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The Stillwater Complex, Montana: a subvolcanic magma chamber?

American Mineralogist

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Abstract

Five magma types occur as sills in the footwall of the Stillwater Complex, all of them coeval with the Stillwater Complex, all of them coeval with the Stillwater in age. Two of the magma types have compositions that suggest they are similar to the magmas from which the cumulates of the Stillwater's Basal and Ultramafic series crystallized. Melting experiments show that the crystallization sequence inferred from the Ultramafic series cumulates is matched only in the mixture of the two sill types at 1.5-3 kbar. Thus, the observed stratigraphy of the Basal and Ultramafic series may result from mixing of two distinct magmas rather than fractionation of a single magma. The permissible pressure range of 1.5-3 kbar implies that the depth of the Stillwater magma chamber was similar to that of subvolcanic magma chambers such as that of Kilauea Volcano, which raises the possibility that the Stillwater magma body may also have been a subvolcanic reservoir. -from Author

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
The Stillwater Complex, Montana: a subvolcanic magma chamber?
Series title:
American Mineralogist
Volume
80
Issue:
11-12
Year Published:
1995
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
American Mineralogist
First page:
1343
Last page:
1346