File:Steamboat Mountain (Upper Pliocene to Lower Pleistocene wyomingite volcanic center in the Leucite Hills, Wyoming, USA).jpg

English: Steamboat Mountain - an eroded wyomingite volcanic center in the Pliocene-Pleistocene of Wyoming, USA. (looking northwest from near Black Rock)

Southwestern Wyoming's Leucite Hills are a group of Pliocene to Pleistocene volcanic centers that erupted lamproite lavas, a rare extrusive igneous lithology. Based on chemistry and mineral content, the Leucite Hills lamproite lavas have been categorized as wyomingite, orendite, or madupite.

Volcanism in this area may possibly be due to Yellowstone Hotspot fringe melting of the mantle. The lamproites appear to be derived from lherzolite-harzburgite mantle rocks that were metasomatically enriched in phlogopitic veins at >1.2 Ga (the latter may be caused by Precambrian subduction along the Wyoming Craton margin).

Age: ~uppermost Pliocene to lower Lower Pleistocene (sensu traditio), 1.70-1.85 Ma

Locality: Steamboat Mountain, northern Leucite Hills Volcanic Province, Great Divide Basin, north of the town of Superior, southwestern Wyoming, USA (41° 58' 00.69" North, 108° 57' 24.85" West)

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Example references on Leucite Hills geology:

Lange, R.A., I.S.E. Carmichael & C.M. Hall. 2000. 40Ar/39Ar chronology of the Leucite Hills, Wyoming: eruption rates, erosion rates, and an evolving temperature structure of the underlying mantle. Earth and Planetary Science Letters 174: 329-340.

Schultz, A.R. & W. Cross. 1912. Potash-bearing rocks of the Leucite Hills, Sweetwater County, Wyoming. United States Geological Survey Bulletin 512. 39 pp.