Keynote Session

Introduction of the Lecture

The world’s oceans are underlain by a system of linear magma-driven hydrothermal systems that encircle the globe along the 65,000 km length of the mid-ocean ridges (MOR). These systems are by far the largest geothermal manifestation on Earth and are inferred to have been operating through most of the last 4 billion years. The flow of ocean water through the geothermal systems (about 1.5 ocean volumes per million years) results in chemical exchange between the oceans and the rocks that is thought to influence seawater chemistry and affect global climate on timescales of millions of years. MOR hydrothermal systems are consequently an important target for thermo-hydro-mechanical-chemical (THMC) modelling. In addition, the enormous amount of information available on fluid fluxes, vent fluid temperatures and chemistry, and tectonic and alteration effects on rock mineralogy and texture, make them an attractive focus for testing and calibrating THMC simulators. This paper provides some examples of how we have applied the TOUGHREACT code to modelling of MOR hydrothermal systems, and the conclusions that result regarding large scale permeabilities, mineral-fluid reaction rates, and the applicability of available thermodynamic and kinetic data on silicate minerals.