Cape Ann Complex (MASOcsm;0)

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
Geologic age	Lower Silurian or Upper Ordovician
Original map label	SOcsm
Comments	Part of Milford-Dedham Zone (Tertiary and Older Rocks) Secondary unit description per MA020.
Primary rock type	monzodiorite
Secondary rock type
Other rock types
Lithologic constituents	Major Igneous > Plutonic > Dioritic > MonzodioriteFine- to medium-grained monzodiorite.
Map references	Unpublished Digital Geologic Map of Massachusetts received from Rudi Hon at Boston College in 1998.
Unit references	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., 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.
Geographic coverage	Essex