The occurrence of moissanite (SiC), as xenocrysts in mantle-derived basaltic and kimberlitic rocks sheds light on the interplay between carbon, hydrogen and oxygen in the lithospheric and sublithospheric mantle. SiC is stable only at ƒ_O2 < ΔIW−6, while the lithospheric mantle and related melts commonly are considered to be much more oxidized. SiC grains from both basaltic volcanoclastic rocks and kimberlites contain metallic inclusions whose shapes suggest they were entrapped as melts. The inclusions consist of Si⁰ + Fe₃Si₇ ± FeSi₂Ti ± CaSi₂Al₂ ± FeSi₂Al₃ ± CaSi₂, and some of the phases show euhedral shapes toward Si⁰. Crystallographically-oriented cavities are common in SiC, suggesting the former presence of volatile phase(s), and the volatiles extracted from crushed SiC grains contain H₂ + CH₄ ± CO₂ ± CO_. Our observations suggest that SiC crystalized from metallic melts (Si-Fe-Ti-C ± Al ± Ca), with dissolved H₂ + CH₄ ± CO₂ ± CO derived from the sublithospheric mantle and concentrated around interfaces such as the lithosphere-asthenosphere and crust-mantle boundaries. When mafic/ultramafic magmas are continuously fluxed with H₂ + CH₄ they can be progressively reduced, to a point where silicide melts become immiscible, and crystallize phases such as SiC. The occurrence of SiC in explosive volcanic rocks from different tectonic settings indicates that the delivery of H₂ + CH₄ from depth may commonly accompany explosive volcanism and modify the redox condition of some lithospheric mantle volumes. The heterogeneity of redox states further influences geochemical reactions such as melting and geophysical properties such as seismic velocity and the viscosity of mantle rocks.

在地幔衍生的玄武岩和金伯利岩中，以辉石为异晶的莫桑石（SiC）的存在，揭示了岩石圈和岩石圈以下地幔中碳，氢和氧之间的相互作用。碳化硅是稳定的仅在ƒ _{Ò 2}  <ΔIW-6，而地幔和相关熔体通常被认为是更为氧化。玄武质火山碎屑岩和金伯利岩中的SiC晶粒均含有金属夹杂物，其形状表明它们被熔体截留。夹杂物包括Si ⁰  + Fe ₃ Si ₇  ±FeSi ₂ Ti±CaSi ₂ Al ₂  ±FeSi ₂ Al ₃  ±CaSi ₂，并且一些相向Si ⁰呈现正方体形状。SiC中常见的晶体取向腔，表明以前存在挥发性相，并且从粉碎的SiC晶粒中提取的挥发物包含H ₂  + CH ₄  ±CO ₂  ±CO _。我们的观察结果表明，SiC从金属熔体（Si-Fe-Ti-C±Al±Ca）中结晶，溶解的H ₂  + CH ₄  ±CO ₂  ±CO来源于地下岩石圈地幔，并集中在岩石圈-软流层等界面附近和地幔边界。当基性/超基性岩浆连续注入H ₂  + CH _4时它们可以逐步还原，直至硅化物熔体不混溶并结晶出SiC等相。在不同构造背景下的火山岩中，SiC的出现表明，H ₂  + CH ₄从深处的释放通常会伴随火山岩的爆发并改变某些岩石圈地幔体积的氧化还原条件。氧化还原态的非均质性进一步影响地球化学反应，例如熔化和地球物理特性，例如地震速度和地幔岩石的粘度。