Revision 1 , 2-2021 1 Immiscible metallic melts in the upper mantle beneath Mount Carmel , Israel : 1 Silicides , phosphides and carbides 2 3

1 Immiscible metallic melts in the upper mantle beneath Mount Carmel, Israel: 1 Silicides, phosphides and carbides 2 3 William L. Griffin, Sarah E.M. Gain, Martin J. Saunders, Jin-Xiang Huang, Olivier Alard, 4 Vered Toledo and Suzanne Y. O’Reilly 5 ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS) and GEMOC, Earth and Environmental 6 Sciences, Macquarie University, NSW 2109, Australia; bill.griffin@mq.edu.au 7 2 Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, WA 6009, Australia 8 Shefa Gems Ltd., Netanya 4210602, Israel 9 10 Abstract 11 Xenolithic corundum aggregates in Cretaceous mafic pyroclastics from Mount Carmel 12 contain pockets of silicate melts with mineral assemblages (SiC (moissanite), TiC, Ti2O3 13 (tistarite), Fe-Ti-Zr silicides/phosphides) indicative of magmatic temperatures and oxygen 14 fugacity (fO2) at least 6 log units below the Iron-Wüstite buffer (IW≤-6). Microstructural 15 evidence indicates that immiscible, carbon-rich metallic (Fe-Ti-Zr-Si-P) melts separated 16 during the crystallization of the silicate melts. The further evolution of these metallic melts 17 was driven by the crystallization of two main ternary phases (FeTiSi and FeTiSi2) and several 18 near-binary phases, as well as the separation of more evolved immiscible melts. 19 Reconstructed melt compositions fall close to cotectic curves in the Fe-Ti-Si system, 20 consistent with trapping as metallic liquids. Temperatures estimated from comparisons with 21 experimental work range from ≥1500 °C to ca 1150 °C; these probably are maximum values, 22 due to the solution of C, H, P and Zr. With decreasing temperature (T), the Si, Fe and P 23 contents of the Fe-Ti-Si melts increased, while contents of Ti and C decreased. The increase 24 in Si with declining T implies a corresponding decrease in fO2, probably to ca IW-9. The 25 solubility of P in the metallic melts declined with T and fO2, leading to immiscibility between 26 Fe-Ti-Si melts and (Ti,Zr)-(P,Si) melts. Decreasing T and fO2 also reduced the solubility of C in 27 the liquid metal, driving the continuous crystallization of TiC and SiC during cooling. The 28 lower-T metallic melts are richer in Cr, and to some extent V, as predicted by experimental 29 studies showing that Cr and V become more siderophile with decreasing fO2. 30 These observations emphasise the importance of melt-melt immiscibility for the 31 evolution of magmas under reducing conditions. The low fO2 and the abundance of carbon 32 This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America. The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press. DOI: https://doi.org/10.2138/am-2021-7934. http://www.minsocam.org/