Description: This study presents electron microprobe data for dunite xenoliths from a lamprophyre dyke located on the island of Qeqertaa, West Greenland. The minimum age of this dyke is Palaeoproterozoic and it experienced amphibolite facies metamorphism and deformation during that era. The samples consist of nearly 200 xenoliths with a size range of 0.5-8 cm. These dunite xenoliths have olivine Mg#, that range from 80.3 to 94.6 (n = 579) with a mean of 92.6. Orthopyroxene is found in three xenoliths and garnet in five others. The latter suggests the depth of the Qeqertaa xenolith suite to be near the diamond stability-field, which is substantiated by the finding of diamonds in bulk samples of the Qeqertaa dyke. This further indicates the presence of a lithospheric mantle domain dominated by high-Mg# dunite to this depth in Palaeoproterozoic time. Cr-rich spinel, in the 0.1-0.2 mm size range, is found within and between olivine grains in individual xenoliths. These Cr-spinels yield Fe-Mg exchange temperatures of 400-600°C. However, the presence of intermediate spinel compositions spanning the lower temperature solvus suggests that equilibration temperatures were 〉550°C. Fe3+#, expressed as 100xFe3+/(Fe3++Al+Cr)), is shown to be a useful parameter in order to screen for altered spinel (Fe3+#〉10) with disturbed Mg# and Cr#. The screened spinel data (Fe3+#〈10) show a distinctly different trend in terms of spinel Cr# versus Mg#, compared to unmetamorphosed xenoliths in Tertiary lavas and dikes from Ubekendt Ejland and Wiedemann Fjord, respectively, also located within the North Atlantic craton. This difference likely reflects amphibolite facies metamorphic resetting of the Qeqertaa xenolith suite by Fe-Mg exchange. Given the similarity of the Qeqertaa xenolith suite with the Ubekendt and Wiedemann suites, in terms of their olivine Mg# and spinel Cr# distribution, high-Mg# dunite is likely to be an important component of the subcontinental lithospheric mantle beneath the North Atlantic craton and appears to have spanned a vertical distance of at least 150 km in this region, even during the Palaeoproterozoic.

Description: Carbonate was micro-sampled from representative listvenite and serpentinite core sections of Hole BT1B for carbonate stable isotope analysis (δ13C, δ18O) and clumped isotope thermometry. This sample subset includes matrix and vein magnesite, vein dolomite from the Upper Serpentinite (BT1B 43–02 and 44–03) and listvenite. The majority of listvenite carbonate samples are from the Lower Listvenite, comprising green, light red and dark red listvenite, plus one additional light red listvenite from the Upper Listvenite. Listvenite matrix carbonate is mainly magnesite except for matrix dolomite from core sections BT1B 72–04 and BT1B 77–03. Listvenite vein dolomite was sampled from the Upper Listvenite (BT1B 32–02) and Lower Listvenite (BT1B 67–04). Carbonate was sampled by using a micro drill with 3.8 mm inner diameter and a handheld Dremel tool from thin-section billets at sites selected based on the petrography. The relatively large diameter of the drill compared to the typical grain size and vein diameter, required sampling of the most homogeneous matrix areas and veins that were macroscopically devoid of crosscutting relationships. Carbonate samples were further crushed to a fine powder using an agate mortar and pestle prior to the analysis. Stable isotope analyses were performed at the GeoLab, Utrecht University, The Netherlands. Before isotope analysis, the mineralogy of each sample powder was constrained by XRD. The duration of acid digestion was adjusted to either dolomite or magnesite according to the dominant carbonate species in the sample powder. Dolomite samples were digested in 103% phosphoric acid at 70°C for 20 minutes and the released CO2 was continuously collected in a liquid nitrogen trap using a Kiel IV carbonate device, coupled to a 253 Plus isotope ratio mass spectrometer (both instruments from Thermo Scientific) and analyzed in Long-Integration Dual-Inlet mode (Müller et al., 2017a, doi: 10.1002/rcm.7878; with 600 seconds integration time per aliquot). The weight of individual aliquots of reference materials and unknown samples ranged between 75–95 µg. Magnesite samples were digested offline, using 10–20 mg solid powder and 1–2 ml 103% phosphoric acid at 100°C for 15–16 hours in individual, sealed vials using a custom-built vacuum line containing a cold trap with liquid nitrogen acetone slush (-96°C) to remove H2O trace quantities from the CO2 gas. The analyses were conducted using the Dual Inlet of a Thermo Fisher Scientific MAT 253 in the traditional way by 8 alternating reference gas-sample gas cycles (208 seconds sample gas integration time per measurement). All analyses were carried out in sequences with intermittent analyses of the carbonate (calcite) reference materials ETH-1, ETH-2, ETH-3. Each unknown sample was analyzed 4 to 14 times. A separate dataset contains the complete summary of all individual analyses of unknown samples and reference materials (Beinlich et al., 2019; doi:10.1594/PANGAEA.908649).

