Pre-Tertiary basic intrusive rocks

Predominantly gabbro and metagabbro; includes hornblendite, peridotite, and pyroxenite. In Nighthawk district and near 49th Parallel in Okanogan County and in Orient district of Stevens County.
State Washington
Name Pre-Tertiary basic intrusive rocks
Geologic age Triassic-Permian
Lithologic constituents
Metamorphic > Amphibolite
Igneous > Plutonic > Gabbroic > GabbroIncludes metagabbro.
Igneous > Plutonic > Ultramafic > Pyroxenite
Igneous > Plutonic > Ultramafic > Hornblendite
Igneous > Volcanic > Mafic-volcanic > Basalt (Dike or sill)
Metamorphic > Metaigneous > Greenstone
Igneous > Plutonic > Ultramafic > Peridotite
Metamorphic > GneissLocalized in Sheep Mountain area in north Okanogan County just west of Asnola gabbro.
Igneous > Plutonic > Granitic > Granodiorite (Dike or sill)
Comments Includes metagabbro, metadiabase, and metanorite in Okanogan County and very minor quartz diorite and diorite in Stevens County. Includes basalt and granodiorite dikes within Asnola gabbro and alaskitic to granodioritic dikes within Palmer Mountain greenstone.
Stratigraphic units Ashnola gabbro, Palmer Mountain greenstone; Chopaka Intrusive Complex (in part)

Huntting, M.T., Bennett, W.A.G., Livingston, V.E.Jr., and Moen, W.S., 1961, Geologic Map of Washington: Washington Division of Mines and Geology, scale 1:500,000.

Stoffel, K.L., Joseph, N.L., Waggoner, S.Z., Gulick, C.W., Korosec, M.A., Bunning, B.B., 1991, Geologic Map of Washington--Northeast Quadrant: Washington Division of Geology and Earth Resources Geologic Map, GM-39, scale 1:250,000.

Rinehart, C.D., and Fox, K.F.Jr., 1972, Geology and Mineral Deposits of the Loomis Quadrangle, Okanogan County, Washington: Washington Division of Mines and Geology Bulletin No. 64, 124 p.

Eaton, G.P. and Staatz, M.H., 1971, Mineral Resources of the Pasayten Wilderness Area, Washington: U. S. Geological Survey Bulletin 1325, 255 p.

Hibbard, M.J., 1971, Evolution of a Plutonic Complex, Okanogan Range, Washington: Geological Society of America Bulletin, v. 82, no. 11, p. 3013-3048.

NGMDB product
Counties Okanogan - Stevens