High-pressure phases in shock-induced melt of the unique highly shocked LL6 chondrite Northwest Africa 757

Jinping Hu, Thomas Sharp

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

Northwest Africa 757 is unique in the LL chondrite group because of its abundant shock-induced melt and high-pressure minerals. Olivine fragments entrained in the melt transform partially and completely into ringwoodite. Plagioclase and Ca-phosphate transform to maskelynite, lingunite, and tuite. Two distinct shock-melt crystallization assemblages were studied by FIB-TEM analysis. The first melt assemblage, which includes majoritic garnet, ringwoodite plus magnetite-magnesiowüstite, crystallized at pressures of 20–25 GPa. The other melt assemblage, which consists of clinopyroxene and wadsleyite, solidified at ~15 GPa, suggesting a second veining event under lower pressure conditions. These shock features are similar to those in S6 L chondrites and indicate that NWA 757 experienced an intense impact event, comparable to the impact event that disrupted the L chondrite parent body at 470 Ma.

Original languageEnglish (US)
Pages (from-to)1353-1369
Number of pages17
JournalMeteoritics and Planetary Science
Volume51
Issue number7
DOIs
StatePublished - Jul 1 2016

    Fingerprint

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science

Cite this