Counting marmots…
Research Article| December 01, 1940 Audubon-Albion stock, Boulder County, Colorado ERNEST E. WAHLSTROM ERNEST E. WAHLSTROM Search for other works by this author on: GSW Google Scholar GSA Bulletin (1940) 51 (12_1): 1789–1820. https://doi.org/10.1130/GSAB-51-1789 Article history received: 23 Feb 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 ERNEST E. WAHLSTROM; Audubon-Albion stock, Boulder County, Colorado. GSA Bulletin 1940;; 51 (12_1): 1789–1820. doi: https://doi.org/10.1130/GSAB-51-1789 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Audubon-Albion stock in Boulder County, Colorado, is a composite intrusive consisting largely of monzonite and injected into and crosscutting pre-Cambrian granite, gneiss, and schist. The sequence is syenogabbro (oldest), monzonite, quartz-bearing monzonite, syenite, and granite. The monzonite probably formed from a syenogabbroic magma by crystal fractionation, but the younger differentiates, including quartz-bearing monzonite, syenite, and granite, resulted from more complex processes involving not only crystal fractionation but also assimilation or syntexis and transfer of materials by mobile, fluid-rich, alkalic solutions.Age relations, the distribution of the various rock types, and the internal structures suggest that the stock was in part emplaced by repeated subsidence of a large conical block and in part by injection of magma into zones of weakness along internal or external contacts. There is little evidence to indicate that the walls of the stock were forced apart by the advancing magma.Chemical analyses of the syenogabbro show an unusually high content of potash and are nearly identical with analyses of the basalt flows interbedded with the sediments of the Denver formation near Golden, Colorado. Correlation establishes the age of the oldest rock in the Audubon-Albion stock as early Eocene or, possibly, Paleocene. The exact age of the younger differentiates is uncertain. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.
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