Igneous rocks of the Highwood Mountains, Montana: Part VII. Petrology

Abstract

Research Article| December 01, 1941 Igneous rocks of the Highwood Mountains, Montana: Part VII. Petrology E. S. LARSEN; E. S. LARSEN Search for other works by this author on: GSW Google Scholar C. S. HURLBUT, JR.; C. S. HURLBUT, JR. Search for other works by this author on: GSW Google Scholar C. H. BURGESS; C. H. BURGESS Search for other works by this author on: GSW Google Scholar B. F. BUIE B. F. BUIE Search for other works by this author on: GSW Google Scholar GSA Bulletin (1941) 52 (12_1): 1857–1868. https://doi.org/10.1130/GSAB-52-1857 Article history received: 26 Mar 1940 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 E. S. LARSEN, C. S. HURLBUT, C. H. BURGESS, B. F. BUIE; Igneous rocks of the Highwood Mountains, Montana: Part VII. Petrology. GSA Bulletin 1941;; 52 (12_1): 1857–1868. doi: https://doi.org/10.1130/GSAB-52-1857 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 SocietyGSA Bulletin Search Advanced Search Abstract In the shonkinite series olivine, leucite, and analcime crystallized only from magmas with over 20 per cent of mafites. At this stage the leucite and analcime inverted to pseudoleucite. Pyroxene crystallized over the whole range of rocks and changed little in composition until the magma reached the composition of nepheline syenite when it became richer in aegirite. A little pale biotite crystallized early, but most of the biotite is dark and crystallized late. A little barium rich sanidine crystallized early. The abundant late feldspar is poor in barium.Four petrographic subprovinces are represented in the area. The older quartz latites are near lime-alkalic rocks, the syenites and monzonites of Highwood Peak are somewhat farther removed, and the shonkinite series are potash-rich alkalic rocks. The alnoites are very rich in lime. The parent mafic magmas of the various subprovinces formed in depth by differentiation of a primary basaltic magma. These parent magmas were erupted toward the surface and there differentiated in a different way. The differentiation of the shonkinite magma was chiefly by settling of augite, olivine, and some biotite. 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.