Heat flow in the Vøring Basin, Mid-Norwegian Shelf

Abstract

In situ temperature and heat flow were determined in 1994 at 159 sites, grouped into 66 clusters between latitude 65 N and 67 30' N at water depths from 669 m to 1464 m. The mean of all cluster heat-flow measurements conducted in this survey was 58.5 mW m 2 , with a standard error of 4.40 mW m 2 . The mean heat flow from IKU well data for the Trøndelag Platform is 56.2 6.65 mW m 2 . Shorter wavelength heat-flow variations appear to be controlled structurally and can be explained by sedimentation and thermal refraction effects. High heat flow associated with faulted structural highs such as the Nyk High and Vema Dome-Rym Fault Zone may also result from hydrothermal convection. Relatively isolated high (106.6 mW m 2 ) heat flow observed at 846 m water depth may be an artefact of bottom water disturbances; however, virtually identical deep-water heat-flow anomalies, believed to be of hydrothermal origin, also exist. While heat-flow measurements made at water depths less than 1000 m should be regarded with caution, there is presently no justification for eliminating those exhibiting linear heat flow with depth. Submarine avalanches seem unimportant in the survey area. Neither crustal thinning, underplating nor sill intrusion, within the last 50 Ma, would have a measurable effect on present-day heat flow. The net effect of crustal thinning may be a reduction of the crustal heat generation potential, depending on the degree of thinning of the upper crust, since the accumulating sediments cannot compensate fully for the lost heat generation from a crystalline basement.

Forward modeling of stretching episodes and paleo heat flow of the Vøring margin, NE Atlantic

“…Ritter et al (2004) made some simple 1-D models in order to interpret new heat flow measurements from the Vøring area. Ritter et al (2004) concluded that neither crustal thinning, underplating nor sill intrusion, within the last 50 My, would have a measurable effect on present day heat flow.…”

Modelling thermal transients from magmatic underplating—an example from the Vøring margin (NE Atlantic)

“…The corresponding surface heat flow is q s = λ · ∂ T/∂z = 6.5 mW m −2 when the heat conductivity is λ = 2.5 W m −1 K −1 . This maximum additional heat flow from underplating is 10% of a typical value for the present day surface heat flow in Vøring area [27].…”

“…This section looks at the possible thermal impact from magmatic underplating for the three scenarios of the extension history reported by Wangen et al [41]. The rock properties used in the simulations are found in Appendix D. The present study does not cover uncertainties in the input data but uses standard data to obtain a surface heat flow that is in accordance with the heat flow measurements collected by Ritter et al [27]. Figure 9a shows the same transect as in Wangen et al [41], where the lithosphere is plotted right after emplacement of the magma.…”

Controls on the location of compressional deformation on the NW European margin

“…In very broad terms, the representative models for the southern part of the area (Fig. 5a-f ) appear to bracket the typical heat flows observed there, whereas the more extensive heat-flow data available for the Norwegian margin and, in particular, the Vøring Basin (Sundvor et al 2000;Ritter et al 2004) suggest a thermal state closer to the warm models than the cool models.…”

“…5i, j). With higher heat flows, which appear more likely in this area (Sundvor et al 2000;Ritter et al 2004), the predicted temperatures within this layer move out of the stability zone for lizardite (note the depths of the 300 and 4008C isotherms in Fig. 5j), so the likelihood of this being a source of weakening is reduced.…”