Petrology of McKinney Basalt, Snake River Plain, Idaho

Abstract

Research Article| December 01, 1976 Petrology of McKinney Basalt, Snake River Plain, Idaho W. P. LEEMAN; W. P. LEEMAN 1Oregon State University, Department of Geology, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar C. J. VITALIANO C. J. VITALIANO 2Indiana University, Department of Geology, Bloomington, Indiana 47401 Search for other works by this author on: GSW Google Scholar Author and Article Information W. P. LEEMAN 1Oregon State University, Department of Geology, Corvallis, Oregon 97331 C. J. VITALIANO 2Indiana University, Department of Geology, Bloomington, Indiana 47401 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1976) 87 (12): 1777–1792. https://doi.org/10.1130/0016-7606(1976)87<1777:POMBSR>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 Email Permissions Search Site Citation W. P. LEEMAN, C. J. VITALIANO; Petrology of McKinney Basalt, Snake River Plain, Idaho. GSA Bulletin 1976;; 87 (12): 1777–1792. doi: https://doi.org/10.1130/0016-7606(1976)87<1777:POMBSR>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 SocietyGSA Bulletin Search Advanced Search Abstract The McKinney Basalt, a composite pahoehoe and pillow lava unit in the Snake River Plain, has been studied by petrographic, chemical, strontium-isotopic, and experimental methods in an attempt to define its origin and evolutionary history. Differences in the compositions of olivine and plagioclase phenocryst cores and in the whole-rock composition of different samples are interpreted as evidence that McKinney Basalt erupted as sequential surges of lava that represent different degrees of fractional crystallization of an olivine tholeiite parental magma. Olivine and plagioclase geothermometry and experimental studies indicate that McKinney pillow lava erupted at a temperature of about 1190° to 1200°C. Compositions of iron-titanium oxides and plagioclase/glass europium partition coefficients indicate that as McKinney lava cooled, oxygen fugacity was buffered near the quartz-fayalite-magnetite buffer.Experimental studies and chemical compositions of McKinney samples suggest that the parental magma underwent significant crystallization only at relatively low pressures (<8 kb). Theoretical calculations involving silica and alumina activities suggest that McKinney parental magma was formed likely by partial fusion of spinel peridotite or aluminous pyroxene peridotite mantle at depths of about 50 to 60 km. Under anhydrous conditions, melting would have occurred at this depth at a minimum temperature of about 1300°C. Under water-undersaturated conditions, melting would have occurred at a significantly lower temperature, whose value would depend on the water content of the magma.Strontium isotopic data suggest that McKinney Basalt, like all other Snake River olivine tholeiites, was derived from a mantle region that is more radiogenic than typical suboceanic mantle. 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.