Mafic and intermediate intrusive rocks

Dikes, plugs, and sills of basalt, diabase, gabbro, and lesser andesite that fed many of the Miocene basalt and andesite flows in units Tc and Tba. Some intrusions are rootless and are invasive into sedimentary sequences; includes related breccia and peperite. Includes the Monument dike swarm of northwestern Grant County (OR061), the Chief Joseph dike swarm principally in Baker and Wallowa Counties (OR093), the Steens Mountain dike swarm in Harney County (OR005; OR094; OR095) and numerous isolated intrusive bodies in southern Lake County and several intrusive masses in and near-vent flows in southern Malheur County (OR023;OR024). May also include some lower Pleistocene(?) rocks
State Oregon
Name Mafic and intermediate intrusive rocks
Geologic age Miocene to Pliocene
Lithologic constituents
Major
Igneous > Plutonic > Gabbroic > Gabbro (Dike or sill, Stock or pipe)
Igneous > Hypabyssal > Mafic-hypabyssal > Hypabyssal-basalt (Dike or sill, Stock or pipe)
Minor
Igneous > Hypabyssal > Mafic-hypabyssal > Hypabyssal-andesite (Dike or sill)
Igneous > Hypabyssal > Mafic-hypabyssal > Hypabyssal-basaltic-andesite (Stock or pipe)
Comments Gabbro dikes, sills, and at least one plug intrude Steens Basalt in Northern Pueblo Mountains and are substantial in size, but too small to appear on State geologic map (OR252)
References

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

Greene, R.C., Walker, G.W., and Corcoran, R.E., 1972, Geologic map of the Burns quadrangle, Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-680, scale 1:250,000.

https://pubs.er.usgs.gov/publication/i680

Walker, G.W. and Repenning, C.A., 1965, Geologic map of Adel quadrangle, Lake, Harney, and Malheur Counties, Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-446, scale 1:250,000.

https://pubs.er.usgs.gov/publication/i446

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.

Kittleman, L.R., Green, A.R., Hagood, A.R., Johnson, A.M., McMurray, J.M., Russell, R.G., and Weeden, D.A., 1965, Cenozoic stratigraphy of the Owyhee region, southeastern Oregon: Eugene, University of Oregon Museum of Natural History Bulletin 1, 45 p.

Kittleman, L.R., Green, A.R., Haddock, G.H., Hagood, A.R., Johnson, A.M., McMurray, J.M., Russell, R.G., and Weeden, D.A., 1967, Geologic map of the Owyhee region, Malheur County, Oregon: Eugene, University of Oregon Museum of Natural History Bulletion 8, scale 1:125,000.

Brooks, H.C., McIntyre, J.R., and Walker, G.W., 1976, Geology of the Oregon part of the Baker 1o by 2o quadrangle: Oregon Department of Geology and Mineral Industries Geologic Map Series GMS-7, scale 1:250,000.

Walker, G.W., 1979, Reconnaissance geologic map of the Oregon part of the Grangeville quadrangle, Baker, Union, Umatilla, and Wallowa Counties, Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-1116, scale 1;250,000.

https://pubs.er.usgs.gov/publication/i1116

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

Thayer, T.P. and Brown, C.E., 1966, Local thickening of basalts and late Tertiary silicic volcanism in the Canyon City quadrangle, northeastern Oregon: U.S. Geological Survey Professional Paper 550-C, p. C73-C78.

https://pubs.er.usgs.gov/publication/pp550C

Taubeneck, W.H., 1970, Dikes of Columbia River Basalt in northeastern Oregon, western Idaho, and southeastern Washington: Columbia River Symposium, 2d, Cheney, Washington, 1969, Proceedings, Eastern Washington State College Press, p. 73-96.

Minor, S.A., Rytuba, J.J., Vander Meulen, D.B., Grubensky, M.J., and Tegtmeyer, K.J., 1987a, Geologic map of the Wildhorse Lake quadrangle, Harney County, Oregon: U.S. Geological Survey Miscellaneous Field Studies Map MF-1915, scale 1: 24,000.

https://pubs.er.usgs.gov/publication/mf1915

Minor, S.A., Rytuba, J.J., Goeldner, C.A., and Tegtmeyer, K.J., 1987b, Geologic map of the Alvord Hot Spring quadrangle, Harney County, Oregon: U.S. Geological Survey Miscellaneous Field Studies Map MF-1916, scale 1:24,000.

https://pubs.er.usgs.gov/publication/mf1916

Brooks, H.C., Ferns, M.L., and Mullen, A.D., 1982, Geology and mineral deposits of the Granite quadrangle, Grant County, Oregon: Oregon Department of Geology and Mineral Industries Geologic Map Series GMS-25, scale 1:24,000.

Evans, J.G., 1989, Geologic map of the Desolation Butte quadrangle, Grant and Umatilla Counties, Oregon: U.S. Geological Survey Geologic Quadrangle GQ-1654, scale 1:62,500.

https://pubs.er.usgs.gov/publication/gq1654

Evans, J.G., 1994, unpub. mapping, Hereford quadrangle, Baker County, Oregon.

Evans, J.G., unpub. mapping, 1994, Fields quadrangle, Harney County

Evans, J.G., unpub. mapping, 1994, Ladycomb Peak quadrangle, Harney County

NGMDB product
Counties Baker - Grant - Harney - Klamath - Lake - Malheur - Union