Sinter Architecture and Dating: Establishing Hot Spring Paleo-Flow Conditions and Locating Possible Hidden Geothermal Resources

Abstract

Discharging alkali chloride hot springs are surface expressions of a deeper geothermal reservoir. As the discharging hot spring fluid cools, silica carried in solution precipitates and accumulates to form rocks referred to as siliceous sinters. Distinctive sinter architecture forms depending on the environmental conditions such as water temperature or flow rate. These textures are preserved over time and throughout diagenesis. Geothermal reservoirs may remain long after hot spring discharge ceases. Therefore ancient sinters provide a direct link with a deeper potentially exploitable geothermal resource in areas where there are no active surface manifestations. Recognition of preserved sinter textures enables mapping of former high temperature vent to low temperature distal-apron flow pathways. Sinter dating enables the tracking of fluid flow to the surface, providing a regional context of fluid movement. The combination of sinter textural mapping and dating complements standard techniques used in assessing a geothermal resource and provides new methodology for assisting in identifying hidden geothermal reservoirs.