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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.
StateWashington
NamePre-Tertiary basic intrusive rocks
Geologic ageTriassic-Permian
Original map labelpTbi
CommentsIncludes 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.
Primary rock typeamphibolite
Secondary rock typegabbro
Other rock typesgneiss; hornblendite; peridotite; pyroxenite; greenstone; basalt; granodiorite
Lithologic constituents
Major
Metamorphic > Amphibolite
Minor
Igneous > Plutonic > Gabbroic > GabbroIncludes metagabbro.
Incidental
Igneous > Plutonic > Granitic > Granodiorite (Dike or sill)
Igneous > Volcanic > Mafic-volcanic > Basalt (Dike or sill)
Metamorphic > GneissLocalized in Sheep Mountain area in north Okanogan County just west of Asnola gabbro.
Igneous > Plutonic > Ultramafic > Pyroxenite
Igneous > Plutonic > Ultramafic > Hornblendite
Igneous > Plutonic > Ultramafic > Peridotite
Metamorphic > Greenstone
Map references
Huntting, M. T., Bennett, W. A. G., Livingston, V. E. Jr., Moen, W. S., 1961, Geologic Map of Washington: Washington Division of Mines and Geology, scale 1:500,000.
Unit references
Huntting, M. T., Bennett, W. A. G., Livingston, V. E. Jr., 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.
Geographic coverageOkanogan - Stevens

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