Narragansett Pier Plutonic Suite

Narragansett Pier Plutonic Suite - granite

Dark-pink to pale-gray, medium-grained equigranular granite, with lesser granodiorite and quartz monzonite. Composed of microcline, oligoclase, quartz, and accessory biotite, magnetite, ilmenite, apatite, sphene, zircon, monazite, apatite, and allanite; muscovite and garnet locally present; secondary chlorite and calcite. Mainly massive, but locally exhibits faint flow foliation. Cut locally by abundant pegmatite, aplite, and composite aplite-pegmatite of mineralogy similar to the host granite. Unit is a 5 km by 40 km batholith that underlies the southern coast of RI. Intrusion during the latter part of Alleghanian deformation of the Narragansett Basin is indicated by its Permian age, rapid cooling, and field relations. The age of the Narragansett Pier is well constrained by several factors. Brown and others (1978) report a Pennsylvanian fossil contained in an inclusion in the pluton. Radiometric ages of 276 Ma by Kocis and others (1978), 272+/-4 Ma by Hermes and others (1981), and 273+/-2 Ma by Zartman and Hermes (1987) are consistently Early Permian. Structural studies by Mosher (1983) and Reck and Mosther (1988) indicate that intrusion began during the third period of deformation in the Narragansett Basin. Argon release patterns (Dallmeyer, 1982) indicate that the granite and intruded sediments had cooled below argon retention temperatures of hornblende by the Late Permian and of biotite by the Early Triassic. Intruded by the Westerly Granite, which has been radiometrically dated at 276+/-7 Ma. The two granites are probably genetically related based on similarities in age, mineralogy, and geochemistry (Hozik, 1992).

State	Rhode Island
Name	Narragansett Pier Plutonic Suite - granite
Geologic age	Permian
Lithologic constituents	Major Igneous > Plutonic > Granitic > Granitedark-pink to pale-gray, medium-grained equigranular granite; Composed of microcline, oligoclase, quartz, and accessory biotite, magnetite, ilmenite, apatite, sphene, zircon, monazite, apatite, and allanite; muscovite and garnet locally present; secondary chlorite and calcite. Mainly massive, but locally exhibits faint flow foliation. Minor Igneous > Plutonic > Granitic > Granodioritewith lesser granodiorite and quartz monzonite Igneous > Plutonic > Syenitic > Quartz-monzonitewith lesser granodiorite and quartz monzonite Incidental Igneous > Plutonic > Granitic > Leucocratic-granitic > PegmatiteCut locally by abundant pegmatite, aplite, and composite aplite-pegmatite of mineralogy similar to the host granite. Igneous > Plutonic > Granitic > Leucocratic-granitic > ApliteCut locally by abundant pegmatite, aplite, and composite aplite-pegmatite of mineralogy similar to the host granite.
Comments	Part of Avalon Terrane Narragansett Pier Plutonic Suite - intrudes both Hope Valley and Esmond-Dedham subterranes (e.g., stitching pluton). Contains abundant veins of pegmatite too small to be mapped individually. Secondary unit description per RI003. Per printed map: age of rock based on radiometric data from RI007 and RI008.
References	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. Hozik, M.J., 1992, Tectonic implications of the brittle fracture history of the Permian Narragansett Pier Granite, Rhode Island, IN Bartholomew, M.J., and others, eds., Basement tectonics 8; Characterization and comparison of ancient and Mesozoic continental margins; proceedings of the eighth international conference on basement tectonics: International Conference on Basement Tectonics Proceedings, no. 8, 8th International Conference, Butte, MT, August, 1988, p. 503-525. Kocis, D.E., 1981, Petrology of the Narragansett Pier Granite and associated country rocks near Narragansett Bay: unpublished MS thesis, University of Rhode Island, Kingston, 132 p. Zartman, R.E., and Hermes, O.D., 1987, Archean inheritance in zircon from late Paleozoic granites from the Avalon zone of southeastern New England: an African connection: Earth and Planetary Science Letters, v. 82, p. 305-315.
NGMDB product	NGMDB product page for 19719
Counties	Washington

Narragansett Pier Plutonic Suite - granite

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.

Kocis, D.E., 1981, Petrology of the Narragansett Pier Granite and associated country rocks near Narragansett Bay: unpublished MS thesis, University of Rhode Island, Kingston, 132 p.

Zartman, R.E., and Hermes, O.D., 1987, Archean inheritance in zircon from late Paleozoic granites from the Avalon zone of southeastern New England: an African connection: Earth and Planetary Science Letters, v. 82, p. 305-315.