1. Szaniszló Bérczi, associate professor,
Evolution of a Chondritic Parent Body Studies on the Antarctic Meteorites Collected by the NIPR Japanese Antarctic Expeditions
Szaniszló Bérczi, associate professor,
Department of Materials Physics, Institute of Physics, Eötvös Loránd University,
Budapest, Hungary
16/01/2019
Lecture on Okayama University

2. Lecture on Okayama University
Introduction 1
Meteorites are fragments of different asteroidal sized bodies. Mineralogical and textural characteristics of various meteorites reveal processes, which help to arrange them into types and calsses.
Many important processes can be fitted into a global evolutionary picture if we assume, that larger bodies suffered thermal transformation during their early lifetime, when radioctive heating warmed up them.
This way main chondritic processes of early classifications to types of Prior, then Urey and Craig, further developments by Wiik, Keil and Fredriksson, and to petrologic class definition of Van Schmus and Wood serve as parallel partial processes in this global picture.
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3. Heritage: Solar abundance of nuclei
Around Sun the solar nebula contains the nuclei of elements in solar abundance, near to the cosmic abundance
Of this composition minerals precipitate or keep balance with the solar nebula
Their composition changes with the solar distance, determining p and T od the solar nebula.
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4. Main minerals of the Lewis-Barshay model
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5. Planetary cross sections in the Lewis-Barshay model
From minerals larger blocks and later planetosimals form.
Collisions of planetosimals form larger bodies.
The largest known bodies are the chondritic asteroids.
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6. Double-crystallisation in the Solar System
Two great periods in the formation of the planetary system
Precipitation of the minerals
Accumulation into planetosimals by collisions.
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7. Lecture on Okayama University
Meteorites 1
The main groups of the meteorites follow the main mineral groups of the condensation model of the Solar System.
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8. A well known carbonaceous chondrite: Kaba
It fall in Hungary in 1857, April 15. at the village of Kaba.
Its type is CV3.
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9. The main type of the meteorites: the chondrites (Mezőmadaras)
Of tha falls of meteorites 85 % is chondritic
Their main characterising components are the chondrules: grains in English.
Their size is bw. Millimeter and some 10 s of micrometers.
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10. New source of meteorites: Antarctica
In this study we use the thin section set of the National Institute of Polar Research, Tokyo, Japan.
It contains 30 polished thin sections of meteorites.
This collection gives a good cross section about the meteorite evolution.
Iron meteorite on the Antarctic snowfield
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11. NIPR Antarctic Meteorite Set
30 polished thin sections.
3 chondrite groups form vSW sequences from 3-to 6 types (H, L, LL).
4 carbonaceous chondrites
12 achondrites.
Excellent collection for teaching the evolution of a chondritic parent body
Lecture note atlas helped students in their studies.
Beautiful collection.
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12. Lecture on Okayama University
Types of chondrules
Once they were in molten state. Droplets were formed by the solar flares.
Their textures formed during their cooling
the first textural type is. Glassy.
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13. Radial – and – porphyritic
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14. Cratered – and – composite
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15. Lecture on Okayama University
CAI: Ca-Al Inclusion
During the early inner zone (belt) of the Sun minerals with refractory composition were formed
Frequently they have amoeboid shape.
Sztrókay Kálmán measured their composition and found it to be mostly composed of spinel.
This is a CAI from the Allende meteorite.
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16. Lecture on Okayama University
Observations - 1
Chondritic texture consists of two main constituents: chonrules and matrix. They form a breccsa like texture of many other constituents.
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17. Chondritic textures, metamorphism
Chondruletypes
Alterations
Thermal
Aqueous
Impact brecciation
Other processes.
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18. First chondritic evolution period (metamorphism)
Samples: A) Samples of first chondritic evolution period (metamorphism) in the set:
Carbonaceous Chondrites: - C1 - NIPR 27, CM2 - NIPR 28, CO3 - NIPR 29, CV3 - NIPR 30.
Unequilibrated Chondrites: EH3 - NIPR 14, H3 - NIPR 15, L3 - NIPR 19, LL3 - NIPR 23.
Equilibrated Chondrites: H4 - NIPR 16, H5 - NIPR 17, H6 - NIPR 18, L4 - NIPR 20, H5 - NIPR 21, H6 - NIPR 22, LL4 - NIPR 24, LL5 - NIPR 25, LL6 - NIPR 26.
Primitive Achondrite: PA - NIPR 13.
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19. Observations/interpretations - 3
Over vS-W stage 6 chondritic mineral assemblage begins to melt partially. This stage is represented by primitive achondrites, like the lodranites.
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20. Observations/interpretations - 4
Two main partial melts appear: - first the metallic sulphide/metal FeNi melts migrate downward, this mineral assemblage can be seen in pallasites.
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21. Observations/interpretations - 5
- second the basaltic liquids migrate upward to produce basaltic achondrites: eucrites, howardites and diogenites.
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22. Eukritok: bazaltok a felszínről
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23. Observations/interpretations - 6
The final remnant of these partial melting processes is a peridotitic rock, similar to ureilites. This mineral assemblage preserve many characteristics of the original chondritic composition.
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24. Lecture on Okayama University
Differentiation
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25. Urey-Craig-Field (UCF) of iron compounds
In 1953 Urey and Craig compiled all good chondritic compositional data and made a metal+sulphide versus oxidized iron compounds compositional field.
They could distinguish two main groups of chondrites
- those with High (H) total iron content
- those with Low (L) total iron content.
Later 3 other groups were defined by Wiik, Friderickson and Keil (E, LL, C).
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26. Chemistry of chondrites
The chond-rites groups of E, H, L, LL, C are arranged in the Urey-Craig Field (UCF).
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27. Lecture on Okayama University
The Urey-Craig field
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28. Projections of Fe-compound data on the UCF
UCF is similar to HRD in astronomy.
We may follow on it the evolutionary trends of various regions in a chondritic body.
We used NIPR Dataset of chondrites (444 chondrites) and projected them to the UCF.
As an example: H3, H4, H5, H6 sequences were projected on the UCF.
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29. Summary of the H, L, LL metamorphic sequences in the NIPR set
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30. Evolutionary paths of chondriter groups in the UCF
In the first period most chondrites are reduced from 3-to-4 vS-W stages
Second they become oxidized
At L and LL iron loss is beginning at stage 6 (and 7)
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31. Cross section of a chondritic body
Meta-morphous steps during evolution of a chondritic body, form concentric belts.
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32. Asteroidal cross section
The stratification of the main achondrite types in the initially chondritic asteroidal body, which later differentiated by migration of melts.
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33. Fragmentation of the Chondritic Parent Body by Collision
Final events before mete-orites reach Earth: collisions in the asteroid belt
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34. Oxigene isotopic ratios
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35. Lecture on Okayama University
Summary
The fragments of various asteroidal bodies are the meteorites.
Their mineralogical and textural characteristics revealed processes.
On the basis of these processes studies arranged them into types, classes; formed transformational sequences from them.
The processes are in accord with a global evolutionary picture.
This thermal transformation occurred during the early life time of the parent body, when radioctive heating warmed up them.
There were two main periods in chondritic evolution:
- thermal metamorphism,
- differentiation into layers of the chondritic body.
This global picture can be deciphered in more details by further studies on meteorites.
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36. Acknowledgments and references
Thanks to NIPR Antarctic Meteorite Research Center, Tokyo, for loan of the Antarctic set.
Thanks for invitation to the university and kind hospitality here.
Some more details can be shown on our homepage:
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