au, Ag)Te2 minerals such as calaverite (AuTe2), sylvanite (AuAgTe4) and krennerite ((Au, Ag)Te2) in epithermal gold telluride ores from Suzaki, Kawazu and Teine are examined. In the ores from Suzaki, (Au, Ag)Te2 minerals occur in microbands of tellurides and fine quartz. The minerals in telluride bands change from krennerite, via calaverite-native tellurium, to sylvanite, in the order of crystallization. A sample from Kawazu contains sylvanite and native tellurium with stutzite, hessite and tetradymite in the coarser gray quartz part. The Teine sample also contains sylvanite and native tellurium with barite and quartz. The peak patterns of XRD of calaverite, krennerite and sylvanite from Suzaki are almost identical to that of JCPDS 43–1472, JCPDS 8–20 and JCPDS 9–477, respectively. The Te, Au, Cu, and Ag contents of calaverite from Suzaki range from 56.4 to 57.9 wt.%, from 41.6 to 42.6 wt.%, from 0.28 to 0.45 wt.% and from 0.14 to 0.31 wt.%, respectively, corresponding to the formula Au0.97Ag0.01Cu0.02Te2. The Te, Au, Ag, and Cu contents of krennerite from Suzaki range from 59.6 to 61.4 wt.%, from 31.3 to 33.6 wt.%, from 4.91 to 6.13 wt.% and from 0.66 to 0.80 wt.%, respectively, corresponding to the formula Au0.71Ag0.22Cu0.05Te2 with Au and Ag ranging from 0.68 to 0.74 and from 0.20 to 0.25, respectively. The Te, Au, Ag, and Cu contents of sylvanite from Suzaki range from 61.5 to 63.4 wt.%, from 24.1 to 27.4 wt.%, from 10.0 to 12.5 wt.% and from 0.00 to 0.12 wt.%, respectively. The Te, Au, Ag, and Cu contents of sylvanite from Kawazu range from 62.7 to 63.3 wt.%, from 23.5 to 24.1 wt.%, from 12.0 to 12.5 wt.% and from 0.09 to 0.16 wt.%, respectively. The Te, Au, Ag, Cu and Fe contents of sylvanite from Teine range from 61.8 to 63.5 wt.%, from 23.6 to 24.7 wt.%, from 11.9 to 13.3 wt.%, from 0.01 to 1.65 wt.% and from 0.00 to 0.02 wt.%, respectively. The average formulae of sylvanite from Suzaki, Kawazu, and Teine are expressed as Au1.06Ag0.94Cu0.02Te4, Au1.00Ag0.95Cu0.02Te4 and Au1.01Ag0.95Cu0.06Te4, respectively. Judging from the mineral assemblages of these ores and other localities, Au–Te mineralization in the Japanese Islands can be divided into four types: native gold–calaverite at Date and Agawa, krennerite(−native tellurium) at Osore-zan and Mutsu, sylvanite–native tellurium–hessite at Teine, Kawazu, Kobetsuzawa, and Kato, and polyminerallic assemblages at Suzaki and Kushikino. The pH–Eh diagram of aqueous tellurium species and tellurium minerals at 250°C indicates that (Au, Ag)Te2 minerals in epithermal gold telluride mineralization would have been formed under middle to low Eh and acidic (to intermediate) pH conditions. It is possible that dilute tellurium-containing fluid would scavenge dilute gold.

Cathodoluminescence (CL) spectroscopy provides useful information about the existence of radiation-induced defect centers with a few micrometer resolutions and therefore has great potential to estimate the accumulated dose of natural radiation in micrometer-ordered mineral grains from radioactive decay. Although great scientific interest exists concerning the CL of various types of minerals, very few investigation have been conducted on the luminescence properties of radiation-induced alkali feldspars. This study, therefore, has sought a clarification of radiation effects on emission centers detected by CL analysis of alkali feldspar implanted with He+ ions at 4.0 MeV, which corresponds to the energy of an α particle derived from radioactive decay of 238U and 232Th. Panchromatic CL images of cross sections of sanidine, orthoclase, and microcline show a dark line with ~1 μm width on the bright luminescent background at 12–15 μm beneath the implanted surface, of which behavior may be corresponding to the electronic energy loss process of 4.0 MeV He+ ion. CL and Raman spectroscopy revealed that He+ ion implantation may leads to a partial destruction of the feldspar framework and Na+ migration, resulting in a quenching of CL emission from alkali feldspar, proportional to the radiation dose. CL spectra of unimplanted and He+-ion-implanted sanidine, orthoclase and microcline have emission bands at ~400–410 nm and at ~730 nm. Deconvolution of the CL spectra can successfully separate these emission bands into emission components at 3.05, 2.81, 2.09, 1.73, and 1.68 eV. These components are assigned to the Ti4+ impurity, Al-O−-Al/Ti defect, a radiation-induced defect center, and Fe3+ impurities on the T1 and T2 sites, respectively. The intensity at 3.05 eV negatively correlates with radiation dose owing to decreases in the luminescence efficiency. A slight Na+ diffusion and breaking of the linkage between Ti4+ and oxygen as a ligand might reduce the activation energy, which decreases the availability of radiative energy in the luminescence process of Ti4+ impurity centers. Furthermore, He+ ion implantation causes electron holes to be trapped at and released from Lowenstein bridges as a consequence of Na+ migration and leads to a partial destruction of Al-O bonds, which might be responsible for an increase and decrease in the intensity of emission component at 2.81 eV. With an enhanced radiation dose, there is a decrease in intensity at 1.73 eV and an increase in intensity at 1.68 eV. Deconvoluted CL spectra of the alkali feldspars reveal a positive correlation between intensity at 2.09 eV and the radiation dose, which may be due to the formation of a radiation-induced defect center. These correlations can be fitted by an exponential curve, where the gradients differ between the alkali feldspars studied, and are largest for the microcline, followed by the orthoclase and then the sanidine. The intensity at 2.09 eV has the potential to be used in geodosimetry and geochronometry.

