Abstract
An extremely differentiated suite of unaltered volcanic rocks dredged from the Galapagos Spreading Center ranges in δ 18O from 5.7 to 7.1‰ At 95°W, low K-tholeiites, FeTi-basalts, andesites and rhyodacites were recovered. Their lithologic and major element geochemical variation can be accounted for by crystal fractionation of plagioclase, pyroxenes, olivine and titanomagnetite in the same proportions and amounts needed to model the δ 18O variation by simple Rayleigh fractionation. More complicated behaviour was observed in a FeTi-basalt suite from 85°W. This study shows that 90% fractionation only enriches the residual melt by about 1.2‰ in 18O. It also implies that the magma chambers along parts of the Galapagos Spreading Center were static and isolated such that extreme differentiation could occur.
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Muehlenbachs, K., Byerly, G. 18O-Enrichment of silicic magmas caused by crystal fractionation at the Galapagos Spreading Center. Contr. Mineral. and Petrol. 79, 76–79 (1982). https://doi.org/10.1007/BF00376963
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DOI: https://doi.org/10.1007/BF00376963