Thermodynamics of Element Volatility and its Application to Planetary Processes

TL;DR

This paper explores the thermodynamics of element volatility and its implications for planetary processes, emphasizing the challenges in understanding gas-condensed phase interactions due to vapor escape and indirect evidence.

Contribution

It introduces a thermodynamic framework for analyzing element volatility in planetary contexts, addressing the limitations of indirect evidence in gas-condensed phase interactions.

Findings

Vaporization processes are often inferred from residual chemical and textural evidence.

The ideal gas law provides a basis for understanding gas behavior in geological processes.

Understanding element volatility aids in interpreting planetary formation and evolution.

Abstract

Despite its importance in geological sciences, our understanding of interactions between gas and condensed phases (comprising solids and liquids) remains clouded by the fact that, often, only indirect evidence remains for their occurrence. This arises from the tendency for the vapour phase to escape from the condensed phase with which it interacts, owing to its much lower density and thus greater volume. For a gas that is sufficiently tenuous that interactions do not occur between its constituent molecules, this relationship is quantified in the ideal gas law (Clapeyron 1834): $PV=nRT$ (1) where $P$ is the total pressure exerted by the gas, $V$ its volume, $n$ is the number of moles, $R$ the gas constant 8.3145 $Jmol^{-1}K^{-1}$, Horstmann, 1873) and $T$ the absolute temperature. One mole of an ideal gas at 273.15 $K$ and $10^5$ $Pa$ (standard temperature and pressure for gases) has a molar volume of 22,711 $cm^3/mol$, $10^3$ x greater than typical silicate liquids or minerals. As a result, vaporisation processes in nature are often informed by chemical and textural evidence remaining in the condensed phase.