Description: The presented serpentine and fuchsite (Cr-muscovite) data were derived from representative carbonate-bearing serpentinite and listvenite samples from Hole BT1B, OmanDP. Electron microprobe analysis was conducted using the JEOL 8530F FE electron microprobe at Centre for Microscopy, Characterization and Analysis (CMCA), The University of Western Australia, using an acceleration voltage of 15 keV and a fully focused beam. The general analytical procedure and application of reference materials follow the method described in Beinlich et al. (2018; doi:10.1038/s41467-018-03039-9).

Description: This database reports the results of bulk rock geochemical measurements realized on 84 rock samples collected from Hole BT1B drilled during ICDP Oman Drilling Project (OmanDP, Kelemen et al. [2020]). 15 samples were collected on-site every 20m during the drilling operations (February-March 2017). 59 samples were selected by the shipboard science party as representative of the different lithologies recovered from Hole BT1B during the description of the cores, on board D/V Chikyu (August 2017). 10 additional listvenites and serpentinites were selected from Sections C5704B-73Z-1 to -75Z-2 (180.01-186.945mbg) for a coordinated on-shore study of the lower serpentinite intervals and neighboring listvenites (thereafter referred to as consortium samples). The purpose of the study was to obtain a high-density and high analytical quality bulk geochemical characterization along the 300.05 meters of continuous cores recovered from OmanDP Hole BT1B, through the transition from the variously carbonated peridotites at the base of the Semail ophiolite mantle section to the underlying metamorphic lithologies. 51 listvenites, 14 serpentinites, and 19 greenshists and greenstones were analyzed. The rock names and grouping by Units were determined on-board D/V Chikyu from macroscopic observations (Visual Core Description; Kelemen et al. [2020]). Major and trace element concentrations were measured by X-ray fluorescence (XRF). XRF analyses of shipboard and on-site samples noted * in the Method columns were realized on-board D/V Chikyu (Note that major oxide concentrations in Kelemen et al. [2020] are recalculated to 100 wt.%) and those noted † in the Method columns were realized at the University of St. Andrews (see Table BT1-T12 in Kelemen et al. [2020]). XRF analyses of consortium samples were realized at Geolabs. FeO concentrations were measured by titration at the University of Lausanne (Switzerland). Total H and C concentrations (noted TH and TC) were determined on-board D/V Chikyu by combustion CHNS elemental analysis (EA) and used to recalculate H2O and CO2 contents. Concentrations of carbon in Ca-carbonates (total inorganic carbon; noted TIC) were determined by coulometry. Trace element compositions were determined using a Quadrupole Inductively-Coupled-Plasma-Mass Spectrometer (Q-ICP-MS) at the University of Montpellier (France). All analyses were performed on samples prepared from non ignited rock-powders, except for XRF major element analyses realized on beads on-board D/V Chikyu. Concentrations are reported in wt.% (10-2g/g) and in ppm (10-6 g/g). Abbreviations: mbg: meters below ground (Chikyu curated depth); Fu-listvenite : fuchsite-bearing listvenite; LOI : Loss on ignition; XRF B : XRF analyses on beads; XRF P : XRF analyses on powder pellets; XRF B/P : XRF major element analyses on beads except for K measured on pellets and recalculated as volatile free; n.a.: not analysed; n.d.: not determined. (Notes, abbreviations & reference at the bottom of the file) ‡ Sample C5704B-60Z-4-1, 24.0--29.0 cm: Green matrix (Host: Sample C5704B-60Z-4-1, 24.0--29.0 cm - H) crosscut by pink vein (Vein : Sample C5704B-60Z-4-1, 24.0--29.0 cm - V) Reference : Kelemen, P. B., J. M. Matter, D. A. H. Teagle, J. A. Coggon, and the Oman Drilling Project Science Team (2020), Proceedings of the Oman Drilling Project, College Station, TX.