Experimentally determined trace element partition coefficients between hibonite, melilite, spinel, and silicate melts

This article provides new data on mineral/melt partitioning in systems relevant to the evolution of chondrites, Calcium Aluminum-Rich Inclusions (CAI) in chondrites and related meteorites. The data set includes experimentally determined mineral/melt partition coefficients between hibonite (CaAl12O19), melilite (Ca2(Al,Mg)2SiO7), spinel (MgAl2O4) and silicate melts for a wide range of trace elements: Sc, Ti, V, Cr, Co, Ni, Cu, Zn, Ga, Ge, Rb, Sr, Y, Zr, Nb, Rh, Cs, Ba, La, Ce, r, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Pb, Th and U. The experiments were performed at high temperatures (1350 °C < T < 1550 °C) and ambient pressure. The experimental run products were analyzed using electron microprobe (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The partition coefficients for 38 trace elements were calculated from the LA-ICP-MS data.


Type of data
Major element data of minerals and quenched melts: data in .xlsx format Trace element data of minerals and quenched melts: data in .xlsx format Mineral/melt trace element partition coefficients: data in .xlsx format Mineral/mineral trace element partition coefficients: data in .xlsx format Experimental features High temperature experiments were run at high temperatures to equilibrate hibonite, melilite, and spinel, with silicate melts. The experimental run products were mounted in epoxy resins and polished using a variety of diamond pastes. The mounts were carbon coated, and major elements were analyzed using EMPA techniques. Subsequently, trace element concentrations of minerals and glasses within the samples were determined using LA-ICP-MS techniques.

Data accessibility Supplementary materials
Value of the data The new trace element partition coefficients supplement the existing database of mineral/melt partition coefficients of minerals that are frequently found in Ca-and Al-rich inclusions in chondritic meteorites.
The new trace element partition coefficients between hibonite, melilite and spinel and silicate melts may be used to test whether these minerals crystallized from or equilibrated with a silicate melt or whether they condensed from a vapor phase.
This partition coefficient data set is based on experiments under oxidizing conditions, since preliminary experiments under reducing conditions, which would have been more relevant to solar nebula processes, resulted in crystals which were too small to be analyzed.
Our mineral/mineral partition coefficients may be used to test whether hibonite, melilite and spinel are in thermodynamic equilibrium or not.

Data
In this article, we report new experimentally determined trace element partition coefficients between hibonite (CaAl 12 O 19 ), melilite (Ca 2 (Al,Mg) 2 SiO 7 ), spinel (MgAl 2 O 4 ), and silicate melts at high temperatures (Tables 3 and 4). Data were generated using high temperature experiments, which were characterized using electron microprobe and LA-ICP-MS methods (Tables 1 and 2).    Ti2-R3  H1-Ti5-R4  H1-Ti5-R5  H2-Ti2-R2  H2-Ti2-R3  H2-Ti5-R4  H2-Ti5- Table 3 Mineral-melt partition coefficients including the available literature data. The 1σ represents the mean absolute standard error on the average and "n" stands for the number of analyzes that had been incorporated in the calculations for the D-values in the form of "n" of the mineral vs. "n" of the silicate melt.
Hibonite   [4]). In total six different starting material mixtures were prepared from high purity oxides and carbonates. The resulting mixtures were homogenized in an agate mortar under acetone and were subsequently fused in a large Pt-crucible at 1500°C for at least 3 h in a Linn VMK (Linn Gmbh, Eschenfelden, Germany) high temperature box furnace. The resulting silicate glasses

Experimental techniques
Experiments were conducted in a vertical tube furnaces (Gero GmbH, Neuhausen, Germany) at atmospheric pressure. We used the so-called "wire-loop technique" [5][6][7] where small amounts of starting material powder are mixed with an organic glue (UHU Gmbh, Flinke Flasche, Germany) and suspended on a 0.1 mm thick Pt wire. The loops are about 3 mm in diameter each. Using a homemade platinum wire "chandelier", several samples could be run simultaneously. The samples were placed in the hot zone of the furnace at 800°C. The temperature paths were designed so that the samples were first heated to temperatures well above the liquidus (i.e. 1550°C, T max in Table 6), the run was left at 1550°C (T max in Table 6) for at least 8-10 h, and then slowly cooled down to the final run temperature (T quench ) to equilibrate crystals with melts. Most experimental runs were performed with a single cooling ramp, whereas some experiments (H1-Ti5-R5, H2-Ti5-R5, H3-Ti5-R5, H2-R8, H3-R8, Mel3-R9; Table 6) were run with a more complex multi step cooling and heating cycle close to the liquidus temperature. In these runs the experiment was first heated to 1550°C, then cooled to 1350°C, left for 10-40 h, then heated with 50°C/h to 1437 or 1450°C (c.f. Table 6), left for a few hours, and then cooled to the final run temperature (T quench ). This technique was employed by Kennedy et al. [2] to facilitate crystal growth. However, we found no significant difference between runs with a single cooling ramp compared to the complex heating/cooling experiments. Table 6 shows that the total run time of the experiments was between 100 and 300 h. The experiments were quenched in air by rapidly removing them from the furnace. Details of all experimental parameters are given in Table 6.
The samples were mounted in epoxy resin, polished, and pre-examined using optical microscopy and a JEOL JSM-6610 LV SEM scanning electron microscope equipped with EDX system at the University of Münster. Samples that contained hibonite, melilite or spinel large enough for further chemical characterization were subsequently analyzed for major and trace elements.

Analytical techniques
Major elements analyses were performed with a JXA-8530F Hyperprobe field emission electron beam microprobe analyzer (EMPA) at the University of Münster. Operating at 15 kV acceleration voltage, a beam diameter of 3 μm and 5 nA beam current for the silicate melts and 15 nA for the minerals. We used a five WDX detector setup with two TAP crystals (Mg, Al), two PET (Ca, Si) and one LiF crystal (Ti). Natural and synthetic materials that were used for standardization are: jadeite (Na 2 O), kyanite (Al 2 O 3 ), sanidine (K 2 O), Cr-diopside (Cr 2 O 3 ), diopside (CaO), San Carlos olivine (MgO), fayalite (FeO), hypersthene (SiO 2 ), rhodonite (MnO) and rutile (TiO 2 ). A number of secondary standards (chromite, olivine, cr-diopside) were measured as unknowns to monitor external precision and accuracy. Trace elements were measured by with a ThermoFisher Element II sector field ICP-MS coupled to a Photon Machines AnalyteG2 ArF Excimer laser at the University of Münster, operating with a 4 J/cm 2 laser fluency and a repetition rate of 5 Hz. A HelEx 2-volume sample cell was used which holds up to 8 one-inch diameter mounts, 6 thin sections and additional reference materials. Prior to sample analyses, the system was tuned with the NIST SRM 612 for high sensitivity, stability, and low oxide rates The NIST 612 standard glass [8] was used as an external standard and the BIR-1G [8] and BCR-2G [8] were analyzed as unknowns over the course of this study to monitor precision and accuracy. Twelve sample measurements were bracketed by three measurements of the NIST 612 glasses. For the hibonite and melilite crystals, 43 Ca was used as an internal standard, for spinel 26 Mg and for the silicate melts 29 Si was used internal standard element.