Boulder batholith and broadly related stocks (MTTKb;0)

State	Montana
Name	Boulder batholith and broadly related stocks
Geologic age	Phanerozoic \| Cenozoic \| Tertiary Cretaceous
Original map label	TKb
Comments	As stated in map explanation, this map unit contains a number of "broadly related stocks". Many of the stocks are named (too many to note). Most of the rocks represented by this unit are Cretaceous in age and hypabyssal, but a large number of smaller cross-cutting Tertiary stocks and intrusives are lumped into the unit as shown on the state map. Also, note that the large TKb body in the SW-most part of the state map actually consists of Proterozoic rocks.
Primary rock type	quartz monzonite
Secondary rock type	diorite
Other rock types	aplite
Lithologic constituents	Major IgneousAs stated in map explanation, this map unit contains a number of "broadly related stocks". Many of the stocks are named (too many to note) and represent a wide variety of lithologies. Most of the rocks represented by this unit are Cretaceous in age and hypabyssal, but a large number of smaller cross-cutting Tertiary stocks and intrusives are lumped into the unit as shown on the state map. Also, note that the large TKb body in the SW-most part of the state map actually consists of Proterozoic rocks.
Map references	Ross, P.R., Andrews, D.A., and Witkind, I.J., 1955, Geologic map of Montana: U.S. Geological Survey, 2 sheets, scale 1:500,000.
Unit references	Ruppel, E.T., O'Neill, J.M., and Lopez, D.A., 1993, Geologic map of the Dillon 1o x 2o quadrangle, Idaho and Montana: U.S. Geological Survey Miscellaneous Investigations Series Map I-1803-H, scale 1:250,000. [http://pubs.er.usgs.gov/publication/i1803H] M'Gonigle, J.W., and Dalrymple, G.B., 1996, 40Ar/39Ar ages of some Challis Volcanic Group rocks and the initiation of Tertiary sedimentary basins in southwestern Montana: U.S. Geological Survey Bulletin 2132, 17 p., 1 plate. [http://pubs.er.usgs.gov/publication/b2132] Lewis, R.S., 1998, Preliminary geologic map of the Butte 1° x 2° quadrangle: Montana Bureau of Mines and Geology Open File Report 363, 16 p, scale 1:250,000. Tysdal, R.G., Ludington, Steve, and McCafferty, A.E., 1996, Mineral and energy resource assessment of the Helena National Forest, west-central Montana: U.S. Geological Survey Open-File Report 96-683-A, 322 p., 6 plates. [http://pubs.er.usgs.gov/publication/ofr96683A] Vitaliano, C.J., and Cordua, W.S., 1979, Geologic map of southern Tobacco Root Mountains, Madison County, Montana: Geological Society of America Map and Chart Series Map MC-31, scale 1:62,500. Tilling, R.I., 1973, Boulder batholith, Montana--A product of two contemporaneous but chemically distinct magma series: Geological Society of America Bulletin, v. 84, p. 3879-3900. Tilling, R.I., 1974, Composition and time relations of plutonic and associated volcanic rocks, Boulder batholith region: Geological Society of America Bulletin, v. 84, p. 1925-1930. Tilling, R.I., Klepper, M.R., and Obradovich, J.D., 1968, K-Ar ages and time span of emplacement of the Boulder batholith, Montana: American Journal of Science, v. 266, p. 671-689. Lund, Karen, Aleinikoff, J.N., Kunk, M.J., Unruh, D.M., Zeihen, G.D., Hodges, W.C., duBray, E.A., and O'Neill, J.M., 2002, SHRIMP U-Pb and 40Ar/39Ar age constraints for relating plutonism and mineralization in the Boulder batholith region, Montana: Econo
Geographic coverage	Beaverhead - Broadwater - Deer Lodge - Granite - Jefferson - Lewis and Clark - Madison - Meagher - Missoula - Powell - Ravalli - Silver Bow