LA-ICP-MS singlespot, median and standard deviation for 29 trace elements including LILEs, HFSEs and REEs for 39 gabbro samples form the Oman Ophiolite (Wadi Gideah Transect)

For in situ analysis of 29 trace elements, carried out at the LA-ICP-MS lab of the Institute of Geosciences at Kiel University, a 193nm ArF-exciplex laser ablation system (GeoLasPro HD, Coherent) coupled to an Agilent 7900s ICP-MS was used for most samples. Some samples have been measured using an older Agilent 7500s ICP-MS, and a minor portion was measured using a Thermo Scientific Element XR ICP-SF-MS. In any case, samples and reference materials were loaded to a Zuerich-type, two-volume low dispersion high capacity laser ablation cell, which was flushed with 995 ml min-1 helium carrier gas. Additionally, 14 ml min-1 hydrogen was added upstream of the cell to enhance ionization at the ICP and reduce oxide formation. Many elements in plagioclase are within the ultra-trace concentration range (< 1 µg/g). Therefore, the laser was operated at a pulse frequency of 16 Hz and a fluence of 18 J cm-2 with a crater size of 120 µm for plagioclase. Clinopyroxene was measured at 10 Hz, 12 J cm-2, and a crater of 44 to 32µm. We could not detect any adverse effects from mass load of the ICP for the elements determined. The oxide production rate was monitored by Th/ThO and kept below 0.1%. Time-resolved data acquisition for each measurement was split into 20 s background, 40 s sample ablation, and 20 s washout monitoring time. Dwell times were optimized for the expected concentration range for each element. Where possible, we aimed to perform five proximal repetitions for five crystals of each phase per sample to evaluate crystal core heterogeneity as well as sample phase heterogeneity.