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11.
Michael Zolensky Takashi Mikouchi Marc Fries Robert Bodnar Peter Jenniskens Qing‐zhu Yin Kenji Hagiya Kazumasa Ohsumi Mutsumi Komatsu Matthew Colbert Romy Hanna Jessie Maisano Richard Ketcham Yoko Kebukawa Tomoki Nakamura Moe Matsuoka Sho Sasaki Akira Tsuchiyama Matthieu Gounelle Loan Le James Martinez Kent Ross Zia Rahman 《Meteoritics & planetary science》2014,49(11):1997-2016
Based upon our characterization of three separate stones by electron and X‐ray beam analyses, computed X‐ray microtomography, Raman microspectrometry, and visible‐IR spectrometry, Sutter's Mill is a unique regolith breccia consisting mainly of various CM lithologies. Most samples resemble existing available CM2 chondrites, consisting of chondrules and calcium‐aluminum‐rich inclusion (CAI) set within phyllosilicate‐dominated matrix (mainly serpentine), pyrrhotite, pentlandite, tochilinite, and variable amounts of Ca‐Mg‐Fe carbonates. Some lithologies have witnessed sufficient thermal metamorphism to transform phyllosilicates into fine‐grained olivine, tochilinite into troilite, and destroy carbonates. One finely comminuted lithology contains xenolithic materials (enstatite, Fe‐Cr phosphides) suggesting impact of a reduced asteroid (E or M class) onto the main Sutter's Mill parent asteroid, which was probably a C class asteroid. One can use Sutter's Mill to help predict what will be found on the surfaces of C class asteroids such as Ceres and the target asteroids of the OSIRIS‐REx and Hayabusa 2 sample return missions (which will visit predominantly primitive asteroids). C class asteroid regolith may well contain a mixture of hydrated and thermally dehydrated indigenous materials as well as a significant admixture of exogenous material would be essential to the successful interpretation of mineralogical and bulk compositional data. 相似文献
12.
Compositional zoning patterns of the major elements and REEs in prograde-zoned garnets whose Mg/(Mg + Fe) atomic ratios increase rimward have been widely used to understand the metamorphic P–T–t trajectories, and the diffusion-limited REE-uptake model is a promising way to interpret their growth rates and the REE diffusion kinetics in the low-temperature eclogite. In order to elucidate their growth kinetics with Skora et al.'s (2006) diffusion-limited REE uptake model for prograde-zoned garnets, we examine the trace-element zoning patterns of two prograde-zoned porphyroblastic garnets (~6 mm in size) in low-temperature eclogites from two different localities. Core-to-rim trace-element profiles in a garnet (prp5–9alm61–67sps1–3grs24–30) of a glaucophane-bearing epidote eclogite of Syros (Cyclades, Greece) are characterized by the presence of Y + HREE peaks in the mantle, which might be attributed to a continuous breakdown of the titanite to form rutile during the garnet growth. In contrast, those in a garnet (prp4–7alm61–68sps3–10grs23–24) extracted from a lawsonite-eclogite of the South Motagua Mélange (SMM) (Guatemala) have prominent central peaks of Y + HREEs. Although the REE profiles of both the garnets can be explained by the diffusion-limited uptake, their Mn profiles suggest that their growth-rate laws are different: i.e., diffusion-controlled (Syros) and interface-controlled (SMM). Prior to the model application, we optimize the number of the parameters as the garnet grows with the interface-controlled processes based on the growth Péclet number. In particular, we propose the ratio of the REE diffusivity in the eclogitic matrix to the garnet growth rate as the new parameter. Visualizing the values of the new parameters allows to readily understand the relationship between the REE profiles and the REE-diffusion/garnet-growth kinetics in low-T eclogite. Our model refinement leads to the simple quantitative characterization of core-to-rim REE profiles in garnet in low-temperature eclogites. 相似文献
13.