Cathodoluminescence (CL) of minerals such as quartz and zircon has been extensively studied to be used as an indicator for geodosimetry and geochronometry. There are, however, very few investigations on CL of other rock-forming minerals such as feldspars, regardless of their great scientific interest. This study has sought to clarify the effect of He+ ion implantation and electron irradiation on luminescent emissions by acquiring CL spectra from various types of feldspars including anorthoclase, amazonite and adularia. CL intensities of UV and blue emissions, assigned to Pb2+ and Ti4+ impurity centers respectively, decrease with an increase in radiation dose of He+ ion implantation and electron irradiation time. This may be due to decrease in the luminescence efficiencies by a change of the activation energy or a conversion of the emission center to a non-luminescent center due to an alteration of the energy state. Also, CL spectroscopy of the alkali feldspar revealed an in-crease in the blue and yellow emission intensity assigned to Al-O−-Al/Ti defect and radiation-induced defect centers with the radiation dose and the electron irradiation time. Taken together these results indicate that CL signal should be used for estimation of the α and β radiation doses from natural radionuclides that alkali feldspars have experienced.

Calcium and magnesium-bearing sabugalite occurs as aggregations of yellowish platy crystals in veinlets or druses in conglomerate from the oxidized parts of the Tono uranium deposit, Central Japan. X-ray powder diffractometry of this mineral has reflections consistent with previous powder diffraction data of sabugalite. It is included in the monoclinic system with space group C2/m and calculated cell parameters of a = 19.68A, b = 9.89A, c = 9.82A α = γ = 90°, β-96.93° and V = 1897.83A3. Chemical analysis yields a formula of (Ca0.10 Mg0.09)Σ0.19Al0.53(UO2)2.04((PO4)1.99(AsO4)0.01)Σ2.00·11.22H2O. EMPA mapping shows that the mineral is compositionally uniform with no micron-scale layering. Charge of cations including Ca and Mg in the cation-H2O layer is 1.98 being identical to that of autunite group minerals. This suggests that the charge balance in the cation-H2O layer of the mineral could be made by the alkaline earth or alkaline elements rather than by hydrogen ions.

Cathodoluminescence (CL) spectra of experimentally radiated albite at 4.0 MeV energy of He+ ion implantation have red emissions at 700−750 nm, of which the intensities increase with an increase in the radiation dose. These emissions are assigned to a radiation-induced defect center. Pseudocolor CL images of the implanted samples show red CL halo on the implanted surface, of which thickness is approximately 14 µm corresponding to a theoretical range of He+ ion implantation of 4.0 MeV. 2D Raman mapping of the peak at 508 cm−1 for CL halo area indicates minimum intensity and maximum full width at half maximum at ∼14 µm from the implanted surface, suggesting production of radiation-induced defect center due to a partial breaking of the framework structure. CL spectral deconvolution of the red emission reveals a Gaussian component at 1.861 eV attributed to the defect center. The integral intensity of this component closely correlates with the radiation dose as a function of radiation-induced defect ce...

He + ion implantation on albite (Minas Gerais, Brazil) at 4.0 MeV, corresponding to the energy of α particle from 238 U fission, has been conducted to clarify the radiation effects of α particles from radioactive minerals on cathodoluminescence (CL) of albite. CL of albite results in various emission bands at ~380, ~560, and ~740 nm, and in the UV range. Red emission at 700–750 nm is detected in the CL spectra of the implanted samples. Total CL intensities of these UV, blue, yellow, red, and IR emissions vary among the samples. High-resolution CL imaging of the cross-section samples shows a CL halo on the implanted surface of approximately 14 μm thickness, which is consistent with a theoretical range of α particles of 4.0 MeV. It was first confirmed experimentally that the CL halo is created by α particles. The deconvolution of CL spectra in the red emission range by Gaussian fitting provides the component at 1.861 eV that is attributed to a radiation-induced defect center produced by He + ion implantation. The intensity of the component at 1.861 eV linearly correlates with the dose density of He + implantation on albite as a function of the population of the radiation-induced defect center, regardless of other factors such as concentration and distribution of other emission centers, existence of microstructures and textures, and crystallographic orientation. The CL spectral deconvolution has a high potential for quantitative evaluation of the radiation dose of α particles from natural radionuclides on albite for a geodosimetry.

