49: Approximate sequence of volcanic eruptions on Semisopochnoi, including analyzed samples and their phenocryst mineralogy * Note- Volcanic sequence after Coats (1959); relative age of late-lateral and late-central eruptions is uncertain. Rock names based on SiO2 content: basalt, <53% SiO2; andesite 53-62% SiO2; dacite, > 62% SiO2. Sample numbers are abbreviated from the USGS laboratory numbers reported by Coats (1959, table 1, p. 514). For example, sample ID-19250 is here referred to as sample 192. (All Semisopochnoi samples had lab numbers beginning with "ID-" and ending with "50".) Pl=plagioclase; Ol=olivine; Aug=augite; Hy=hypersthene; Pig=pigeonite; Hbl=hornblende; Ap=apatite. * Analyzed for REE and isotopic composition. *

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50: Major and trace-element data for volcanic rocks from Semisopochnoi * Note - SiO2 and K2O in wt% (Coats, 1959). Trace-element concentrations in ppm: Rb, Sr, and Ni from DeLong (1974); others by x-ray fluorescence spectrometry at Woods Hole Oceanographic Institution (see Schroeder et al. 1980 for analytical details). (super a)Mg#(molar)=100xMgO/(FeO*+MgO) *

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51: Isotopic, rare earth, and other trace-element data for selected samples from Semisopochnoi * Note - trace-element analyses by spark-source mass spectrometry (Taylor and Gorton 1977); concentrations in ppm; precision is +/- 5% (1sigma), except for high concentrations of Ba, which is +/-10%. Analytical techniques for isotopic measurements as given by McCulloch and Perfit (1981). (super a) Sr composition is normalized to 86Sr/88Sr = 0.1194, and 87Sr/86Sr is adjusted to a value of 0.71022 for NBS987. (super b) Nd composition is normalized to 146Nd/142Nd = 0.636151. (super c) e Nd = [((143Nd/144Nd) meas.)/((143Nd/144Nd)CHUR) - 1] x10^4 where (143Nd/144Nd) CHUR = 5.11836. *

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