Proterozoic anorogenic two-mica granites: Silver Plume and St. Vrain batholiths of Colorado

Abstract

Research Article| March 01, 1985 Proterozoic anorogenic two-mica granites: Silver Plume and St. Vrain batholiths of Colorado J. Lawford Anderson; J. Lawford Anderson 1Department of Geological Sciences University of Southern California Los Angeles, California, 90089 Search for other works by this author on: GSW Google Scholar Warren M. Thomas Warren M. Thomas 1Department of Geological Sciences University of Southern California Los Angeles, California, 90089 Search for other works by this author on: GSW Google Scholar Author and Article Information J. Lawford Anderson 1Department of Geological Sciences University of Southern California Los Angeles, California, 90089 Warren M. Thomas 1Department of Geological Sciences University of Southern California Los Angeles, California, 90089 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1985) 13 (3): 177–180. https://doi.org/10.1130/0091-7613(1985)13<177:PATGSP>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation J. Lawford Anderson, Warren M. Thomas; Proterozoic anorogenic two-mica granites: Silver Plume and St. Vrain batholiths of Colorado. Geology 1985;; 13 (3): 177–180. doi: https://doi.org/10.1130/0091-7613(1985)13<177:PATGSP>2.0.CO;2 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 SocietyGeology Search Advanced Search Abstract The two-mica, sillimanite-bearing Silver Plume and St. Vrain batholiths of Colorado are representative of a distinctly peraluminous section of the 1.4 to 1.5 Ga anorogenic province of North America. Indicative of fundamental variations of lower-crust composition in this region of the continent, these granitic magmas were generated from an oxidized peraluminous quartzofeldspathic source at P ⩾ 10 kbar (⩾36 km). Despite mineralogic similarities, the rocks remain distinct from S-type orogenic granitoids in a high abundance of K, Ba, light rare earth elements, and other incompatible elements. This enrichment, although less than in some coeval metaluminous granites, results from limited partial melting under vapor-undersaturated conditions. Emplacement occurred at a depth possibly as shallow as 8 to 9 km (2.3 kbar) at a PH2O of 487 to 560 bar and temperature of 740 to 760 °C. These temperatures and pressures fall well beyond the conventional stability field of muscovite-melt equilibria and point to an enhanced stability of muscovite owing to its ferric and titaniferous nature in plutonic occurrences. 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.