monchiquite (RIJm;0)

monchiquite

Dark-gray to greenish-black, fine-grained lamprophyre dikes, with flow-banding parallel to contacts; contains microphenocrysts of titaniferous augite, olivine, kaersutite, phlogopite, apatite, and opaque minerals enclosed in a matrix of analcite and calcite; ocellar texture locally developed. Locally abundant megacrysts (up to 5 cm) of pyroxene, and rounded xenoliths (up to 8 cm) composed of olivine, enstatite, chrome-diopside, and chrome-spinel.

State	Rhode Island
Name	monchiquite
Geologic age	Jurassic
Lithologic constituents	Major Igneous > Hypabyssal > Lamprophyre (Dike or sill)
Comments	Part of Avalon Terrane. Per printed map: age of rock based on radiometric data from RI006.
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. Hermes, O.D., Rao, J.M., Dickenson, M.P., and Pierce, T.A., 1984, A transitional alkalic dolerite dike suite of Mesozoic age in southeastern New England: Contributions to Mineralogy and Petrology, v. 86, p. 386-397.
NGMDB product	NGMDB product page for 19719
Counties	Washington

monchiquite

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., Rao, J.M., Dickenson, M.P., and Pierce, T.A., 1984, A transitional alkalic dolerite dike suite of Mesozoic age in southeastern New England: Contributions to Mineralogy and Petrology, v. 86, p. 386-397.