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Title: Petrology and comparative thermal and mechanical histories of clasts in breccia 62236

Abstract

Lunar breccia 62236 contains large lithic fragments of troctolite, norite, and anorthosite. The mafic phases, olivine, inverted pigeonite, and augite, fill interstitial areas between larger plagioclases and appear to be cumulate phases with extensive adcumulus growth. Pyroxene compositional homogeneity indicates that cation exchange during cooling was limited to an area of about 1 mm. Primary augite and pigeonite both contain 30 ..mu..m-wide lamellae of the other along '001'. Pigeonite inverted to orthopyroxene without retaining any crystallographic orientation and subsequently exsolved fine lamellae of augite on (100). Profiles across orthopyroxene-augite interfaces obtained in the analytical transmission electron microscope show an increase of approx.5% wollastonite in augite within 0.5 ..mu..m of the interface, suggesting that short-range cation exchange continued to temperatures below 500 /sup 0/C. The entire sample has undergone heterogeneous shock deformation. Shock melting of the troctolitic clast suggests pressures of 200-300 kb and well-developed basal twinning in augite from the norite clasts suggest pressures of 50-300 kbars. The present evidence indicates that 62236 contains parts of a slowly cooled microlayered accumulate that has been heterogeneously shocked several times and combined into the present breccia.

Authors:
;
Publication Date:
Research Org.:
959 National Center, U. S. Geological Survey, Reston, Virginia 22092
OSTI Identifier:
5939802
Resource Type:
Journal Article
Journal Name:
J. Geophys. Res.; (United States)
Additional Journal Information:
Journal Volume: 88:S1
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; MOON; PETROLOGY; PLANETARY EVOLUTION; ANORTHOSITES; CHEMICAL COMPOSITION; DEFORMATION; LUNAR MATERIALS; MINERALOGY; OLIVINE; TWINNING; ALKALINE EARTH METAL COMPOUNDS; GABBROS; GEOLOGY; IGNEOUS ROCKS; IRON COMPOUNDS; IRON SILICATES; MAGNESIUM COMPOUNDS; MAGNESIUM SILICATES; MATERIALS; MINERALS; OXYGEN COMPOUNDS; PLUTONIC ROCKS; ROCKS; SATELLITES; SILICATE MINERALS; SILICATES; SILICON COMPOUNDS; SOLAR SYSTEM EVOLUTION; TRANSITION ELEMENT COMPOUNDS; 640107* - Astrophysics & Cosmology- Planetary Phenomena

Citation Formats

Nord, Jr, G L, and Wandless, M. Petrology and comparative thermal and mechanical histories of clasts in breccia 62236. United States: N. p., 1983. Web. doi:10.1029/JB088iS02p0A645.
Nord, Jr, G L, & Wandless, M. Petrology and comparative thermal and mechanical histories of clasts in breccia 62236. United States. https://doi.org/10.1029/JB088iS02p0A645
Nord, Jr, G L, and Wandless, M. 1983. "Petrology and comparative thermal and mechanical histories of clasts in breccia 62236". United States. https://doi.org/10.1029/JB088iS02p0A645.
@article{osti_5939802,
title = {Petrology and comparative thermal and mechanical histories of clasts in breccia 62236},
author = {Nord, Jr, G L and Wandless, M},
abstractNote = {Lunar breccia 62236 contains large lithic fragments of troctolite, norite, and anorthosite. The mafic phases, olivine, inverted pigeonite, and augite, fill interstitial areas between larger plagioclases and appear to be cumulate phases with extensive adcumulus growth. Pyroxene compositional homogeneity indicates that cation exchange during cooling was limited to an area of about 1 mm. Primary augite and pigeonite both contain 30 ..mu..m-wide lamellae of the other along '001'. Pigeonite inverted to orthopyroxene without retaining any crystallographic orientation and subsequently exsolved fine lamellae of augite on (100). Profiles across orthopyroxene-augite interfaces obtained in the analytical transmission electron microscope show an increase of approx.5% wollastonite in augite within 0.5 ..mu..m of the interface, suggesting that short-range cation exchange continued to temperatures below 500 /sup 0/C. The entire sample has undergone heterogeneous shock deformation. Shock melting of the troctolitic clast suggests pressures of 200-300 kb and well-developed basal twinning in augite from the norite clasts suggest pressures of 50-300 kbars. The present evidence indicates that 62236 contains parts of a slowly cooled microlayered accumulate that has been heterogeneously shocked several times and combined into the present breccia.},
doi = {10.1029/JB088iS02p0A645},
url = {https://www.osti.gov/biblio/5939802}, journal = {J. Geophys. Res.; (United States)},
number = ,
volume = 88:S1,
place = {United States},
year = {Tue Feb 15 00:00:00 EST 1983},
month = {Tue Feb 15 00:00:00 EST 1983}
}