The chemistry and mode of occurrences of native tellurium in the epithermal gold ores from Teine, Kobetsuzawa, Mutsu, Kawazu, Suzaki and Iriki in Japan are examined. Mineral assemblages in contact with native tellurium are: quartz-sylvanite at Teine, quartz-hessite-sylvanite-tellurantimony at Kobetsuzawa, quartz at Mutsu, quartz-stutzite-hessite-sylvanite-tetradymite at Kawazu, quartz at Suzaki, and quartz-goldfieldite at Iriki. The peak patterns of XRD for native tellurium from these six ores are nearly identical to that of JCPDS 4–554. Their chemical compositions of Te range from 98.16 to 100.73 wt.%, showing nearly pure tellurium. Other elements detected are: Se of 0–0.85 and Cu of 0–0.74 at Teine, Sb of 0.45–0.47 and Se of 0.19–0.27 at Kawazu, Se of 0.22–1.11 and Sb of 0–0.49 at Suzaki, and Cu of 0.69–0.98, As of 0.22–0.28 and Bi of 0–0.22 wt.% at Iriki. No other elements are detected in the ores of Kobetsuzawa and Mutsu. The ranges of associated minor compositions are consistent with those of the experimental phase. The differences would be related to associate minerals. The mineral assemblages in these ores agree well with the previously proposed experimental phase relations in Au-Ag-Te ternary system for 120–280°C. The Suzaki ore has high Te-Au assemblage: from calaverite-sylvanite-krennerite via native tellurium to petzite, with changing mineralization stage, whereas the Kobetsuzawa and the Kawazu ores have high Te-Ag assemblage of tellurium-hessite, and native tellurium-stutzite-hessite-sylvanite, respectively. The Teine ore has intermediate assemblage of native tellurium-sylvanite. The mineral assemblages in the Au-Ag-Te system are related to the hydrothermal environment especially to the pH condition, i.e. Au rich assemblages under acidic and Ag rich assemblages under intermediate pH conditions, being supported by alteration mineral species. The other telluriferous epithermal gold deposits not in association with native tellurium such as Agawa, Date, Takeno, Chugu, Chitose, Sado and Kushikino are estimated to have been formed under higher pH conditions as adularia and calcite occur in these deposits. The pH-Eh diagram for aqueous tellurium species and tellurium minerals at 250°C indicates that the region of native tellurium occurs between those of aqueous telluride and tellurous species at lower pH, being consistent with their mineral assemblages in ores and alteration envelopes.

Mineral assemblages of sulfides in the mantle peridotite xenoliths embedded in the alkali basalts of the Kurose reef, northern Kyushu, Japan and the chemical compositions of the mineral assemblages are described. Sulfides occur as 1) inclusions and 2) interstitial sulfides in olivine or pyroxene. The mineral assemblages of sulfides that occur as inclusions are pentlandite, pentlandite + chalcopyrite, pentlandite + bornite, monosulfide solid solution (mss) + chalcopyrite ± pentlandite, pentlandite + pyrrhotite, and millerite; and the mineral assemblage of sulfides as interstitial sulfides is pyrrhotite + pentlandite + chalcopyrite. The contents of Ni, Fe, and S in pentlandite are 22.91-33.45, 18.77-28.82, and 46.57-48.31 at%, respectively. The chemical composition of mss is variable. On the basis of the crystallization temperature of olivine and/or pyroxene and the phase relationship between the Fe-Ni-S and the Fe-Cu-S systems, it can be inferred that the mineral assemblage of mss + chalcopyrite ± pentlandite found in olivine is considered to have been initially trapped as a solid-phase Cu-bearing mss and that the other mineral assemblages were trapped as a sulfide liquid. The diversity of mineral assemblages of sulfides in the mantle peridotite xenoliths and the various chemical compositions of the mineral assemblages are due to timing of differential crystallization of mss and its capture in silicate minerals. It can also be inferred that the chemical composition of the initial sulfide liquid in the Kurose lherzolite is the S-poor portion of the Cu-bearing mss. This suggests that initial sulfide liquids in the upper mantle might have similar compositions.

Detailed quantitative cathodoluminescence (CL) imaging analysis was carried out for radiation-damage halos observed by CL (CL halo) created in natural quartz by implantation of 4 MeV He+ ions. The band of CL halo was approximately 14 μm in width and was constant for any He+ ion dose. The width of the halo is consistent with the theoretical range of 4He ions in quartz. A quantitative response of CL intensity to He+ ion dose was obtained, leading to the application of CL halos to geodosimetrical use. The CL intensity increases exponentially in the luminescent band from the implantation surface to the inside, until it reaches a maximum at 14 μm depth, with a rapid decrease beyond this point. This result is as predicted by Bragg's law, although we find some differences between the CL intensity and the theoretical stopping power.

