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Some Chemical Features of Lavas from the Manu'a Islands, Samoa

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Title:Some Chemical Features of Lavas from the Manu'a Islands, Samoa
Authors:Hubbard, Norman J.
Date Issued:Apr 1971
Publisher:University of Hawai'i Press
Citation:Hubbard NJ. 1971. Some chemical features of lavas from the Manu'a Islands, Samoa. Pac Sci 25(2): 178-187.
Abstract:The lavas of the Manu'a Islands have chemical compositions typical
of oceanic island alkali lavas. They have rare earth abundances with chondrite
normalized lanthanum:ytterbium ratios around 10 and ytterbium concentrations
about 2.2 ppm. Strontium concentrations are greater than 400 ppm and within
the range of strontium values for Hawaiian alkalic lavas. Potassium:rubidium
ratios are generally between 300 and 400 but three samples have potassium:
rubidium ~700, suggesting heterogeneity of source materials. The 87strontium:
86strontium ratios average 0.7046 ± .0003, and are the highest known for oceanic
islands. Low pressure differentiation is controlled by olivine and plagioclase.
These lavas were segregated from a normal oceanic upper mantle at >40 km depth
and the percentage of partial melting was in the range of 3 to 7 percent. The
chemical composition of the probable original magma is estimated using combined
trace element, major element, and partition coefficient data.
Appears in Collections: Pacific Science Volume 25, Number 2, 1971

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