Structural and lithologic relationships in the Raleigh metamorphic belt near Lake Gaston, Virginia and North Carolina
- Geological Survey, Reston, VA (United States)
Preliminary results of mapping along the NC-VA State line eastward from the Buggs Is. granite about 35 km to the Hollister fault zone yield new information about structural and lithologic relationships in the Raleigh metamorphic belt. The layered rocks are predominantly two-mica schist and sillimanite-mica schist interlayered with lesser amounts of muscovite-biotite-quartz-plagioclase paragneiss and hornblende-biotite gneiss. The overall rock assemblage here differs from those along strike near Goochland, VA, and near Raleigh, NC, and is reminiscent of an accretionary complex. Bodies of foliated to massive two-mica granite are abundant and commonly contain garnet. One body, the Wise pluton, contains a N--NW-striking, steeply dipping foliation, but the intrusive contact of the granite with the metamorphic rocks is discordant. The most prominent regional foliation, parallel to transposed compositional layering, is axial planar to relict, reclined, isoclinal outcrop-scale folds. This foliation is folded at both outcrop and map scale by open folds plunging NW and SW. Some foliated, two-mica granite sheets are warped by the open folds; other bodies of similar granite cut across these folds. Sillimanite needles are locally aligned with the hinges of some of the open folds, an indication that sillimanite-muscovite-grade metamorphism was associated with this folding event. The two-mica granites resemble other late Paleozoic granites in the region. If these granites prove to be late Paleozoic (Alleghanian), then the deformation and metamorphism that produced sillimanite along the hingelines also must be Alleghanian. Relatively younger, NW- and SE-plunging crenulations and chevron folds are associated with a crenulation cleavage that dips steeply NE or SW. Sillimanite needles are folded by these crenulations. Crenulation cleavage and related folds may have developed in response to transpression of these rocks between the dextral Lake Gordon and Hollister mylonite zones.
- OSTI ID:
- 6077935
- Report Number(s):
- CONF-9304188-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:4; Conference: 42. annual Geological Society of America (GSA) Southeastern Section meeting, Tallahassee, FL (United States), 1-2 Apr 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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