FirstIn SituTerrestrial Osbornite (TiN) in the Pyrometamorphic Hatrurim Complex, Israel

Abstract

AbstractOsbornite (TiN) is extremely rare in nature (commonly found in enstatite meteorites) and has not yet been identified correctly to form naturally in terrestrial settings. Due to its thermodynamic stability and thermal shock resistance, TiN has wide industrial applications, mainly as coatings. However, as the melting temperature of TiN is very high (~3000°С), coatings are produced at much lower temperatures via physical or chemical vapor deposition. Also, anthropogenic analogues of osbornite are often observed in pyrometallurgical slags. Therefore, it is critical to distinguish between anthropogenic and naturally occurring osbornite. A detailed petrographic study was undertaken on in situ osbornite found within unusual gehlenite-bearing breccias from wadi Zohar, Negev Desert of the pyrometamorphic Hatrurim Complex. The Hatrurim Complex, which extends through Israel, Palestine, and Jordan within the Dead Sea Rift zone, mainly comprises larnite, gehlenite, and spurrite rocks. Osbornite, in close association with iron phosphides, barringerite, and schreibersite, occurs at contacts between gehlenite, paralava, and calcinated clasts of host sedimentary rocks. Based on investigation of pseudowollastonite and Fe-P series phases, osbornite is formed at low pressure, extremely high temperatures (~1200-1500°С), and reduced conditions, following pyrolysis of organic matter contained in the sedimentary protolith. This is the first identification of in situ osbornite in terrestrial rocks and indicates that high-temperature and highly reduced conditions, which are common for meteorites, may occur at/near the Earth’s surface as a result of sustained pyrometamorphism in particular settings. Our findings also provide relevant data and criteria for comparing osbornite occurrences elsewhere and ultimately evaluating their origins.