Gas-solid reactions

Abstract

In this chapter we have shown that gas-solid reactions occur in a range of Earth and planetary settings. Because gas transport is effective, we should expect to find traces of these reactions in many rocks. Nonetheless, gas-solid reactions have received little attention because in the past these reactions have been difficult to decipher. In part, this has arisen because reaction products commonly evolve over time (Figs. 4, 11-13; Tables 1-3); reaction products may dissolve (e.g., salts; Figs. 15 and 16; Table 4) or escape (gas products), and host rocks may brecciate, anneal or become modified during typical geologic processes (Figs. 3b, 9, 10, 15, 17 and 23). This chapter provides a conceptual framework using techniques from chemistry, physics and chemical engineering to help constrain how reaction processes in Earth and planetary systems may be modelled (e.g., Fig. 14; Tables 1-3). Case studies show that these approaches can be merged to explain phenomena encountered in nature, but previously viewed as too difficult to constrain. We also show how standard approaches, such as equilibrium thermodynamics, may have limitations, but remain useful for predicting gas-solid reaction products (e.g., Figs. 24-29), particularly if paired with homogenization approaches (Fig. 14) as well as energy and momentum transfer models (Case Study 3). Finally, we show that there is much to explore in this relatively young field of research, as illustrated further in the following chapters in this volume. Show more