Geochemical and Microbiological Analysis of Sambe Hot Springs,Shimane Prefecture,Japan     

Keiko Sasaki  Yoshitaka Uejima  Atsushi Sakamoto  Qianqian Yu  Junichiro Ishibashi  Naoko Okibe  Tsuyoshi Hirajima 《Resource Geology》2013,63(2):155-165

Microbiological contribution to the formation of the manganese deposits in Sambe hot springs, Shimane, was investigated in combination with water chemistry, characterization of sediments and microbial community structure. Analysis of bacterial and fungal community structure based on DNA extracted from a Mn‐oxidizing enrichment culture indicated close matches with Pseudomonas putida, Phoma sp. and Plectosphaerella cucumerina, all Mn‐oxidizing microorganisms. These sediments were poorly crystalline and formed at neutral pH values, which is characteristic of biogenic precipitates. The EPMA results demonstrated a positive correlation between Mn and Ba contents in well‐crystalline Mn oxide grains. Substantial Ba contents were observed inside Mn oxide grains. These findings indicated that Ba contents in sediments are influenced by not only aqueous Ba²⁺ concentrations but also crystallinity of biogenic birnessite. Barium would be incorporated in birnessite during biomineralization.  相似文献   

Behavior of Siderophile and Chalcophile Elements in the Subcontinental Lithospheric Mantle beneath the Changbaishan Volcano,NE China   总被引：1，自引：0，他引：1  

WANG Jian  LIU Jinlin  HATTORI Keiko  XU Wenliang  XIE Zhipeng  SONG Yue 《《地质学报》英文版》2012,86(2):409-421

The mantle xenoliths in the Quaternary ChangbaishanVolcano in southern Jilin Province contain spinel-facies lherzolites. The equilibration temperatures for these samples range from 902oC to 1064oC based on the two-pyroxene thermometer of Brey and K?hler (1990), and using the oxybarometry of Nell and Wood (1991), the oxidation state was estimated from FMQ-1.32 to -0.38 with an average value of FMQ-0.81 (n?=?8), which is comparable to that of abyssal peridotites and the asthenospheric mantle. The fO2 values of peridotites, together with their bulk rock compositions (e.g., Mg#, Al2O3, CaO, Ni, Co, Cr) and mineral compositions (e.g., Mg# of olivine and pyroxene, Cr# [=Cr/[Cr+Al]] and Mg# [=Mg/[Mg+Fe2+] of spinel), suggest that the present-day subcontinental lithospheric mantle (SCLM) beneath the Changbaishan Volcano most likely formed from an upwelling asthenosphere at some time after the late Mesozoic and has undergone a low degree of partial melting. The studied lherzolite xenoliths show low concentrations of S, Cu, and platinum group elements (PGE), which plot a flat pattern on primitive-mantle normalized diagram. Very low concentrations in our samples suggest that PGEs occur as alloys or hosted by silicate and oxide minerals. The compositions of the studied samples are similar to those of peridotite xenoliths in the Longgang volcanic field (LVF) in their mineralogy and bulk rock compositions including the abundance of chalcophile and siderophile elements. However, they are distinctly different from those of peridotite xenoliths in other areas of the North China Craton (NCC) in terms of Cu, S and PGE. Our data suggest that the SCLM underlying the northeastern part of the NCC may represent a distinct unit of the newly formed lithospheric mantle.  相似文献   

Ground motion characteristics and shaking damage of the 11th March 2011 M w9.0 Great East Japan earthquake     

Katsuichiro Goda  Antonios Pomonis  Siau Chen Chian  Mark Offord  Keiko Saito  Peter Sammonds  Stuart Fraser  Alison Raby  Joshua Macabuag 《Bulletin of Earthquake Engineering》2013,11(1):141-170

