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Porphyritic granite

Porphyritic granite - Gray to gray-green, seriate to porphyritic biotite granite containing clots and streaks of biotite, epidote, and sphene. Mafic inclusions common. Gneissic in New Bedford area. Intrudes Zgs.
StateMassachusetts
NamePorphyritic granite
Geologic ageProterozoic Z
Original map labelZpgr
CommentsPart of Milford-Dedham Zone (Tertiary and Older Rocks)
Primary rock typegranite
Secondary rock type
Other rock types
Lithologic constituents
Major
Igneous > Plutonic > Granitic > GraniteGray to gray-green, seriate to porphyritic biotite granite containing clots and streaks of biotite, epidote, and sphene. Mafic inclusions common. Gneissic in New Bedford area.
Map references
Unpublished Digital Geologic Map of Massachusetts received from Rudi Hon at Boston College in 1998.
Unit references
Zen, E-An (ed.), Goldsmith, R. (comp.), Ratcliffe, N.M. (comp.), Robinson, P. (comp.), Stanley, R.S. (comp.), Hatch, N.L., Jr., Shride, A.F., Weed, E.G.A., Wones, D.R., 1983, Bedrock Geologic Map of Massachusetts: U.S. Geological Survey, Reston, VA, scale 1: 250,000.
Geographic coverageBristol - Plymouth

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