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GEOREF RECORD

Petrology of impact melt rocks from the Chesapeake Bay Crater, USA

Axel Wittmann, Ralf Thomas Schmitt, Lutz Hecht, David A. Kring, Wolf Uwe Reimold and Harold Povenmire
Petrology of impact melt rocks from the Chesapeake Bay Crater, USA (in The ICDP-USGS deep drilling project in the Chesapeake Bay impact structure; results from the Eyreville core holes, Gregory S. Gohn (editor), Christian Koeberl (editor), Kenneth G. Miller (editor) and Wolf Uwe Reimold (editor))
Special Paper - Geological Society of America (2009) 458: 377-396

Abstract

The Eyreville B drill core in the inner annular moat of the 85-km-diameter Chesapeake Bay impact structure recovered the first coherent impact melt volumes from within the crater as two bodies, 1 and 5.5 m thick. This study focuses on the petrogenesis of these well-preserved rocks. Mixing calculations reveal that the chemical composition of these melts can be modeled as a hybrid of approximately 40% sedimentary target and approximately 60% crystalline basement component. The melt rocks contain abundant lithic and mineral clasts that display all stages of shock metamorphism. Zircon clasts record the cooling of the melt from temperatures above 1700 degrees C to below 1200 degrees C within the first minutes after formation. Glassy melt with a peraluminous, rhyolitic composition that contains approximately 5 wt% water is preserved. This melt records a crystallization sequence of aluminum-rich orthopyroxene and hercynitic spinel, followed by plagioclase, titano-magnetite and cordierite, and late sanidine. Spherulitic aluminosilicate-SiO (sub 2) -cordierite aggregates that are comparable to buchites at temperatures below approximately 1465 degrees C complement this assemblage. Lack of hyaloclastic fragmentation suggests dry emplacement conditions. Complete cooling by conductive heat transfer took approximately 7 weeks and approximately 4 years for the 1-m- and the 5.5-m-thick melt bodies, respectively. Alteration stages below approximately 100 degrees C produced smectite, phillipsite, chalcedony, and a rare zeolite phase that is tentatively identified as terranovaite.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 458
Title: Petrology of impact melt rocks from the Chesapeake Bay Crater, USA
Title: The ICDP-USGS deep drilling project in the Chesapeake Bay impact structure; results from the Eyreville core holes
Author(s): Wittmann, AxelSchmitt, Ralf ThomasHecht, LutzKring, David A.Reimold, Wolf UwePovenmire, Harold
Author(s): Gohn, Gregory S.editor
Author(s): Koeberl, Christianeditor
Author(s): Miller, Kenneth G.editor
Author(s): Reimold, Wolf Uweeditor
Affiliation: Lunar and Planetary Institute, Houston, TX, United States
Affiliation: U. S. Geological Survey, Reston, VA, United States
Pages: 377-396
Published: 2009
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 978-0-8137-2458-4
References: 53
Accession Number: 2010-012505
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendix
Illustration Description: illus. incl. 4 tables
N37°19'00" - N37°19'00", W75°58'60" - W75°58'60"
Secondary Affiliation: University of Vienna, AUT, AustriaRutgers State University of New Jersey, USA, United StatesHumboldt University Berlin, DEU, Federal Republic of GermanyHumboldt University Berlin, DEU, Federal Republic of GermanyFlorida Institute of Technology, USA, United States
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: 201008
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