Orthopyroxene fractionation in the Grande Ronde Basalt--Columbia River Basalt group

Technical Report · Fri Dec 01 04:00:00 EST 1978

DOI:https://doi.org/10.2172/6292167· OSTI ID:6292167

Reidel, S. P.; Ross, M. E.; Long, P. E.

Six orthopyroxenes were microprobed; five orthopyroxenes were from the Grande Ronde Basalt, and one was from the Buford flow of the Saddle Mountains Basalt. The orthopyroxenes are primarily bronzite in composition, but some analyses show that hypersthene is present. The reaction rims of all analyzed orthopyroxene crystals are pigeonite, while the groundmass pyroxene is both augite and pigeonite. Preliminary results from the least-squares linear modeling of the Grande Ronde Basalt indicate orthopyroxene is a necessary phase for mass balancing between flow compositions. Three models were tried in order to determine if selected mineral phases could be used to model the chemical compositions of the flows. These models suggest that orthopyroxene and plagioclase are phases common to the Grande Ronde Basalt. The similarity of orthopyroxene and plagioclase occurrences suggests that they are important intratelluric phases of the Grande Ronde Basalt which reacted out when the basaltic liquids were erupted at the surface.

• Research Organization: Atomics International Div., Richland, WA (USA). Rockwell Hanford Operations
• DOE Contract Number: EY-77-C-06-1030
• OSTI ID: 6292167
• Report Number(s): RHO-BWI-SA-5; CONF-781246-1
• Country of Publication: United States
• Language: English

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