Provenance diversification within an arc‐trench system induced by batholith development: the Cretaceous Japan case     

Kazumasa Aoki  Yukio Isozaki  Daisuke Kofukuda  Tomohiko Sato  Atsushi Yamamoto  Kenshi Maki  Shuhei Sakata  Takafumi Hirata 《地学学报》2014,26(2):139-149

By comparing detrital zircon U–Pb age spectra of coeval fore‐arc and back‐/intra‐arc basin sandstones, we identified the overall distributary pattern of terrigenous clastic material within the Cretaceous arc system of SW Japan. Abundant Proterozoic (c. 1500–2500 Ma) detrital grains from the interior of East Asia are present in the Cretaceous intra‐arc basin. However, after a barrier mountain range formed during batholith emplacement, Proterozoic clastics were rarely transported into the fore‐arc domain. Episodic batholith formation in Pacific‐type orogens likely played a major role in controlling terrigenous supply routes between coeval back‐arc and fore‐arc domains. The Cretaceous orogen in Japan thus provides a good template for analysing the tectono‐sedimentary development of other arc‐related basins.  相似文献   

Viscoelastic damage model for asphalt concrete   总被引：1，自引：1，他引：0  

Daisuke Katsuki  Marte Gutierrez 《Acta Geotechnica》2011,6(4):231-241

The strain rate-dependent mechanical behavior of asphalt concrete was characterized using unconfined compression tests carried out at different loading rates. It was shown that at high strain rates, the elastic deformation and peak axial stress are highly sensitive to strain rate. Both increase as the strain rate increases. At very low strain rates, elastic response and unconfined compressive strength are relatively independent of the loading rate. Based on the experimental observations, a simple viscoelastic damage model is proposed for the strain rate-dependent unconfined compression behavior of asphalt concrete. In the model, strain rate response is modeled by a two-component viscoelastic model consisting of a constant elastic modulus and a viscous modulus that is related by a power-law function to the axial strain rate. Failure and strain softening are modeled via a damage formulation where damage evolution in the asphalt concrete is given by a simple form of the Weibull distribution function. The model was shown to be capable of describing the strain rate-dependent deformation, compressive strength, strain-softening and creep behavior of asphalt concrete. The model is relatively simple and requires only five material parameters.  相似文献   

Numerical simulation of a possible origin of the positive radial metallicity gradient of the thick disk     

Awat Rahimi  Kenneth Carrell  Daisuke Kawata 《中国天文和天体物理学报》2014,(11)

We analyze the radial and vertical metallicity and [α/Fe] gradients of the disk stars of a disk galaxy simulated in a fully cosmological setting with the chemodynamical galaxy evolution code GCD+. We study how the radial abundance gradients vary as a function of height above the plane and find that the metallicity([α/Fe]) gradient becomes more positive(negative) with increasing height, changing sign around1.5 kpc above the plane. At the largest vertical height(2 |z| 3 kpc), our simulated galaxy shows a positive radial metallicity gradient. We find that the positive metallicity gradient is caused by the age-metallicity and age-velocity dispersion relation, where younger stars have higher metallicity and lower velocity dispersion. Due to the agevelocity dispersion relation, a greater fraction of younger stars reaches |z| 2 kpc at the outer region, because of the lower gravitational restoring force of the disk, i.e.flaring. As a result, the fraction of younger stars with higher metallicity due to the age-metallicity relation becomes higher at the outer radii, which makes the median metallicity higher at the outer radii. Combining this result with the recently observed age-metallicity and age-velocity dispersion relation for the Milky Way thick disk stars suggested by Haywood et al., we argue that the observed(small) positive radial metallicity gradient at large heights of the Milky Way disk stars can be explained by flaring of the younger thick and/or thin disk stars.  相似文献   

Pulsation at the tip of the first giant branch?     

