sional process, their rejected alternative (Juhlin et al. 2000, Fig 10b), with an extension followed by compression could also explain the structures. If the deep-seated western part is associated with an uplift due to extension, the gradual roll-over of the structures could be explained with prograding uplift and eastwards migration of the zones at more shallow levels. The Sveconorwegian Frontal Deformation Zone (SFDZ) was defined by Wahlgren et al. (1994) as the easternmost lineaments with ductile Sveconorwegian deformation, and this concept could be suitable to mark the eastern limit of the PZ. However, brittle, most probably Sveconorwegian thrusts with the same west-side-up kinematic pattern as in the ductile zones, proceed far to east of this zone (see for instance profile 1, bed-rock map Finspång NV, Wikström & Karis 1989).

Onshore crustal reflectivity of the Archaean-Proterozoic boundary and comparison with BABEL Lines 2 and 3, northern Sweden

The Askersund granitoid (age 1845-1850 Ma) is the oldest member of the Transscandinavian Igneous Belt which forms a major structure in the Scandinavian peninsula. The external, metamorphic and gneissic parts of this older generation have the same age as the more central and isotropic parts. A petrographical investigation of samples collected in two traverses from the macroscopically isotropic part to the gneissic part of the intrusion has been complemented with studies of the anisotropy of the magnetic susceptibility of the rocks. The mean degree of anisotropy (P-J) is different from site to site and increases from the macroscopically isotropic part to the gneissic part. The shape of the susceptibility ellipsoid is slightly oblate in the former part and prolate in the latter. Under the microscope this change can be correlated with a change in textures indicating deformation in a partly crystallized magma to more solid state deformation structures. A major conclusion of this investigation with regard to the geological development of the area, is that the emplacement of the granite magma took place contemporaneously with regional deformation that continued after the intrusion.

The Balinge conglomerate has played a key role in the lithostratigraphy of northern Sweden. The conglomerate, with pebbles dominated by granodiorites and tonalites in a generally biotite-rich matrix, borders volcanic rocks with unclear relative age relationships. In nearby areas these volcanites have been intruded by plutonic rocks (c. 1.9 Ga) which are similar to the pebble material. On these grounds, the conglomerate has been regarded as younger than the volcanic rocks and an important marker in the geological evolution of the region. In this preliminary study, it is suggested that the features displayed by the Balinge conglomerate are not compatible with an epiclastic origin. On the contrary, they indicate that this rock represents a hydraulic breccia where the roundness of the granitoid 'pebbles' has resulted from erosion in a fluidised, heterogeneous and magmatic environment. In the actual area the 'conglomerate' must thus be dismissed as a stratigraphic marker horizon. It belongs to the early Svecofennian evolution.

U–Pb zircon ages of 1848±15 and 1842+23 -13 Ma have been obtained for the coarse porphyritic Askersund granite (‘Filipstad type’) and for its marginal augen gneiss, respectively. The results indicate that the onset of magmatism in the Transscandinavian Igneous Belt (TIB) took place in connection with the late Svecofennian orogenic development. They also support a structural model implying that regionally deformed and folded marginal parts of older granitoid intrusions in the TIB have similar ages as the isotropic and discordant central parts. The deformation is reflected in the morphology of the zircons but does not affect the isotopic ages.

Abstract Samples of garnet-cordierite rocks have been investigated in order to check if the estimated high-amphibolite facies conditions of the sampling areas (absence of orthopyroxene), also are reflected in different geothermometers (garnet-cordierite and garnet-biotite) when compared with a similar investigation of similar rocks in a nearby granulite facies area. The sampled garnet-cordierite rocks differ somewhat in geological character. At Svenshyttan they are similar to other high-grade Svecofennian veined gneisses in the region, at Kinkhyttan they have a characteristic, massive appearance, while the rocks at Nygården are mobilized and back-vein a norite. A thermal metamorphic peak is present in the area, displayed by the Kinkhyttan samples which, according to the garnet-cordierite thermometers, have reached temperatures of at least 650–700°C. This metamorphism is most likely associated with a near lobe of Småland-Värmland granitoids. Along the western contact of this lobe, the granulite facies conditions prevail. A comparison between the results of the present investigation and those from the granulite facies area demonstrates that the garnet-cordierite thermometers show only minor differences for the peak metamorphism while the garnet-biotite thermometers indicate more pronounced retrograde metamorphism in the studied area. Key Words: Geothermometrygarnet-cordierite rockshigh amphibolite faciescontact/regional metamorphismSmåland-Värmland granitoidsNygården norite

