Die mineralogische Zusammensetzung des Meteoriten von Kiel |
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| Authors: | D Ackermand P Raase |
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| Institution: | (1) Mineralogisches Institut der Universität Kiel, Deutschland |
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| Abstract: | The mineralogical composition of the meteorite of Kiel was analyzed microscopically and with the electron microprobe. The meteorite consists mainly of chondrules, which are recrystallized to some extend and which are embedded in a recrystallized ground-mass. The chondrite contains 55 Vol.-% olivine of composition (Fa24,2Fo75,3Te0,5), 28 Vol.-% orthopyroxene (Fs21,4 En76,8Wo1,8), 9 Vol.-% plagioclase (An9,4 Ab85,1 Or5,5), 4,5 Vol.-% troilite and 2,5 Vol.-% Fe-Ni-metal grains, consisting of kamazite, zonal taenite and plessite; furthermore the chondrite contains chromite, whitlockite and a very small amount of ilmenite, native copper, chalcopyrrhotine and valeriite.The kamazite is partly monocrystalline, in part polycrystalline and contains 6–7% Ni. The Ni-contents of the zonal taenites increase from approximately 30% in the core to 50% at the rim. The rim rich in Ni is broader adjacent to troilite and kamazite than adjacent to silicates. Some zonal taenite grains are partially replaced by a mixture of Ni-rich taenite, kamazite and troilite. The plessites have an average Ni-content of 15–20%. The two phases of a coarsely disintegrated plessite contain 55% and 4–5% Ni. According to Wood (1967) a primary cooling rate of 1–10° C per one million years can be deducted from the zonal structure of the taenite. The formation of the taenite rims rich in Ni, of the taenite-troilite-kamazite-replacements, and of the coarsely disintegrated plessites is probably due to a long lasting annealing or a very slow passage through the temperature range of about 300–400° C.The meteorite of Kiel is a L6-chondrite according to the petrological classification of chondrites (van Schmus and Wood, 1967). The deformation of the olivines, pyroxenes and plagioclases indicates a slight to moderate shock deformation with a peak pressure of about 150–200 kbar.
Dank. Die Mikrosonde wurde von der Stiftung Volkswagenwerk bereitgestellt. Wir bedanken uns bei Herrn Prof. Dr. F. Karl (gestorben am 15. 8. 1972) für sein Interesse an dieser Arbeit. |
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