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EDWARD R. D. SCOTT ALEXANDER N. KROT AKIRA YAMAGUCHI 《Meteoritics & planetary science》1998,33(4):709-719
Abstract— Carbonates in Martian meteorite Allan Hills 84001 occur as grains on pyroxene grain boundaries, in crushed zones, and as disks, veins, and irregularly shaped grains in healed pyroxene fractures. Some carbonate disks have tapered Mg-rich edges and are accompanied by smaller, thinner and relatively homogeneous, magnesite microdisks. Except for the microdisks, all types of carbonate grains show the same unique chemical zoning pattern on MgCO3-FeCO3-CaCO3 plots. This chemical characteristic and the close spatial association of diverse carbonate types show that all carbonates formed by a similar process. The heterogeneous distribution of carbonates in fractures, tapered shapes of some disks, and the localized occurrence of Mg-rich microdisks appear to be incompatible with growth from an externally derived CO2-rich fluid that changed in composition over time. These features suggest instead that the fractures were closed as carbonates grew from an internally derived fluid and that the microdisks formed from a residual Mg-rich fluid that was squeezed along fractures. Carbonate in pyroxene fractures is most abundant near grains of plagioclase glass that are located on pyroxene grain boundaries and commonly contain major or minor amounts of carbonate. We infer that carbonates in fractures formed from grain boundary carbonates associated with plagioclase that were melted by impact and dispersed into the surrounding fractured pyroxene. Carbonates in fractures, which include those studied by McKay et al. (1996), could not have formed at low temperatures and preserved mineralogical evidence for Martian organisms. 相似文献
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Solution Chemistry and the 36~(th) International Conference on Solution Chemistry (36 ICSC) in Xining,China 
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下载免费PDF全文 Toshio YAMAGUCHI 《盐湖研究》2019,(2)
<正>Solution chemistry covers a broad and interdisciplinary area in chemistry,physics,biology,pharmaceutical,and medical sciences,as well as various application fields. With the advent of new theories,analytical methods,computers,and technology,the research area of solution chemistry has now been widely and deeply 相似文献
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This paper investigates the possible sources of errors associated with tropical cyclone (TC) tracks forecasted using the Global/Regional Assimilation and Prediction System (GRAPES). In Part I, it is shown that the model error of GRAPES may be the main cause of poor forecasts of landfalling TCs. Thus, a further examination of the model error is the focus of Part II. Considering model error as a type of forcing, the model error can be represented by the combination of good forecasts and bad forecasts. Results show that there are systematic model errors. The model error of the geopotential height component has periodic features, with a period of 24 h and a global pattern of wavenumber 2 from west to east located between 60°S and 60°N. This periodic model error presents similar features as the atmospheric semidiurnal tide, which reflect signals from tropical diabatic heating, indicating that the parameter errors related to the tropical diabatic heating may be the source of the periodic model error. The above model errors are subtracted from the forecast equation and a series of new forecasts are made. The average forecasting capability using the rectified model is improved compared to simply improving the initial conditions of the original GRAPES model. This confirms the strong impact of the periodic model error on landfalling TC track forecasts. Besides, if the model error used to rectify the model is obtained from an examination of additional TCs, the forecasting capabilities of the corresponding rectified model will be improved. 相似文献
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Abstract— We have studied a unique impact-melt rock, the Ramsdorf L chondrite, using optical and scanning microscopy and electron microprobe analysis. Ramsdorf contains not only clast-poor impact melt (Begemann and Wlotzka, 1969) but also a chondritic portion (>60 g) with what appears at low magnification to be a normal, well-defined chondritic texture. However, detailed studies at high magnification show that >90 vol% of the crystals in the chondritic portion were largely melted by the impact: the chondrules lack normal microtextures and are ghosts of the original features. The only relics from the precursor chondrules are olivine crystals, which have the highest melting temperature (～1620 °C). Pyroxene-rich chondrules were so extensively melted that no phenocrysts were preserved and the melt crystallized in situ before significant mixing with exterior olivine-rich melts. Fine-grained pyroxene chondrule ghosts have sharper boundaries with the matrix than porphyritic olivine and pyroxene chondrule ghosts, probably because pyroxene-rich melts are significantly more viscous. Complex textures that formed by injection of melt along cracks and fractures in relic olivines suggest that the chondritic portion of Ramsdorf formed directly from petrologic type 3–4 material by strong shock. We infer that Ramsdorf was largely melted by shock pressures of ～75–90 GPa and that chondrule ghosts and relic olivine phenocrysts were locally preserved by rapid cooling. Quenching was not due to the addition of cold clasts into the melt but to heterogeneous shock heating that only caused internal melting of large olivines and pyroxenes. Ramsdorf appears to be one of the most heavily shocked meteorites that has retained some trace of its original texture. 相似文献
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Michael K. WEISBERG Caroline SMITH Gretchen BENEDIX Christopher D. K. HERD Kevin RIGHTER Henning HAACK Akira YAMAGUCHI Hasnaa CHENNAOUI AOUDJEHANE Jeffrey N. GROSSMAN 《Meteoritics & planetary science》2010,45(3):449-493
Abstract– In this edition of The Meteoritical Bulletin, a total of 506 newly approved meteorite names with their relevant data are reported. These include 354 from northwest Africa, 31 from the Americas, 15 from Antarctica (Koreamet), 85 from Asia, 20 from Australia, and 1 from Europe. Among these meteorites are 2 falls, Grimsby (Canada) and Santa Lucia (2008) (Argentina). Also described are a CM with low degree of alteration, new ungrouped chondrites and achondrites, and 4 Martian meteorites. 相似文献
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