The Bilimoia deposit (2.23 Mt, 24 g/t Au), located in the eastern Central Mobile Belt of mainland Papua New Guinea, is composed of fault-hosted, NW–NNW-trending Irumafimpa–Kora and Judd–Upper Kora Au-quartz veins hosted by Middle–Late Triassic basement that was metamorphosed to medium-grade greenschist facies between Middle–Late Triassic and Early–Middle Jurassic. Mineralizing fluids were introduced during crustal thickening, rapid uplift, change of plate motions from oblique to orthogonal compression, active faulting and S3 and S4 events in an S1–S4 deformation sequence. The Bilimoia deposit is spatially and temporally related to I-type, early intermediate to felsic and late mafic intrusions emplaced in Late Miocene (9–7 Ma). Hydrothermal alteration and associated mineralization is divided into 10 main paragenetic stages: (1) chlorite–epidote-selvaged quartz–calcite–specularite vein; (2) local quartz–illite–pyrite alteration; (3) quartz–sericite–mariposite–fuchsite–pyrite wall-rock alteration that delimits the bounding shears; (4) finely banded, colloform-, crustiform- and cockade-textured and drusy quartz ± early wolframite ± late adularia; (5) hematite; (6) pyrite; (7) quartz ± amethyst-base metal sulfides; (8) quartz–chalcopyrite–bornite–Sn and Cu sulfides–Au tellurides and Te ± Bi ± Ag ± Cu ± Pb phases; (9) Fe ± Mn carbonates; and (10) supergene overprint. Fluid inclusions in stage 4 are characterized by low salinity (0.9–5.4 wt% NaCl equivalent), aqueous–carbonic fluids with total homogenization temperatures ranging from 210 to 330°C. Some of the inclusions that homogenized between 285 and 330°C host coexisting liquid- and vapor-rich (including carbonic) phases, suggesting phase separation. Fluid inclusions in quartz intergrown with wolframite have low salinity (0.9–1.2 wt% NaCl equivalent), aqueous–carbonic fluids at 240–260°C, defining the latter’s depositional conditions. The ore fluids were derived from oxidized magmatic source initially contaminated by reduced basement rocks. Wall-rock alteration and involvement of circulating meteoric waters were dominant during the first three stages and early part of stage 4. Stage 5 hematite was deposited as a result of stage 4 phase separation or entrainment of oxygenated groundwater. Gold is associated with Te- and Bi-bearing minerals and mostly precipitated as gold-tellurides during stage 8. Gold deposition occurred below 350°C due to a change in the sulfidation and oxidation state of the fluids, depressurization and decreasing temperature and activities of sulfur and tellurium. Bisulfides are considered to be the main Au-transporting complexes. The Bilimoia deposit has affinities that are similar to many gold systems termed epizonal orogenic and intrusion-related. The current data allow us to classify the Bilimoia deposit as a fault-controlled, metamorphic-hosted, intrusion-related mesothermal to low sulfidation epithermal quartz–Au–Te–Bi vein system.

The occurrence, lithology, and stratigraphic setting of buried manganese deposits and associated host sediments in cores obtained on Legs 123–210 of the Ocean Drilling Program (ODP) are examined in order to establish the formative environment and conditions of preservation. Fossil manganese nodule and crusts are found to have formed or deposited throughout the period from 100 Ma to the present, with an additional example of formation near 137 Ma, suggesting that the deep-sea environment has been oxic and suitable for the formation of manganese nodules and crusts since the Cretaceous. Many manganese nodules and crusts occur on horizons corresponding to hiatuses in sedimentation or periods of slow sedimentation, consistent with the environment in which modern nodules form (sedimentation rate less than 10 m/m.y.). Sediments overlying the fossil nodules and crusts are oozes or biogenic sediments with sedimentation rates of 1–18 m/m.y. Low total organic carbon ( 25 mM) in interstitial water around the manganese horizon suggest that no strong reduction occurred within the overlying sediments. Coverage by biogenic sediments containing only small amounts of organic matter is therefore considered important for the preservation of manganese nodules and crusts. Manganese carbonate occurs sporadically as nodules, concretions or thin layers in various host sediments, including clay, calcareous ooze and siliceous ooze with sedimentation rates of 6–125 m/m.y. Hiatuses are rare around the host sediments of manganese carbonate. Higher total organic carbon (0.2–1.8 wt%) in the host sediments and lower sulfate content (0–25 mM) in interstitial water around the manganese carbonate horizon suggest that reduction in association with decomposition of organic matter would have proceeded in the host sediments.

Inorganic chemical compositions are determined for late Early Triassic siliceous claystone (‘Toishi-type’ shale) and associated chert from Oritate area, Sambosan Belt, Kyushu, southwest Japan. The siliceous claystone is similar in chemical composition to Post-Archean Australian Shale (PAAS), but is depleted in Ca, Sr, Mn, and Fe and slightly enriched in Cu, Zn, P, and rare earth elements (REEs). The siliceous claystone and associated chert have flat REE patterns with positive Eu anomalies and no distinct Ce anomaly. The siliceous claystone and associated chert have largely constant Ti/Al, Th/Al, and Nb/Al ratios compared to the variable ratios found in siliceous shale and sandstone deposited close to land in a trench setting. This suggests that the claystone and chert were deposited in a deep-sea pelagic environment and were derived mainly from the suspended fraction, including eolian dust and material transported from distant lands, rather than from turbidity currents that occurred close to land. The low Ca contents of the analyzed rocks indicate deposition below the calcium-carbonate compensation depth. The depletion of Mn and Fe, and no distinct Ce anomaly in the Oritate siliceous claystone are also evident, being similar to those in samples from the Sasayama and Kinkazan sections in the Mino-Tanba Belt, where oceanic anoxia developed during the Late Permian to earliest Triassic. This might suggest that oceanic anoxia prevailed through to the late Early Triassic.

