Auxiliary Material for Paper 2012GC004163 Effects of variable magma supply on mid-ocean ridge eruptions: Constraints from mapped lava flow fields along the Galapagos Spreading Center Alice Colman and John M. Sinton Department of Geology and Geophysics, University of Hawai'i at Manoa, Honolulu, Hawaii, USA Scott M. White and J. Timothy McClinton Department of Earth and Ocean Sciences, University of South Carolina, Columbia, South Carolina, USA Julie A. Bowles Institute for Rock Magnetism, University of Minnesota, Minneapolis, Minnesota, USA Kenneth H. Rubin Department of Geology and Geophysics, University of Hawai'i at Manoa, Honolulu, Hawaii, USA Mark D. Behn Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA Buffy Cushman La Pietra Hawaii School for Girls, Honolulu, Hawaii, USA Deborah E. Eason Department of Geology and Geophysics, University of Hawai'i at Manoa, Honolulu, Hawaii, USA Tracy K. P. Gregg Department of Geology, State University of New York at Buffalo, Buffalo, New York, USA Karl Gronvold Nordic Volcanological Center, University of Iceland, Reykjavik, Iceland Silvana Hidalgo Instituto Geofisico, Escuela Polytecnica Nacional, Quito, Ecuador Julia Howell Department of Earth and Ocean Sciences, University of South Carolina, Columbia, South Carolina, USA Owen Neill Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, USA Chris Russo Department of Geology and Geophysics, University of Hawai'i at Manoa, Honolulu, Hawaii, USA Colman, A., et al. (2012), Effects of variable magma supply on mid-ocean ridge eruptions: Constraints from mapped lava flow fields along the Galapagos Spreading Center, Geochem. Geophys. Geosyst., 13, QXXXXX, doi:10.1029/2012GC004163. Introduction This data set contains major element compositions of glass samples analyzed by electron microprobe at the University of Hawaii in spring- summer 2010 (2012gc004163-ts01.txt). Probe data were collected with an accelerating voltage of 15keV, 10 nA beam current, and 10 μm beam diameter. Three points were measured on each of three to six glass chips per sample (for an average of 14 points per sample), and the results were averaged. Peak and background counting times were 60 seconds for S; 50 seconds for Al, K, and Mg; 40 seconds for Si and Ca; 30 seconds for Ti, Na, Fe, and P; and 20 seconds for Mn. Samples were calibrated using Makaopuhi glass standard A-99 (Si, Al, Ca, Mg), Juan de Fuca glass standard VG-2 (Fe), and mineral standards Amelia albite (Na), sphene glass (Ti), orthoclase (K), Verma garnet (Mn), fluorapatite (P), and troilite (S). Glass standards VG-2 and A-99 were run as unknowns throughout the analyses to monitor instrument drift. A ZAF matrix correction was applied to all analyses. FeO* is total Fe expressed as FeO. Average major element compositions for each eruptive unit, calculated using these sample analyses, are given in Table 1 in the paper. Average values, standard deviations, and accepted values [Jarosevich et al., 1980] of analyses of glass standards VG2 (n=378) and A99 (n=378) that were analyzed throughout each analytical run are given in the table "2012gc004163-ts02.txt". In addition, this data set includes a table of observed hydrothermal features (2012gc004163-ts03.txt). The feature's location, fluid temperature (if measured), and feature name as given in Haymon et al. [2008] (if applicable) are given. 1. 2012gc004163-ts01.txt Major element glass compositions of glass samples. 1.1 Column “SAMPLE”, sample name 1.2 Column “SiO2”, wt. %, SiO2 content 1.3 Column “TiO2”, wt. %, TiO2 content 1.4 Column “Al2O3”, wt. %, Al2O3 content 1.5 Column “FeO”, wt. %, FeO content 1.6 Column “MnO”, wt. %, MnO content 1.7 Column “MgO”, wt. %, MgO content 1.8 Column “CaO”, wt. %, CaO content 1.9 Column “Na2O”, wt. %, Na2O content 1.10 Column “K2O”, wt. %, K2O content 1.11 Column “P2O5”, wt. %, P2O5 content 1.12 Column “S”, wt. %, S content 1.13 Column “SUM”, wt. %, analytical sum 1.14 Column “Latitude”, degrees, latitude of sample location 1.15 Column “Longitude”, degrees, longitude of sample location 1.16 Column “Depth”, m, depth below sea level of sample location 2. 2012gc004163-ts02.txt Analyses of glass standards A99 and VG2. 2.1 Column “SiO2”, wt. %, SiO2 content 2.2 Column “TiO2”, wt. %, TiO2 content 2.3 Column “Al2O3”, wt. %, Al2O3 content 2.4 Column “FeO”, wt. %, FeO content 2.5 Column “MnO”, wt. %, MnO content 1.6 Column “MgO”, wt. %, MgO content 1.7 Column “CaO”, wt. %, CaO content 1.8 Column “Na2O”, wt. %, Na2O content 1.9 Column “K2O”, wt. %, K2O content 1.10 Column “P2O5”, wt. %, P2O5 content 1.11 Column “S”, wt. %, S content 1.12 Column “SUM”, wt. %, analytical sum 3. 2012gc004163-ts03.txt Locations and descriptions of observed hydrothermal features 2.1 Column “Latitude”, degrees, latitude of hydrothermal feature 2.2 Column “Longitude”, degrees, longitude of hydrothermal feature 2.3 Column “Depth”, m, depth below sealevel of hydrothermal feature 2.4 Column “Deployment”, Alvin dive or TowCam tow during which feature was observed 2.5 Column “Haymon”, feature name in Haymon [2008], if given 2.6 Column “Temp”, degrees Celsius, temperature of fluids emitting from actively venting features, if measured 2.7 Column “Observations”, observations of feature. References Haymon, R. M., S. M. White, E. T. Baker, P. G. Anderson, K. C. Macdonald, and J. A. Resing (2008), Geochem. Geophys. Geosyst., 9, Q12006, doi:10.1029/2008GC002114. Jarosevich, E., J. A. Nelen, and J. A. Norberg (1980), Reference samples for electron microprobe analysis, Geostand. Newsl., 4, 43-47.