Carbon (C) and hydrogen (H) are crucial volatile elements that govern key physical and chemical processes throughout the solid Earth, from the deep mantle to shallow crust. Influenced by pressure–temperature regimes and redox conditions, these elements exist in diverse forms within mineral structures, melts, and fluids. Through processes such as slab subduction, mantle convection, and the migration of melts and fluids, C and H are exchanged between Earth’s deep and shallow reservoirs. The cycling of these elements, in turn, shapes the dynamics and evolution of both the mantle and the crust. Notably, H and C exert considerable control over magma evolution and volcanic eruptions. Moreover, the formation of energy resources such as hydrocarbons and natural hydrogen likely involves chemical and thermal inputs from the mantle. A comprehensive understanding of deep carbon and hydrogen across spatial scales and Earth’s interior systems is therefore crucial for deciphering the functioning and evolution of our planet.
This session aims to integrate geochemical, petrological, experimental, computational, and modeling approaches to advance insights into the behavior of C and H within the silicate Earth. We welcome contributions addressing: (i) the speciation and fractionation of C and H in minerals, melts, and fluids under varying redox conditions; (ii) the budgets and cycling of C–H in the bulk silicate Earth; (iii) the roles of C and H throughout Earth’s history; and (iv) implications for the formation of C–H-bearing minerals and energy resources.