stripes
In the northeastern corner of Rhode Island peralkaline granites occur which have been correlated with the Quincy granite lying some 40 km to the northeast. They comprise microperthite, quartz, up to 10% sodic amphibole and 7% aegirine; patches and veins of purple fluorite are common. They are associated with a granite porphyry in which fluorite is also abundant. Amongst the East Greenwich Group of granites in the East Greenwich Quadrangle of central Rhode Island, the Cowesett granite contains sodic pyroxene and amphibole, while the Scituate granite gneiss lying north and west of the East Greenwich Group also sometimes has a peralkaline mineralogy and chemistry.
HERMES, O.D., GROMET, L.P. and ZARTMAN, R.E. 1981. Zircon geochronology and petrology of plutonic rocks in Rhode island. In J.C. Boothroyd and O.D.Hermes (Eds). Guidebook, 73rd Annual Meeting of the New England Intercollegiate Geologic Conference: 315-38.
LYONS, P.C. and KRUEGER, H.W. 1976. Petrology, chemistry, and age of the Rattlesnake pluton and implications for other alkalic granite plutons of southern New England. Memoir, Geological Society of America, 146: 71-102.
QUINN, A.W. 1971. Bedrock geology of Rhode Island. Bulletin, United States Geological Survey, 1295: 1-68