Cumulate Xenoliths in the Lodgepole, Enos Mountain and Susie Peak Intrusions: A Guide
Route
Start point
Big Timber, Montana
End point
various locations
Roads (and Trails)
Montana 298; East Boulder River Road; Elk Creek Road; access to the Lodgepole intrusion requires a 3-mile hike and 2,400 vertical feet of climbing without trails
Total distance
Geology
Summary
The Lodgepole, Enos Mountain and Susie Peak plutons represent multiple intrusions of intermediate magma that were emplaced at depths ranging from near-surface to 2 km during the Late Cretaceous....These intrusions lie, respectively, 8, 9 and 12 km north of the nearest outcrops of the Stillwater Complex. The Lodgepole intrusion is composed of an early, dacitic phase and a later, dioritic phase; the diorite contains abundant xenoliths (maximum 31 cm diameter) in the area north of Clover Basin near its west margin. These xenoliths include foliated mafic amphibolite, gneiss, Paleozoic sedimentary rocks and mafic cumulates. Smaller xenoliths of similar rock types are found in the Enos Mountain and Susie Peak intrusions....Mineral compositions and textures lead to the conclusion that the cumulate xenoliths were brought up from a buried underlying extension of the Stillwater Complex.
Key Lithologic Features
- Cretaceous dacitic to dioritic intrusions with metamorphic, sedimentary, and igneous (mafic cumulate) xenoliths
- Tertiary volcanic agglomerate
Structures
Landforms
Other Features
Reference
Brozdowski, R.A., 1985, Cumulate xenoliths in the Lodgepole, Enos Mountain and Susie Peak intrusions: a guide,
in Czamanske, G.K., and Zientek, M.L., eds.,
The Stillwater Complex, Montana: Geology and Guide : Montana Bureau of Mines and Geology Special Publication 92, p. 368-372.
Availability
Order from the Montana Bureau of Mines and Geology. Search for
this publication's record at the MBMG for ordering information.
