Chemical composition and rare gas content of four new detected antarctic meteorites

Within a region of 5 km × 10 km on a downhill slope of the Yamato Mounties, in 1969 the Japanese Expedition Team collected many stones. 9 of them were recognized as meteorites. On 4 of these findings we determined the chemical composition and the rare gas content. According to the mineralogical and the chemical composition, Yamato (a) is an enstatite chondrite, Yamato (b) a Ca-poor achondrite, Yamato (c) seems to be a carbonations chondrite Type III and Yamato (d) a olivine bronzite chondrite. Exposure ages are 1.7, 31, 25 and 4.3 my respectively.     

Evidence for a late thermal event of unequilibrated enstatite chondrites: A Rb-Sr study of Qingzhen and Yamato 6901 (EH3) and Khairpur (EL6)

Abstract— The Rb-Sr whole rock and internal systematics of two EH3 chondrites, Qingzhen and Yamato 6901, and of one EL6 chondrite, Khairpur, were determined. Sulfides were separated using a stepwise dissolution technique. The mineral species in each fraction were estimated based on the chemical analyses of 12 major elements. The internal Rb-Sr systematics of the EH3 chondrites are highly disturbed. Fractions corresponding to sulfide phases show excess ⁸⁷Sr, while other fractions corresponding to silicate phases produce a linear trend on a Rb-Sr evolution diagram. If these linear relations are interpreted as isochrons, the ages of the silicate phases are 2.12 ± 0.23 Ga and 2.05 ± 0.33 Ga with the initial Sr isotopic ratios of 0.7112 ± 0.0018 and 0.7089 ± 0.0032, for Qingzhen and Yamato 6901, respectively. The process of the isotopic disturbance probably involved the breakdown of the major K-bearing sulfide (djerfisherite), and a lack of isotopic exchange between sulfide and silicate phases indicates moderate temperatures of reheating. Although a complete Sr isotopic re-homogenization among silicate phases was not attained, we interpret the Rb-Sr results as indicative of a late thermal event about 2 Ga ago on the parent bodies of these EH3 chondrites. These ages agree well with previously published K-Ar ages. An older isochron age of 4.481 ± 0.036 Ga with a low initial Sr isotopic ratio of 0.69866 ± 0.00038 was obtained for the data from silicate fractions of Khairpur, indicating early petrological equilibration on the parent body of EL6 chondrites.     

THE CHEMICAL COMPOSITION OF MAJOR ELEMENTS AND HEAVY TRACE METALS IN CHONDRITES PARAMBÙ AND MARILIA

The chemical composition of the newly observed fallen chondrites Parambù, 1967, and Marilia, 1971, was determined. Wet chemical methods were used for major elements analyses and the abundances of heavy trace elements from tungsten to uranium were determined by spark source mass spectrometry. The chemical composition confirmed the classification of Marilia as an H-group chondrite by Avanzo et al. (1973): Parambù was classified as an LL-group chondrite.     

CHEMICAL COMPOSITION,PETROGRAPHY AND MINERALOGY OF THE SHIBAYAMA CHONDRITE FOUND IN SHIBAYAMA-MACHI,SANBU-GUN,CHIBA-KEN,JAPAN

In April 1969, the chondrite was accidentally found in the side wall of the vegetable storage excavated at Shibayama-machi, Sanbu-gun, Chiba-ken, Japan, by Mr. A. Ishii and his grandson, Mr. S. Ito. The chondrite named Shibayama has been weathered thoroughly for a long period of burial underground. The bulk chemical composition, especially total Fe (21.41%) and ratios of Fe_total/SiO₂(0.557), SiO₂/MgO (1.59) and molar composition of olivine (Fa₂₃) and pyroxene (Fs₂₂) as well as mineral composition, indicate that Shibayama is a typical olivine-hypersthene chondrite. If the oxidized Fe is assumed only from metallic Fe, the original metallic Fe (7.75%) and Fe_metal/Fe_total(0.361) also support the above conclusion. From the well-recrystallized texture, indistinct and obliterated chondrule-matrix boundary, homogeneous composition of olivine and pyroxene, absence of igneous glass, and interstitial and well-developed plagioclase, this chondrite could be classified in petrologic type 6. Mosaic texture, kink bands, undulatory extinction of silicate grains and maskelynitization of plagioclase indicate that Shibayama suffered from a heavy shock effect, as is seen in other L-6 group chondrites.     

A state boundary surface model for improving the dilatancy simulation of granular material in reinforced anchors

It is acknowledged that for extending the experimental results to real scale design, it is necessary to use an appropriate numerical analysis. The good analysis in geotechnical problems needs to adopt a suitable constitutive model for the materials. This paper presents a modeling approach to investigate the complex behavior of granular trench and reinforcement system. For this purpose, an experimental and numerical investigation has been carried out on the behavior of pullout resistance of an embedded anchor (circular plate) with and without geogrid reinforcement layers in stabilized loose and dense sand using a granular trench. Different parameters have been considered, such as number of geogrid layers, embedment ratios, relative density of soil, and height ratios of granular trench. Finite element analysis with Hardening Soil Model was utilized for sand and CANAsand constitutive model was used for granular trench to investigate failure mechanism and the associated rupture surfaces. Results showed that, when soil was improved with the granular-geogrid trench, the uplift force significantly increased, but in geogrid-reinforced granular trench condition, the ultimate pullout resistance at failure increased as the number of geogrid layers increased up to the third layer, the fifth layer had a negligible effect in comparison with the third layer of reinforcement. The ultimate uplift capacity of anchor plate and the variation of surface deformation for all the tests indicated a close agreement between the experimental and numerical models.     

Assessing building vulnerability to tsunami using the PTVA-3 model: A case study of Chabahar Bay,Iran

Chabahar Bay, in southeastern Iran, lies at the north of the Gulf of Oman and close to the Makran Subduction Zone, which makes it a region that is susceptible to tsunamis. This bay has an increasingly important role in Iran’s international trade, and therefore the assessment of the regional vulnerability to the effects of a tsunami is vital. Based on both the details of historical events and the results of numerical modeling of the propagation pattern of a tsunami in this region, this study assessed the vulnerability of buildings within the Chabahar Bay region to a tsunami event. The Papathoma Tsunami Vulnerability Assessment (PTVA) model was used to calculate a relative vulnerability index (RVI) for the affected buildings based on their physical and structural characteristics. The results showed that in a postulated worst-case-scenario tsunami event in the Chabahar Bay area, approximately 60 % of the residential buildings would be affected, a level of damage that is categorized as “Average” in the RVI classification. Overall, the economic losses related to the damage of residential buildings due to a tsunami in the Chabahar Bay area are anticipated to be the equivalent of US$ 16.5 million.     

Study on the managanese nodule

Chemical and X-ray analyses were performed on the fifteen manganese nodules collected from the Pacific Ocean floor. The results were discussed compared with the previous data on the manganese nodules. Minerals were found to be todorokite, δ-MnO₂ and other silicates, montmorillonite, illite, phillipsite and α-SiO₂. Average composition shows that copper is concentrated on the deep sea nodules more than the shallow ones, and that the todorokite rich nodules contain more copper and nickel than the δ-MnO₂ rich ones. The analyses of fresh water iron-manganese precipitates by bacterial activity suggest that biological process is one of the important factors on the genesis of the sedimentary iron-manganese deposits, including the manganese nodule. The Institute of Physical and Chemical Research     

Cosmic-ray-produced40K and50V in the metal phase of chondrites

Cosmic-ray-produced⁴⁰K in the metal phase of six chondrites and⁵⁰V in that of one chondrite were determined using a surface ionization mass spectrometer. The²²Ne_total/⁴⁰K_metal ratios of the chondrites are explained in part by shielding effects during cosmic-ray irradiation. The wide variation of this ratio in some groups of meteorites is explained in terms of partial loss of rare-gas nuclides. Radiation ages for the chondrites were determined using⁴⁰K measurements and production-rate estimates from thick target calculations.     

TWO NEW CHONDRITE-FALLS IN JAPAN

In the summer of 1984, two meteorites fell in the northern part of Honshu, Japan; Aomori, at 1:50 p.m. on June 30, and Tomiya, at 1:35 p.m. on August 22. Coordinates of the falls of the Aomori and the Tomiya are at 140°47.1'E., 40°48.6'N., and 140°51.9'E., 38°22.0'N., respectively. Results of chemical analyses of major elements, ratios of Fe_total/SiO₂ (0.546 and 0.803) and Fe_metal/Fe_total (0.332 and 0.581), and molar compositions of olivines (Fa₂₅ and Fa₁₉) indicate that the Aomori and the Tomiya are typical L- and H-group ordinary chondrites, respectively. In the Aomori, chondrules are present as relicts in the well-recrystallized matrix. Olivine and pyroxene are homogeneous in composition, and coarse clear feldspar, up to 100 micrometers in size, is well developed in the chondrules and matrix. Though the Aomori is a petrologic type 6 based on its texture and mineralogy, it includes a few grains of multiple twinned clinobronzite which is rarely observed in highly equilibrated ordinary chondrites. In the Tomiya, chondrules possess a fine-grained mesostasis, and both orthopyroxene and clinobronzite are noticeable in thin sections. Plagioclase is mostly microcrystalline, but is also sparsely present as tiny, visible grains. Thus, the Tomiya was classified to be petrologic type between 4 and 5. The deformation texture of olivine, pyroxene and plagioclase indicates that both meteorites were shocked by 0.2-0.25 Mb. In conjunction with the discussion of the frequency of meteorite-falls, all observed falls of meteorites in Japan are tabulated in this paper.     

THE CHEMICAL COMPOSITIONS OF THE STONE METEORITES YAMATO (a), (b), (c) and (d), AND NUMAKAÍ

The stone meteorites Yamato (a), (b), (c) and (d) were found in Antarctica in 1969, and the chondrite Numakai was seen to fall in Hokkaido, Japan, in 1925. The chemical compositions of these meteorites have been determined by classical and instrumental methods. With the help of the stepwise fractional dissolution method the chemical composition confirmed the author's previous classification of Yamato (a), (b), (c) and (d) as enstatite chondrite, Ca-poor achondrite, type III carbonaceous chondrite and H-group chondrite, respectively. Numakai is classified as an H-group olivine-bronzite chondrite. The distribution of the major elements in each phase of these chondrites is discussed.