Mineralizations of Base Metal Deposits of Acid-Sulfate Type Coexisting with Adularia-Sericite Type     

Hideki IMAI 《Resource Geology》1999,49(3):147-156

Abstract: Two types of ores are recognized in the Huanzala mine, Peru. Zinc and lead ore of adularia-sericite type, is accompanied by pyrite body and skarn. Orthoclase (adularia), sericite and calcite are found in the skarn and altered country rocks. On the other hand, copper and silver (tin) ore of acid-sulfate type, is characterized by enargite, luzonite and bornite, accompanied by tin, silver and tellurium minerals. Although sericite and calcite are found only at the earlier stage in the mineralization of acid-sulfate type, kaolinite appears in the country rocks at a subsequent stage. It is interpreted that the ore-forming fluid of the acid-sulfate type separated from the adularia-sericite type by boiling in the early stage of mineralization. The separated fluid was nearly neutral just after boiling and changed into acidic by the oxidation of H₂S into HSO₄^-. Both types of mineralizations are studied in terms of fo₂-fs₂-pH-temperature diagrams. The adularia-sericite type might correspond to the hot-water system of a geothermal area, and the acid-sulfate type to the vapor-dominated system.
The copper ores from the Teine mine, Hokkaido, Japan and the Chinkuashih mine, Taiwan are acid-sulfate type, characterized by the occurrence of enargite and luzonite. However, zinc and lead ores of the adularia-sericite type are also present in these deposits. Both types in the Teine and Chinkuashih deposits are supposed to have formed in the similar relation as in the Huanzala deposits. The enargite and luzonite ores in the Hokuetsu mine, Japan are closely associated with native sulfur of solfataric origin.  相似文献   

Identification of Pathways for Hydrogen Gas Migration in Fault Zones with a Discontinuous,Heterogeneous Permeability Structure and the Relationship to Particle Size Distribution of Fault Materials     

Masakazu?NiwaEmail author  Hideki?Kurosawa  Koji?Shimada  Tsuneari?Ishimaru  Hideki?Kosaka 《Pure and Applied Geophysics》2011,168(5):887-900

Previous studies have reported that high concentrations of H₂ gas are released from active fault zones. Experimental studies suggest that the H₂ gas is derived from the reaction of water with free radicals formed when silicate minerals are fractured at hypocenter depths during fault activities. However, the pathways for migration of deep-seated fluids to surface are still unknown. In this study we performed quick, multipoint H₂ gas measurements across a fault zone using a portable gas monitor and a hand drill. The fault zone studied includes a smectite-rich fault core dividing two clearly distinguishable damage zones: granite cataclasite and welded tuff fault breccia. The measurements show that H₂ gas emissions collected in 2–3 h sampling periods from start of measurement range from 320.3 to 446.2 ppm/min in the granite cataclasite and 60.5 to 137.8 ppm/min in the welded tuff fault breccias. Negligible quantities of H₂ gas could be collected from the fault core. Particle size distribution analyses of fault rocks indicate that the granite cataclasite tends to be rich in particles that are finer, i.e., less cohesive and easy to disaggregate, which leads to the inference that the granite cataclasite has high permeability. Based on the H₂ gas measurements and the particle size distribution analyses, the H₂ gas is considered to have migrated in permeable damage zones mostly by advection with groundwater. Multipoint H₂ gas measurement will be effective in qualitative delineation of variations in permeability of regional structures.  相似文献   

Theoretical Evaluation of the Mechanical Behavior of Unsaturated Soils     

Michinori Honda  Shintaro Ohno  Atsushi Iizuka  Katsuyuki Kawai  Hideki Ohta 《Geotechnical and Geological Engineering》2011,29(2):171-180

An evaluation method for the mechanical behavior of unsaturated soils is studied in this paper. Although the mechanical behavior of unsaturated soils is complicated, a simple modeling is preferable in practice. This is because the soil properties are not homogeneous and ground data is limited when structures are being designed. In addition, in order to evaluate the reliability of the design, the physical meanings of the parameters applied in the prediction model should be clear. Firstly, the authors study the relationship between compaction curves and compression indexes in the unsaturated state that is used in the proposed constitutive model. Based on the constitutive model, the stress paths for constant volume shear tests are formulated under a constant void ratio condition and the stress paths for undrained shear tests are calculated under a constant water content condition. In the case of unsaturated specimens, the volume of these specimens changes with the shear deformation and the stress paths depend on the initial degree of saturation. The results of the calculation qualitatively describe the test results by considering the changes in effective confining pressure in the undrained condition and the water retention curves.  相似文献   

U–Pb ages of zircons from metamorphic rocks in the upper sequence of the Hidaka Metamorphic Belt,Hokkaido, Japan: Identification of two metamorphic events and implications for regional tectonics     

Yutaka Takahashi  Masumi Mikoshiba  Toshiaki Shimura  Mitsuhiro Nagata  Hideki Iwano  Tohru Danhara  Takafumi Hirata 《Island Arc》2021,30(1):e12393

