Spatiotemporal characterization of land surface temperature in Mount Kilimanjaro using satellite data     

Eduardo Eiji Maeda  Pekka Hurskainen 《Theoretical and Applied Climatology》2014,118(3):497-509

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Petrography of Yamato 984028 lherzolitic shergottite and its melt vein: Implications for its shock metamorphism and origin of the vein     

Shin Ozawa  Masaaki Miyahara  Eiji Ohtani  Makoto Kimura  Yoshinori Ito 《Polar Science》2011,4(4):550-557

Yamato 984028 (Y984028) is a newly identified lherzolitic shergottite, recovered from the Yamato Mountains, Antarctica, in 1999. As part of a consortium study, we conducted petrographic observations of Y984028 and its melt vein in order to investigate its shock metamorphism. The rock displays the typical non-poikilitic texture of lherzolitic shergottite, characterized by a framework of olivine, minor pyroxene (pigeonite and augite), and interstitial maskelynite. Shock metamorphic features include irregular fractures in olivine and pyroxene, shock-induced twin-lamellae in pyroxene, and the complete conversion of plagioclase to maskelynite, features consistent with those found in other lherzolitic shergottites. The melt vein is composed of coarse mineral fragments (mainly olivine) entrained in a matrix of fine-grained euhedral olivine (with several modes of compositional zoning) and interstitial glassy material. Some coarse olivine fragments consist of an assemblage of fine-grained euhedral to subhedral olivine crystals, suggesting shock-induced fragmentation, recrystallization, and/or a process of sintering. The implication is that the fine-grained olivine crystals in the matrix of the melt vein represent complicated crystallization environments and histories.  相似文献   

The design of diamond Compton telescope     

Kinya Hibino  Toshisuke Kashiwagi  Shoji Okuno  Kaori Yajima  Yukio Uchihori  Hisashi Kitamura  Takeshi Takashima  Mamoru Yokota  Kenji Yoshida 《Astrophysics and Space Science》2007,309(1-4):541-544

We have developed radiation detectors using the new synthetic diamonds. The diamond detector has an advantage for observations of “low/medium” energy gamma rays as a Compton telescope. The primary advantage of the diamond detector can reduce the photoelectric effect in the low energy range, which is background noise for tracking of the Compton recoil electron. A concept of the Diamond Compton Telescope (DCT) consists of position sensitive layers of diamond-striped detector and calorimeter layer of CdTe detector. The key part of the DCT is diamond-striped detectors with a higher positional resolution and a wider energy range from 10 keV to 10 MeV. However, the diamond-striped detector is under development. We describe the performance of prototype diamond detector and the design of a possible DCT evaluated by Monte Carlo simulations.   相似文献   

Eccentricity cycles shown by early Pleistocene planktonic foraminifers of the Omma Formation, Sea of Japan     

Akihisa Kitamura  Katsunori Kimoto 《Global and Planetary Change》2007,55(4):273-283

There is a continuous record of planktonic foraminifers for oxygen isotope stages 50 to 26 (ca. 1.5–1.0 Ma) in the early Pleistocene Omma Formation near Kanazawa City, Central Japan, on the Sea of Japan coast. The warm-water species Globigerinoides ruber entered the Sea of Japan with the Tsushima Current during all interglacial periods and went locally extinct in the succeeding glacial periods. This implies that the marine climate of the Sea of Japan varied predominantly with the 41,000-year period of Earth's orbital obliquity. However, the relative abundances of G. ruber in marine isotope stages 47, 43 and 31 are significantly higher than those in other interglacial stages. These stages correspond to periods when eccentricity-modulated precession extremes were aligned with obliquity maxima. The Tsushima Current is a branch of the warm Kuroshio Current which is the strong northwestern component of the subtropical North Pacific Ocean gyre. Our data imply that the early Pleistocene climate in the northwestern Pacific was influenced not only by obliquity cycles but also by eccentricity cycles. This study also supports the climate model regarding eccentricity's role in the origin of low-frequency climate changes before the late Pleistocene ice ages.  相似文献   

Oxygen isotopic anomaly and solar nebular photochemistry     

Y. Kitamura  M. Shimizu 《Earth, Moon, and Planets》1983,29(2):199-202

At the cool periphery of the solar nebula, oxygen could photochemically be formed from water. The mixing of¹⁷O and¹⁸O enriched by the self-shielding effect of¹⁶O₂ to the dust grain melted by the shock waves there would explain the oxygen isotopic anomaly in the high-temperature mineral of the carbonaceous meteorites.  相似文献   

Further investigation on distributions of tangential discontinuity in the solar wind     

Ousuke Saka  Tai-Ichi Kitamura 《Planetary and Space Science》1976,24(11):1043-1047

The frequency of the occurrence of the tangential discontinuity (TD) was investigated at thirteen interacting regions (the leading edges) of the solar wind, where each averaged value of the total pressure reaches very much higher values, ranging from 3 × 10^?10 to 12 × 10^?10 erg/m³, than the non-interacting regions (the troughs or the high velocity regions, ?2 × 10^?10 erg/cm³).The present result that the degree of the occurrence is considerably higher in the interacting region than in the non-interacting region was confirmed to be consistent with our previous result. It was discovered that the occurrence frequency at the interacting region increases when strong interaction has occurred.  相似文献   