Tsuyoshi Komiya Shinji Yamamoto Shogo Aoki Keiko Koshida Masanori Shimojo Yusuke Sawaki Kazumasa Aoki Shuhei Sakata Takaomi D. Yokoyama Kenshi Maki Akira Ishikawa Takafumi Hirata Kenneth D. Collerson 《地学前缘(英文版)》2017,8(2):355-385
The Archean continental crusts account for ca.20% of the present volume,but the thermal history of the Earths' mantle suggests much more continental crusts were formed in the early Archean.Because the Archean continental crust underwent severe metamorphism,it is important to avoid influence by the later thermal events.We carried out a comprehensive geochronological work of Cathodoluminescence(CL) observation and U-Pb dating of zircons from orthogneisses and supracrustal rocks over the Saglek Block to obtain their protolith ages.The zircons were classified into three domains of core,mantle and rims,and the cores were further classified into three groups of inherited,altered and zoned cores based on the zonation on the CL images.We estimated the protolith ages from Pb-Pb ages of the zoned-cores of zircons with low U contents.We made a detailed sketch of a small outcrop in St.John's Harbour South(SJHS) area,and classified the orthogneisses and mafic enclaves into seven generations based on the geologic occurrence.The first and second generations comprise mafic rocks and lack magmatic zircons.We conducted CL imaging and U-Pb dating of zircons from the third,sixth and seventh generation of the orthogneisses to estimate the protolith ages at 3902 L 25,3892 ± 33 and 3897 ± 33 Ma for each,supporting the presence of the over 3.9 Ca Iqaluk Gneiss.The geological occurrence that the mafic rocks occur as enclaves within the 3.9 Ga Iqaluk Gneiss indicates that they are the oldest supracrustal rocks in the world.Our geochronological and geological studies show the Uivak Gneiss is quite varied in lithology and age from 3.6 to 3.9 Ga,and tentatively classified into six groups based on their ages.The oldest Uivak Gneiss components including the Iqaluk Gneiss are present around the SJHS area,and the orthogneisses become young as it is away.The lines of evidence of overprinting of younger granitoid on older granitoid in small outcrops and geological-map scale as well as presence of inherited zircons even in the oldest suite suggests that crustal reworking played an important role on erasing the ancient crusts. 相似文献
14.
Kazumasa Iwai Masumi Shimojo Shinichiro Asayama Tetsuhiro Minamidani Stephen White Timothy Bastian Masao Saito 《Solar physics》2017,292(1):22
The absolute brightness temperature of the Sun at millimeter wavelengths is an important diagnostic of the solar chromosphere. Because the Sun is so bright, measurement of this property usually involves the operation of telescopes under extreme conditions and requires a rigorous performance assessment of the telescope. In this study, we establish solar observation and calibration techniques at 2.6 mm wavelength for the Nobeyama 45 m telescope and accurately derive the absolute solar brightness temperature. We tune the superconductor–insulator–superconductor (SIS) receiver by inducing different bias voltages onto the SIS mixer to prevent saturation. Then, we examine the linearity of the receiver system by comparing outputs derived from different tuning conditions. Furthermore, we measure the lunar filled beam efficiency of the telescope using the New Moon, and then derive the absolute brightness temperature of the Sun. The derived solar brightness temperature is \(7700 \pm 310~\mbox{K}\) at 115 GHz. The telescope beam pattern is modeled as a summation of three Gaussian functions and derived using the solar limb. The real shape of the Sun is determined via deconvolution of the beam pattern from the observed map. Such well-calibrated single-dish observations are important for high-resolution chromospheric studies because they provide the absolute temperature scale that is lacking from interferometer observations. 相似文献
15.
Yuji Watanabe Atsushi Yamaguchi Hiroshi Ishida Takashi Harimoto Shinya Suzuki Yoshio Sekido Tsutomu Ikeda Yoshihisa Shirayama Masayuki Mac Takahashi Takashi Ohsumi Joji Ishizaka 《Journal of Oceanography》2006,62(2):185-196
The first CO2 exposure experiments on several species of pelagic copepods inhabiting surface and deep layers in the western North Pacific
were conducted. Living organisms were collected from two layers between the surface and 1,500 m between latitudes of 11 and
44°N, and they were exposed aboard ship to various pCO2 up to about 98,000 μatm. Mortality of copepods from both shallow and deep layers in subarctic to subtropical regions increased with increasing
pCO2 and exposure time. Deep-living copepods showed higher tolerance to pCO2 than shallow-living copepods. Furthermore, deep-living copepods from subarctic and transitional regions had higher tolerances
than the subtropical copepods. The higher tolerances of the deep-living copepods from subarctic and transitional regions may
be due to the adaptation to the natural pCO2 conditions in the subarctic ocean. 相似文献
16.
During the long-term stability assessment of underground disposal repositories buried in sedimentary formations, one of crucial
scientific problems is to determine parameters of site formations. The analysis of response of the pore pressure due to atmospheric
loading provides a possible way of accurate estimation of formation parameters. In this paper, an analytical solution of response
of the pore pressure to atmospheric loading was derived starting from the Biot’s poroelasticity, and its corresponding numerical
solutions were developed by finite element methods for 1D and 2D situations. With comparison to the analytical solution, the
experimental results show that the numerical schemes sound reasonable to implement the assessment of response of the pore
pressure in horizontal multilayer sedimentary formations. In particular, it is effective for a 2D model over large area with
consideration of background horizontal groundwater flow. A highlight of this work is to construct a reasonable approach to
capture responses of the pore pressure to atmospheric loading, and at the same time to provide the feasibility of integrated
analysis of well monitoring data of pore pressure variance in Horonobe Underground Research Laboratory (URL), Hokkaido, Japan. 相似文献
17.
