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21.
Takashi Ninomiya Sho Taniguchi Shoichi Shimoyama Koichiro Watanabe Tohru Danhara Hideki Iwano Kazuyuki Shiraishi Chitaro Gouzu 《Island Arc》2017,26(6)
The Okinoshima Formation crops out on Okinoshima Island and comprises a thick sequence (> 200 m) of pyroclastic rocks and alternating beds of sandstone and mudstone. Because Okinoshima Island is located between Honshu and Tsushima Island, the Okinoshima Formation potentially provides an important record of volcanism during the opening of the Japan Sea in northwest Kyushu, as well as a record of the formation of the present Genkai Sea region. In consideration of the lack of previous geochronological work, dating (fission‐track and U–Pb) of igneous zircons extracted from the Okinoshima Formation were undertaken and studied the clay mineral alteration in the pyroclastic material in order to reveal its thermal history. These data are used to constrain the age of the Okinoshima Formation and the present Genkai Sea region. Our results show that no thermal event has reset the fission‐track age after deposition of the pyroclastic rocks, and that the Okinoshima Formation was deposited at 16.2 Ma. The present Genkai Sea region is a deep‐sea basin, and its formation at 16.2 Ma was accompanied by submarine volcanism and rapid subsidence that marked the climactic stage of Japan Sea formation. After 16 Ma, the tectonic setting of the present Genkai Sea region changed from one of extension (related to the formation of the Japan Sea) to one of compression, with uplift occurring under the influence of the clockwise rotation of southwest Japan. Consequently, after 16 Ma the present Genkai Sea region became isolated from the forming processes of the Japan Sea. 相似文献
22.
Takaaki Noguchi Akira Tsuchiyama Hirohide Demura Hideaki Miyamoto Tomoki Nakamura Sho Sasaki Takashi Kubota Michael E. Zolensky 《Icarus》2010,206(1):319-326
On the sub-kilometer S-type asteroid, 25143 Itokawa, some boulders on rough terrains seem to be exposed without any powdery material covering. Based on surface morphological features, there are two major types of boulders: one has rounded edges and corners (rounded boulders), while the other has angular edges and corners (angular boulders). The surface features of the rounded boulders suggest that they have hardness heterogeneity and that some may be breccias. The angular boulders appear to be more resistant to impact disruption than the rounded ones, which may be due to a difference in lithology. The major constituents of Itokawa may be LL chondrite-like brecciated lithology (rounded boulders) along with a remarkable number of boulders suggesting that lithology is atypical among LL chondrites (angular boulders). Some of both types of boulders contain intersecting and stepped planar foliations. Comparison with meteorite ALH76009 suggests that the planar foliations may be marks where rocks were torn apart. As lithified breccias cannot be formed on present-day sub-kilometer-sized Itokawa, it is reasonable that boulders with various lithologies on Itokawa were formed on its large ancestor(s). The rubble-pile structure of Itokawa suggested by its low density (∼1.9 g/cm3) indicates that boulders on Itokawa are reassembled fragments formed by catastrophic disruption of large ancestor(s). 相似文献
23.
At the Kingking porphyry copper-gold deposit, Compostela Valley, south-eastern Mindanao, Philippines, bornite pods occur in the brecciated parts in the biotite diorite porphyry, together with the volcanic rock and diorite fragments without associated stockworks of quartz veinlets. These pods are generally elongated in shape and measure several centimeters across their longest axes. They are composed of bornite and chalcopyrite with traces of calaverite. The δ34 S of bornite and subordinate chalcopyrite of bornite pods ranging from −2.2‰ to +0.1‰ are similar to the δ34 S of sulfides associated with quartz veinlets such as bornite and chalcopyrite ranging from −4.7‰ to ±0.0‰. This suggests that the ultimate source of sulfur is identical for bornite pods and sulfides associated with quartz veinlets. Bornite pods are associated with volcanic rock and dioritic fragments in the brecciated portion of the biotite diorite porphyry. It was observed that some dioritic fragments contain quartz veinlets, which may indicate an earlier episode of mineralization. Fragments of the earlier dioritic intrusive rocks and the volcanic rocks, together with the sulfides were incorporated into the biotite diorite porphyry magma. A molten sulfide is possible for the composition between bornite and intermediate solid solution at ∼800°C. The sulfides from the earlier dioritic intrusive rocks in the molten state were segregated and then eventually coalesce to form the bornite pods in the brecciated section of the biotite diorite porphyry. 相似文献
24.
