Subduction–accretion–collision history along the Gondwana suture in southern India: A laser ablation ICP-MS study of zircon chronology     

Kei Sato  M. Santosh  Toshiaki Tsunogae  T.R.K. Chetty  Takafumi Hirata 《Journal of Asian Earth Sciences》2011,40(1):162-171

We report the petrological characteristics and preliminary zircon geochronology based on laser ablation ICP mass spectrometry of the various units in an accretionary belt within the Palghat-Cauvery Shear/Suture Zone in southern India, a trace of the Cambrian Gondwana suture. Zircons extracted from a plagiogranite in association with an ophiolite suite within this suture possess internal structure that suggests magmatic crystallization, and yield mid Neoproterozoic ²⁰⁶Pb/²³⁸U age of 817 ± 16 Ma (error: 1σ) constraining the approximate timing of birth of the Mozambique Ocean floor. Compiled age data on zircons separated from a quartzite and metamorphosed banded iron formation within the accretionary belt yields a younger intercept age of 759 ± 41 Ma (error: 1σ) which we relate to a mid Neoproteozoic magmatic arc. Detrital zircons extracted from the quartzite yield ²⁰⁷Pb/²⁰⁶Pb age peaks of about 1.9–2.6 Ga suggesting that they were sourced from multiple protolithis of Neoarchean and Paleoproterozoic. Metamorphic overgrowths on some zircon grains record ca. 500–550 Ma ages which are in good harmony with the known ages for the timing of high-grade metamorphism in this zone during the final stage of continent collision associated with the birth of the Gondwana supercontinent in the latest Neoproterozoic-Cambrian. The preliminary geochronological results documented in our study correlate with the subduction–accretion–collision history associated with the closure of the Mozambique Ocean and the final amalgamation of the Gondwana supercontinent.  相似文献   

Prediction of pile response to lateral spreading by 3-D soil–water coupled dynamic analysis: Shaking in the direction perpendicular to ground flow     

R. Uzuoka  M. Cubrinovski  H. Sugita  M. Sato  K. Tokimatsu  N. Sento  M. Kazama  F. Zhang  A. Yashima  F. Oka 《Soil Dynamics and Earthquake Engineering》2008,28(6):436-452

The 1995 Kobe earthquake seriously damaged numerous buildings with pile foundations adjacent to quay walls. The seismic behavior of a pile group is affected by movement of quay walls, pile foundations, and liquefied backfill soil. For such cases, a three-dimensional (3-D) soil–water coupled dynamic analysis is a promising tool to predict overall behavior. We report predictions of large shake table test results to validate 3-D soil–water coupled dynamic analyses, and we discuss liquefaction-induced earth pressure on a pile group during the shaking in the direction perpendicular to ground flow. Numerical analyses predicted the peak displacement of footing and peak bending moment of the group pile. The earth pressure on the pile in the crustal layer is most important for the evaluation of the peak bending moment along the piles. In addition, the larger curvatures in the bending moment distribution along the piles at the water side in the liquefied ground were measured and predicted.  相似文献   

A computational procedure for joining separate map sheets     

Takashi Sato  Yukio Sadahiro  Atsuyuki Okabe 《GeoJournal》2000,52(3):253-262

Map sheets have been often used as a basic spatial unit for managing spatial data produced from paper maps. This often results in incompatibility between adjacent map sheets, because spatial objects do not cross the boundaries smoothly and even the boundaries themselves do not match their neighbors exactly. To solve the problem this paper proposes a computational procedure for joining separate map sheets to obtain seamless spatial data. Line objects digitized separately in different map sheets are considered, which are frequently used to represent road networks, gas pipelines, and boundaries of polygon objects. The procedure consists of three steps: (1) extraction of end nodes, (2) detection of matching nodes, and (3) transformation of the map sheet. Each step goes interactively so that unexpected errors can be avoided by human observation. To test the validity of the procedure, map sheets are combined containing the road network data of Tokyo 23-ku area, Japan. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Star formation in NGC 6334 I and I(N)     

W. H. McCutcheon  G. Sandell  H. E. Matthews  T. B. H. Kuiper  E. C. Sutton  W. C. Danchi  T. Sato 《Monthly notices of the Royal Astronomical Society》2000,316(1):152-164

