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Precambrian reidite discovered in shocked zircon from the Stac Fada impactite, Scotland

S. M. Reddy, T. E. Johnson, S. Fischer, W. D. A. Rickard and R. J. M. Taylor
Precambrian reidite discovered in shocked zircon from the Stac Fada impactite, Scotland
Geology (Boulder) (August 2015) 43 (10): 899-902


Terrestrial impact events have had a profound influence on Earth's geological, geochemical, and biological evolution. However, the record of Precambrian impacts is poorly constrained due to the dynamic nature of plate tectonics, erosion, and deposition of younger rocks that may destroy or cover the evidence. Here we report the first Precambrian occurrence of the rare mineral reidite (ZrSiO (sub 4) ) within grains of shocked zircon in the ca. 1.18 Ga Stac Fada Member (Stoer Group), northwestern Scotland. The reidite, preserved as <2-mu m-wide lamellae, is unambiguous evidence of shock pressures in excess of approximately 30 GPa and confirms the impact origin for the Stac Fada Deposit. The reidite lamellae are locally deformed, and sites of deformation record its decomposition to baddeleyite (ZrO (sub 2) ) and amorphous silica, the first natural example of this transformation. The findings demonstrate that reidite and baddeleyite may form and be transported in high-energy ejecta without physical or chemical breakdown and are stable during sedimentary diagenesis and low-grade metamorphism. Thus, reidite may be preserved over time scales exceeding 1 b.y., establishing the use of reidite within detrital shocked zircon from Precambrian strata as a viable and valuable means of recognizing and characterizing ancient terrestrial impact events.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 43
Serial Issue: 10
Title: Precambrian reidite discovered in shocked zircon from the Stac Fada impactite, Scotland
Affiliation: Curtin University, Institute for Geoscience Research, Department of Applied Geology, Perth, West. Aust., Australia
Pages: 899-902
Published: 20150821
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 28
Accession Number: 2015-089163
Categories: Igneous and metamorphic petrologyMineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch map
N54°40'00" - N61°00'00", W08°30'00" - W00°45'00"
Secondary Affiliation: University of Saint Andrews, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, 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: 201538
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