Evolution of crystalline target rocks and impactites in the Chesapeake Bay impact structure, ICDP-USGS Eyreville B core

Horton, J. Wright; Kunk, Michael J.; Belkin, Harvey E.; Aleinikoff, John N.; Jackson, J. C.; Chou, I-Ming

doi:10.1130/2009.2458(14)

Cited by 14 publications

(65 citation statements)

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“…Zeolites (phillipsite, heulandite, and mordenite) were reported by Horton et al. (2009) filling the voids of the impact melt rocks and altering melt particles in suevite from the Eyreville B drill core.…”

Section: Discussionmentioning

confidence: 99%

“…The melt‐poor bottom part of the impact breccia sequence with larger basement‐derived clasts and gneiss blocks, and generally scarce melt particles, with no evidence of aerial transport, is thought to be of ground‐surge origin (Bartosova et al. 2009a; Horton et al. 2009b).…”

Section: Introductionmentioning

confidence: 99%

“…Toward the top of the impact breccia section the proportion of fallback material increases and the uppermost section, with small clasts of all different types and abundant melt particles, some of which are shard‐like, is clearly a fallback material (Bartosova et al. 2009a; Horton et al. 2009b; Wittmann et al.…”

Section: Introductionmentioning

confidence: 99%

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Melt in the impact breccias from the Eyreville drill cores, Chesapeake Bay impact structure, USA

Bartošová

Hecht

Koeberl

et al. 2011

Meteorit & Planetary Scien

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Abstract– The center of the 35.3 Ma Chesapeake Bay impact structure (85 km diameter) was drilled during 2005/2006 in an ICDP–USGS drilling project. The Eyreville drill cores include polymict impact breccias and associated rocks (1397–1551 m depth). Tens of melt particles from these impactites were studied by optical and electron microscopy, electron microprobe, and microRaman spectroscopy, and classified into six groups: m1—clear or brownish melt, m2—brownish melt altered to phyllosilicates, m3—colorless silica melt, m4—melt with pyroxene and plagioclase crystallites, m5—dark brown melt, and m6—melt with globular texture. These melt types have partly overlapping major element abundances, and large compositional variations due to the presence of schlieren, poorly mixed melt phases, partly digested clasts, and variable crystallization and alteration. The different melt types also vary in their abundance with depth in the drill core. Based on the chemical data, mixing calculations were performed to determine possible precursors of these melt particles. The calculations suggest that most melt types formed mainly from the thick sedimentary section of the target sequence (mainly the Potomac Formation), but an additional crystalline basement (schist/gneiss) precursor is likely for the most abundant melt types m2 and m5. Sedimentary rocks with compositions similar to those of the melt particles are present among the Eyreville core samples. Therefore, sedimentary target rocks were the main precursor of the Eyreville melt particles. However, the composition of the melt particles is not only the result of the precursor composition but also the result of changes during melting and solidification, as well as postimpact alteration, which must also be considered. The variability of the melt particle compositions reflects the variety of target rocks and indicates that there was no uniform melt source. Original heterogeneities, resulting from melting of different target rocks, may be preserved in impactites of some large impact structures that formed in volatile‐rich targets, because no large melt body exists, in which homogenization would have taken place.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Melt in the impact breccias from the Eyreville drill cores, Chesapeake Bay impact structure, USA

Bartošová

Hecht

Koeberl

et al. 2011

Meteorit & Planetary Scien

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“…They are often associated with sphalerite, sphene, hematite, or ilmenite (Figure a). Hematite is prevalent in the altered samples and is a product of magnetite alteration [ Horton et al ., , , ] (and own observations). Despite some differences in their pre‐impact alteration state, all these magnetite grains show a similar magnetic behavior.…”

Section: Microstructural Observations and Magnetic Measurementsmentioning

confidence: 99%

Origin of two Verwey transitions in different generations of magnetite from the Chesapeake Bay impact structure, USA

Mang

Kontny

2013

JGR Solid Earth

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[1] We observed two different Verwey transition temperatures in fragments of crystalline basement rocks and impact sediments from the Chesapeake Bay impact structure, USA. Our study aims to the question if this feature can be used as shock indicator in impact craters. We distinguished three generations of magnetite. (1) Primary magnetite in crystalline basement rocks has average grain sizes up to several hundreds of micrometers and shows a regular T V at ≈ 121 K. (2) Shocked magnetite occurs in fragments of crystalline basement rocks and also in the suevite and impact breccia. These magnetites show two Verwey transitions-a regular one and a "low-temperature transition" (LT V ) at around 89 K. LT V is related to a small grain size fraction, whereas a larger grain size fraction (some hundreds of micrometers) causes the regular T V . The small grain size fraction contains a distinctly higher amount of superficially oxidized material due to the high surface/volume ratio, which causes a decrease of the Verwey transition temperature (LT V ). (3) A secondary magnetite generation shows also two Verwey transition temperatures, one at 121 K and a LT V range between 91 and 105 K. The LT V in this generation is also linked to thin oxidized surface layers. This study shows that especially the Verwey transition temperature of small magnetite grains reacts very sensitively to surface oxidation and can therefore not be used as a reliable pressure indicator for impact structures on Earth.Citation: Mang, C., and A. Kontny (2013), Origin of two Verwey transitions in different generations of magnetite from the Chesapeake Bay impact structure, USA,

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“…Complications can occur in impactites that formed in marine targets, with resurge deposits being swept back into the crater and, even, further redeposition by water oscillations within the crater (e.g. Ormö et al, 2007;Horton et al, 2008Horton et al, ,2009). parautochthonous target rocks of the crater floor have been identified in breccia dikes, indicating the downward sense of transportation (e.g.…”

Section: Proximal Varietiesmentioning

confidence: 99%

Impactites: Their Characteristics and Spatial Distribution

Grieve

Therriault

2012

Impact Cratering

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Evolution of crystalline target rocks and impactites in the Chesapeake Bay impact structure, ICDP-USGS Eyreville B core

Cited by 14 publications

References 0 publications

Melt in the impact breccias from the Eyreville drill cores, Chesapeake Bay impact structure, USA

Melt in the impact breccias from the Eyreville drill cores, Chesapeake Bay impact structure, USA

Origin of two Verwey transitions in different generations of magnetite from the Chesapeake Bay impact structure, USA

Impactites: Their Characteristics and Spatial Distribution

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