Diagenesis of Mars Sediments : Coupled Water - Rock Interaction and Mass - Transfer Model

Introduction: Recently published reports on chemical and physical properties of Mars sediments indicate that diagenetically altered volcanic rocks were reworked by sedimentary processes [1]. Furthermore, compositional and petrographic aspects of sediments show varying degrees of elemental enrichment as well as complex interaction between the minerals in partially saturated or saturated conditions [2,3]. Two types of mechanisms have been proposed to address the volcanic rock alteration and iron-sulfate mineral precipitation. The first mechanism invokes direct interaction of volcanic vapor and gases with Martian basalt [4], whereas the second mechanism attempts to explain the formation of iron-sulfates in an evaporative basin condition [5]. Although both processes address certain aspects of how volcanic rocks may alter and sulfate salts precipitate, neither mechanism sufficiently identifies the network of water-rock interaction and mass-transfer processes that must be considered together to explain the observed sediment alteration trends. Thus, a new comprehensive chemical model is proposed here that addresses a much broader spectrum of processes.