Heat flow and geothermal processes in Iceland

Crustal modeling of the North Atlantic from spectrally correlated free-air and terrain gravity

“…However, this argument is based on seismic observations (Bjarnason et al, 1993;Staples et al, 1997;Smallwood et al, 1999) and S-wave travel paths (Menke and Levin, 1994) that rather poorly sample the Icelandic neovolcanic areas. To reconcile their thermal modeling and seismic observations, Menke and Sparks (1995) invoked the problematically high crustal thermal conductivity of 15 W/m • K that is considerably greater than the average 2.0 W/m • K thermal conductivity for Iceland rocks (Flóvenz and Saemundsson, 1993). This large thermal conductivity was attributed to regional hydrothermal effects despite the fact that these processes may minimally affect Icelandic heat transfer (Flóvenz and Saemundsson, 1993).…”

“…We may conservatively estimate crustal temperature in a neovolcanic zone assuming a below-average heat flow of 150 mW/m 2 for the superposed plume and ridge system, and crustal thermal conductivity of 2.0 W/m K and heat production of H = 300 × 10 −12 W/m 3 and h r = 10 km (Pálmason, 1973;Flóvenz and Saemundsson, 1993). H = 300 × 10 −12 W/m 3 is about an order of magnitude smaller than most oceanic basalt.…”

Earthquake swarms at Upptyppingar, north-east Iceland: A sign of magma intrusion?

“…The occurrence of deep, long-period (LP) earthquakes, mostly with emergent onsets, has been confirmed recently near to the Askja caldera, and also at Herðubreið (Soosalu et al, 2008). In the same study, the brittle crust was estimated to be 67 km thick near to Askja and Herðubreið, which accords with a crustal heat gradient of 90100C km 1 (Flóvenz and Saemundsson, 1993;Björnsson et al, 2005), reaching a brittle-ductile transition at ~600C (McKenzie et al, 2005;Boettcher et al, 2007).…”

Reservoir Definition

“…A large active volcanic zone, corresponding to the mid-oceanic ridge, is running SW-NE, and displays various heat sources (dikes and magma chambers). Seawater, meteoric water, and volcanic fluids are mixed in pressurized water-dominated reservoirs, often associated with young tectonic fractures, carrying heat from several kilometers depth toward the surface (Flóvenz and Saemundsson, 1993;Arnórsson, 1995). The regional temperature gradient varies from 50 to 150 • C km −1 and the highest values are found close to the volcanic rift zone.…”