Modeling multiphase non-isothermal fluid flow and reactive geochemical transport in variably saturated fractured rocks: 2. Applications to supergene copper enrichment and hydrothermal flows

Reactive fluid flow and geochemical transport in unsaturated fractured rock s has been of increasing interest to investigators in the areas of geo- and environmental- sciences, To test geochemical hypotheses based on petrologi c observation and to predict geochemical reactions that occur through a com plex dynamic interplay of physical and chemical processes, we use the metho ds presented in a companion paper (part 1, this issue p. 16-33) to investig ate two problems: (1) supergene copper enrichment in unsaturated-saturated media and (2) predicted effects of thermohydrology on geochemistry during t he Drift Scale Heater Test at the Yucca Mountain potential nuclear waste re pository, Nevada. Through these two examples we address the importance of t he following Issues on geochemical processes: (1) participation of gas phas e in transport and reaction, (2) interactions between fractures and rock ma trix for water and chemical constituents, (3) heat effects on fluid flow an d reaction properties and processes. In the supergene enrichment system, ox ygen gas diffusion from the land surface through fractured rock promotes th e alteration of the primary sulfide minerals and the subsequent deposition of secondary minerals, Modeling of the large-scale heater test shows effect s of fracture-matrix interaction, heat-driven vaporizing fluid flow, and CO 2 degassing on mineral alteration patterns. The two examples also serve as a demonstration of our methods for reactive transport in variably saturated fractured rocks.