Hypabyssal intrusive rocks (Miocene and Miocene?) (ORThi;0)

Hypabyssal, medium-grained, hornblende diorite and quartz diorite in small stocks and large dikes; includes intrusions of medium- to fine-grained gabbro and plugs and small stocks of medium-grained, holocrystalline, olivine andesite. Also includes medium-grained, commonly porphyritic biotite quartz monzonite and leucocratic granodiorite. Many of these intrusive bodies are moderately to intensely propylitized, as are wallrocks they intrude; locally, along shears, the rocks also are sericitized. Potassium-argon ages on several of these shallow intrusions range from about 8 Ma to about 22 Ma (Wise, 1969; Bikerman, 1970; Sutter, 1978; Power and others, 1981a, b; Fiebelkorn and others, 1983)

State	Oregon
Name	Hypabyssal intrusive rocks (Miocene and Miocene?)
Geologic age	Miocene
Original map label	Thi
Primary rock type	diorite
Secondary rock type	quartz diorite
Other rock types	gabbro; andesite; quartz monzonite; granodiorite
Lithologic constituents	Major Igneous > Plutonic > Dioritic > Quartz-diorite (Stock or pipe) Igneous > Plutonic > Dioritic > Diorite (Stock or pipe) Minor Igneous > Plutonic > Dioritic > Diorite (Dike or sill) Igneous > Plutonic > Dioritic > Quartz-diorite (Dike or sill) Incidental Igneous > Hypabyssal > Mafic-hypabyssal > Hypabyssal-andesite (Dike or sill) Igneous > Hypabyssal > Mafic-hypabyssal > Hypabyssal-andesite (Stock or pipe) Igneous > Plutonic > Granitic > Granodiorite (Stock or pipe) Igneous > Plutonic > Granitic > Granodiorite (Dike or sill) Igneous > Plutonic > Syenitic > Quartz-monzonite (Dike or sill) Igneous > Plutonic > Syenitic > Quartz-monzonite (Stock or pipe) Igneous > Plutonic > Gabbroic > Gabbro (Stock or pipe) Igneous > Plutonic > Gabbroic > Gabbro (Dike or sill)
Map references	Walker, G.W. and MacLeod, N.S., 1991, Geologic map of Oregon: U.S. Geological Survey, scale 1:500,000.
Unit references	Walker, G.W. and MacLeod, N.S., 1991, Geologic map of Oregon: U.S. Geological Survey, scale 1:500,000. Wise, W.S., 1969, Geology and petrology of the Mount Hood area-a study of High Cascade volcanism: Geological Society of America Bulletin, v. 80, p. 969-1006. Bikerman, M., 1970, K-Ar ages of Laurel Hill pluton and dike, Oregon: the Ore Bin, v. 32, p.211-215. Sutter, J.F., 1978, K-Ar ages of Cenozoic volcanic rocks from the Oregon Cascades west of 121o 30': Isochron/West, no. 21, p. 15-21. Power, S.G., Field, C.W., Armstrong, r.L., and Harakal, J.E., 1981a, K-Ar ages of plutonism and mineralization, western Cascades, Oregon and southern Washington: Isochron/West, no. 31, p. 27-29. Power, S.G., Field, C.W., Armstrong, r.L., and Harakal, J.e., 1981a, K-Ar ages of plutonism and mineralization, western Cascades, Oregon and Washington; additional information: Isochron/West, no. 32, p. 3. Fiebelkorn, R.B., Walker, G.W., Macleod, N.S., McKee, E.H., and Smith, J.G., 1983, Index to K-Ar determinations for the State of Oregon: Isochron/West, no. 37, p. 3-60.
Geographic coverage	Clackamas - Douglas - Jackson - Lane - Linn - Marion