Mineral Resources On-Line Spatial Data
Mineral Resources > Online Spatial Data > Geology > by state > Massachusetts
|Geologic age||Proterozoic Z|
|Original map label||Zdngr|
|Comments||Part of Milford-Dedham Zone (Tertiary and Older Rocks) Secondary unit description per MA018. Proterozoic Z age of Dedham is based on the following isotopic dates: . 1. 630 +/-15 Ma by U/Pb methods on zircon (Zartman and Naylor, 1984) from Dedham Granite. 2. 595 +/-17 Ma by Rb/Sr whole rock methods (Kovach and others, 1977) from Dedham Granite north of Boston. 3. 640 +/-14 Ma by K/Ar methods on hornblende (Zartman and Naylor, 1984) per MA007.|
|Primary rock type||granite|
|Secondary rock type||granodiorite|
|Other rock types|
Igneous > Plutonic > Granitic > GranodioriteGray granite to granodiorite more mafic than Zdgr north of Boston.
Igneous > Plutonic > Granitic > GraniteGray granite to granodiorite more mafic than Zdgr north of Boston.
Unpublished Digital Geologic Map of Massachusetts received from Rudi Hon at Boston College in 1998.
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.
|Geographic coverage||Essex - Middlesex|
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