Cape Ann Complex - Squam Granite

Fine- to medium-grained monzodiorite. Squam Granite, though included in the Cape Ann Complex of this report, is probably not genetically related to the Cape Ann Granite and the Beverly Syenite, the dominant lithological types of the Complex. The origin of the granitic melt of the Cape Ann was likely under water-deficient conditions, but the origin of the Squam Granite, described here as a two-feldspar ferrohornblende biotite granite, remains obscure (Hon and others, 1993).
State Massachusetts
Name Cape Ann Complex - Squam Granite
Geologic age Lower Silurian or Upper Ordovician
Lithologic constituents
Igneous > Plutonic > Dioritic > MonzodioriteFine- to medium-grained monzodiorite.
Comments Part of Milford-Dedham Zone (Tertiary and Older Rocks). Secondary unit description per MA020.

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., and Wones, D.R., 1983, Bedrock Geologic Map of Massachusetts: U.S. Geological Survey, Reston, VA, scale 1: 250,000.

Hon, Rudolph, Paige, M.L. and Loftenius, C.J., 1993, Petrogenesis of two diverse mid-Paleozoic complexes of eastern Massachusetts; A-type Cape Ann Granite and I-type Sharpners Pond Quartz Diorite, IN Cheney, J.T., and Hepburn, J.C., eds., Field trip guidebook for the northeastern United States; 1993 Boston GSA; Volume 2: University of Massachusetts, Geology Department Contribution, no. 67, Joint annual meeting of Geological Society of America, and New England Intercollegiate Geological Conference, 85th, Boston, MA, October 25-28, 1993, p. Q1-Q28.

NGMDB product
Counties Essex