Yoshifusa Ita  Toshihiko Tanabé  Noriyuki Matsunaga  Yasushi Nakajima  Chie Nagashima  Takahiro Nagayama  Daisuke Kato  Mikio Kurita  Tetsuya Nagata  Shuji Sato  Motohide Tamura  Hidehiko Nakaya  Yoshikazu Nakada 《Monthly notices of the Royal Astronomical Society》2002,337(3):L31-L34

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Supersonic motions of galaxies in clusters     

Andreas Faltenbacher  rey V. Kravtsov  Daisuke Nagai  Stefan Gottlöber 《Monthly notices of the Royal Astronomical Society》2005,358(1):139-148

We study motions of galaxies in galaxy clusters formed in the concordance Λ cold dark matter cosmology. We use high-resolution cosmological simulations that follow the dynamics of dark matter and gas and include various physical processes critical for galaxy formation: gas cooling, heating and star formation. Analysing the motions of galaxies and the properties of intracluster gas in a sample of eight simulated clusters at z = 0, we study the velocity dispersion profiles of the dark matter, gas and galaxies. We measure the mean velocity of galaxy motions and gas sound speed as a function of radius and calculate the average Mach number of galaxy motions. The simulations show that galaxies, on average, move supersonically with the average Mach number of ≈1.4, approximately independent of the cluster-centric radius. The supersonic motions of galaxies may potentially provide an important source of heating for the intracluster gas by driving weak shocks and via dynamical friction, although these heating processes appear to be inefficient in our simulations. We also find that galaxies move slightly faster than the dark matter particles. The magnitude of the velocity bias,   b _v ≈ 1.1  , is, however, smaller than the bias estimated for subhaloes in dissipationless simulations. Interestingly, we find velocity bias in the tangential component of the velocity dispersion, but not in the radial component. Finally, we find significant random bulk motions of gas. The typical gas velocities are of order ≈20–30 per cent of the gas sound speed. These random motions provide about 10 per cent of the total pressure support in our simulated clusters. The non-thermal pressure support, if neglected, will bias measurements of the total mass in the hydrostatic analyses of the X-ray cluster observations.  相似文献   

Stellar halo constraints on simulated late-type galaxies     

Chris B. Brook  Daisuke Kawata  Brad K. Gibson  Chris Flynn 《Monthly notices of the Royal Astronomical Society》2004,349(1):52-56

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Sodium‐metasomatism in chondrules in CO3 chondrites: Relationship to parent body thermal metamorphism     

Kazushige Tomeoka  Daisuke Itoh 《Meteoritics & planetary science》2004,39(8):1359-1373

Abstract— We have studied the mineralogy and petrology of mesostases of 783 type I chondrules in seven CO3 chondrites that range in petrologic subtype from 3.0 to 3.7. Chondrule mesostases in the CO chondrite of subtype 3.0 consist mainly of primary glass and plagioclase, while chondrule mesostases in the CO chondrites of higher subtypes (3.2–3.7) contain various amounts of nepheline in addition to glass and plagioclase. Nepheline has replaced glass and plagioclase, forming finegrained aggregates and thin parallel lamellar intergrowths with plagioclase. The nephelinization has proceeded preferentially from the outer margins of chondrules toward the inside. Although the degree of nephelinization differs widely among chondrules in each of the metamorphosed chondrites, our modal analyses and bulk chemical analyses of individual mesostases indicate that the amounts of nepheline in chondrules systematically increase with the increasing petrologic subtype of the host chondrites. Nepheline also has a tendency to increase in grain size with increasing petrologic subtype. We conclude that nepheline in chondrules in the CO3 chondrites has formed largely as a result of effects related to heating on the meteorite parent body. We suggest that nepheline initially formed as hydrous nepheline under the presence of aqueous fluids and subsequently was dehydrated after exhaustion of aqueous fluids. The degree of hydrothermal activity must have increased with increasing degree of heating, and thus, chondrules in more thermally metamorphosed chondrites produced larger amounts of nepheline. The results imply that CO3 chondrites have gone through low‐grade aqueous alteration and subsequent dehydration at the early stage of heating on the meteorite parent body.  相似文献   

Compositional variations,chemical weathering,and provenance of sands from the Cox’s Bazar and Kuakata beach areas,Bangladesh     

