HR: 0800h
AN: V31B-1433    [Abstracts]
TI: The Liquid Line of Descent of the Alkali-Olivine Basalts From Floreana Island, Galapagos, Ecuador
AU: * McClure, M
EM: mccl2144@uidaho.edu
AF: University of Idaho, Geological Sciences, Moscow, ID 83844 United States
AU: Geist, D
EM: dgeist@uidaho.edu
AF: University of Idaho, Geological Sciences, Moscow, ID 83844 United States
AB: Melting experiments have been performed on two alkali-olivine basalts, Fl03-51 and Fl03-75, from Floreana Island of the Galapagos, Ecuador. The experiments were conducted in a 1 atm gas-mixing furnace, and oxygen fugacity was set at the Ni-NiO buffer. The experiments were designed to define the liquid lines of descent for the two magmas, and to test whether high-MgO Floreana magmas are related to low-MgO magmas by crystallization. The samples were selected so as to minimize incorporation of xenolithic debris, which can be pervasive in Floreana lavas. Sample Fl03-51 contains 7.60 percent MgO and crystallizes plagioclase at 1200 C and olivine at 1180 C. The high MgO sample, Fl03-75, has 12.39 percent MgO and has olivine on the liquidus at 1305øC. Compositional variations as a function of temperature indicate that the two liquid lines of descent intersect at about 1180 C. Microprobe analyses of olivine crystals show that sample Fl03-51 more closely resembles the primary magma. Sample Fl03-75 contains an abundance of xenolithic debris, especially olivine, and is not directly related to Fl03-51 by crystallization.
DE: 3630 Experimental mineralogy and petrology
DE: 3640 Igneous petrology
DE: 3655 Major element composition
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting