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    Tytuł:
    Mineralogy of the Baszkówka chondrite (L5 S1): new data on silicates, opaques and minor minerals
    Autorzy:
    Borucki, J.
    Stępniewski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059302.pdf
    Data publikacji:
    2001
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Baszkówka
    meteorites
    ordinary chondrites
    minerals
    spinel
    picotite
    Opis:
    The mineral composition of the Baszkówka meteorite comprises: olivine, pyroxenes, plagioclase, Fe,Ni metal, troilite and chromite with minor chlorapatite, whitlockite, magnetite, haematite, spinel, idaite, calcite and native Cu. A rare variety of spinel (picotite), probably the oldest among the minerals of Baszkówka, was identified in the only two chondrules named: panda and chevron. The composition of the olivine (Fa 26.2š1.8 wt.%) and the high degree of chondrite homogenisation, a result of thermal metamorphism, are consistent with earlier results and indicate the L5 group. No distinct shock effects were observed in Baszkówka, classified as S1. Troilite-Fe,Ni and Fe,Ni metal lumps are defined and interpreted as molten planetesimals impact splashes.
    Źródło:
    Geological Quarterly; 2001, 45, 3; 229-256
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Two spinel-bearing compound chondrules from the Baszkówka meteorite
    Autorzy:
    Borucki, J.
    Stępniewski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059304.pdf
    Data publikacji:
    2001
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Baszkówka
    meteorites
    ordinary chondrites
    spinel
    Opis:
    The present paper describes two compound chondrules labelled panda and chevron, discovered in the Baszkówka meteorite. Optical microscope, electron microscope and electron microprobe studies revealed an unusual mineral composition and fabric. Both chondrules include "primary" and "secondary" components. The panda and chevron chondrules have apparent diameters of ~0.86 and ~0.54 mm respectively with spinel dominant in primary components and olivine-plagioclase in secondary components overlain by thin microcrystalline rims. Euhedral or subhedral Mg, Fe2+/Al, Cr-spinel crystals from the panda's primary component (zoned, cavernous or homogeneous) were not found in Mg-Fe chondrules in Baszkówka, where Cr occurs exclusively as chromite. Olivine crystals from panda's primary (Fa27.1) and secondary (Fa26.5) component have similar compositions to those from panda's rim (Fa26.4) and comparable to olivine from other Baszkówka Mg-Fe chondrules (average ~Fa25.7). The Ca-plagioclase laths from the groundmass of panda's primary component has an extremely variable composition (~An49 to ~An60), evidently more calcic than those in other chondrules of the meteorite (mean ~An13). The primary components of the two spinel-bearing chondrules may have been formed in a fireball generated by powerful impact during early accretion of a protoplanet. After crystallisation the spinel crystals were abraded and polished, probably during rapid flight through a dense cloud of interplanetary dust. The moderately reducing conditions of the hypothetical fire ball were replaced by a more reducing environment during the condensation of the rims of both chondrules.
    Źródło:
    Geological Quarterly; 2001, 45, 3; 281-288
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Songyuan ordinary chondrite (China) - rich in alien rock fragments and its reclassification
    Autorzy:
    Borucki, J.
    Giro, L.
    Orłowski, R.
    Stępniewski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059203.pdf
    Data publikacji:
    2009
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Songyuan
    meteorites
    ordinary chondrites
    classification
    rock fragments
    Opis:
    The Songyuan chondrite is composed mostly of minerals and chondrule types common in equilibrated ordinary chondrites. More distinctively, the Songyuan material includes numerous sintered cryptocrystalline rock lumps, possible chondrule precursors, and less frequent fragments of olivine-pyroxene basalt. The moderate porosity (estimated under the polarizing microscope at a few percent by volume) and un compacted metal grains, suggest that the meteorite came from very shallow horizons of the regolith. The shallow original position of the Songyuan fragment on its parent body is consistent also with the abundance of numerous euhedral crystals of the main meteoritic components present in the interstitial pores. They crystallized most probably from fluids migrating through the superficial horizons from the in ner parts of the Songyuan parent body. The structural characteristics and slight differentiation in olivine composition suggests a high degree of homogenization and, together with the median value of the fayalite content (26.2 š0.24 wt.%), corre sponds to the L5 chemical-petrologic group of equilibrated ordinary chondrites. More over, the homogenous extinction in the olivine crystals and the absence of multiple planar fractures indicate the lowest level of the shock metamorphism (S1), whereas the lack of any oxide rims around kamacite and troilite grains points to the lowest level of weathering (W0).
    Źródło:
    Geological Quarterly; 2009, 53, 2; 187-198
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Comparative Mössbauer studies of the Baszkówka ordinary chondriteand some other meteorites
    Autorzy:
    Gałązka-Friedman, J.
    Bauminger, E. R.
    Nowik, I.
    Bakun-Czubarow, N.
    Stępniewski, M.
    Siemiątkowski, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059308.pdf
    Data publikacji:
    2001
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    ordinary chondrites
    parent body
    Mössbauer spectroscopy
    Q angle
    troilite
    kamacite
    olivine
    pyroxene
    weathering
    oxidation
    Opis:
    It was suggested that perhaps Mössbauer parameters of troilite could serve as a criterion for an interpretation of the origin of various meteorites. It was found that in three meteorites coming from the same parent body (Baszkówka, Mt. Tazerzait and Songyuan) the angle between the principal axis of the electric field gradient (EFG) and the direction of the magnetic field in troilite is around 60o. Further investigations showed that in some other meteorites, not belonging to this group, this angle is close to 90o.
    Źródło:
    Geological Quarterly; 2001, 45, 3; 319-326
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-4 z 4

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