Shock stage distribution of 2280 ordinary chondrites—Can bulk chondrites with a shock stage of S6 exist as individual rocks?

· by · in , , , , ,

Addi Bischoff, Maximilian Schleiting, Markus Patzek

Meteoritics & Planetary Science
First published: 21 October 2018

LINK

“The brecciation and shock classification of 2280 ordinary chondrites of the meteorite thin section collection at the Institut für Planetologie (Münster) has been determined. The shock degree of S3 is the most abundant shock stage for the H and LL chondrites (44% and 41%, respectively), while the L chondrites are on average more heavily shocked having more than 40% of rocks of shock stage S4. Among the H and LL chondrites, 40–50% are “unshocked” or “very weakly shocked.” Considering the petrologic types, in general, the shock degree is increasing with petrologic type. This is the case for all meteorite groups. The main criteria to define a rock as an S6 chondrite are the solid‐state recrystallization and staining of olivine and the melting of plagioclase often accompanied by the formation of high‐pressure phases like ringwoodite. These characteristics are typically restricted to local regions of a bulk chondrite in or near melt zones. In the past, the identification of high‐pressure minerals (e.g., ringwoodite) was often taken as an automatic and practical criterion for a S6 classification during chondrite bulk rock studies. The shock stage classification of many significantly shocked chondrites (>S3) revealed that most ringwoodite‐bearing rocks still contain more than 25% plagioclase (74%). Thus, these bulk chondrites do not even fulfill the S5 criterion (e.g., 75% of plagioclase has to be transformed into maskelynite) and have to be classified as S4. Studying chondrites on typically large thin sections (several cm2) and/or using samples from different areas of the meteorites, bulk chondrites of shock stage S6 should be extremely rare. In this respect, the paper will discuss the probability of the existence of bulk rocks of S6. “

Related posts (automatically generated):

  1. Shock physics mesoscale modeling of shock stage 5 and 6 in ordinary and enstatite chondritesOPEN ACCESS 
  2. Primordial, thermal, and shock features of ordinary chondrites: Emulating bulk X‐ray diffraction using in‐plane rotation of polished thin sections
  3. Quantitative determination of the shock stage of L6 ordinary chondrites using X-ray diffraction
  4. Raman Spectroscopy Studies of Equilibrated Ordinary Chondrites with H and L Group and Shock Metamorphism DegreesOPEN ACCESS 
  5. Brecciation among 2280 ordinary chondrites – constraints on the evolution of their parent bodies
  6. Electron Backscatter Diffraction (EBSD) study of seven heavily metamorphosed chondrites: Deformation systematics and variations in pre-shock temperature and post-shock annealing
  7. Ordinary chondrite shock stage quantification using in situ 2‐D X‐ray diffraction of olivine
  8. Investigation of the shocked Viñales ordinary chondrite (L6) meteorite fall – Implications for shock classification, fragmentation, and collision dynamics
  9. Chemical-Petrographic Types and Shock Metamorphism of 184 Grove Mountains Equilibrated Ordinary ChondritesOPEN ACCESS 
  10. Demagnetization of Ordinary Chondrites under Hydrostatic Pressure up to 1.8 GPa
Tags: , ,