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A petrographic and fluid inclusion assessment of hydrothermal alteration of some impactites and crystalline rocks in the Chesapeake Bay impact structure, ICDP-USGS Eyreville B core

David A. Vanko
A petrographic and fluid inclusion assessment of hydrothermal alteration of some impactites and crystalline rocks in the Chesapeake Bay impact structure, ICDP-USGS Eyreville B core (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: 543-557

Abstract

Core samples from the International Continental Scientific Drilling Program (ICDP)-U.S Geological Survey (USGS) Eyreville B core, located in the central crater of the Chesapeake Bay impact structure, were studied to determine the degree to which postimpact hydrothermal activity is recorded in secondary minerals and fluid inclusions. The Chesapeake Bay impact event occurred approximately 35 Ma ago on the siliciclastic continental shelf of eastern North America, in up to several hundred meters of water. The combination of hot materials, such as impact melts and suevite breccias, with overlying crater-fill material and seawater is hypothesized to have led to postimpact hydrothermal circulation. Secondary minerals are distinguished from pre-impact minerals by textural features such as the presence or absence of shock metamorphic effects. Minerals in veins and cavities that are shown to have formed after the impact include secondary calcite, chalcedony, phillipsite, clinoptilolite-heulandite, mordenite, and montmorillonite. Some secondary calcite contains liquid-only fluid inclusions with trapping temperatures constrained to be less than or equal to approximately 50 degrees C. Salinities of the inclusion fluids are mostly around 4.3+ or -1 wt% NaCl equivalent, or approximately 43+ or -10 g/L total dissolved solids. This salinity is similar to that of the anomalously saline groundwater that currently exists within the crater-fill material, and that could be relict brine that originated just after the impact.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 458
Title: A petrographic and fluid inclusion assessment of hydrothermal alteration of some impactites and crystalline rocks in the Chesapeake Bay impact structure, ICDP-USGS Eyreville B core
Title: The ICDP-USGS deep drilling project in the Chesapeake Bay impact structure; results from the Eyreville core holes
Author(s): Vanko, David A.
Author(s): Gohn, Gregory S.editor
Author(s): Koeberl, Christianeditor
Author(s): Miller, Kenneth G.editor
Author(s): Reimold, Wolf Uweeditor
Affiliation: Towson University, Department of Physics, Astronomy and Geosciences, Towson, MD, United States
Affiliation: U. S. Geological Survey, Reston, VA, United States
Pages: 543-557
Published: 2009
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 978-0-8137-2458-4
References: 42
Accession Number: 2010-012511
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: NSF Grant MRI-0421141
Illustration Description: illus. incl. 1 plate, 1 table, geol. sketch map
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 Germany
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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