Modeling thermal convection in supradetachment basins: example from western Norway

Abstract

The juxtaposition of fault-bounded sedimentary basins, above crustal-scale detachments, with warmer exhumed footwalls can lead to thermal convection of the fluids in the sediments. The Devonian basins of western Norway are examples of supradetachment basins that formed in the hanging wall of the Nordfjord-Sogn Detachment Zone. In the central part of the Hornelen and Kvamshesten basins, the basin-fill is chiefly represented by fluvial sandstones and minor lacustrine siltstones, whereas the fault margins are dominated by fanglomerates along the detachment contact. Prominent alteration and low-greenschist facies metamorphic conditions are associated with the peak temperature estimates of the sediments close to the detachment shear zone. Fluid circulation may have been active during the burial of the sediments, and we quantify the potential role played by thermal convection in redistributing heat within the basins. Different models are tested with homogeneous and layered basin-fill and with material transport properties corresponding to sandstones and siltstones. We found that thermally driven fluid flow is expected in supradetachment basins as a transient process during the exhumation of warmer footwalls. We demonstrate that the fluid flow may have significantly affected the temperature distribution in the upper five kilometers of the Devonian basins of western Norway. The temperature anomaly induced by the flow may locally reach about 80°C. The sedimentary layering formed by sand-and siltstones strata does not inhibit fluid circulation at the scale of the basin. The presence of fluid pathways along the detachment has an important impact on the flow and allows an efficient drainage of the basin by channelizing fluids upward along the detachment.

High-temperature metamorphism during extreme thinning of the continental crust: a reappraisal of the North Pyrenean passive paleomargin

“…In addition, we can envisage that various modes of opening induced a variety in hydrothermal circulations. If some circulations were externally derived, which is actually not identified in Albian basins using a stable-isotope characterization of veins , they may have produced differences in regional temperature, the coolest temperatures being likely found in the basins with the most efficient cooling circulations (e.g., Souche et al, 2014). …”

Metamorphosed cumulate gabbros from the Støren Group of the Upper Allochthon, northern Western Gneiss Region, Norway: petrology and metamorphic record

“…Rare aluminous layers in the Støren Group developed fine spongy garnet porphyroblasts and even staurolite. Such heating of a cool upper plate, transported along a detachment fault into contact with a hot, deeply exhumed lower plate, has also been described elsewhere (e.g., Little et al, 1995;Wells et al, 2005;Souche et al, 2013).…”

Improving the Estimation of Porosity and Permeability Distribution by Linking Basin Modelling to Diagenetic Evolution of Carbonate Reservoirs

“…In many sedimentary basins, convection in the fault zones drive large-scale fluid fluxes (e.g. Lewis and Couples, 1999;Matthäi et al, 2004;Davies and Smith, 2006;Wilson et al, 2007;Lupi et al, 2010;Saller and Dickson, 2011;Souche et al, 2013). Although PetroMod TM provides a complete set of equations to calculate the temporal thermal evolution of a sedimentary basin, it has some limitations for the systems considered here.…”

“…This will provide us with better locations and more realistic geometries of the faults, which are potentially key controls on the basinscale fluid flow (e.g. Lewis and Couples, 1999;Mätthai et al, 2004;Davies and Smith, 2006;Wilson et al, 2007;Lupi et al, 2010;Saller and Dickson, 2011;Souche et al, 2013). The overall integration of the different software packages envisioned here is shown in Fig.…”