The energy balance over land and oceans: an assessment based on direct observations and CMIP5 climate models   总被引：2，自引：0，他引：2  

Martin Wild  Doris Folini  Maria Z. Hakuba  Christoph Schär  Sonia I. Seneviratne  Seiji Kato  David Rutan  Christof Ammann  Eric F. Wood  Gert König-Langlo 《Climate Dynamics》2015,44(11-12):3393-3429

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Hydrous peridotites with Ti-rich chromian spinel as a low-temperature forearc mantle facies: evidence from the Happo-O’ne metaperidotites (Japan)   总被引：1，自引：0，他引：1  

Mohamed Zaki Khedr  Shoji Arai 《Contributions to Mineralogy and Petrology》2010,159(2):137-157

The Happo-O’ne peridotite complex is situated in the northeastern part of the Hida Marginal Tectonic Zone, central Japan, characterized by the high-P/T Renge metamorphism, and is considered as a serpentinite mélange of Paleozoic age. Peridotitic rocks, being massive or foliated, have been subjected to hydration and metamorphism. Their protoliths are mostly lherzolites to harzburgites with subordinate dunites. We found a characteristic mineral assemblage, olivine + orthopyroxene + tremolite + chlorite + chromian spinel, being stable at low-T, from 650 to 750°C, and high-P, from 16 to 20 kbar, tremolite–chlorite peridotites of the tremolite zone. Olivines are Fo₈₈–Fo_91, and orthopyroxenes (Mg# = 0.91) show low and homogenous distributions of Al₂O₃ (up to 0.25 wt%), Cr₂O₃ (up to 0.25 wt%), CaO (up to 0.36 wt%) and TiO₂ (up to 0.06 wt%) due to the low equilibration temperature. Chromian spinels, which are euhedral and enclosed mainly in the orthopyroxenes, have high TiO_2, 3.1 wt% (up to 5.7 wt%) on average, and high Cr# [=Cr/(Cr + Al) atomic ratio], 0.95 on average but low Fe³⁺ [=Fe³⁺/(Cr + Al + Fe³⁺) atomic ratio, <0.3]. The bulk-rock chemistry shows that the Happo-O’ne metaperidotites with this peculiar spinel are low in TiO₂ (0.01–0.02 wt%), indicating no addition of TiO₂ from the outside source during the metamorphism; the high TiO₂ of the peculiar spinel has been accomplished by Ti release from Ti-bearing high-T pyroxenes during the formation of low-T, low-Ti silicates (<0.1 wt% TiO₂) during cooling. Some dunites are intact from hydration: their olivine is Fo₉₂ and spinel shows high Cr#, 0.72. The Happo-O’ne metaperidotites (tremolite–chlorite peridotites), being in the corner of the mantle wedge, are representative of a hydrous low-T, high-P mantle peridotite facies transitional from a higher T anhydrous peridotite facies (spinel peridotites) formed by in situ retrograde metamorphism influenced by fluids from the subducting slab. They have suffered from low-T (<600°C) retrogressive metamorphism to form antigorite and diopside during exhumation of the Renge metamorphic belt.  相似文献   

Re-Os geochronology of the Iimori Besshi-type massive sulfide deposit in the Sanbagawa metamorphic belt, Japan     

Tatsuo Nozaki  Yasuhiro Kato  Katsuhiko Suzuki 《Geochimica et cosmochimica acta》2010,74(15):4322-1090

Besshi-type Cu deposits are strata-bound volcanogenic massive sulfide deposits usually associated with mafic volcanic rocks or their metamorphic equivalents. Although there are numerous Besshi-type deposits in the Sanbagawa metamorphic belt, Japan, their tectonic settings and depositional environments remain controversial because of a lack of depositional age constraints. We report Re-Os data for the Iimori deposit, one of the largest Besshi-type deposits in western Kii Peninsula, in order to examine the robustness of the Re-Os isotope system for dating sulfide minerals in the high-P/T metamorphic belt and to elucidate the primary depositional environment of the Iimori sulfide ores. An 11-point Re-Os isochron plot yields an age of 156.8 ± 3.6 Ma. As this Re-Os isochron age is significantly older than the timing of the Sanbagawa peak metamorphism (110-120 or ∼90 Ma) and a well-defined isochron was obtained, the Re-Os age determined here is most likely the primary depositional age. Despite high-grade metamorphism at up to 520 ± 25 °C and 8-9.5 kbar, the Re-Os isotope system of the Iimori sulfides was not disturbed. Hence, we consider that the whole-rock Re-Os closure temperature for the Iimori sulfide ores was probably higher than 500 °C. As the accretion age of the Sanbagawa metamorphic belt is considered to be 120-130 or 65-90 Ma on the basis of radiolarian and radiometric ages, we estimated the time from the Iimori sulfide deposition on the paleo-seafloor to its accretion at the convergent plate boundary to be greater than 25 Myr. Consequently, the depositional environment of the Iimori sulfide ores was not in the marginal sea, but was truly pelagic.  相似文献   

