Amphibolite after gabbro, diabase, and diorite; Middle Proterozoic sill-like intrusions; southern and northern Belt provinces (IDYibm;0)

State	Idaho
Name	Amphibolite after gabbro, diabase, and diorite; Middle Proterozoic sill-like intrusions; southern and northern Belt provinces
Geologic age	Middle Proterozoic
Original map label	PCi; pKi; pKim; Ki?
Comments	Yibm includes foliated amphibolite and garnet amphibolite, interpreted as meta-gabbro, meta-diabase, and meta-diorite, derived from predominantly sill-like mafic intrusions. A large composite body of Yibm is spatially and temporally associated with a large Yifm pluton in the Salmon River Mountains. Age determinations from this mafic intrusive complex are 1364 +/- 9 and 1379 +/- 1 Ma. Other amphibolites, also interpreted as meta-mafic intrusions, are present in the Salmon River Arch, and in the Boehls Butte metamorphic complex, where sill-like amphibolite bodies parallel sill-like anorthosite bodies. These amphibolites are included in the Yibm map unit, but have not been isotopically dated.
Primary rock type	amphibolite
Secondary rock type	gabbro
Other rock types	diabase; diorite
Lithologic constituents	Major Metamorphic > Amphiboliteamphibolite and garnet amphibolite after mafic intrusions Minor Igneous > Plutonic > Gabbroic > Gabbro (Pluton)gabbro in thick mafic sills Incidental Igneous > Plutonic > Dioritic > Diorite (Pluton)diorite in differentiated mafic sills Igneous > Hypabyssal > Mafic-hypabyssal > Hypabyssal-basalt (Diabase)diabase dikes and pods in granitic augen gneiss
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	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. 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] Griggs, A.B., 1973, Geologic map of the Spokane quadrangle, Washington, Idaho, and Montana: U.S. Geological Survey Map I-768, scale 1:250,000. [http://pubs.er.usgs.gov/publication/i768] Rember, W.C., and Bennett, E.H., 1979, Geologic map of the Hamilton quadrangle, Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, Geologic Map Series, Hamilton 2o quadrangle, 1:250,000 scale. Doughty, P.T., and Chamberlain, K.R., 1996, Salmon River Arch revisited: new evidence for 1370 Ma rifting near the end of deposition in the Middle Proterozoic Belt basin: Canadian Journal of Earth Sciences, v. 33, no. 7, p. 1037-1052. Heitanen, Anna, 1963, Anorthosite and associated rocks in the Boehls Butte quadrangle and vicinity, Idaho: U.S. Geological Survey Professional Paper 344-B, 78 p., with map 1:48,000 scale. [http://pubs.er.usgs.gov/publication/pp344B]
Geographic coverage	Clearwater - Idaho - Lemhi - Shoshone