The Hidaka Metamorphic Belt is a well-known example of island-arc crustal section, in which metamorphic grade increases westwards from unmetamorphosed sediment up to granulite facies. It is divided into lower (granulite to amphibolite facies) and upper (amphibolite to greenschist facies) metamorphic sequences. The metamorphic age of the belt was considered to be ~55 Ma, based on Rb – Sr whole-rock isochron ages for granulites and related S-type tonalities. However, zircons from the granulites in the lower sequence yield U – Pb ages of ~21 – 19 Ma, and a preliminary report on zircons from pelitic gneiss in the upper sequence gives a U – Pb age of ~40 Ma. In this paper we provide new zircon U – Pb ages from two pelitic gneisses in the upper sequence to assess the metamorphic age and also the maximum depositional age of the sedimentary protolith. The weighted mean ²⁰⁶Pb/²³⁸U ages from a biotite gneiss in the central area of the belt yield 39.6 ± 0.9 Ma for newly grown metamorphic rims and 53.1 ± 0.9 Ma for the youngest detrital cores. The ages of zircons from a cordierite–biotite gneiss in the southern area are 35.9 ± 0.7 Ma for metamorphic rims and 46.5 ± 2.8 Ma for the youngest detrital cores. These results indicate that metamorphism of the upper sequence took place at ~40 – 36 Ma, and that the sedimentary protolith was deposited after ~53 – 47 Ma. These metamorphic ages are consistent with the reported ages of ~37–36 Ma plutonic rocks in the upper sequence, but contrast with the ~21–19 Ma ages of metamorphic and plutonic rocks in the lower sequence. Therefore, we conclude that the upper and lower metamorphic sequences developed independently but coupled with each other before ~19 Ma as a result of dextral reverse tectonic movement.  相似文献   

Potential of submarine-cave sediments and oxygen isotope composition of cavernicolous micro-bivalve as a late Holocene paleoenvironmental record   总被引：2，自引：1，他引：1  

Akihisa Kitamura  Nagisa Yamamoto  Tomoki Kase  Shu-ichi Ohashi  Mayumi Hiramoto  Hitoshi Fukusawa  Tsuyoshi Watanabe  Tomohisa Irino  Hiroshi Kojitani  Michiyo Shimamura  Ikuo Kawakami 《Global and Planetary Change》2007,55(4):301-316

A sediment layer (43 cm thick) and surface sediments (5 cm thick) in a submarine limestone cave (31 m water depth) on the fore-reef slope of Ie Island, off Okinawa mainland, Japan, were examined by visual, mineralogical and geochemical means. Oxygen isotope analysis was performed on the cavernicolous micro-bivalve Carditella iejimensis from both cored sediments and surface sediments, and the water temperature within the cave was recorded for nearly one year. These data show that: (1) water temperature within the cave is equal to that at 30 m deep in the open sea; (2) the biotic and non-biotic environments within the cave have persisted for the past 2000 years; (3) mud-size carbonate detritus is a major constituent of the submarine-cave deposit, and may have come mainly from the suspended carbonate mud produced on the emergent Holocene reef flat over the past two millennia; (4) the δ¹⁸O-derived temperature (T_δ18_O) of C. iejimensis suggests that the species grows between April and July; (5) the T_δ18_O of C. iejimensis from cored sediments implies that there were two warmer intervals, at AD 340 ± 40 and AD 1000 ± 40, which correspond to the Roman Warm Period and Medieval Warm Period, respectively. These suggest that submarine-cave sediments provide unique information for Holocene reef development. In addition, oxygen isotope records of cavernicolous C. iejimensis are a useful tool to reconstruct century-scale climatic variability for the Okinawa Islands during the Holocene.  相似文献   

Nutrient status of Otsuchi Bay (northeastern Japan) following the 2011 off the Pacific coast of Tohoku Earthquake     

Hideki Fukuda  Ryosuke Katayama  Yanhui Yang  Hiroyuki Takasu  Yuichiro Nishibe  Atsushi Tsuda  Toshi Nagata 《Journal of Oceanography》2016,72(1):39-52

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Modeling three-dimensional forest structures to drive canopy radiative transfer simulations of bidirectional reflectance factor     

Wei Yang  Hideki Kobayashi  Xuehong Chen  Kenlo Nishida Nasahara  Rikie Suzuki  Akihiko Kondoh 《International Journal of Digital Earth》2018,11(10):981-1000