The northern section of the molecular cloud complex NGC 6334 has been mapped in the CO and CS spectral line emission and in continuum emission at a wavelength of 1300 μm. Our observations highlight the two dominant sources, I and I(N), and a host of weaker sources. NGC 6334 I is associated with a cometary ultracompact H  ii region and a hot, compact core ≤10 arcsec in size. Mid-infrared and CH₃OH observations indicate that it is also associated with at least two protostellar sources, each of which may drive a molecular outflow. For region I we confirm the extreme high-velocity outflow first discovered by Bachiller & Cernicharo and find that it is very energetic with a mechanical luminosity of 390 L_⊙. A dynamical age for the outflow is ∼3000 yr. We also find a weaker outflow originating from the vicinity of NGC 6334 I. In CO and CS this outflow is quite prominent to the north-west, but much less so on the eastern side of I, where there is very little molecular gas. Spectral survey data show a molecular environment at position I which is rich in methanol, methyl formate and dimethyl ether, with lines ranging in energy up to 900 K above the ground state. NGC 6334 I(N) is more dense than I, but cooler, and has none of the high-excitation lines observed toward I. I(N) also has an associated outflow, but it is less energetic than the outflow from I. The fully sampled continuum map shows a network of filaments, voids and cores, many of which are likely to be sites of star formation. A striking feature is a narrow, linear ridge which defines the western boundary. It is unclear if there is a connection between this filament and the many potential sites of star formation, or if the filament existed prior to the star formation activity.  相似文献   

Spectrum of the relic neutrino background from past supernovae and cosmological models     

Tomonori Totani  Katsuhiko Sato 《Astroparticle Physics》1995,3(4):367-376

It is greatly expected that the relic neutrino background from past supernovae will be detected by Superkamiokande (SK) which is now under construction. We calculate the spectrum and the event rate at SK systematically by using the results of simulations of a supernova explosion and reasonable supernova rates. We also investigate the effect of a cosmological constant, Λ, on the spectrum, since some recent cosmological observations strongly suggest the existence of Λ. We find following results. (1) The spectrum has a peak at about 3 MeV, which is much lower than that of previous estimates (6–10 MeV). (2) The event rate at SK in the range from 10 MeV to 50 MeV, where the relic neutrinos from past supernovae are dominant, is about 25h₅₀²(R_SN/0.1 yr⁻¹)(n_Gh₅₀⁻³/0.02 Mpc⁻³) events per year, where R_SN is the supernova rate in a galaxy, n_G is the number density of galaxies, and h₅₀ = H₀/(50 km/s Mpc), where H₀ is the Hubble constant. (3) The event rate is almost insensitive to Λ. The flux increases in the low energy side (< 10 MeV) with increasing Λ, but decreases in the high energy side (> 10 MeV) in models in which the integrated number of supernovae in one galaxy is fixed.  相似文献   

Effects of Fetch on Turbulent Flow and Pollutant Dispersion Within a Cubical Canopy     

Takenobu Michioka  Hiroshi Takimoto  Hiroki Ono  Ayumu Sato 《Boundary-Layer Meteorology》2018,168(2):247-267

The effects of fetch on turbulent flow and pollutant dispersion within a canopy formed by regularly-spaced cubical objects is investigated using large-eddy simulation. Six tracer gases are simultaneously released from a ground-level continuous pollutant line source placed parallel to the spanwise axis at the first, second, third, fifth, seventh and tenth rows. Beyond the seventh row, the standard deviations of the fluctuations in the velocity components and the Reynolds shear stresses reach nearly equivalent states. Low-frequency turbulent flow is generated near the bottom surface around the first row and develops as the fetch increases. The turbulent flow eventually passes through the canopy at a near-constant interval. The mean concentration within the canopy reaches a near-constant value beyond the seventh row. In the first and second rows, narrow coherent structures frequently affect the pollutant escape from the top of the canopy. These structures increase in width as the fetch increases, and they mainly affect the removal of pollutants from the canopy.  相似文献   

High-pressure and ultrahigh-temperature metamorphism at Komateri, northern Madurai Block, southern India   总被引：1，自引：0，他引：1  

Toshiaki Tsunogae  M. Santosh  Hiroyuki Ohyama  Kei Sato 《Journal of Asian Earth Sciences》2008,33(5-6):395-413

