|Name||Sharpners Pond Diorite|
Igneous > Plutonic > Granitic > TonaliteNon-foliated, medium-grained equigranular biotite-hornblende tonalite and diorite.
Igneous > Plutonic > Dioritic > DioriteNon-foliated, medium-grained equigranular biotite-hornblende tonalite and diorite.
|Comments||Part of Nashoba Zone (Silurian and Older Rocks). Sharpners Pond Diorite covers an area of about 150 sq km. Includes diorite, tonalite, and small amounts of granodiorite. Intrudes Nashoba and Marlboro Formations, and older gneissic phase of Andover Granite. Intruded by pegmatites, younger phase of Andover Granite, and biotite granite. Age is Silurian based on reliable U-Pb zircon date of 430 +/-5 Ma (Zartman and Naylor, 1984) (Wones and Goldsmith, 1991) per MA007.|
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.
Wones, D.R. and Goldsmith, Richard, 1991, Intrusive rocks of eastern Massachusetts, Chapter I, IN Hatch, N.L., Jr., ed., The bedrock geology of Massachusetts: U.S. Geological Survey Professional Paper, 1366-E-J, p. I1-I61.
|Counties||Essex - Middlesex|