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Middle Miocene to Oligocene shallow intrusions

Generally very fine-grained, porphyritic rhyolite to dacite in small, irregular-shaped bodies formed as subvolcanic intrusions in volcanic fields of southern and western Arizona, or in concentrated zones of dikes in the Mohave and Black Mountains of northwestern Arizona. The unit consists of mafic tuff, breccia and shallow intrusions at Buell Park in northeastern Arizona. (14-35 Ma)
State Arizona
Name Middle Miocene to Oligocene shallow intrusions
Geologic age Oligocene to Middle Miocene
Comments Includes Navajo volcanic field minettes
Primary rock type dacite
Secondary rock type rhyolite
Other rock types porphyry; rhyolite; conglomerate; sandstone; sedimentary breccia
Lithologic constituents
Major
Igneous > Hypabyssal > Felsic-hypabyssal > Hypabyssal-dacite (Stock or pipe)includes dacite porphyry
Igneous > Hypabyssal > Felsic-hypabyssal > Hypabyssal-rhyolite (Stock or pipe)includes rhyolite porphyry
Minor
Igneous > Hypabyssal > Felsic-hypabyssal > Hypabyssal-dacite (Dike or sill)includes dacite porphyry
Igneous > Hypabyssal > Felsic-hypabyssal > Hypabyssal-rhyolite (Dike or sill)includes rhyolite porphyry
Incidental
Igneous > Hypabyssal > Lamprophyre (Dike or sill)al”nite, katungite, vogesite, minette, monchiquite, serpentinized ultramafic breccia, shonkinite
Igneous > Hypabyssal > Lamprophyre (Stock or pipe)al”nite, katungite, vogesite, minette, monchiquite, serpentinized ultramafic breccia, shonkinite
Igneous > Hypabyssal > Mafic-hypabyssal > Hypabyssal-mafic-alkaline (Dike or sill)leucitite
Igneous > Hypabyssal > Mafic-hypabyssal > Hypabyssal-mafic-alkaline (Stock or pipe)leucitite
Igneous > Plutonic > Dioritic > Quartz-diorite (Dike or sill)
Igneous > Plutonic > Dioritic > Quartz-diorite (Stock or pipe)
Map references
Richard, S. M., Reynolds, S.J., Spencer, J. E., and Pearthree, P. A., 2000, Geologic Map of Arizona: Arizona Geological Survey Map 35, 1 sheet, scale 1:1,000,000.
Unit references
Richard, S. M., Reynolds, S.J., Spencer, J. E., and Pearthree, P. A., 2000, Geologic Map of Arizona: Arizona Geological Survey Map 35, 1 sheet, scale 1:1,000,000.
Nealey, L.D., and Sheridan, M.F., 1989, Post-Laramide volcanic rocks of Arizona and northern Sonora, Mexico, and their inclusions, in Jenney, J.P., and Reynolds, S.J., editors, Geologic evolution of Arizona: Arizona Geological Society Diges
Spencer, J.E., and Reynolds, S.J., 1989, Middle Tertiary tectonics of Arizona and adjacent areas, in Jenney, J.P., and Reynolds, S.J., editors, Geologic evolution of Arizona: Arizona Geological Society Digest 17, p. 539-574.
Counties Apache - Cochise - Graham - La Paz - Maricopa - Mohave - Pima - Yuma