Occurrence of water ponding on soil surfaces depending on infiltration rates on Mongolian rangeland 
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下载免费PDF全文 Katori Miyasaka Sho Shiozawa Kazuhiro Nishida Siilegmaa Batsukh Shuichiro Yoshida Undarmaa Jamsran 《水文研究》2017,31(22):3996-4005
The occurrence of water ponding on soil surfaces during and after heavy rainfall produces surface run‐off or surface water accumulation in low‐lying areas, which might reduce the water supply to soils and result in a reduction of the soil water that plants can use, especially in arid climates. On Mongolian rangeland, we observed ponded water on the surface of a specific soil condition subjected to a heavy rainfall of 30 mm/hr. By contrast, ponded water was not observed for the same type of soil where livestock grazing had been removed for 6–8 years via a fence or for nearby soil containing less clay. We measured the infiltration rate (the saturated hydraulic conductivity of the surface soil, Ks) of the three sites by applying ponded water on the soil surface (an intake rate test). The results showed that Ks in the rangeland was lower than the rainfall intensity in the site where water ponded on the soil surface; however, Ks of the soil inside of the fence has recovered to 3 times that of the soil outside of the fence to exceed the rainfall intensity. Heavy rainfall that exceeds the infiltration rate occurs several times a year at the livestock grazing site where we observed ponded water. Slight water repellency of the soil reduces rain infiltration to increase the possibility of surface ponding for the soil. 相似文献
25.
Takahiro Hiroi Hiroshi Kaiden Keiji Misawa Takafumi Niihara Hideyasu Kojima Sho Sasaki 《Polar Science》2011,5(3):337-344
Martian meteorite chip samples stored at the National Institute of Polar Research (NIPR) have been studied by a visible and near-infrared (VNIR) spectrometer. Measured spots are about 3 × 2 mm in size, which are clearly marked on photographs of the meteorite chips. Rock types and approximate mineral compositions of studied meteorites have been identified or obtained through this spectral survey with no sample preparation required. This study demonstrates that this kind of spectral survey is effective in classifying and describing Marian meteorites, and that such a VNIR spectrometer on a Mars rover would be useful for identifying these kinds of unaltered Mars rocks. Further studies which utilize a smaller spot size are desired for improving the accuracy of identifying the clasts and mineral phases in the rocks. 相似文献
26.
The role of bedrock groundwater in rainfall–runoff processes is poorly understood. Hydrometric, tracer and subsurface water potential observations were conducted to study the role of bedrock groundwater and subsurface flow in the rainfall–runoff process in a small headwater catchment in Shiranui, Kumamoto prefecture, south‐west Japan. The catchment bedrock consists of a strongly weathered, fractured andesite layer and a relatively fresh continuous layer. Major chemical constituents and stable isotopic ratios of δ18O and δD were analysed for spring water, rainwater, soil water and bedrock groundwater. Temporal and spatial variation in SiO2 showed that stream flow under the base flow condition was maintained by bedrock groundwater. Time series of three components of the rainstorm hydrograph (rainwater, soil water and bedrock groundwater) separated by end member mixing analysis showed that each component fluctuated during rainstorm, and their patterns and magnitudes differed between events. During a typical mid‐magnitude storm event, a delayed secondary runoff peak with 1·0 l s−1 was caused by increase in the bedrock groundwater component, whereas during a large rainstorm event the bedrock groundwater component increased to ≈ 2·5 l s−1. This research shows that the contribution of bedrock groundwater and soil water depends strongly on the location of the groundwater table, i.e. whether or not it rises above the soil–bedrock interface. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
27.