Eocene continental dyke swarm from Central Iran (Khur area)     

Ghodrat Torabi  Shoji Arai  Hamideh Abbasi 《Petrology》2014,22(6):617-632

The Eocene dyke swarm with east-west general trend intrudes the Cretaceous sedimentary rocks in ～25 km north of the Khur city (Central Iran). Some of the studied dykes can be followed for over 7 km, but the majority of exposures in the area are less than 5 km long. The dykes commonly exhibit a chilled contact with the wall rocks. These dykes are trachybasalt and basalt in composition. The trachybasalt dykes are much more abundant. The basaltic dykes cross cut the trachybasalt dykes in some locations, indicating that trachybasalt dykes are older than the basaltic ones. Primary igneous minerals of the basaltic dykes are olivine (chrysolite), clinopyroxene (diopside, augite), plagioclase (labradorite), sanidine, magnetite, orthopyroxene (enstatite), spinel and phlogopite, and secondary minerals are zeolite (natrolite and mesolite), chlorite (diabantite), calcite and serpentine. The trachybasalt dykes are composed of clinopyroxene (diopside), plagioclase (labradorite), sanidine, mica (biotite and phlogopite), amphibole (magnesio-hastingsite) and magnetite as primary minerals, and chlorite and calcite as secondary ones. Whole rocks geochemical data of the studied dykes indicate their basic and calc-alkaline nature and suggest that these two set of dykes were derived from the same parental magma. The chondrite-normalized REE patterns and the primitive mantle-normalized multi-elemental diagram of the Khur dykes show enrichment of light rare earth elements (LREE) relative to heavy rare earth elements (HREE), and negative anomalies of high field strength elements (HFSE) (e.g. Ti, Nb and Ta). These rocks show enrichment of the large ion lithophile elements (LILE) (e.g. Cs, Ba, Th and U) and depletion of the HREE and Y relative to MREE, Zr and Hf. In the chondrite-normalized REE diagram, the basalts show elevated REE abundances relative to the trachybasalt samples. Geochemical analyses of the studied samples suggest a spinel lherzolite from the mantle as the source rock and confirm the role of subduction in their generation. The chemical characteristics of the Khur dykes resemble those of continental arc rocks, and they were possibly formed by subduction of the Central-East Iranian microcontinent (CEIM) confining oceanic crust and decompression melting of a lithospheric subcontinental mantle spinel lherzolite enriched by subduction.  相似文献   

Podiform chromitite formation in a low-Cr/high-Al system: An example from the Southwest Indian Ridge (SWIR)   总被引：1，自引：0，他引：1  

Betchaida D. Payot  Shoji Arai  Henry J. B. Dick  Natsue Abe  Yuji Ichiyama 《Mineralogy and Petrology》2014,108(4):533-549

Recent reassessment of abyssal peridotites obtained during the dredging of the oblique supersegment and the easternmost subsection of the Southwest Indian Ridge by the R/V Knorr Cruise 162 and the R/V Yokosuka YK98-07 revealed the occurrence of dunites containing podiform chromitites and dunites with variable chromite concentration closely associated with lherzolite and harzburgite. The size of the chromitite pods varies from a few mm to 2 cm in width. Chromites in the podifom chromitites have very low Cr# (=0.22–0.23) and low TiO₂ (<0.17 wt%). They are almost free of silicate inclusions except for a few euhedral sulfide grains which occur far from cracks and lamellae and are considered primary in origin. The lherzolite which possibly represents the wallrock hosting the dunites with podiform chromitites also show low spinel Cr#(=0.16) and low Cr# in the clinopyroxenes (=0.09–0.10) and orthopyroxenes (=0.07–0.09). The small size of the SWIR podiform chromitites is strongly controlled by the low Cr/Al available in the wallrock and the invading melt. The presence of sulfide inclusions and the absence of PGEs further attest to the low Cr/Al (i.e. low refractoriness) in the system involved in the genesis of the SWIR podiform chromitites. Lastly, the discovery of podiform chromitites in the SWIR implies that the formation of podiform chromitite at mid-oceanic ridges, regardless of its spreading rate, is highly possible.  相似文献   