Chemical and sulfur isotopic compositions were obtained for a series of rocks within the chert-clastic sequence surrounding the Kajika massive sulfide ore horizon at Shibukawasawa in the Ashio copper-mining district, Ashio Terrane, central Japan. The sequence is lithologically classified into three units: chert, siliceous shale with basic volcanics, and sandstone-shale, in ascending stratigraphic order. The Kajika ore horizon corresponds to the lowermost part of the unit that contains siliceous shale with basic volcanics. The rocks around the Kajika ore horizon are enriched in P2O5 (max. 0.22 %), Ba (max. 2400 ppm), Cu (595 ppm), V (323 ppm), Pb (168 ppm), Zn (124 ppm), and Mo (24 ppm) in siliceous shale; and Ba (4220 ppm), Zr (974 ppm), Cr (718 ppm), Ni (492 ppm), V (362 ppm), Zn (232 ppm), Nb (231 ppm), and Co (71 ppm) in the basic volcanics. The siliceous shale is enriched in a number of redox-sensitive elements such as Cu, V, Pb, Zn, and Mo, which are known to be enriched in black shale and anoxic and hydrothermal sediments. The δ34S values of sulfides in the chert and sandstone-shale lie in the range of 0±2 %, and those in the siliceous shale range from -5 to -14 %. The measured δ34S values in the basic volcanics are -0.3, -2.7, and -31.5 %. These heavier δ34S signatures (around 0 %) recorded throughout the sequence indicate that the rocks formed under anoxic bottom-water conditions. Slightly lighter δ34S values recorded in siliceous shale might reflect significant mixing of sulfides that formed by sulfate-reducing bacteria in an overlying oxic environment. The long-term duration of anoxic conditions indicated by the heavier δ34S signature is considered to have played an important role in protecting the Kajika sulfide ores from oxidative decomposition and preserving the ores in sedimentary accumulations.

Inorganic chemical compositions are determined for a series of rocks crossing an Early Jurassic stratiform manganese ore deposit in a chert-dominant sequence at Katsuyama, in the Mino Terrane of central Japan. The lithology in the vicinity of the manganese ore bed is classified into lower bedded chert, black shale, massive chert, manganese ore and upper bedded chert, in ascending order. The rocks surrounding the manganese deposit are anomalously high in certain elements: Pb (max. 29 ppm), Ni (1140) and Co (336) in the lower bedded chert, Mo (438), As (149), Tl (29) and U (12) in the black shales, V (210) and Cr (87) in the massive chert, and MnO and W (24) in the manganese ore. The aluminum-normalized profiles reveal a distinct zonation of redox-sensitive elements: Pb-Zn, Ni-Co-Cu(-Zn) and U-Cr in the lower bedded chert, Mo-As-Tl in the black shale, V(-Cr) in the massive chert, and Mn-Fe-Ba-W in the manganese ore, in ascending order. The lower and upper bedded cherts and manganese ore generally exhibit flat rare earth element patterns with positive Ce anomalies, whereas the uppermost part of the lower bedded chert, the black shale and massive chert have flat patterns with weak or nonexistent negative Ce anomalies and weak positive Eu anomalies. The strong enrichment in Ni, Co, W, Tl and As detected in the Katsuyama section is not recognized in other sediments, including those of anoxic deposition origin, but is identified in modern ferromanganese nodules, suggesting that metal enrichment in the Katsuyama section is essentially due to the formation of ferromanganese nodules rather than to deposition in an anoxic environment. The observed elemental zonation is well explained by equilibrium calculations, reflecting early diagenetic formation and associated gradual reduction with depth. The concentration profiles in combination with litho- and biostratigraphical features suggest that formation of these bedded manganese deposits was triggered by an influx of warm, saline and oxic water into a stagnant deep ocean floor basin in Panthalassa at the end of the middle Early Jurassic. Paleoceanographic environmental controls thus appear to be important factors in the formation and preservation of this type of stratiform manganese deposit.