We report for the first time the evidence for prograde high-pressure (HP) metamorphism preceding a peak ultrahigh-temperature (UHT) event in the northernmost part of the Madurai Block in southern India. Mg–Al-rich Grt–Ged rocks from Komateri in Karur district contain poikiloblastic garnet with numerous multi-phase inclusions. Although most of the inclusion assemblages are composed of gedrite, quartz, and secondary biotite, rare staurolite + sapphirine and spinel + quartz are also present. The X_Mg (=Mg/[Fe+Mg]) of staurolite (0.45–0.49) is almost consistent with that reported previously from Namakkal district in the Palghat–Cauvery Shear Zone system (X_Mg = 0.51–0.52), north of the Madurai Block. The HP event was followed by peak UHT metamorphism at T = 880–1040 °C and P = 9.8–12.5 kbar as indicated by thermobarometric computations in the Grt–Ged rock and associated mafic granulite. Symplectic intergrowth of spinel (X_Mg = 0.50–0.59, ZnO < 1.7 wt.%) and quartz, a diagnostic indicator of UHT metamorphism, probably formed by decompression at UHT conditions. The rocks subsequently underwent retrograde metamorphism at T = 720–760 °C and P = 4.2–5.1 kbar. The P–T conditions and clockwise exhumation trajectory of the Komateri rocks, comparable to similar features recorded from the Palghat–Cauvery Shear Zone system, suggest that the Madurai Block and the Palghat–Cauvery Shear Zone system underwent similar HP and UHT metamorphic history probably related to the continent–continent collision during the final stage of amalgamation of Gondwana supercontinent.  相似文献   

Trace element geochemistry and Sr-Nd characteristics of Mesoproterozoic mafic intrusive rocks from Rondonia, Brazil, SW Amazonian Craton： Petrogenetic and tectonic inferences     

Girardi  V.A. V. Teixeira  W. Bettencourt  J.S. Andrade  S. Navarro  M.S. Sato  K. 《《幕》》2008,31(4):392-400

The Amazonian Craton comprises an Archean domain surrounded by four successively younger Proterozoic tectonic provinces. Within the Rio-Negro-Juruena province the Serra da Providencia Intrusive Suite （1.60 and 1.53 Ga） consists of A-type rapakivi gran- ites, charnockites and mangerites genetically associated with diabase dikes, gabbros and amphibolites. The original mafic melts were derived from a depleted mantle source （εN（T） ＋2.5 to ＋2.8;εSr（T） -12.1）. Underplated mafic magma induced melting of a short-lived felsic crust, thus originating coeval felsic-mafic magmatism in a conti- nental intraplate setting. The Colorado Complex, assigned to the Rondonian-San Ignacio province, comprises 1.35-1.36 Ga intrusive bimodal magmatism represented by monzonite gneisses associated with amphibolite, gabbro and metadiabase dikes intercalated with metasediments with detrital zircon that yield U- Pb ages of 1.35 to 1.42 Ga. Mafic samples dis- play juvenile signatures （εNd（T） 0.0 to ＋5.2; εSr（T） --5.0 to --30.7） and are less contaminated than the Serra da Previdencia and Nova Brasilandia ones. The generation of the basaltic magma is related to the subduction of an oceanic slab below the peridotite wedge （intraoceanic arc setting）. Fluids and/or small melts from the slab impregnated the mantle. The Nova Brasilandia Sequence （Sunsas-Aguapef province） comprises a metasedimentary sequence intruded by 1.10-1.02 Ga metadia- bases, gabbros, meta-gabbros, and amphibolites associated with granitic plutons （bimodal mag- matism）. The original tholeiitic magmas, derived from a depleted source （εNd（T） = ＋3.1 to ＋5.0）, in a proto-oceanic setting, underwent subsequent contamination by the host rocks, as indicated by the isotopic and trace element data.  相似文献   

Numerical calculation of modes of oscillation of the Earth's core   总被引：7，自引：0，他引：7  

D. E. Smylie  Xianhua Jiang  B. J. Brennan  Kachishige Sato 《Geophysical Journal International》1992,108(2):465-490

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Cyclic crustal movement, steady uplift of marine terraces, and evolution of the island arc-trench system in southwest Japan     

Toshinori Sato  Mitsuhiro Matsu'ura 《Geophysical Journal International》1992,111(3):617-629

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