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GEOREF RECORD

Shocking rocks by cavitation and bubble implosion

John G. Spray
Shocking rocks by cavitation and bubble implosion
Geology (Boulder) (August 1999) 27 (8): 695-698

Abstract

Cavitation is proposed as a mechanism for the discrete generation of high-pressure--high-temperature polymorphs in veins within meteorites and hypervelocity impact structures. Cavitation involves the inception, isothermal growth, and adiabatic implosion of bubbles; their collapse has the potential of generating ultrahigh temperatures and pressures. The formation of pseudotachylytic melt veins within the shocked target is critical to the cavitation process. These veins facilitate bubble growth on decompression and subsequent bubble collapse on relaxation within the liquid. Asymmetric bubble implosion can lead to the rapid inrush of liquid to form a supersonic jet. If the liquid jet strikes a solid surface (i.e., melt-vein walls or suspended clasts) at high velocities, then temperatures of several thousand kelvin and pressures of 10 GPa or more can be realized in the area of jet impact. These conditions are capable of generating high-pressure phases, such as ringwoodite, the spinel-structured polymorph of olivine, which requires formation pressures of >50 GPa. These extreme effects are transient and localized, being restricted to microscopic regions of liquid-solid impact within the cavitating melt vein. The presence of high-pressure polymorphs in meteorites and impact structures does not necessarily imply that the primary shock event attained the conditions necessary for polymorph formation. Instead, the presence of polymorphs may be the result of extreme pressure-temperature excursions due to cavitation.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 27
Serial Issue: 8
Title: Shocking rocks by cavitation and bubble implosion
Author(s): Spray, John G.
Affiliation: University of New Brunswick, Impact Geology Group, Fredericton, NB, Canada
Pages: 695-698
Published: 199908
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 33
Accession Number: 1999-055481
Categories: Petrology of meteorites and tektitesStructural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
S27°30'00" - S26°45'00", E27°00'00" - E27°30'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 199919
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