Iridium anomaly but no shocked quartz from Late Archean microkrystite layer: Oceanic impact ejecta?

Title:
Iridium anomaly but no shocked quartz from Late Archean microkrystite layer: Oceanic impact ejecta?
Authors:
Simonson, Bruce M.; Davies, Darian; Wallace, Malcolm; Reeves, Shane; Hassler, Scott W.
Abstract:
Samples from a ca. 2.54 Ga layer rich in microkrystites (sand-size spherules of former silicate melt) in the Hamersley Group (Western Australia) are enriched in Ir up to 50 fold over associated carbonates and shales, but few of the other siderophile elements display significant anomalies or chondritic interelement ratios. However, similar concentrations and interelement ratios are observed in ejecta from the ca. 590 Ma Acraman impact structure and have been attributed to diagenetic redistribution. The microkrystite layer also contains sand-size quartz grains with internal textures typical of regionally metamorphosed rocks rather than evidence of shock metamorphism. We suggest that the microkrystites were created by an impact that took place in a deep ocean basin rather than on a continent, and that the associated quartz is epiclastic detritus brought in by unusually high energy waves and/or currents, not as ballistic ejecta.
Citation:
Simonson, B.M., D. Davies, M. Wallace, S. Reeves, and S.W. Hassler. 1998. "Iridium anomaly but no shocked quartz from Late Archean microkrystite layer: Oceanic impact ejecta?" Geology 26(3): 195-198.
Publisher:
Geological Society of America
DATE ISSUED:
1998-03
Department:
Geology
Type:
article
PUBLISHED VERSION:
10.1130/0091-7613(1998)026<0195:IABNSQ>2.3.CO;2
PERMANENT LINK:
http://hdl.handle.net/11282/309624

Full metadata record

DC FieldValue Language
dc.contributor.authorSimonson, Bruce M.en_US
dc.contributor.authorDavies, Darianen_US
dc.contributor.authorWallace, Malcolmen_US
dc.contributor.authorReeves, Shaneen_US
dc.contributor.authorHassler, Scott W.en_US
dc.date.accessioned2013-12-23T16:13:31Z-
dc.date.available2013-12-23T16:13:31Z-
dc.date.issued1998-03en
dc.identifier.citationSimonson, B.M., D. Davies, M. Wallace, S. Reeves, and S.W. Hassler. 1998. "Iridium anomaly but no shocked quartz from Late Archean microkrystite layer: Oceanic impact ejecta?" Geology 26(3): 195-198.en_US
dc.identifier.issn0091-7613en_US
dc.identifier.urihttp://hdl.handle.net/11282/309624-
dc.description.abstractSamples from a ca. 2.54 Ga layer rich in microkrystites (sand-size spherules of former silicate melt) in the Hamersley Group (Western Australia) are enriched in Ir up to 50 fold over associated carbonates and shales, but few of the other siderophile elements display significant anomalies or chondritic interelement ratios. However, similar concentrations and interelement ratios are observed in ejecta from the ca. 590 Ma Acraman impact structure and have been attributed to diagenetic redistribution. The microkrystite layer also contains sand-size quartz grains with internal textures typical of regionally metamorphosed rocks rather than evidence of shock metamorphism. We suggest that the microkrystites were created by an impact that took place in a deep ocean basin rather than on a continent, and that the associated quartz is epiclastic detritus brought in by unusually high energy waves and/or currents, not as ballistic ejecta.en_US
dc.language.isoen_USen_US
dc.publisherGeological Society of Americaen_US
dc.identifier.doi10.1130/0091-7613(1998)026<0195:IABNSQ>2.3.CO;2-
dc.subject.departmentGeologyen_US
dc.titleIridium anomaly but no shocked quartz from Late Archean microkrystite layer: Oceanic impact ejecta?en_US
dc.typearticleen_US
dc.identifier.journalGeologyen_US
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