Petrographic and geochemical comparisons between the lower crystalline basement-derived section and the upper granite and amphibolite megablocks of the Eyreville-B core, Chesapeake Bay impact structure, USA.
- Autor(en)
- Gabrielle Townsend, Roger L. Gibson, J. Wright Horton, Jr., Wolf Uwe Reimold, Ralf Thomas Schmitt, Katerina Bartosova
- Abstrakt
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.
- Organisation(en)
- Department für Lithosphärenforschung
- Externe Organisation(en)
- University of Witwatersrand, United States Geological Survey, Humboldt-Universität zu Berlin
- Journal
- Geological Society of America. Special Papers
- Band
- 458
- Seiten
- 255-275
- Anzahl der Seiten
- 21
- ISSN
- 0072-1077
- DOI
- https://doi.org/10.1130/2009.2458(13)
- Publikationsdatum
- 2009
- Peer-reviewed
- Ja
- ÖFOS 2012
- 105101 Allgemeine Geologie
- Link zum Portal
- https://ucris.univie.ac.at/portal/de/publications/petrographic-and-geochemical-comparisons-between-the-lower-crystalline-basementderived-section-and-the-upper-granite-and-amphibolite-megablocks-of-the-eyrevilleb-core-chesapeake-bay-impact-structure-usa(d10f814a-9967-47b6-87db-c2f75d2bbf0b).html