Topsfield Granodiorite

Gray to gray-green, porphyritic granodiorite containing blue quartz; usually cataclastically foliated and altered. Intrudes Zrdi, Zv. Topsfield Granite occupies area of 80 sq km between Middleton and Newbury, eastern MA. Occurs as part of Dedham batholith. Composition ranges from granite to tonalite. Intrudes unnamed diorite and gabbro unit, and unnamed mafic and felsic metavolcanic rocks. Bounded on northwest by faults bordering Newbury and Middleton basins and by northwest extensions of Bloody Bluff (and Mystic?) faults, and on southeast by a splay(?) of Bloody Bluff fault. Probably overlain by Silurian and Devonian Newbury Volcanic Complex (Dennen, 1975), but contact is now a fault. Although not radiometrically dated, considered to be Proterozoic Z in age because it is similar in mineralogy to Dedham Granite and it intrudes Proterozoic Z mafic complex (Wones and Goldsmith, 1991).
State Massachusetts
Name Topsfield Granodiorite
Geologic age Proterozoic Z
Lithologic constituents
Major
Igneous > Plutonic > Granitic > GranodioriteGray to gray-green, porphyritic granodiorite containing blue quartz; usually cataclastically foliated and altered.
Comments Part of Milford-Dedham Zone (Tertiary and Older Rocks). Secondary unit description per MA007.
References
NGMDB product
Counties Essex