Rhyolite and dacite domes and flows and small hypabyssal intrusive bodies

Mostly light-gray to red, dense, flow-banded, nonporphyritic and porphyritic rhyolite and dacite in nested domes, small intrusive bodies, and related flows. Includes some near-vent breccias, pumice-lapilli tuffs, and coarse pumicites. Commonly associated with mercury mineralization. Includes several small hypabyssal intrusions of diorite, granodiorite, and quartz monzonite exposed in Paisley Hills of Lake County (Muntzert, 1969; Muntzert and Field, 1968). In many places represents vents for lava flows and tuff of unit Tsf
State Oregon
Name Rhyolite and dacite domes and flows and small hypabyssal intrusive bodies
Geologic age Late Eocene to Miocene
Lithologic constituents
Major
Igneous > Volcanic > Felsic-volcanic > Dacite (Dome, Flow, Pyroclastic-air fall)
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Dome, Flow, Pyroclastic-air fall)Also containsd acite, diorite, granodiorite, and quartz monzonite
Minor
Igneous > Hypabyssal > Felsic-hypabyssal > Hypabyssal-dacite (Stock or pipe)
Igneous > Hypabyssal > Felsic-hypabyssal (Pluton)
Igneous > Hypabyssal > Felsic-hypabyssal > Hypabyssal-rhyolite (Stock or pipe)
References

Walker, G.W. and MacLeod, N.S., 1991, Geologic map of Oregon: U.S. Geological Survey, scale 1:500,000.

Ferns, M.L., Brooks, H.C., Evans, J.G., and Cummings, M.L., 1993b, Geologic map of the Vale 30 x 60 minute quadrangle, Malheur County Oregon: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-77, scale 1:100,000.

Swanson, D.A., 1969a, Reconnaissance geologic map of the east half of the Bend quadrangle, Crook, Wheeler, Jefferson, Wasco, , and Deschutes Counties, Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-568, scale 1:250,000.

https://pubs.er.usgs.gov/publication/i568

Walker, G.W., 1977, Geologic map of Oregon east of the 121st meridian: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-902, scale 1:500,000.

https://pubs.er.usgs.gov/publication/i902

Robinson, P.T., 1975, Reconnaissance geologic map of the John Day Formation in the southwestern part of the Blue Mountains and adjacent areas, north-central Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-872, scale 1:125,000.

https://pubs.er.usgs.gov/publication/i872

Muntzert, J.K., 1969, Geology and mineral deposits of the Bratain district, Lake County, Oregon: Corvallis, Oregon State University, master's thesis, 70 p.

Muntzert, J.K. and Field, C.W., 1968, Geology and mineral deposits of the Brattain district, Lake County, Oregon [abs.]: Geological Society of America Special Paper 121, p. 616-617.

Brooks, H.C. and Ferns, M.L., 1979, Geologic map of the Bullrun Rock quadrangle, Baker and Grant Counties, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-79-6, scale 1:24,000.

Evans, J.G., 1996, Geologic map of the Monument Peak quadrangle, Malheur County, Oregon: U.S. Geological Survey Miscellaneous Field Studies Map MF-2317, scale 1:24,000.

https://pubs.er.usgs.gov/publication/mf2317

Brooks, H.C., Ferns, M.L., Nusbaum, R.L., and Kovich, P.M., 1979, Geologic map of the Rastus Mountain quadrangle, Baker and Grant Counties, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-79-7, scale 1:24,000.

Ferns, M.L. and Gilbert, Deborah, 1992, Preliminary geologic map of the Rockville quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-92-12, scale 1:24,000.

Vander Meulen, D.B., Rytuba, J.J., Grubensky, M.J., and Goeldner, C.A., 1987, Geologic map of the Bannock Ridge 7.5' quadrangle, Malheur County, Oregon: U.S. Geological Survey Miscellaneous Field Studies Map MF-1903A, scale 1:24,000.

https://pubs.er.usgs.gov/publication/mf1903

Vander Meulen, B.B., Rytuba, J.J., Grubensky, M.J., Vercoutere, T.L., and Minor, S.A., 1987, Geologic map of the Pelican Point quadrangle, Malheur County, Oregon: U.S. Geological Survey Miscellaneous Field Studies Map MF-1904, scale 1:24,000.

https://pubs.er.usgs.gov/publication/mf1904

Vander Meulen, D.B., Rytuba, J.J., Minor, S.A., and Harwood, C.S., 1989, Preliminary geologic map of the Three Fingers Rock quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 89-344, scale 1:24,000.

https://pubs.er.usgs.gov/publication/ofr89344

Vander Meulen, D.B., Rytuba, J.J., Vercoutere, T.L., and Minor, S.A., 1987, Geologic map of the Rooster Comb 7.5' quadrangle, Malheur County, Oregon: U.S. Geological Survey Miscellaneous Field Studies Map MF-1902C, scale 1:24,000.

https://pubs.er.usgs.gov/publication/mf1902

NGMDB product
Counties Baker - Crook - Grant - Harney - Jefferson - Lake - Malheur - Wasco - Wheeler