Sources and drains: Major controls of hydrothermal fluid flow in the Kokanee Range, British Columbia, Canada

Vein fields are fractured domains of the lithosphere that have been infiltr ated by hydrothermal fluids, which deposited minerals in response to changi ng physico-chemical conditions. Because oxygen is a major component of the infiltrating fluid and the surrounding rock matrix, the oxygen isotope comp osition of minerals found in veins is used to decipher ancient fluid flow w ithin the lithosphere. We use a numerical model to simulate oxygen isotope transport in the Kokanee Range silver-lead-zinc vein field. The model consi ders advective, dispersive, and reactive transport in a three-dimensional p orous rock matrix intersected by high-permeability planes representing frac ture zones. Here we show that it is the geometrical configuration of the so urces and of the drains of hydrothermal fluids, combined with the fracture pattern, that exerts the main control on the oxygen isotope distribution. O ther factors that affect, to a lesser extent, the values and positions of o xygen isopleths are the fluids and rock-matrix isotopic compositions, the i sotopic fractionation, the reaction rate constant, and hydraulic conductivi ties of the rock matrix and fracture zones.