Syenite, quartz syenite, monzodiorite, quartz diorite, gabbro, pyroxenite, and hornblendite; Late Proterozoic plutons; east-central Idaho (IDZisy;0)

State	Idaho
Name	Syenite, quartz syenite, monzodiorite, quartz diorite, gabbro, pyroxenite, and hornblendite; Late Proterozoic plutons; east-central Idaho
Geologic age	Late Proterozoic
Original map label	PCi
Comments	Four stocks of Zis are present along Big Creek. They are (north-northwest to south-southeast): the composite stocks of Ramey Ridge, Acorn Butte, Rush Creek Point, and Middle Fork Peak. They contain syenite to quartz syenite, syenodiorite to quartz diorite, gabbro, pyroxenite, and hornblendite (ID038). One age determination is 650 Ma (ID025).
Primary rock type	syenite
Secondary rock type	quartz syenite
Other rock types	monzodiorite; quartz diorite; gabbro; pyroxenite; hornblendite
Lithologic constituents	Major Igneous > Plutonic > Syenitic > Syenite (Stock or pipe)composite stocks Minor Igneous > Plutonic > Dioritic > Quartz-diorite (Stock or pipe)composite stocks Igneous > Plutonic > Dioritic > Monzodiorite (Stock or pipe)composite stocks Igneous > Plutonic > Syenitic > Quartz-syenite (Stock or pipe)composite stocks Incidental Igneous > Plutonic > Ultramafic > Hornblendite (Stock or pipe)composite stocks Igneous > Plutonic > Ultramafic > Pyroxenite (Stock or pipe)composite stocks Igneous > Plutonic > Gabbroic > Gabbro (Stock or pipe)composite stocks
Map references	Bond, J.G., Kauffman, J.D., Miller, D.A., and Venkatakrishnan, Ramesh, 1978, Geologic map of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, with contributions from U.S. Geological Survey, scale 1:500,000.
Unit references	Mitchell, V.E.., and Bennett, E.H., 1979, Geologic map of the Ashton quadrangle, Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, Geologic Map Series, Ashton 2o Quadrangle, scale 1:250,000. Evans, K.V. and Green, G.N., 2003, Geologic map of the Salmon National Forest and vicinity, east-central Idaho: U.S. Geological Survey Geological Investigations Series I-2765, scale 1:100,000 with pamphlet, 19 p. [http://pubs.er.usgs.gov/publication/i2765] Lund, Karen, in press, Geology of the Payette National Forest, Valley, Idaho, Washington and Adams counties, Idaho: U.S. Geological Survey Professional Paper 1666, scale 1:100,000. [http://pubs.er.usgs.gov/publication/pp1666] Cater, F.W., Pinckney, D.M., Hamilton, W.B., Parker, R.L., Weldin, R.D., Close, T.J., and Zilka, N.T., 1973, Mineral resources of the Idaho Primitive Area and vicinity, Idaho; an evaluation of the mineral potential of the area, with a section on the Thunder Mountain district by B.F. Leonard, and a section on Aeromagnetic interpretation by W.E. Davis: U.S. Geological Survey Bulletin 1304, 431 p. [http://pubs.er.usgs.gov/publication/b1304]
Geographic coverage	Idaho - Lemhi - Valley