A catastrophic M _w9.0 earthquake and subsequent giant tsunami struck the Tōhoku and Kanto regions of Japan on 11th March 2011, causing tremendous casualties, massive damage to structures and infrastructure, and huge economic loss. This event has revealed weakness and vulnerability of urban cities and modern society in Japan, which were thought to be one of the most earthquake-prepared nations in the world. Nevertheless, recorded ground motion data from this event offer invaluable information and opportunity; their unique features include very strong short-period spectral content, long duration, and effects due to local asperities as well as direction of rupture/wave propagation. Aiming at gaining useful experience from this tragic event, Earthquake Engineering Field Investigation Team (EEFIT) organised and dispatched a team to the Tōhoku region of Japan. During the EEFIT mission, ground shaking damage surveys were conducted in Sendai, Shirakawa, and Sukagawa, where the Japan Meteorological Agency intensity of 6+ was observed and instrumentally recorded ground motion data were available. The damage survey results identify the key factors for severe shaking damage, such as insufficient lateral reinforcement and detailing in structural columns from structural capacity viewpoint and rich spectral content of ground shaking in the intermediate vibration period range from seismic demand viewpoint. Importantly, inclusion of several ground motion parameters, such as nonlinear structural response, in shaking damage surveys, can improve the correlation of observed ground motion with shaking damage and therefore enhance existing indicators of potential damage.  相似文献   

A primitive dark inclusion with radiation‐damaged silicates in the Ningqiang carbonaceous chondrite     

Michael ZOLENSKY  Keiko NAKAMURA  Michael K. WEISBERG  Martin PRINZ  Tomoki NAKAMURA  Kazumasa OHSUMI  Akihiro SAITOW  Masae MUKAI  Matthieu GOUNELLE 《Meteoritics & planetary science》2003,38(2):305-322

Abstract— A petrologic and TEM study of a remarkable dark inclusion (DI) in the Ningqiang CV3 chondrite reveals that it is a mixture of highly primitive solar nebula materials. The DI contains two lithologies. The first, lithology A, contains micron‐sized olivine and pyroxene grains rimmed by amorphous materials with compositions similar to the underlying crystalline grains. The second, lithology B, appears to preserve the mineralogy of lithology A before formation of the amorphous rims. Overall, the Ningqiang DI appears to record the following processes: 1) formation (condensation and Fe‐enrichment) of olivine crystals in the nebula with compositions of Fo_42–62; 2) irradiation, resulting in amorphitization of the olivine and pyroxene to varying degrees; 3) partial annealing, resulting in formation of fairly large, euhedral olivine and pyroxene grains with remnant amorphous sharply‐bounded rims; 4) in some cases, prolonged annealing, resulting in the formation of microcrystalline olivine or pyroxene rims. The latter annealing would have been a natural consequence of irradiation near the critical temperature for olivine; and 5) mixture of the above materials (lithology A) with nebular condensate high‐Ca pyroxene and olivine, which escaped nebular processing, to become lithology B. We suggest that the amorphous rims in lithology A formed in an energetic solar event such as a bi‐polar outflow or FU‐orionis flare.  相似文献   

Complex aromatic hydrocarbons in Stardust samples collected from comet 81P/Wild 2     

Simon J. CLEMETT  Scott A. SANDFORD  Keiko NAKAMURA‐MESSENGER  Friedrich H RZ  David S. McKAY 《Meteoritics & planetary science》2010,45(5):701-722

Abstract– The successful return of the Stardust spacecraft provides a unique opportunity to investigate the nature and distribution of organic matter in cometary dust particles collected from comet 81P/Wild 2. Analysis of individual cometary impact tracks in silica aerogel using the technique of two‐step laser mass spectrometry demonstrates the presence of complex aromatic organic matter. While concerns remain as to the organic purity of the aerogel collection medium and the thermal effects associated with hypervelocity capture, the majority of the observed organic species appear indigenous to the impacting particles and are hence of cometary origin. While the aromatic fraction of the total organic matter present is believed to be small, it is notable in that it appears to be N rich. Spectral analysis in combination with instrumental detection sensitivies suggest that N is incorporated predominantly in the form of aromatic nitriles (R–C≡N). While organic species in the Stardust samples do share some similarities with those present in the matrices of carbonaceous chondrites, the closest match is found with stratospherically collected interplanetary dust particles. These findings are consistent with the notion that a fraction of interplanetary dust is of cometary origin. The presence of complex organic N containing species in comets has astrobiological implications as comets are likely to have contributed to the prebiotic chemical inventory of both the Earth and Mars.  相似文献   

