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Shock metamorphism in lunar samples.
Science (New York, N.Y.)
|January 30, 1970
Summary
Shock metamorphism in lunar rocks reveals high-pressure deformation and melting. Two impact sources and distinct melt chemistries suggest different lunar terrains were affected.
Area of Science:
- Geology
- Planetary Science
- Impact Cratering
Background:
- Shock metamorphism is a key indicator of impact events on planetary bodies.
- Lunar crystalline rocks and breccias preserve evidence of extreme pressures and temperatures.
Purpose of the Study:
- To investigate the effects of shock metamorphism on lunar crystalline rocks and breccias.
- To differentiate between primary and secondary impact shock sources.
- To analyze the chemical variations in shock-induced melts.
Main Methods:
- Microscopic examination of rock samples for deformation structures.
- Analysis of plagioclase and pyroxene for shock features.
- Chemical analysis of shock-induced melt glasses.
Main Results:
- Shock metamorphism evident in fine materials and breccias, rare in coarse fragments.
- Observed deformation structures in plagioclase and pyroxene, diaplectic glasses, and shock melts.
- Identified two primary shock sources: meteorite impacts and crater ejecta impacts.
- Distinguished two major chemical types of shock-induced melts.
Conclusions:
- Lunar rocks exhibit significant shock metamorphism from high-pressure events.
- Impact shock waves originate from both primary and secondary impact events.
- Chemical differences in melts correlate with impact locations in mare and highland regions.
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