Biotite tonalite gneiss

Predominantly chalky-white-weathering, massive biotite tonalite gneiss. Passes laterally into white, fine-grained trondhjemitic aplite near contacts with larger screens of paragneiss. U-Pb zircon Thermal Ionization Mass Spectrometry (TIMS) age of 1329±37 Ma (McLelland and Chiarenzelli, 1990) obtained from exposure 1.5 km west of Austin Hill on the west side of South Bay, west of Whitehall, N.Y. Contains lenses and screens of rusty sulfidic garnet-biotite-feldspar-quartz schist, dark-gray garnet-feldspar quartzite, and calc-silicate gneiss on south end of Austin Hill. Unit interpreted as intrusive into some paragneiss units that are here older than 1328±32 Ma (McLelland and Chiarenzelli, 1990). Rocks of the Adirondacks in Vermont and in the Whitehall, N.Y., area.
State Vermont
Name Biotite tonalite gneiss
Geologic age Middle Mesoproterozoic
Lithologic constituents
Major
Metamorphic > Metasedimentary > ParagneissPredominantly chalky-white-weathering, massive biotite tonalite gneiss.
Minor
Igneous > Plutonic > Granitic > Leucocratic-granitic > AplitePasses laterally into white, fine-grained trondhjemitic aplite near contacts with larger screens of paragneiss.
References
NGMDB product
Counties Rutland