Shogo Aoki Kazumasa Aoki Mayuko Fukuyama Masatsugu Ogasawara Yuta Tsuchiya 《Island Arc》2021,30(1):e12420
In this study, the LA-ICP-MS zircon U–Pb dating of the Shimo-ondori diorites in the Shimanto accretionary complex of SW Japan provides ~130 Ma, representing the timing of their crystallization ages. Combined with the geological occurrence, that age clearly indicates that the diorites occur as blocks, not as intrusive rocks as suggested by previous studies. Moreover, the ages of the Shimo-ondori diorites are suggesstive that they could be influential for the estimate of the early-Cretaceous tectonic evolution for the eastern Asian margin. Their whole-rock chemical compositions show high MgO, Ni and Cr contents, and low total FeO/MgO ratios, indicating that they were crystallized from high magnesian andesite (HMA) magmas. Moreover, their TiO2 and REE compositions suggest that they were formed by the same processes as the sanukites. And, the zircon Hf isotopic ratios (εHf [~130 Ma] = +9.9 − +17.5), which is close to or slightly lower than that of the ~130 Ma depleted mantle, suggest that the wedge-mantle materials were predominantly involved in the formation of the dioritic magmas. Their geochronological and geochemical similarities of the Shimo-ondori diorites with the early Cretaceous adakites and HMAs in the eastern Asian margin suggest that they might have been formed possibly by the same slab rollback of the Izanagi plate at the early Cretaceous. After the crystallization of the Shimo-ondori diorites, they were delivered and deposited as blocks in a trench site with the surrounding sedimentary rocks of the Shimanto accretionary complex. 相似文献
18.
Ryoko Fujiyoshi Masanori Okabayashi Yousuke Sakuta Kazumasa Okamoto Takashi Sumiyoshi Ivan Kobal Janja Vaupotič 《Environmental Earth Sciences》2013,70(3):1159-1167
Soil radon (222Rn) has been monitored during winter months under cool-temperate deciduous stands of different surface geology in Tomakomai and in Sapporo, Hokkaido, Japan. Radon level was lower in Tomakomai of immature soil of porous volcanic ash emitted from an active volcano (Mt. Tarumae), compared with those in Sapporo of alluvial sediments. In Tomakomai, mean value of the 222Rn activity concentration was higher in winter (570 Bq m?3) than in summer (350 Bq m?3) at a depth of 1 m, which is consistent with the results in cold and dry winter reported in the literature. In contrast, soil radon decreasing with decreasing soil temperature from mid-September (5.0 kBq m?3) remained low (2.6 kBq m?3) under persistent snow in Sapporo, which had already been observed in the same location. Measurements of the activity concentrations of 222Rn in snow and in snow air as well as in soil air indicate that the small amount of 222Rn is released from the ground surface to the overlying snowpack with a 222Rn flux density of 0.4 mBq m?2 s?1 under thick snow cover in Sapporo. 相似文献
19.
Yuto Kurumada Shogo Aoki Kazumasa Aoki Daichi Kato Mototaka Saneyoshi Khishigjav Tsogtbaatar Brian F. Windley Shinobu Ishigaki 《地学学报》2020,32(4):246-252
To verify the usefulness of calcite U–Pb measurement for vertebrate‐bearing strata in the Eastern Gobi, Mongolia, we performed laser ablation‐inductively coupled plasma‐mass spectrometry calcite U–Pb and trace element analyses of three caliche (calcrete) of the Bayn Shire Formation. The trace element analysis demonstrates high concentration of U in the calcites. Two meaningful calcite U–Pb ages were obtained; 95.9 ± 6.0 and 89.6 ± 4.0 Ma, which are consistent with published ages from the Bayn Shire Formation. Our results demonstrate that the calcite U–Pb method can be powerful tool for age determination of vertebrate‐bearing strata in the Gobi that do not contain index fossils or beds, but do contain caliches. This would make it possible for a comparison of biostratigraphy between the Gobi and other areas yielding abundant vertebrate fossils in Asia, North America and Europe, based on chronological data. 相似文献
20.
Kazumasa Mizumura 《Coastal Engineering》1982,6(3):217-231
It is a very important and difficult problem to operate gates at the inlets of tidal lakes to control water quality and quantity, simultaneously. The main purpose of gate operation at the inlets of tidal lakes are flood control and irrigation. That is to say, the gate operation must sufficiently satisfy two purposes. As the first step to optimize the effect of gate control, the water levels downstream of the gate are predicted by a combined model between regression theory and control theory. The prediction model consists of two parts. The regression equation is used to predict the water levels downstream of the gate by the sea levels in the first part. The causality in this part is physically evident. The Kalman filtering algorithm is employed to identify parameters which construct the state equation in the second part. The prediction is made by joining the two parts.By applying this process to the prediction of water levels on the downstream side of the gate at the inlet of Lake Kahokugata, Kanazawa, Japan, it becomes possible to predict the fluctuations of the water levels under arbitrary gate operations before one or two hours. As the state equation in the Kalman filtering algorithm, first- and second-order Markov models are adopted for the prediction. The result of the latter is better than that of the former. 相似文献