Chemistry and sulfur isotopes are analyzed for a series of rocks in the chert-dominant sequence around the stratiform manganese ore deposit of the Noda-Tamagawa mine in the northern Kitakami Terrane, northeast Japan. The sequence is litholog-ically classified into six units in ascending order: lower bedded chert, lower black shale, massive chert, manganese ore, upper black shale, and upper bedded chert. The rocks around the manganese ore deposit exhibit anomalous enrichment in Ni (max. 337 ppm), Zn (102) and U (30) in the upper part of lower bedded chert, Mo (122), Tl (79) and Pb (33) in the lower black shale, MnO, Cu (786) and Co (62) in the manganese ore, and As (247) and Sb (17) in the upper black shale. The aluminum-normalized profiles reveal zonal enrichment of redox-sensitive elements around the manganese bed: Zn-Ni-Fe-Mo-U(-Co), Tl-Pb(-Mo), Mn-Fe-Cu-V-Cr-Co(-Zn) and As-Sb in ascending order. The uppermost part of the lower bedded chert and black shale exhibit negative Ce/Ce* values, whereas the massive chert, manganese ore and lower part of the upper bedded chert display positive values. The isotopic δ34S values are 0±6 % in the lower part of the lower bedded chert, -19 to -42 % in the upper part of the lower bedded chert, -36 to -42 % in the lower black shale, -28 to -35 % in the massive chert, manganese ore and upper black shale, and -23±5 % in the upper bedded chert. Thus, there is a marked negative shift in δ34S values in the lower bedded chert, and an upward-increasing trend in δ34S through the manganese ore horizon. The present data provide evidence for a change in the paleoceanographic environmental resulting from inflow of oxic deepwater into the stagnant anoxic ocean floor below the manganese ore horizon. This event is likely to have triggered the precipitation of manganese oxyhydroxides. The redistribution of redox-sensitive elements through the formation of metalliferous black shale and manganese carbonate ore may have occurred in association with bacterial decomposition of organic matter during early diagenesis of initial manganese oxyhydroxides.

Numerous bedded manganese deposits sporadically distributed throughout the Tamba district, southwestern Japan are intercalated within chert sequence. It is well known that radiolarian remains are commonly included in both bedded manganese deposits and host cherts. The Gen-otani mine, one of these deposits, is located at Otani, Keihoku-Shimonaka, northern Kyoto City. Chemical composition and age of the chert sequence at the mine were examined. Mainly according to SiO2 and MnO contents together with lithology, the chert sequence is divided into three sections; lower massive chert, middle bedded manganese deposit and upper bedded chert sections. Radiolarian faunas consisting of middle Jurassic species such as Eucyrtidiellum unumaense, Dictyomitrella(?) kamoensis, Parvicingula dhimenaensis, Sethocapsa aitai, Sethocapsa kodrai, Transhsuum brevicostatum, Tricolocapsa plicarum, Unuma echinatus and others were extracted from both the middle manganese section and overlying bedded chert of the upper section. This examination reveals that the bedded manganese deposit at the Gen-otani mine formed until Bajocian to early Bathonian (middle Middle Jurassic) in age.

The pulsed ESR technique was employed in the present study to obtain the spin-spin relaxation times of the E 1 ′ center (an unpaired electron at an oxygen vacancy) in natural quartz with and without irradiation. The relaxation times of the heat treated E 1 ′ center in natural unirradiated quartz of a granite and of uranium ore were 3.5– 7.1 μ s . Electron and gamma ray irradiated quartz showed the relaxation times of 7.1– 15.7 μ s while He ion implanted quartz showed 1.0– 2.0 μ s , much less than the other samples. The intensity of the E 1 ′ center increased in stepwise heating up to 300 ∘ C before decreasing above that temperature except for He implanted sample which showed monotonic decrease on heating. The present experimental results showed that the characteristics of the E 1 ′ center created by high linear energy transfer (LET) radiation is different from that by low LET radiation, suggesting that, in nature, the oxygen vacancies are created by low LET radiation, i.e. external beta and gamma rays, rather than by alpha particles and alpha recoil nuclei.

A comprehensive investigation was carried out on the distribution of both trace fossils and sulfur isotopes in mud-stones in the Hokuroku district, northeast Japan, in the hope of delineating the depositional environment of the mudstones in which the Kuroko deposits are embedded. The mudstones are generally massive in structure and usually contain large trace fossils, being indicative of an aerobic biofacies. On the other hand, some mudstones in and above the Kuroko ore horizon are partly laminated and usually contain smaller trace fossils, being assignable to an anaerobic or dysaerobic biofacies. The δ34S values of sulfides in the mudstones above and below the ore horizon range from -40 to -12 %o, indicating mostly oxic depositional conditions in equilibrium with the inferred aerobic biofacies. In the mudstones in the ore horizon, the δ34S values exhibit regionally discriminated variations: -44 to -12 %o in areas far (>1 km) from the known Kuroko deposits and -24 to +6 %o in areas closer to them. The latter high δ34S group implies the temporal occurrence of local anoxic basins in the vicinity of the known Kuroko deposits. At the time of late Nishikurosawa Stage (i.e. the currently assumed Kuroko metallogenic epoch), an intense oceanic stagnation is suggested to have taken place to form the local anoxic basins responsible for the formation and preservation of Kuroko deposits. This oceanic environmental event is considered to be most likely due to increasing biological productivity primarily triggered and enhanced by upwelling of NADW in the paleo-Sea of Japan at that time.