H. M. Zakir Hossain  Quazi Hasna Hossain  Atsushi Kamei  Daisuke Araoka 《Arabian Journal of Geosciences》2018,11(23):749

The modal and chemical composition of sands from Cox’s Bazar beach (CBB) and Kuakata beach (KB) areas of Bangladesh has been investigated to infer their maturity, chemical weathering, and provenance signatures. The CBB and KB sands are typically high quartz, low feldspar, and lithic fragments, representing a recycled orogen source. Major element compositions of CBB sands are characterized by high SiO₂ (83.52–89.84 wt%) and low Al₂O₃ (4.39–6.39 wt%), whereas KB sands contained relatively low SiO₂ (63.28–79.14 wt%) and high Al₂O₃ (9.00–11.33 wt%) contents. The major, trace and rare earth element (REE) compositions of beach sands display comparable distribution patterns with enriched Th and SiO₂ for both sands relative to upper continental crust (UCC). Pb, Rb, Y, and Fe for KB sands are little higher than UCC and the rest of the elements are marked depleted for both suites reflecting destruction of plagioclase and K-feldspar during fluvial transportation. The CBB and KB sands are compositionally low mature to immature in nature subsequently classified as subarkose and litharenite, respectively. Chondrite-normalized REE patterns for CBB and KB sands show LREE enrichment and nearly flat HREE (La_N/Yb_N, 7.64–9.38 and 5.48–8.82, respectively) coupled with prominent Eu anomalies (Eu/Eu*, 0.51–0.72 and 0.52–0.76, respectively), suggesting felsic source provenance. The provenance discrimination diagrams, immobile trace element ratios (Th/Sc, Zr/Sc, Ce/Sc, and Ti/Zr), and REE (∑LREE/HREE, Eu/Eu* and Gd_N/Yb_N) parameters indicate that CBB and KB sands were largely derived from felsic source rocks, with compositions close to average rhyolite, granodiorite, granite, and UCC.  相似文献   

Topographic and geologic controls on landslides induced by the 2015 Gorkha earthquake and its aftershocks: an example from the Trishuli Valley,central Nepal   总被引：1，自引：0，他引：1  

Ching-Ying Tsou  Masahiro Chigira  Daisuke Higaki  Go Sato  Hiroshi Yagi  Hiroshi P. Sato  Akihiko Wakai  Vishnu Dangol  Shanmukhesh C. Amatya  Akiyo Yatagai 《Landslides》2018,15(5):953-965

The devastating Gorkha earthquake (M _w 7.8) on April 25, 2015 and its aftershocks triggered numerous landslides across the Lesser and Higher Himalayas of central Nepal. This study aims to characterize these landslides, based on the local topography and geology, and to develop data for landslide hazard zoning. This study focused on a mountainous catchment of the Trishuli River, where a digital elevation model was used to examine hilllslope and river profiles, aerial photos were used to identify 155 coherent landslides, and satellite images were used to map 912 earthquake-induced landslides. The topography of this area is mainly characterized by incised V-shaped inner gorges and steep (> 35°) SW-facing scarp slopes. Although most of the coherent landslides were not reactivated by the earthquakes, the Gogane landslide was affected by the earthquake and partly failed. A majority of the earthquake-induced landslides (91%) were new landslides, while the others were enlarged old landslides. The earthquake-induced landslides occurred mainly on the steep slopes of V-shaped inner gorges and scarp slopes, in gneiss and quartzite strata of the Lesser Himalayas, and they were primarily associated with fractured rock masses. This analysis provides a framework for zoning areas vulnerable to earthquake-induced landslides.  相似文献   

A trachyte–syenite core within a basaltic nest: filtering of primitive injections by a multi-stage magma plumbing system (Oki-Dōzen,south-west Japan)     

Marco Brenna  Setsuya Nakada  Daisuke Miura  Kiyoshi Toshida  Hisatoshi Ito  Natsumi Hokanishi  Shun’ichi Nakai 《Contributions to Mineralogy and Petrology》2015,169(2):1-21

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