Experimental aqueous alteration of cometary dust     

Keiko NAKAMURA‐MESSENGER  Simon J. CLEMETT  Scott MESSENGER  Lindsay P. KELLER 《Meteoritics & planetary science》2011,46(6):843-856

Abstract– Recent spacecraft missions to comets have reopened a long‐standing debate about the histories and origins of cometary materials. Comets contain mixtures of anhydrous minerals and ices seemingly unaffected by planetary processes, yet there are indications of a hydrated silicate component. We have performed aqueous alteration experiments on anhydrous interplanetary dust particles (IDPs) that likely derived from comets. Hydrated silicates rapidly formed from submicrometer amorphous silicates within the IDPs at room temperature in mildly alkaline solution. Hydrated silicates may thus form in the near‐surface regions of comets if liquid water is ever present. Our findings provide insight into origins of cometary IDPs containing both anhydrous and hydrated minerals and help reconcile the seemingly inconsistent observations of hydrated silicates from the Stardust and Deep Impact missions.  相似文献   

Low and high frequency Madden–Julian oscillations in austral summer: interannual variations     

Takeshi Izumo  Sébastien Masson  Jérome Vialard  Clément de Boyer Montegut  Swadhin K. Behera  Gurvan Madec  Keiko Takahashi  Toshio Yamagata 《Climate Dynamics》2010,35(4):669-683

The Madden–Julian oscillation (MJO) is the main component of intraseasonal variability of the tropical convection, with clear climatic impacts at an almost-global scale. Based on satellite observations, it is shown that there are two types of austral-summer MJO events (broadly defined as 30–120 days convective variability with eastward propagation of about 5 m/s). Equatorial MJO events have a period of 30–50 days and tend to be symmetric about the equator, whereas MJO events centered near 8°S tend to have a longer period of 55–100 days. The lower-frequency variability is associated with a strong upper-ocean response, having a clear signature in both sea surface temperature and its diurnal cycle. These two MJO types have different interannual variations, and are modulated by the Indian Ocean Dipole (IOD). Following a negative IOD event, the lower-frequency southern MJO variability increases, while the higher-frequency equatorial MJO strongly diminishes. We propose two possible explanations for this change in properties of the MJO. One possibility is that changes in the background atmospheric circulation after an IOD favour the development of the low-frequency MJO. The other possibility is that the shallower thermocline ridge and mixed layer depth, by enhancing SST intraseasonal variability and thus ocean–atmosphere coupling in the southwest Indian Ocean (the breeding ground of southern MJO onset), favour the lower-frequency southern MJO variability.  相似文献   

Mixing efficiency in decaying stably stratified turbulence     

Derek D. Stretch  James W. Rottman  S.Karan Venayagamoorthy  Keiko K. Nomura  Chris R. Rehmann 《Dynamics of Atmospheres and Oceans》2010