Germanium-bearing colusite occurs with sphalerite, galena, tetrahedrite-tennantite, chalcopyrite and pyrite in microdruses and veinlets in the siliceous black ore from the Ezuri Kuroko deposit in the Hokuroku district of Japan. X-ray microdiffractometry of this mineral gives strongest lines at 1.60, 1.32 and 1.09 A, which are consistent with the known powder diffraction data of colusite. On the basis of 32 S atoms per formula unit, electron microprobe analyses yield empirical chemical formulae of (Cu24 0Fe0.3Zn1.0)σ25.3V1.9(As4.8Sb0.2)σ5.0Ge 1.3S32 for Ge-bearing colusite in close association with sphalerite, and (Cu24.6Fe0.9)σ25.4V1.8(As4.1 Sb0.2)σ4.3Ge1.7S32 for that coexisting with chalcopyrite, consistent with the ideal formula of Cu24+xV2(As, Sb)6-x(Sn, Ge)xS32 (x = 0 to 2) proposed by Spry et al. (1994) for this mineral species. The Ge-bearing colusite mineralization is suggested to have occurred concurrently with consolidation of the siliceous black ore, possibly during hydrothermal modification in association with the igneous activity of the Ohtaki quartz diorite of the later Onnagawa stage. It is likely that biogenic siliceous ooze, a possible precursor of the siliceous black ore, may have served as an in situ source of Ge as well as other essential rare elements, leading to the formation of Ge-bearing colusite during transformation or recrystallization of biogenic opal into a-quartz.

A series of mudstones corresponding to N.8 to N.17 of Blow from the Uyashinai Mudstone Member, the Onnagawa Formation and the Funakawa Formation in the Taiheizan area of the central Green Tuff region, northeast Japan, was examined by chemical analysis. According to conventional chemical systematics, the mudstones are analyzed in terms of detrital, biogenic-A (siliceous), biogenic-B (calcareous) and hydrogenous components. The relative contribution of the biogenic-A (siliceous) component increases in upward succession in the Uyashinai and Onnagawa mudstones, whereas the contribution of the biogenic-B (calcareous) component is restricted to the lower Uyashinai mudstones. The contribution of hydrogenous components Zn, Pb, Cu and Ba tends to increase during the Nishikurosawa stage, and decreases near the Nishikurosawa/Onnagawa boundary (Pb and Ba) or in the Onnagawa stage (Zn and Cu). The observed enrichment of heavy metals in the Uyashinai mudstones is attributed to the onset of vigorous upwelling of deep water with higher nutrient and metal content associated with a contemporaneous change in global deep-water circulation.

Sulfur isotope ratios are analyzed for a series of mudstones in a successive section in the Taiheizan area in the central Green Tuff region, northeast Japan. The δ34S values for the Uyashinai Mudstone Member (Nishikurosawa stage), the Onnagawa Formation and the Funakawa Formation range from -45 to -14%, -20 to +4% and -30 to -10%, respectively. There is a marked positive shift in δ34S values at the Nishikurosawa/Onnagawa boundary and an upward δ34S-decreasing trend in the Onnagawa and Funakawa Formations. The present data provides evidence for environmental change in the form of stratification of the seawater, initiated at the Nishikurosawa/Onnagawa boundary and persisting during deposition of the Onnagawa Formation, followed by gradual oxygenation during deposition of the Funakawa Formation.

¶In cathodoluminescence (CL) images of synthetic low-quartz samples after He+ implantation at 4 MeV with a dose density over 1.14 × 10−4 C cm−2, bright CL halos of about 14 µm in width from the implantation surface are recognized. These widths are consistent with the theoretical range. This confirms experimentally that the CL halos in low-quartz found in geological samples are formed by alpha radiation. It also shows that CL colour continuously changes with dose density, demonstrating that it is possible to use the CL halo as a new dosimeter that is useful for dating and analysis of radionuclide migration in natural geological media.

Abundant benthic foraminifera have been identified in thin sections of the siliceous black ore in the Ezuri Kuroko deposit, Hokuroku, Japan. By treating samples with conventional hydrofluoric acid digestion techniques, sponge spicules and radiolaria have also been recognized in the residue. Under microscopic observations, 94 individual foraminiferal specimens have been detected. However, as it is difficult to identify species or genera by means of microscope observations alone, only a small number of genera have been identified based on morphology. The foraminiferal assemblage is composed predominantly of agglutinated species (83%) with subordinate calcareous species (17%), and is assigned to the Cyclammina Assemblage based on the preponderance of Cyclammina (57%). The foraminifera are generally well preserved within micro-crystalline to cryptocrystalline quartz, and exhibit no obvious features related to compaction or secondary deformation. Textural observations suggest that the siliceous component of this rock was not derived from an allochthonous block but instead constitutes autochthonous proto-Kuroko sediment. The Cyclammina Assemblage in the ore is different from recently described foraminiferal assemblages in the vicinity of present deep-sea hydrothermal vents, but is identical to those found in black shales of the Onnagawa to Funakawa stages in the Green Tuff region. The proto-Kuroko sediment is assumed to have been deposited in an oxygen-deficient environment within a closed, deep-seated basin. The existence of siliceous microfossils suggests that the silica in the siliceous ore did not originate from silica sinter deposits produced by submarine hydrothermal activities, but from a biogenic siliceous ooze, probably composed of diatoms. Sulfide mineralization in the interstices of some of the microfossils is inferred to relate primarily to bacterial sulfate reduction associated with the decomposition of organic matter. The later sulfide mineralization associated with larger crystals (which contain fluid inclusions with homogenization temperatures of approximately 250C) cuts across the siliceous masses and foraminiferal septa, and may have been formed after consolidation of the siliceous ooze, accompanying the formation of acidic intrusive rocks during the late Onnagawa stage.

