Evolution of a Chondritic Parent Body Studies on the Antarctic Meteorites Collected by the NIPR Japanese Antarctic Expeditions

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Evolution of a Chondritic Parent Body Studies on
the Antarctic Meteorites Collected by the
NIPRJapanese Antarctic Expeditions
Szaniszló Bérczi, associate professor,
Department of Materials Physics,Institute of
Physics, Eötvös Loránd University, Budapest,
Hungary
bercziszani_at_ludens.elte.hu
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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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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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Main minerals of the Lewis-Barshay model
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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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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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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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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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The main type of the meteoritesthe chondrites
(Mezomadaras)

• 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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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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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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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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Radial and porphyritic
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Cratered and composite
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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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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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Chondritic textures, metamorphism

• Chondruletypes
• Alterations
• Thermal
• Aqueous
• Impact brecciation
• Other processes.

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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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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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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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Observations/interpretations - 5

• - second the basaltic liquids migrate upward to
  produce basaltic achondrites eucrites,
  howardites and diogenites.

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Eukritok bazaltok a felszínrol
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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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Differentiation
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Urey-Craig-Field (UCF) of iron compounds

• In 1953 Urey and Craig compiled all good
  chondritic compositional data and made a
  metalsulphide 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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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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The Urey-Craig field
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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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Summary of the H, L, LL metamorphic sequences in
the NIPR set
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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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Cross section of a chondritic body

• Meta-morphous steps during evolution of a
  chondritic body, form concentric belts.

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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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Fragmentation of the Chondritic Parent Body by
Collision

• Final events before mete-orites reach Earth
  collisions in the asteroid belt

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Oxigene isotopic ratios
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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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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
  http//planetologia.elte.hu/