Melt inclusion data for the central-eastern Aleutian volcanoes

We present data for 296 melt inclusions from central-eastern Aleutian volcanoes. The samples were collected during joint GeoPRISMS-DCO-AVO field campaigns in 2015 and 2016 (PIs: Roman, Plank, Hauri). Most melt inclusion hosts were found as loose olivine crystals in the 0.5-2 mm ash size fraction of tephra samples. In the Clevland volcano samples, a few of the melt inclusion hosts were found in a crushed bomb. Melt inclusions were doubly polished and analyzed by Fourier Transform Infrared Spectroscopy (FTIR) and Electron Microprobe Analysis (EMPA). FTIR analyses were conducted on a Thermo-Nicolet Nexus 670 FTIR spectrometer at the American Museum of Natural History (AMNH). Absorption coefficients are from Dixon et al. (1997) for total H2O and Dixon and Pan (1995) for CO3. Background position was determined using a cubic spline interpolation with the method described by Rasmussen et al. (2020). Major and minor elements were measured by EMPA using a Cameca SX-100 at the AMNH. Analyses were conducted using a 10 micron beam, 15 keV, variable on-peak time, and both 5 and 50 nA depending on the element (see metadata for details). Raw analytical results were normalized to check standard compositions for major elements. The check standard used for the normalization is 892-1. Sulfur concentrations were corrected for measurements that were performed off peak using an empirical approach, which will be detailed in a publication that is in preparation. In short, we used measured a subset of melt inclusions using multipe peak locations, and we consider the measurement that yield the highest sulfur content as the most accurate measurement. The offset between the off-center S measurement and the most-accurate measurement is a function of the total sulfur content, which we consider a proxy for sulfur speciation and the position of the sulfur peak. We use the relationship between the offset and sulfur content to calculate a correction factor for the entire dataset. Trace elements were measured using laser ablation ICP-MS at Lamont-Doherty Earth Observatory and at the Carnegie Department of Terrestrial Magnetism. The melt inclusions are not corrected for post-entrapment crystallization. The objectives of the work are to understand magmatic processes and characterize along-arc geochemical trends in the Aleutians. Bulk rock and host olivine data from these samples samples are also published in Earthchem. A report that includes more information on the samples presented here can be found online: Plank, T., Rasmussen, D., Stelling, P., Roman, D. 2020. Field Report for the Collection of Mafic Tephra from the Aleutians Islands between Unimak and the Island of Four Mountains (Alaska, USA), Version 1.0. Interdisciplinary Earth Data Alliance (IEDA).