HR: 0800h
AN: H11B-0483    [Abstracts]
TI: Numerical Modeling of Multiphase Fluid Flow in Ore-Forming Hydrothermal Systems
AU: * Weis, P
EM: weis@erdw.ethz.ch
AF: Fluids and Mineral Deposits Group, ETH Zurich, Insitute of Isotope Geochemistry and Mineral Resources, ETH Zentrum NW, Zurich, 8092, Switzerland
AU: Driesner, T
EM: driesner@erdw.ethz.ch
AF: Fluids and Mineral Deposits Group, ETH Zurich, Insitute of Isotope Geochemistry and Mineral Resources, ETH Zentrum NW, Zurich, 8092, Switzerland
AU: Coumou, D
EM: coumou@erdw.ethz.ch
AF: Fluids and Mineral Deposits Group, ETH Zurich, Insitute of Isotope Geochemistry and Mineral Resources, ETH Zentrum NW, Zurich, 8092, Switzerland
AU: Heinrich, C A
EM: heinrich@erdw.ethz.ch
AF: Fluids and Mineral Deposits Group, ETH Zurich, Insitute of Isotope Geochemistry and Mineral Resources, ETH Zentrum NW, Zurich, 8092, Switzerland
AB: Two coexisting fluid phases - a variably saline liquid and a vapor phase - are ubiquitous in ore-forming and other hydrothermal systems. Understanding the dynamics of phase separation and the distinct physical and chemical evolution of the two fluids probably plays a key role in generating different ore deposit types, e.g. porphyry type, high and low sulfidation Cu-Mo-Au deposits. To this end, processes within hydrothermal systems have been studied with a refined numerical model describing fluid flow in transient porous media (CSP~5.0). The model is formulated on a mass, energy and momentum conserving finite-element-finite-volume (FEFV) scheme and is capable of simulating multiphase flow of NaCl-H20 fluids. Fluid properties are computed from an improved equation of state (SOWAT~2.0). It covers conditions with temperatures of up to 1000 degrees~C, pressures of up to 500 MPa, and fluid salinities of 0~to 100%~NaCl. In particular, the new set-up allows for a more accurate description of fluid phase separation during boiling of hydrothermal fluids into a vapor and a brine phase. The geometric flexibility of the FEFV-meshes allows for investigations of a large variety of geological settings, ranging from ore-forming processes in magmatic hydrothermal system to the dynamics of black smokers at mid-ocean ridges. Simulations demonstrated that hydrothermal convection patterns above cooling plutons are primarily controlled by the system-scale permeability structure. In porphyry systems, high fluid pressures develop in a stock rising from the magma chamber which can lead to rock failure and, eventually, an increase in permeability due to hydrofracturing. Comparisons of the thermal evolution as inferred from modeling studies with data from fluid inclusion studies of the Pb-Zn deposits of Madan, Bulgaria are in a strikingly good agreement. This indicates that cross-comparisons of field observations, analytical data and numerical simulations will become a powerful tool towards a more thorough understanding of hydrothermal fluid processes. One such attempt will incorporate geometric data of veins in the Bingham porphyry Cu-Mo-Au deposit into our numerical model. The presentation will introduce the numerical model and show examples and first results of the aforementioned applications.
DE: 1847 Modeling
DE: 3611 Thermodynamics (0766, 1011, 8411)
DE: 3653 Fluid flow
DE: 8424 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135)
SC: Hydrology [H]
MN: 2007 Fall Meeting