A strange, unidentified, Cu-Fe bearing zinc sulfide occurs in the Laloki massive sulfide deposit, Papua New Guinea. The mineral is optically uniform in texture but is chemically variable and zoned even within a single grain. Copper contents vary from 0.1 up to 8.85 wt%. Iron reaches 18.31 wt% at maximum and decreases as Cu increases. It is remarkable, however, that the total Fe+Cu remains essentially unchanged between roughly 18 and 20 wt%. Zn and S are least variable, giving 45.85–47.84 wt% and 33.48–34.58 wt%, respectively. Other trace elements such as Cd and Mn are in general less than 0.2 wt%. It is strongly suggested that the mineral in question constitutes a unique Fe-Cu substitutional solid solution series belonging essentially to the Zn–Fe–Cu–S system. The ideal chemical formula of the solid solution series can well be presented as Zn10(Fe, Cu)5S15 or Zn2(Fe, Cu)S3, where Fe is always greater than Cu. It is intriguing that chalcopyrite blebs are recognizable restrictively only in nearby portions of the Cu-rich end member with the ideal composition close to Zn10Fe3Cu2S15. It has been confirmed by vacuum-sealed heating experiments that this mineral is decomposed to produce chalcopyrite and Fe-bearing normal sphalerite at temperatures below 200C. This would provide another evidence for the existence of such distinct phase as suggested here.

Osmotic and ionic regulatory ability were examined in the giant freshwater prawn, Macrobrachium rosenbergii in response to varying salinities. In freshwater, and under conditions of low salinity, hemolymph osmolality was maintained around 450 mOsm. Under high salinity, osmolality values increased in a time-wise manner until reaching levels of the surrounding rearing water. Changes in sodium concentration generally paralleled osmotic change, and potassium and magnesium concentrations increased upon exposure to extremely high salinity. In contrast, total calcium concentration was maintained at high levels regardless of salinity treatment. Examination of crystalline structure and ionic composition of the cuticle revealed that it was comprised principally of an α -chitin-like material, and calcite (calcium carbonate). Calcite accounted for 25% of total bulk weight in freshwater, while sodium, potassium and magnesium constituents combined comprised less than 2.5% of this total. Although sodium, potassium and magnesium contents increased nearly 2-fold in response to changing salinity, calcium levels remained relatively constant.

The Bilimoia gold deposit (1.77 Moz), Papua New Guinea (PNG), is a fault-hosted quartz-gold vein system hosted by 290–221 Ma years old basement that was regionally metamorphosed to greenschist facies at ∼45 Ma. Mineralisation occurred during S3-S4 ductile events in a S1-S4 deformation sequence, rapid uplift, crustal thickening and when the plate motions changed from oblique-transpressional to orthogonal convergence. It is spatially and temporally related to I-type, intermediate-felsic 9–7 Ma year-old porphyries. Distal quartz-specularite-calcite veins with chlorite-epidote selvage is the earliest hydrothermal event. Wallrock has been altered to quartz-illite-pyrite and quartz-sericite-mariposite/fuchsitepyrite, respectively. Infilling stages are divided into quartz±ferberite ±adularia, hematite, pyrite, quartz-sphalerite-galena-chalcopyrite, quartz-Cu±Sn sulphides-gold-tellurides-Te-Ag-Sb-Bi±Cu phases and carbonates-clays, respectively. Hypogene gold occurs as native gold, electrum, calaverite, kostovite, petzite and sylvanite; calaverite hosts 90–95% of the total gold. Gold distribution in the supergene zone (

Cathodoluminescence (CL) spectra of unirradiated, He+ ion-implanted and electron-irradiated plagioclase minerals contain the following emission bands: (1) below 300 nm due to Pb2+, (2) at ~320 and ~350 nm to Ce3+, (3) at 380–420 nm to Eu2+, Ti4+ and/or Al–O−–Al/Ti defects, (4) at 560–580 nm to Mn2+ and (5) at 720–760 nm to Fe3+. During the implantation of He+ ion, much of their energy may be dissipated by partial destruction and strain of the feldspar framework, resulting in quenching of CL. Deconvolution of CL spectra acquired from albite and oligoclase reveals an emission component at 1.86 eV (666 nm) assigned to a radiation-induced defect center associated with Na+ atoms. As its intensity increases with radiation dose, this emission component has potential for geodosimetry and geochronometry. Electron irradiation causes Na+ migration in plagioclase, and then a considerable reduction in intensity of emissions assigned to impurity centers, which is responsible for an alteration in the energy state or a decrease in luminescence efficiency following the change of activation energy. Emission intensity at 1.86 eV positively correlates with electron irradiation time for unimplanted and He+ ion-implanted albite and oligoclase, but negatively for the implanted albite above 1.07 × 10−4 C/cm2. It implies that radiation halo produced by α-particles should not be measured using CL spectroscopy to estimate β radiation dose on albite in the high radiation level.