Alkaline Rocks and Carbonatites of the World

Setup during HiTech AlkCarb: an online database of alkaline rock and carbonatite occurrences

Little Belt Mountains

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Occurrence number: 
174-00-033
Country: 
United States
Region: 
Montana
Location: 
Longitude: -110.75, Latitude: 47
Carbonatite: 
No

Numerous laccoliths and other igneous intrusions have domed and warped both Precambrian crystalline rocks and sedimentary rocks in the central Little Belt Mountains. A broad range of rock types is present from rhyolite and granite porphyries through latites and syenite to shonkinites and lamprophyres. Few of these rocks are peralkaline but a little analcime and other zeolites occur in some syenites and possible sodalite has been identified (Witkind, 1973, Table 4).

Age: 
K-Ar ages on a range of minerals and whole rocks lie between 48 and 54 Ma (Marvin et al., 1973).
References: 

MARVIN, R.F., WITKIND, I.J., KEEFER, W.R. and MEHNERT, H.H. 1973. Radiometric ages of intrusive rocks in the Little Belt Mountains, Montana. Bulletin of the Geological Society of America, 84: 1977-86.
WITKIND, I.J. 1973. Igneous rocks and related mineral deposits of the Barker Quadrangle, Little Belt Mountains, Montana. Professional Paper, United States Geological Survey, 752: 1-58

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith