The Stillwater Complex, Montana; a subvolcanic magma chamber?

Abstract

Other| December 01, 1995 The Stillwater Complex, Montana: A subvolcanic magma chamber? Rosalind Tuthill Helz Rosalind Tuthill Helz U. S. Geological Survey, Reston, VA, United States Search for other works by this author on: GSW Google Scholar American Mineralogist (1995) 80 (11-12): 1343–1346. https://doi.org/10.2138/am-1995-11-1225 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Rosalind Tuthill Helz; The Stillwater Complex, Montana: A subvolcanic magma chamber?. American Mineralogist 1995;; 80 (11-12): 1343–1346. doi: https://doi.org/10.2138/am-1995-11-1225 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Five magma types occur as sills in the footwall of 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 performed on samples of these two magma types and on a 50–50 mix of the two types show that the crystallization sequence inferred from the Ultramafic series cumulates (olivine > orthopyroxene > plagioclase > augite) 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. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.