Mixing efficiency in stratified flows is a measure of the proportion of turbulent kinetic energy that goes into increasing the potential energy of the fluid by irreversible mixing. In this research direct numerical simulations (DNS) and rapid distortion theory (RDT) calculations of transient turbulent mixing events are carried out in order to study this aspect of mixing. In particular, DNS and RDT of decaying, homogeneous, stably-stratified turbulence are used to determine the mixing efficiency as a function of the initial turbulence Richardson number R_it0=(N_L0/_u0)²$R{i}_{t0}={(N{L}_0/u_0)}^2$, where N   is the buoyancy frequency and _L0$L_0$ and _u0$u_0$ are initial length and velocity scales of the turbulence. The results show that the mixing efficiency increases with increasing R_it0$R{i}_{t0}$ for small R_it0$R{i}_{t0}$, but for larger R_it0$R{i}_{t0}$ the mixing efficiency becomes approximately constant. These results are compared with data from towed grid experiments. There is qualitative agreement between the DNS results and the available experimental data, but significant quantitative discrepancies. The grid turbulence experiments suggest a maximum mixing efficiency (at large R_it0$R{i}_{t0}$) of about 6%, while the DNS and RDT results give about 30%. We consider two possible reasons for this discrepancy: Prandtl number effects and non-matching initial conditions. We conclude that the main source of the disagreement probably is due to inaccuracy in determining the initial turbulence energy input in the case of the grid turbulence experiments.  相似文献   

Myctophid fishes of the genusMyctophum (myctophidae) in the pacific and Indian oceans     

Kouichi Kawaguchi  Keiko Aioi 《Journal of Oceanography》1972,28(4):161-175

The key to the nine species:M. nitidulum Garman,M. aurolaternatum Garman,M. spinosum (Steindachner),M. asperum Richardson,M. obtusirostrum Tåning,M. orientale (Gilbert),M. phengodes (Lütken),M. selenoides Wisner andM. brachygnathum (Bleeker), was prepared for the genusMyctophum, typical surface migrating myctophid fishes, from the Pacific and Indian Oceans. The three species ofM. cuvieri (Castelnau),M. indicus (Day),M. novaeseelandidae (Steindachner) were excluded from the present key, since they have not been reported since they were originally described.M. lychnobium Bolin formsM. spinosumlychnobium complex and was also excluded. The systematic accounts were given for seven species.  相似文献   

Diverse metal sources of Archaean gold deposits: evidence from in situ lead-isotope analysis of individual grains of galena and altaite in the Ross and Kirkland Lake deposits,Abitibi Greenstone belt,Canada     

Keiko Hattori 《Contributions to Mineralogy and Petrology》1993,113(2):185-195

Lead isotope compositions for individual grains of galena and altaite (PbTe) were determined in situ using a secondary ion mass spectrometer (SIMS). Galena was collected from the Ross deposit and altaite from the Kirkland Lake (KL) deposits in the southern Abitibi greenstone belt, Superior Province of Canada. The samples from KL are more radiogenic than those from the Ross deposit. Isotopic compositions vary significantly between different grains in each deposit and form broad linear arrays in ²⁰⁷Pb/²⁰⁴Pb-²⁰⁶Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb-²⁰⁶Pb/²⁰⁴Pb diagrams. The linear arrays of Pb-isotope data are attributed to mixing of Pb from different sources. At least two sources are required for individual deposits: one with low U/Pb and Th/Pb ratios and the other with high ratios. Lead minerals occurring with Au are less radiogenic than those that are not obviously associated with Au, suggesting that Au was supplied from low U/Pb sources such as sulphides or older ultramafic-mafic rocks. While most data are consistent with the derivation from local rocks, highly radiogenic Pb with relatively low ²⁰⁷Pb/²⁰⁶Pb ratios recorded at KL require post-Archaean mineralization or derivation of the Pb from an unusual crustal source with low . The latter interpretation is favored because of the lack of textural evidence and because it is difficult to dissolve and precipitate altaite at low temperatures. The presence of a Pb reservoir with low is also inferred from the data of Archaean banded iron formations and volcanogenic massive sulphide deposits. Different isotopic patterns of the two deposits suggest different sources of metals in the two deposits. While this conclusion does not reject the derivation of fluids from the lower crust or mantle, the data are not in accord with conceptual models invoking a common source reservoir for metals. The study suggests that fluids, which may have a common origin, leached metals and other constituents from the upper crustal rocks during their ascent. The proposed model, different origins for different constituents, explains much of the conflicting evidence presented by Archaean Au deposits, including provinciality of mineralogy and relatively uniform fluid inclusion and C-isotope data from many Au deposits.  相似文献