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FRIGN zircon; the only terrestrial mineral diagnostic of high-pressure and high-temperature shock deformation

Aaron J. Cavosie, Nicholas E. Timms, Ludovic Ferriere and Pierre Rochette
FRIGN zircon; the only terrestrial mineral diagnostic of high-pressure and high-temperature shock deformation
Geology (Boulder) (October 2018) 46 (10): 891-894


Minerals that record high-pressure deformation from meteorite impact are relatively common on Earth; however, minerals that record both high-pressure and high-temperature effects of impact are rare, and they occur mostly in meteorites. Here, we report new occurrences of a type of granular zircon that is the only terrestrial mineral known that uniquely records both high-pressure and high-temperature conditions diagnostic of impact. Granular zircon grains in impact melt rock from the Luizi impact structure (Democratic Republic of the Congo) and in glass from the recently described Pantasma structure (Nicaragua) consist of approximately 1-mu m-sized neoblasts in multiple domains that are systematically oriented such that all (001) poles are approximately orthogonal and coincide with a <110> direction from adjacent domains. The neoblast orientations are produced uniquely by transformation to the high-pressure polymorph reidite and its subsequent reversion to neoblastic zircon at high-temperature conditions, as evidenced by the occurrence of ZrO (sub 2) . We here refer to such granular grains that preserve orientation evidence for reversion from reidite as "former reidite in granular neoblastic" zircon, or FRIGN zircon, in order to distinguish this type of granular zircon from those that do not record high-pressure conditions. In addition to the localities described here, examples of what can now be classified as FRIGN zircon have been documented at Meteor Crater (Barringer crater, USA), at the Acraman impact structure (Australia), and in Australasian tektites. Occurrences thus span five continents, range in age from Precambrian (ca. 590 Ma) to recent (ca. 49 ka), and serve as a diagnostic indicator of impact metamorphism that may be present throughout much of the geological record. FRIGN zircon further has potential to be found in extraterrestrial samples, where granular zircon has previously been reported.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 46
Serial Issue: 10
Title: FRIGN zircon; the only terrestrial mineral diagnostic of high-pressure and high-temperature shock deformation
Affiliation: Curtin University, School of Earth and Planetary Science, Perth, West. Aust., Australia
Pages: 891-894
Published: 201810
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 26
Accession Number: 2018-080126
Categories: Mineralogy of silicatesPetrology of meteorites and tektites
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2018325
Illustration Description: illus. incl. sketch maps
S13°00'00" - N05°15'00", E12°00'00" - E32°00'00"
N10°40'00" - N15°00'00", W87°40'00" - W83°04'60"
Secondary Affiliation: Natural History Museum, AUT, AustriaAix-Marseille Universite, FRA, France
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201844
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