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Porphyry (dacite or rhyolite)

Porphyry (dacite or rhyolite) - Light-colored, very fine grained, massive porphyry with phenocrysts of quartz, feldspar, and biotite; muscovite and accessory fluorite in groundmass.
State Connecticut
Name Porphyry (dacite or rhyolite)
Geologic age Permian
Comments Part of Central Lowlands; Iapetus (Oceanic) Terrane - Connecticut Valley Synclinorium
Primary rock type rhyolite
Secondary rock type dacite
Other rock types
Lithologic constituents
Major
Igneous > Volcanic > Felsic-volcanic > DacitePorphyry (dacite or rhyolite) - Light-colored, very fine grained, massive porphyry with phenocrysts of quartz, feldspar, and biotite; muscovite and accessory fluorite in groundmass.
Igneous > Volcanic > Felsic-volcanic > RhyolitePorphyry (dacite or rhyolite) - Light-colored, very fine grained, massive porphyry with phenocrysts of quartz, feldspar, and biotite; muscovite and accessory fluorite in groundmass.
Map references
Connecticut Geological and Natural History Survey, DEP, in cooperation with the U.S. Geological Survey, 2000, Bedrock Geology of Connecticut, data format: shapefile, file name: bedrock, downloaded from: http://magic.lib.uconn.edu/cgi-bin/MAGIC_DBsearch2.pl?Geography=37800&Loc=0000 on 9/18/2003, scale 1:50,000.
Unit references
Rodgers, John, compiler, 1985, Bedrock Geological Map of Connecticut: Connecticut Geological and Natural History Survey, Hartford, Connecticut, 2 sheets, scale 125,000.
Counties Fairfield