West Halifax Trondhjemite

Cream-colored, light-gray- to whitish-gray-weathering, coarse-grained chlorite-biotite-muscovite-quartz-plagioclase (±garnet ±hornblende) metatrondhjemite and metatonalite; southern lens near Massachusetts State line is coextensive with trondhjemite in the Hawley Formation. 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 West Halifax Trondhjemite
Geologic age Ordovician and Late Cambrian
Lithologic constituents
Major
Metamorphic > Metaigneous > Metaintrusive > MetatonaliteCream-colored, light-gray- to whitish-gray-weathering, coarse-grained chlorite-biotite-muscovite-quartz-plagioclase (±garnet ±hornblende) metatrondhjemite and metatonalite.
Metamorphic > Metaigneous > Metaintrusive > Metatonalite > MetatrondhjemiteCream-colored, light-gray- to whitish-gray-weathering, coarse-grained chlorite-biotite-muscovite-quartz-plagioclase (±garnet ±hornblende) metatrondhjemite and metatonalite.
Comments Original unit label is Ontw; but age is listed as Ordovician and Late Cambrian. Age confirmed by U-Pb age in unit description. Changed unit label to OCAntw.
References
NGMDB product
Counties Windham