Dioritic phase [of Preston Gabbro]

Medium- to dark-gray, streaked or speckled, medium-grained diorite and quartz diorite, gneissic where sheared near contact, composed of plagioclase, hornblende, and biotite, and locally quartz and relic pyroxene.
State Connecticut
Name Dioritic phase [of Preston Gabbro]
Geologic age Middle Ordovician or older
Lithologic constituents
Major
Igneous > Plutonic > Dioritic > Quartz-dioriteMedium- to dark-gray, streaked or speckled, medium-grained diorite and quartz diorite, gneissic where sheared near contact, composed of plagioclase, hornblende, and biotite, and locally quartz and relic pyroxene.
Igneous > Plutonic > Dioritic > DioriteMedium- to dark-gray, streaked or speckled, medium-grained diorite and quartz diorite, gneissic where sheared near contact, composed of plagioclase, hornblende, and biotite, and locally quartz and relic pyroxene.
Incidental
Metamorphic > Gneissgneissic where sheared near contact
Comments Part of Eastern Uplands; Iapetus (Oceanic) Terrane - Merrimack Synclinorium
References

Rodgers, John, compiler, 1985, Bedrock Geological Map of Connecticut: Connecticut Geological and Natural History Survey, Hartford, Connecticut, 2 sheets, scale 1:125,000.

NGMDB product
Counties New London