Photometric study of new southern SU UMa-type dwarf novae and candidates – III. NSV 10934, MM Sco, AB Nor and CAL 86     

Taichi Kato  Peter Nelson  Chris Stockdale  Berto Monard  Tom Richards  Rod Stubbings  Hitoshi Yamaoka  Bernard Heathcote  Roland Santallo 《Monthly notices of the Royal Astronomical Society》2004,347(3):861-872

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A normal and superoutburst study of the eclipsing SU UMa star: DV Ursae Majoris     

Daisaku Nogami  †  Taichi Kato  Hajime Baba  Rudolf Novák  J. J. Lockley  M. Somers 《Monthly notices of the Royal Astronomical Society》2001,322(1):79-84

We report on time-resolved photometry carried out during the 1995 short outburst and the 1997 long outburst in the eclipsing dwarf nova DV UMa. The revised orbital period is 0.0858526172 (67) d. We detected gigantic superhumps with an amplitude of ∼0.6 mag in the mid-phase of the 1997 outburst, revealing the SU UMa nature of DV UMa. The superhump period is 0.0887 (4) d. The superhumps became less clear during the late phase of the superoutburst, and we found two possible periods of 0.0885 (15) and 0.0764 (15). During both outbursts, the eclipse was wide and shallow near the maximum, and then became narrower and deeper, which is qualitatively well explained by the current disc instability theory.  相似文献   

Hydrothermal Precipitation of Chromites     

ARAI Shoji 《《地质学报》英文版》2015,89(Z2):2-2

<正>Chromite is a typical refractory igneous mineral,precipitated from mafic magmas at relatively high temperatures.Chromites commonly occur in sedimentary,metamorphic and metasomatic rocks,where they are interpreted as relics of an igneous phase and serve as the source of Cr for low-temperature Cr-bearing minerals.We  相似文献   

Middle to late Triassic mélange exhumation along a pre-Andean transpressional fault system: coastal Chile (26°–42° S)     

Terence T. Kato  Estanislao Godoy 《International Geology Review》2015,57(5-8):606-628

Mélanges occur as discontinuous, mappable, units along an extensive N–S-trending, steeply dipping zone of distributed shear in metamorphic complexes along the coast of central Chile. Large mélange zones, from north to south, near Chañaral, Los Vilos, Pichilemu, and Chiloé Island, contain variations in lithologic and structural detail, but are consistent in exhibiting cross-cutting fabric features indicating a progressive transition from earlier ductile to more brittle deformation. In the Infiernillo mélange near Pichilemu, Permian to Early Triassic, sub-horizontal schistosity planes of the Western Series schist are disrupted, incorporated into, and uplifted along high-angle, N–S- to NNE–SSW-trending brittle–ductile shears. Mylonitic and cataclastic zones within the mélange matrix indicate active lateral shear during cumulative exhumation from depths exceeding 12 km in some areas. Exotic lithologies, such as Carboniferous mafic amphibolite and blueschist, formed during earlier Gondwanide subduction, match well with similar rocks in the Bahia Mansa to Los Pabilos region 750 km to the south, suggesting possible dextral offset. The development of the Middle to Late Triassic, N–S=trending, near-vertical shear zones formed weaknesses in the crust facilitating later fault localization, gravitational collapse, and subduction erosion along the continental margin. The length and linearity of this zone of lateral movement, coincident with a general hiatus of regional arc magmatism during the Middle to Late Triassic, is consistent with large-scale dextral transpression, or possible transform movement, during highly oblique NNE–SSW convergence along the pre-Andean (Gondwana) margin. The resultant margin parallel N–S-trending shear planes may be exploited by seismically active faults along the present coastal area of Chile. The palaeo-tectonic setting during the transitional period between earlier Gondwanide (Devonian to Permian) and later Andean (Late Jurassic to present) subduction may have had some similarity to the presently active San Andreas transform system of California.  相似文献   

A possible origin of magnetic fields in galaxies and clusters: strong magnetic fields at  z∼ 10 ?     

Yutaka Fujita †  Tsunehiko N. Kato 《Monthly notices of the Royal Astronomical Society》2005,364(1):247-252

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