Hope Valley Alaskite Gneiss

Light-pink to gray, medium- to coarse-grained, locally porphyritic, variably lineated and foliated alaskitic gneiss, composed of microcline, quartz, albite or oligoclase, and minor magnetite, and locally biotite and muscovite. Lineation formed by rods of quartz. Locally contains quartz-sillimanite nodules.
State Connecticut
Name Hope Valley Alaskite Gneiss
Geologic age Proterozoic Z?
Lithologic constituents
Major
Metamorphic > GneissLight-pink to gray, medium- to coarse-grained, locally porphyritic, variably lineated and foliated alaskitic gneiss, composed of microcline, quartz, albite or oligoclase, and minor magnetite, and locally biotite and muscovite. Lineation formed by rods of quartz. Locally contains quartz-sillimanite nodules.
Comments Part of Eastern Uplands; Avalonian (Continental) Terrane; Avalonian Anticlinorium; Sterling Plutonic Group (Proterozoic Z?). Isotopic age of 630 Ma by U/Pb methods on zircon is reported by Zartman and Naylor (1984) from a sample in MA. Age of 601 +/-5 Ma by U/Pb methods on zircon is reported by Hermes and Zartman (1985) from a sample in RI (Wones and Goldsmith, 1991) per CT015.
References
NGMDB product
Counties New London - Tolland - Windham