|Name||alkali-feldspar granite of Cumberland|
|Geologic age||Devonian? or Mississippian?|
Igneous > Plutonic > Granitic > Alkali-feldspar-graniteGray to blue-gray. medium- to coarse-grained, equigranular to porphyritic alkali-feldspar granite (phenocrysts of perthite). Massive to locally foliated. Contains perthite, quartz, abundant accessory riebeckite and aegerine, and lesser astrophyllite, anegmatite, zircon, allanite, fluorite, and opaque minerals. Plagioclase is notably absent. Hypersolvus, strongly peralkaline granite.
|Comments||Part of Esmond-Dedham Subterrane (West Bay Area). Per printed map: age of rock based on radiometric data from RI005.|
Hermes, O.D. (comp.), Gromet, L.P. (comp.), Murray, D.P. (comp.), Hamidzada, N.A., Skehan, J.W., and Mosher, S., 1994, Bedrock geologic map of Rhode Island: Rhode Island Map Series No. 1, Kingston, Rhode Island, scale 1:100,000.
Hermes, O.D., and Zartman, R.E., 1985, Late Precambrian and Devonian plutonic terrane within the Avalon Zone of Rhode Island: Geological Society of America Bulletin, v. 96, p. 272-282.