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- Andréasson, Per Gunnar, et al.
(författare)
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Seve terranes of the Kebnekaise Mts., Swedish Caledonides, and their amalgamation, accretion and affinity
- 2018
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 140:3, s. 264-291
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Tidskriftsartikel (refereegranskat)abstract
- A major allochthon of the Scandinavian Caledonides, the Seve belt has traditionally been considered to be derived from the rifted margin and continent-ocean transition (COT) of Baltica. However, geochronological results obtained from its inferred northern equivalent, the Kalak Nappe Complex (KNC), have been taken to indicate an exotic affinity of this complex and of also Seve terranes, an interpretation adopted in recent palaeogeographic models. In the Kebnekaise Mts., the COT is represented by the Kebnekaise terrane composed of amphibolitized dykes of gabbro and dolerite of depleted magma source and rare felsic and ultramafic rocks. Coronitic dolerite and gabbro with abundant rutile suggest high pressures before or during amalgamation with the underlying Mårma terrane, composed of quartzofeldspathic gneisses intruded by mafic and granitic rocks, the latter including a previously dated c. 845 Ma-old granite. The granite mingled with mildly alkaline dolerites chemically similar to transitional basalts of continental rifts. Following emplacement at shallow (andalusite stability) crustal levels, the igneous complex and host rocks underwent extensive deformation, metamorphism within the sillimanite-kyanite stability field and local migmatization. The Kebnekaise and Mårma terranes amalgamated in early Ordovician as indicated by the U-Pb age of 487±7 Ma obtained from titanite fabrics of deformed granite in thrust vicinity, and by 40Ar-39Ar results. The pressure increase in both terranes suggests that amalgamation occurred during initial subduction and imbrication. Correlation of the Mårma terrane with the KNC is discussed. Results obtained in this study give no reason to ascribe an exotic affinity to the Seve terranes of the Kebnekaise Mts.
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| 2. |
- Rosberg, Jan-Erik, et al.
(författare)
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Re-injection of groundwater by pressurizing a segmental tunnel lining with permeable backfill
- 2010
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 1878-4364 .- 0886-7798. ; 25:2, s. 129-138
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Tidskriftsartikel (refereegranskat)abstract
- Recently, within a tunneling project, a method for reinjecting discharged groundwater at tunnel level has been investigated. The method was performed by pressurizing a long section of the lining With ungrouted pea gravel as backfill, in a rock mass with low hydraulic conductivity. Water was reinjected through watertight lining into a section where un-grouted pea gravel was used as backfill. The pressure response was measured both behind the lining and in the rock mass, the latter by means of several observation wells drilled from ground level. Reinjecting water into a rock mass by pressurizing a lining with a permeable backfill (Such as un-grouted pea gravel) was found to be possible and feasible. Well testing methods developed for vertically drilled wells, such as a step injection test and constant head/pressure tests, Were used and found to be applicable, even for testing at tunnel level. It was also found that well known analytical Solutions, developed for vertically drilled wells, can be used for interpretation, e.g. transmissivity from tests performed at tunnel level and from the pressure response in two of the observation wells. (c) 2009 Elsevier Ltd. All rights reserved.
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