越南红河流域沉积物的镜下碳屑分析实验室处理方法对比研究   总被引：2，自引：1，他引：1       下载免费PDF全文

陆岸青  李珍  李杰  Xuan Phong Dang  Eiji Matsumoto 《第四纪研究》2009,29(4):825-830

本文设计4个不同的实验方法,以越南红河流域原始森林区、河漫滩区和水下三角洲区3个不同沉积环境下的9个样品为实验对象,对镜下碳屑不同的实验室处理方法进行对比研究,实验发现样品用六偏磷酸钠分散法(方法A)和盐酸分散法(方法B)处理后,镜下碳屑形态不易分辨,杂质多,而用氢氟酸处理法(方法C)和附加醋酸酐混合液处理法(方法D),镜下碳屑的形态清晰,杂质少,碳屑数量容易统计,但是方法D中利用醋酸酐与浓硫酸混合液去纤维素与染色过程会使纤维素碳化,结果显示碳屑浓度明显比用前3种方法处理的浓度高。以上实验结果表明方法C是最优的。另外,本研究在进行碳屑统计时,利用NIS­Elements Br 3.0软件的自动统计计数功能,不仅可以减小人为计数产生的误差,还可以实现碳屑的多参数统计,有利于古环境、古气候、古植被变化的多信息解译。  相似文献   

Majoritic garnet: A new approach to pressure estimation of shock events in meteorites and the encapsulation of sub-lithospheric inclusions in diamond   总被引：2，自引：0，他引：2  

Kenneth D. Collerson  Quentin Williams  Soichi Omori  Eiji Ohtani 《Geochimica et cosmochimica acta》2010,74(20):5939-5957

A means for estimating pressures in natural samples based on both the coupled substitution (Na+)^[1+] (Ti + ^[VI]Si)^[4+] = (M)^[2+] (Al + Cr)^[3+], and the classic pyroxene-stoichiometry majorite-substitution into garnet at high-pressure, is derived for garnets with majoritic chemistry. The technique is based on a compilation of experimental data for different bulk compositions. It is compositionally and thermally robust and can be used to estimate pressures experienced by natural materials during formation of majoritic garnet. In addition, it can be used either retrospectively, or in new experimental studies to establish the pressures of crystallization of reaction products, and determine if disequilibrium is recorded by the chemistries of majoritic garnets. Pressures are calculated based on majoritic chemistries in chondritic meteorites and diamond inclusions. Majoritic garnets associated with Mg perovskite in shocked L chondrites (n = 4) yield uniform pressures of 23.8 ± 0.2 GPa that are slightly higher than pressures recorded by majoritic garnet in shock-derived melt veins in L chondrites (22.4 ± 0.6 GPa; n = 5). Similar pressures are also exhibited by shock-derived majoritic garnets in H chondrites (22.2 ± 1.1 GPa; n = 3). Diamond inclusions with eclogitic and peridotitic majoritic garnet chemistries exhibit mean pressures of 10.7 ± 2.7 GPa (n = 30) and 8.3 ± 1.6 GPa (n = 15) respectively, consistent with a sub-lithospheric origin. However, pressures defined by majoritic diamond inclusions from Jagersfontein (22.3 ± 0.8 GPa and 16.9 ± 1 GPa), Monastery (15.7 ± 7 GPa) and Kankan (15.5 ± 0.2 GPa) show that these inclusions originated from the mantle transition zone. Thus, this new single-phase method for pressure estimation has unmatched potential to map the depth of formation of garnets with majoritic chemistries that occur as diamond inclusions in all parageneses except those that include Ca silicate perovskite. The derived pressures confirm the sub-lithospheric origin of eclogitic majoritic diamond inclusions, and thus provide a more comprehensive picture of the important role of storage of oceanic lithosphere in the transition zone.  相似文献   

How to cut a sediment core for 210Pb geochronology     

Xueqiang Lu  Eiji Matsumoto 《Environmental Geology》2005,47(6):804-810

²¹⁰Pb geochronology is described mathematically, but how to cut a sediment core is not explicit. Thick sectioning may reduce dating reliability; but on the contrary, thin sectioning is time-consuming. Considering the counting error of excess ²¹⁰Pb, a new method was proposed for the determination of meaningful thickness for sectioning. The authors applied this method to a core from Tokyo Bay. To increase the thickness with depth, the treatment is helpful in reducing the sample number for measurement and improving the dating accuracy. In addition, the averaging effect involved in sectioning was discussed, and it was confirmed that the averaging effect in the new method on ²¹⁰Pb geochronology may generally be neglected.  相似文献   

Immiscible two-liquid regions in the Fe-O-S system at high pressure: Implications for planetary cores     

Kyusei Tsuno  Eiji Ohtani  Hidenori Terasaki 《Physics of the Earth and Planetary Interiors》2007,160(1):75-85

We have determined phase relations in the Fe-O and Fe-O-S systems in the range of 15-21 GPa and 1825-2300 °C. Below the liquidus temperatures, solid FeO and metallic liquids are observed in both the Fe-O and the Fe-O-S systems. An immiscible two-liquid region exists in the Fe-O binary system in the pressure range investigated, and the immiscibility gap between Fe-rich metallic liquid and FeO-rich ionic liquid does not greatly change with either pressure or temperature. On the other hand, an immiscible two-liquid region in the Fe-O-S ternary system narrows significantly with increasing pressure at constant temperature and vice versa, and it almost disappears at 21 GPa, and 2300 °C. Immiscible two-liquid regions are thus not expected to exist in the Fe-O-S system in the Earth's core, suggesting that both oxygen and sulfur can be incorporated into the core. Our results are consistent with a geochemical model for the core containing 5.8 wt.% oxygen and 1.9 wt.% sulfur as proposed by McDonough and Sun [McDonough, W.F., Sun, S.-S., 1995. The composition of the Earth. Chem. Geol. 120, 223-253].  相似文献