Branch Brook dike and sill complex - South Pond facies

Light- to dark-gray and steel-blue to apple-green, fine- grained hornblende-chlorite-plagioclase amphibolite, locally containing significant calcite and pyrite and interlayered felsic layers of metatrondhjemite or metadacite. Similar in part to the mixed gneiss facies (Onbm). North River Igneous Suite (502±4 Ma to 471.4±3.7 Ma): collection of metatonalite, metatrondhjemite, and metabasalt occurring as intrusive dikes, sills, and small stocks, and possibly meta-andesite and metadacitic tuffs. Correlative with extrusive dacitic metavolcanic and meta-andesitic rocks of the Moretown and Cram Hill Formations. Coextensive in part with igneous rocks of the Hawley Formation of Massachusetts. Part of the Volcanic-arc intrusive and volcanic rocks of the North River Igneous Suite of the Rowe-Hawley zone. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
State Vermont
Name Branch Brook dike and sill complex - South Pond facies
Geologic age Ordovician and Late Cambrian
Lithologic constituents
Major
Metamorphic > AmphiboliteLight- to dark-gray and steel-blue to apple-green, fine- grained hornblende-chlorite-plagioclase amphibolite.
Minor
Metamorphic > Metaigneous > Metaintrusive > Metatonalite > MetatrondhjemiteInterlayered felsic layers of metatrondhjemite or metadacite.
Metamorphic > Metaigneous > Metavolcanic > MetadaciteInterlayered felsic layers of metatrondhjemite or metadacite.
Comments Original unit label is Onbs; but age is listed as Ordovician and Late Cambrian. Age confirmed by U-Pb age in unit description. Changed unit label to OCAnbs.
References
NGMDB product
Counties Windham