NJG87-1/2-01
2007
Interplay between the Scandes and the Trans-Scandinavian Igneous Belt: integrated thermo-rheological and potential field modelling of the Central Scandes profile
87
1, 2
pp. 3-12
978-82-92-39437-3

Analysis of the gravity anomalies associated with the Scandinavian mountain range (i.e. the Scandes) suggests that the compensating loads are located at relatively shallow depths in the crust and/or in the mantle lithosphere. Potential crustal loads leading to positive buoyancy are the light TransScandianvian Igneous Belt (TIB) granitoids that meet the Scandes in their central segment. In order to understand the mechanisms that led to theuplift of the Scandes, it is therefore of prime importance to determine the thickness and depth extent of such bodies and their role in maintaining the observed surface topography. The present paper focuses on the Central Scandes profile (CSP) running from west to east from Trondheim, in mid-Norway, to Östersund, in mid-Sweden, and crossing both the Central Scandes and an underlying TIB granitoid. Firstly, by means of potential field modelling, we show that different crustal geometries and, in particular, very different thicknesses for the TIB granitoid can equally fit the available geophysical data. Then, we apply thermo-rheological modelling to get additional constraints on the crustal geometry along the CSP. We concentrate on two "end-member" crustal models and, using newly acquired heat generation data, proceed to model their respective thermal regimes. Model A involving a 20 km thick TIB granitoid results in both very high surface heat flow (80 to 90 ) /m2) and Moho temperatures (~750 ºC) and unreasonably low strength for the lithosphere. Reasonable heat flow values (60 to 70 mW/m2 ), Moho temperatures (~600 ºC) and lithosphere strength are found in Model B where the TIB granitoid is reduced to a thickness of 12 kms. We therefore suggest that the contribution of the TIB granitoid to the isostatic state of the Central Scandes is less important than previously proposed.

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