Three-dimensional (3-D) Monte Carlo-based radiative transfer (MCRT) models are usually used for benchmarking in intercomparisons of the canopy radiative transfer (RT) simulations. However, the 3-D MCRT models are rarely applied to develop remote sensing algorithms to estimate essential climate variables of forests, due mainly to the difficulties in obtaining realistic stand structures for different forest biomes over regional to global scales. Fortunately, some of important tree structure parameters such as canopy height and tree density distribution have been available globally. This enables to run the intermediate complexities of the 3-D MCRT models. We consequently developed a statistical approach to generate forest structures with intermediate complexities depending on the inputs of canopy height and tree density. It aims at facilitating applications of the 3-D MCRT models to develop remote sensing retrieval algorithms. The proposed approach was evaluated using field measurements of two boreal forest stands at Estonia and USA, respectively. Results demonstrated that the simulations of bidirectional reflectance factor (BRF) based on the measured forest structures agreed well with the BRF based on the generated structures from the proposed approach with the root mean square error (RMSE) and relative RMSE (rRMSE) ranging from 0.002 to 0.006 and from 0.7% to 19.8%, respectively. Comparison of the computed BRF with corresponding MODIS reflectance data yielded RMSE and rRMSE lower than 0.03 and 20%, respectively. Although the results from the current study are limited in two boreal forest stands, our approach has the potential to generate stand structures for different forest biomes.  相似文献   

Paleoenvironmental analysis of the Mawaki archaeological site,central Japan,in relation to the stratigraphic position of dolphin bones     

Yasuto Itoh  Keiji Takemura  Toshio Nakamura  Shin Hasegawa  Hideki Takada 《Geoarchaeology》2011,26(4):461-478

In order to elucidate the paleoenvironment associated with the early Holocene Mawaki archaeological site on the Noto Peninsula of central Japan, a high‐resolution stratigraphic study was conducted of 17 boreholes drilled at the archaeological site. We selected three boreholes for which lithological and/or chronological data are reported. Initial magnetic susceptibility was utilized for correlation of clastic core samples with the assistance of 26 radiocarbon dates. Four lithological units (A, B, C, and D in ascending order) were identified and interpreted as a sequence in a cycle of marine transgression and regression. Dated coastal horizons were chosen to indicate former sea levels. A Holocene relative sea level curve was generated on the basis of the geological data, and a rapid rise from 8000cal. yr B.P. to 7000cal. yr B.P. and a succeeding minor sea level fall represent the basic eustatic trend around the Sea of Japan because hydroisostatic and tectonic effects are moderate in the study area. Abundant dolphin bones lay just above the top of the marine sequence (boundary between Units C and D), located in the seashore environment. Cultural artifacts are found in a subaerial deposit (Unit D) near the dolphin bone level that is assigned to a period of high, stable sea level after the post‐glacial eustatic highstand. Dolphin bones are associated with stone artifacts (arrowheads, knives, and scrapers) and ritual wood columns, indicating the presence of a longstanding fishery during the early Holocene on the Sea of Japan coast. © 2011 Wiley Periodicals, Inc.  相似文献   

On spatial distributions of old globular clusters in clusters of galaxies     

Kenji Bekki  Hideki Yahagi 《Monthly notices of the Royal Astronomical Society》2006,372(3):1019-1033

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A possible Caledonide arm through the Barents Sea imaged by OBS data     

Asbjrn Johan Breivik  Rolf Mjelde  Paul Grogan  Hideki Shimamura  Yoshio Murai  Yuichi Nishimura  Asako Kuwano 《Tectonophysics》2002,355(1-4)

The assembly of the crystalline basement of the western Barents Sea is related to the Caledonian orogeny during the Silurian. However, the development southeast of Svalbard is not well understood, as conventional seismic reflection data does not provide reliable mapping below the Permian sequence. A wide-angle seismic survey from 1998, conducted with ocean bottom seismometers in the northwestern Barents Sea, provides data that enables the identification and mapping of the depths to crystalline basement and Moho by ray tracing and inversion. The four profiles modeled show pre-Permian basins and highs with a configuration distinct from later Mesozoic structural elements. Several strong reflections from within the crystalline crust indicate an inhomogeneous basement terrain. Refractions from the top of the basement together with reflections from the Moho constrain the basement velocity to increase from 6.3 km s⁻¹ at the top to 6.6 km s⁻¹ at the base of the crust. On two profiles, the Moho deepens locally into root structures, which are associated with high top mantle velocities of 8.5 km s⁻¹. Combined P- and S-wave data indicate a mixed sand/clay/carbonate lithology for the sedimentary section, and a predominantly felsic to intermediate crystalline crust. In general, the top basement and Moho surfaces exhibit poor correlation with the observed gravity field, and the gravity models required high-density bodies in the basement and upper mantle to account for the positive gravity anomalies in the area. Comparisons with the Ural suture zone suggest that the Barents Sea data may be interpreted in terms of a proto-Caledonian subduction zone dipping to the southeast, with a crustal root representing remnant of the continental collision, and high mantle velocities and densities representing eclogitized oceanic crust. High-density bodies within the crystalline crust may be accreted island arc or oceanic terrain. The mapped trend of the suture resembles a previously published model of the Caledonian orogeny. This model postulates a separate branch extending into central parts of the Barents Sea coupled with the northerly trending Svalbard Caledonides, and a microcontinent consisting of Svalbard and northern parts of the Barents Sea independent of Laurentia and Baltica at the time. Later, compressional faulting within the suture zone apparently formed the Sentralbanken High.  相似文献