| Abstract: | The Eyreville B core from the Chesapeake Bay impact structure, Virginia, USA, contains a lower basement-derived section (1551.19 m to 1766.32 m deep) and two megablocks of dominantly (1) amphibolite (1376.38 m to 1389.35 m deep) and (2) granite (1095.74 m to 1371.11 m deep), which are separated by an impactite succession. Metasedimentary rocks (muscovite-quartz-plagioclase-biotite-graphite ± fibrolite ± garnet ± tourmaline ± pyrite ± rutile ± pyrrhotite mica schist, hornblende-plagioclase-epidote-biotite-K-feldspar-quartz-titanite-calcite amphibolite, and vesuvianite-plagioclase-quartz-epidote calc-silicate rock) are dominant in the upper part of the lower basement-derived section, and they are intruded by pegmatitic to coarse-grained granite (K-feldspar-plagioclase-quartz-muscovite ± biotite ± garnet) that increases in volume proportion downward. The granite megablock contains both gneissic and weakly or nonfoliated biotite granite varieties (K-feldspar-quartz-plagioclase-biotite ± muscovite ± pyrite), with small schist xenoliths consisting of biotite-plagioclase-quartz ± epidote ± amphibole. The lower basement-derived section and both megablocks exhibit similar middle- to upper-amphibolite-facies metamorphic grades that suggest they might represent parts of a single terrane. However, the mica schists in the lower basement-derived sequence and in the megablock xenoliths show differences in both mineralogy and whole-rock chemistry that suggest a more mafic source for the xenoliths. Similarly, the mineralogy of the amphibolite in the lower basement-derived section and its association with calc-silicate rock suggest a sedimentary protolith, whereas the bulk-rock and mineral chemistry of the megablock amphibolite indicate an igneous protolith. The lower basement-derived granite also shows bulk chemical and mineralogical differences from the megablock gneissic and biotite granites. |
| Genre: | Article |
| ProdID: | 70003483 |
| Citation Author: | Townsend, Gabrielle N.; Gibson, Roger L.; Horton, J. Wright Jr.; Reimold, Wolf Uwe; Schmitt, Ralf T.; Bartosova, Katerina |
| Citation Contributing Office: | Eastern Geology and Paleoclimate Science Center |
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| Citation End Page: | 275 |
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| Citation Language: | English |
| Citation Larger Work Title: | Special Paper of the Geological Society of America |
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| Citation Phsyical Description: | 21 p. |
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| Citation Publisher: | Geological Society of America |
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| Citation Search Results Text: | Petrographic and geochemical comparisons between the lower crystalline basement-derived section and the granite megablock and amphibolite megablock of the Eyreville-B core, Chesapeake Bay impact structure; 2009; Article; Journal; Special Paper of the Geological Society of America; Townsend, Gabrielle N.; Gibson, Roger L.; Horton, J. Wright Jr.; Reimold, Wolf Uwe; Schmitt, Ralf T.; Bartosova, Katerina |
| Citation Start Page: | 255 |
| Citation Volume: | 458 |
| Citation Year: | 2009 |
| Type: | citation/reference |
| Text: | Petrographic and geochemical comparisons between the lower crystalline basement-derived section and the granite megablock and amphibolite megablock of the Eyreville-B core, Chesapeake Bay impact structure; 2009; Article; Journal; Special Paper of the Geological Society of America; Townsend, Gabrielle N.; Gibson, Roger L.; Horton, J. Wright Jr.; Reimold, Wolf Uwe; Schmitt, Ralf T.; Bartosova, Katerina |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (INDEX PAGE): | http://specialpapers.gsapubs.org/content/458/255.abstract |
| Date Other: | Wed, 5 Oct 2011 00:00 -0500 |
| Publisher: | Geological Society of America |