Makoto Taguchi Tetsuya Fukuhara Masahiko Futaguchi Mitsuteru Sato Takeshi Imamura Kazuaki Mitsuyama Masato Nakamura Munetaka Ueno Makoto Suzuki Naomoto Iwagami George L. Hashimoto 《Icarus》2012,219(1):502-504
Mid-infrared images of almost the entire Venus nightside hemisphere obtained by the Longwave Infrared Camera (LIR) onboard Akatsuki on December 9 and 10, 2010 reveal that the brightness temperature of the cloud-top ranges from 237 K in the cold polar collars to 243 K in the equatorial region, significantly higher than the values obtained by Venera 15. Other characteristic features of the temperature distributions observed are zonal belt structures seen in the middle and low latitudes and patchy temperature structures or quasi-periodic streaks extending in a north–south direction in the northern middle latitudes and southern low latitudes. 相似文献
28.
N. Iwagami T. Shibaki T. Suzuki H. Sekiguchi N. Takegawa W. H. Morrow 《Journal of Atmospheric and Solar》2003,65(16-18):1349-1360
Atomic oxygen density and airglow volume emission rate profiles measured in the rocket experiment S-310-29 carried out as a part of the Waves in Airglow Structures Experiment over Kagoshima in 2000 (WAVE2000) campaign are presented, and the excitation processes of the atomic oxygen 557.7 nm line and the molecular oxygen atmospheric band airglow emissions are discussed. The volume emission rate profiles calculated from the measured atomic oxygen densities using the methods and parameters proposed by the ETON campaign (EATON model) are found to well represent the shapes of measured twin-peak emission rate profiles seen during this campaign suggesting that the EATON model is valid for a perturbed atmosphere. There is some discrepancy in the modeled absolute values for the emissions. Applying the model to the current O density measurements results in predicted emission rates that are a factor of 3.2 and 1.5 too high for the 557.7 nm line and Atmospheric band, respectively. This suggests either that the atomic oxygen densities of the present campaign are too large by a factor of 1.2 (=1.51/2) to 1.5 (=3.21/3), or that those of the ETON campaign were too small by the same factor or that the combined errors in both campaigns can account for the discrepancy (the modeled volume emission rates of the 557.7 nm line and atmospheric band are roughly in proportion to [O]3 and [O]2, respectively). Our present data findings do not favor the 2-step more than the 1-step excitation process for the atmospheric band because a calculation of the quantum efficiency based on the observed O density does not show a steep gradient around 100 km. 相似文献
29.
The nitric oxide density profile between the altitudes 72 and 120 km was obtained by means of the airglow γ(1, 0) band measured with a rocket-borne radiometer flown at Syowa Station (69°S, 40°E). The NO density was found to have two peaks with a value of 1.5× 108cm?3 at 90 and 110 km, and is much larger than those in the middle and low latitudes. Because of a long lifetime of NO in the mesosphere, the observed NO enhancement may be due to the after-effect of the particle precipitation event which occurred within the half day before, despite no polar disturbance during the rocket flight. 相似文献
30.
Hiroshi?IshidaEmail author Yuji?Watanabe Tatsuo?Fukuhara Sho?Kaneko Kazushi?Furusawa Yoshihisa?Shirayama 《Journal of Oceanography》2005,61(5):835-843
In order to evaluate the environmental impact associated with sequestration of carbon dioxide in the deep sea, a free fall
type field experimental device, the benthic chamber, was developed. In situ experiments to expose deep-sea communities to elevated concentrations of carbon dioxide (average of 20,000 ppm, 5,000 ppm
and control) were carried out using this device 3 times, viz., in the winter of 2002 and in the spring and the summer of 2003,
in the Kumano Trough at a depth of 2,000 m. In the long-term experiments (about two weeks in winter of 2002 and summer of
2003), the abundance of meiobenthos declined whereas that of bacteria increased under the condition of 20,000 ppm carbon dioxide
compared with the control. Among meiofauna, the abundance of foraminifers at the same concentration of carbon dioxide became
less than the control even in the short-term (3 days in spring of 2003) experiment, suggesting that organisms with a calcium
carbonate exoskeleton are more sensitive to the raised concentration of carbon dioxide. The respiration rate of the benthic
community exposed to 20,000 ppm was lower in the early stage of the experiment than in the latter half, whereas it was opposite
under the condition of 5,000 ppm. The increase of biological activity in the 20,000 ppm exposure group is probably due to
an increase of bacteria adapted to high carbon dioxide concentrations. The present results suggest that the influence of carbon
dioxide on the deep-sea benthic ecosystem does not follow a simple, linear relationship with concentration. 相似文献