Beschreibung: The GLITTER software package was used for raw data reduction, applying initial calibration with NIST-SRM612 as the primary standard, using CaO g/100g for the internal count to mass fraction reference. Potential errors from surface contamination have been avoided by excluding the first seconds of data acquisition from integration. The signal trace over time for each element (m/z) measured was checked for its analytical and geological reasoning and excluded in case of abnormal pattern or spikes (e.g., vertical transitions into different mineral phases during ablation, mineral inclusions, sulfide micro nuggets in clinopyroxene). A second, matrix-matched calibration step was realized by correcting against mean offset factors of median values from at least three repetitive measurements on nano-particulate pressed powder tablets of reference materials USGS-BHVO-2NP, USGS-BIR-1NP, and GSJ-JGb-1NP. All reference materials were analyzed multiple times throughout each analytical session for bracketing and drift correction. Some sessions have been calibrated against the USGS glass microanalytical reference materials USGS-BHVO-2G and USGS-BIR-1G. Results of glass vs. pellet reference materials show no significant quality difference and lead to similar correction factors. Analytical measurement uncertainties were found to be in the range of 1% to 3% RMAD (1MAD) at mass fractions 〉10x LOD for most elements analyzed. For monitoring deviations from preferred or “true” values, the MPI-DING glasses GOR-128G, GOR-132G, and StHs6/80-G have been measured as unknowns. Additionally, JF-1P with extremely low mass fractions for most trace elements has been measured during most analytical sessions. Estimated deviations from preferred values of all analyzed reference materials are, for most elements, in the range of 5 to 10 RMSD% and within the uncertainties of the preferred or compiled values.

Beschreibung: Here we present a profile of 39 gabbros through the plutonic section of the Oman ophiolite paleocrust (Wadi Gideah Transect; Wadi Tayin block). Major and trace element core compositions for co-existing plagioclase and clinopyroxene progressively evolve up section from layered gabbros through foliated gabbros up to the varitextured gabbros. Calculated parental melts correspond to typical Oman MORB but reveal differences in the plagioclase-clinopyroxene equilibrium and crystallization style along the profile. Layered gabbro mineral cores have crystallized under equilibrium and stable boundary conditions. Rims show a pronounced inverse zonation of plagioclase Ca# and, to some extent, of clinopyroxene Mg#. Contrastingly, incompatible trace elements indicate progressive fractionation from the core to the rim and up section. For regression of the temperature inversion, we wrote a custom R script (https://doi.org/10.5281/zenodo.5702686) calling the MASS::rlm function to perform an iterated re-weighted least squares (IWLS) robust linear fit between REEs in the Ln(Dj)-A and Bj-1000 space calculated following Sun and Liang (2017, https://doi.org/10.1007/s00410-016-1326-9). We create an in situ crystallization-temperature depth profile through the lower Oman paleocrust. The estimated temperatures are consistent with temperatures established based on the plagioclase anorthite content, revealing a relationship of T-REE-An [°C] = 6.1 ± 0.2 * An + 706 ± 19. Crystallization temperatures of the layered gabbros cover a narrow median range of 1216 ± 14 °C. Considerable temperature variability of 1077 to 1231 °C is observed for the upper gabbros, featuring a thermal minimum within the foliated gabbros. This dataset includes petrographic descriptions for all 39 samples, average values for EPMA measurements, spot and median data for LA-ICP-MS measurements, the associated standard deviations, related quality control parameters, and calculated REE-temperatures.