Moissanite in serpentinite from the Dabie Mountains in China

Abstract

Although moissanite has been found in various rocks, reliable primary moissanite has been reported only from kimberlites and meteorites. The Dabie Mountain moissanite reported in this paper is the first occurrence of primary moissanite hosted by serpentinite. It differs from synthetic silicon carbide in optical properties, inclusions and infrared spectrum. The biaxiality of the Dabie Mountain moissanite is thought to be the result of intracrystal deformation. In reference to the ultrahigh pressure (7—8 GPa) signature of exsolution of rod-like apatite, clinopyroxene and rutile in garnets, and magnetite lamellae in olivine reported in the Dabieshan, we inferred that the moissanite from the Dabie Mountains was probably generated at a depth of 180 km; and then subducted to a depth of 210—250 km, where the moissanite became biaxial before its exhumation.

Carbon Mineralogy and Crystal Chemistry

“…Although rare and volumetrically trivial as reservoirs of carbon in the crust, they may represent a significant volume of carbon in Earth's deep interior, and thus may provide insight to the deep carbon cycle (Dasgupta 2013;Wood et al 2013). Since its discovery in 1893 by Henri Moissan in mineral residues from the Canyon Diablo meteor crater in Arizona (Moissan 1904b), natural moissanite has been found in dozens of localities, including meteorites, serpentinites, chromitites, ophiolite complexes, and in close association with diamond in kimberlites and eclogites (Lyakhovich 1980;Leung et al 1990;Alexander 1990Alexander , 1993Di Pierro et al 2003;Lee et al 2006;Qi et al 2007;Xu et al 2008;Trumbull et al 2009;Shiryaev et al 2011;see also http://MinDat.org). While some occurrences of moissanite are apparently of near-surface origin, including sites of forest fires and contact metamorphism of silicate magmas with coal beds (Sameshima and Rodgers 1990), silicon carbide also represents one of the deepest mantle minerals known to reach the surface.…”

Natural moissanite (SiC) – a low temperature mineral formed from highly fractionated ultra-reducing COH-fluids

“…In mantle compositions, serpentine or brucite are only stable at relatively low temperatures (<700°C) as could be expected for fluid-percolation in supra-subduction mantle or during orogenic metamorphism. In fact, SiC has been reported from serpentinites (Xu et al 2008). Moissanite accounting for 8% of a rock with a bulk X Mg = 0.998 has been reported from a beach pebble which matrix is brucitedominated (Di Pierro et al 2003).…”

“…Natural occurrences are manifold (Lyakhovich, 1980;Trumbull et al 2009) but many fall into three categories: (i) peridotites, serpentinites (Xu et al, 2008) and podiform chromitites (Bai et al, 2000); (ii) kimberlites Shiryaev et al, 2011); and (iii) metasomatic rocks (Lyakhovich, 1980;Di Pierro et al, 2003). In most cases, moissanite is recovered from heavy mineral separates with little textural and phase assemblage information available.…”

Tracking the timing and nature of protolith, metamorphism, and partial melting of tourmaline‐bearing migmatites by zircon U–Pb and Hf isotopic compositions in the Yuka terrane, North Qaidam UHP metamorphic belt

“…Moissanite represents one of the deepest-sourced reported mantle minerals found on the Earth's surface. It can occur in UHP to low-and medium-pressure environments and may not be an indicator of UHP metamorphism (Lyakhovich, 2010;Perraki & Faryad, 2014;Qi et al, 2007;Xu et al, 2008). However, the moissanite and graphite inclusions in zircon rims may indicate that the anatectic melts formed in reduced environments (Hazen, Downs, Jones, & Kah, 2013), or they may have been inherited from the migmatite protoliths.…”