Mineral and glass data for rock samples collected offshore McDonald Islands

Major and minor element abundances of clinopyroxene, glass, olivine, biotite, and orthoclase were determined for seven rock samples from three sea knolls around McDonald Islands. The samples were dredged from the sea knolls during the RV Investigator voyage IN2016_V01 and are curated at the University of Tasmania.The dataset includes seven files: 1. The location and petrographic descriptions of the samples, 2. Raw LA-ICP-MS data files (2 files), 3. Summary of analytical results for glass geochemistry, 4, Summary of analytical results for mineral geochemistry, 5. Raw electron microprobe mineral data and 6. Raw electron microprobe glass data.Sample SelectionSamples selected for analysis are a subset of samples collected from each dredge. Following macroscopic examination of the samples, polished rock thin sections were made of the least altered rocks. Following examination under petrographic microscope, the least altered samples were selected for mineral analysis.Sample PreparationAfter weathered material was removed from the outer edge of the rock samples, rock pieces were cut from the freshest part of the sample and placed in 25 mm circular resin mounts. The exposed sample surface was polished and carbon coated for electron microprobe analysis. After electron microprobe analysis the carbon coat was removed by polishing before laser-inductively coupled plasma mass spectrometery (LA-ICP‐MS) was completed.Electron Microprobe MethodsMajor and minor element abundances of clinopyroxene, glass, olivine, biotite, and orthoclase from selected McDonald Islands sea knoll samples were measured with a JEOL JXA-8530F Plus field emission electron microprobe at the Central Science Laboratory, University of Tasmania. Analytical conditions were 15 kV acceleration voltage, 20 nA beam current, and a beam size of 10 µm. The peak-counting times were 10 s for Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, and Ni, and 30 s for F. Off-peak-counting times were 10 s for Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, and Ni, and 32 s for F on each side of the peak. The standards were rutile (Ti), Rhodonite (Mn), Eskolaite (Cr), Nickel Oxide (Ni), Orthoclase (K), Celestine (S), Fluor-Apatite (P), Hematite (Fe), Tugtupite (Cl), San Carlos Olivine NMNH 111312-44 (Mg), Kakanui Anorthoclase, NMNH 133868 (Na), Lake County Plagioclase NMNH 115900 (Al), Wollastonite (Ca, Si), Topaz (F), and calcium vanadate (V).Laser ICP-MS MethodsTrace element abundances of clinopyroxene, glass, olivine, biotite, and orthoclase were determined using an Agilent 7500cs quadrupole inductively coupled plasma mass spectrometer (ICP‐MS) coupled to a RESOlution HR laser ablation system at the University of Tasmania. Samples were ablated with a Agilent 7500cs quadrupole inductively coupled plasma mass spectrometer (ICP‐MS) coupled to a RESOlution HR laser ablation system equipped with a 193 nm Coherent COMPex Pro ArF Excimer Laser and a S155 ablation cell with constant geometry design at the University of Tasmania. A flow of He carrier gas at a rate of 0.35 L/min carried aerosols ablated by the laser out of the chamber to be mixed with Ar gas and carried to the plasma torch. Quantification was performed using NIST612 as the calibration reference material (Jochum and Stoll, 2008) and Ca as the internal standard element. Both BCR‐2g and GSD‐1g (Jochum and Stoll, 2008) were used as secondary standards for quality monitoring. Primary and secondary standards were analysed at the beginning and end of each batch to correct for instrument drift. Data quantification was performed using an in‐house data reduction spreadsheet.ReferencesJochum, K. P., and Stoll, B. I. (2008). Reference materials for elemental and isotopic analyses by LA‐(MC)‐ICP‐MS: Successes and outstanding needs. In P. Sylvester (Ed.), Laser ablation ICPMS in the earth sciences: Current practices and outstanding issues, Short Course (Vol. 40, pp. 147-168). Mineralogical Association of Canada.