Paper by Peter Niemz et al., (Geothermics) describes seismic observations from the circulation tests at FORGE using only the regional (near-)surface network of the UUSS.
Propylitic Alteration
A term borrowed from studies of hydrothermal ore deposits that refers to an assemblage of secondary hydrothermal minerals which forms in igneous rocks. This assemblage is made up of chlorite, illite, feldspar (both Na and K-rich varieties), epidote, calcite and pyrite, imparting a dark green tint to the appearance of altered rocks. It is commonly developed in volcanic-plutonic sequences that host high-temperature geothermal reservoirs.
Geothermal Glossary
Word of the Week – Drill Core
Drill Core Intact cylindrical shaped sample of rock obtained during drilling with a special coring bit. Although commonly narrow in diameter (e.g., 1-4" or 25-100 mm), it preserves a geological record that makes it possible to interpret the sequence of mineral...
Word of the Week – Drill Cuttings
Drill Cuttings Small chips of rocks (e.g., <1/8 inch or <3 mm) obtained during drilling with a rotary bit that are continuously returned to the surface by the circulation of mud. Drill cuttings are the main source of geological and stratigraphic interpretation...
Word of the Week – Enhanced Geothermal System
Enhanced Geothermal System Unconventional geothermal resources that contain heat similar to conventional hydrothermal resources but lack the necessary groundwater and/or rock characteristics (e.g., permeability) to enable energy extraction without stimulation.