Thin layers of yellow sandstone and some sandstone dikes have been found on a gently dipping, unweathered surface of granite on the northeastern shore of the island Stora Röknen in the northem part of Lake Vättern. The granite is penetrated by local shear zones with a 'western-side-up' sense of shear, typical for the Protogine zone in the region. The sandstone dikes fill fractures oriented along the shear zones and the layers of fine-grained sandstone rest discordantly on the sheared granite, which demonstrates a considerable hiatus between the shear zone development and the dcposition of the sandstone. Key Words: Visingsö groupLemunda formationsandstonebasement-cover relationProtogine zone deformationStora Röknen

Some late-plutonic, net-veined composite dikes occur both in the older Svecofennian calcalkaline ‘primorogenic’ igneous suite and in the late Svecofennian, syntectonic, somewhat more alkaline Småland-Värmland suite. Earlier developments in these two major suite generations are characterized by large-scale magma-mixing and magma-mingling. Because mafic enclaves are very rare in the ‘serorogenic’ S-type granites some scattered findings of composite dikes related to these granites are also discussed. Based on comparison with models published elsewhere, it is suggested that mafic magmas are involved in the generation of all major groups of Svecofennian granites in Sweden; in the case of the S-type granites probably mainly as a heat source. A prominent fracture pattern in the Småland-Värmland granitoids can be related to the late crystallization phase since the composite dikes occur both parallel to the magmatic flow directions and closely associated with the fracture pattern.

A lobe of Early Svecofennian high-grade, metamorphic rocks surrounded and intruded by rocks of the Småland-Värmland batholith east of Karlskoga, central southern Sweden, has been studied. Application of geothermobarometry reveals that these rocks have suffered granulite facies metamorphism at conditions constrained to 670–770°C, 4.0–4.5 kbar and aH2O0.1–0.3. The metamorphism has transformed biotite granite into charnockite, intermediate volcanite into pyroxene granulite, and lower grade presumably semipelitic gneiss into garnet-cordierite gneiss. Extensive partial melting accompanied the metamorphism in the garnet-cordierite gneisses and granulites, but not in the charnockites. The metamorphism is attributed to a local contact metamorphic peak, associated with the emplacement of the Småland-Värmland granitoids and related mafic plutonics, in the penecontemporaneous, amphibolite facies, regional “serorogenic Svecofennian” episode.

Structural relationships are described along parts of the eastern margin of the 1.76-1.84 Ga old batholith, known as the Transscandinavian Igneous Belt (TIB). They demonstrate that the Svecofennian structures of the country rocks are highly dependent on the shape of the younger granitoids which themselves have margins folded in the same Svecofennian structures. This pattern is attributed to an interference between forces created by the diapiric intrusion and those following the last lateral movements of the Svecofennian. The TIB would then be syn-tectonic, late Svecofennian. Local cross-cutting relationships alone are insufficient criteria for the "postorogenic" label commonly applied to these granitoids.

Discussion sur les articles de Wilkstrom A. et Kresten P. paru en 1988 dans Geologiska Foreningens i Stockholm Forhandlingar vol 110, pp 191-194 et 194-195

Discussion sur les articles de Wikstrom, A. 1984 A possible relationship between augen gneiss and postorogenic granites in S.E. Sweden Journal of Structural Geology no 6, pp. 409-415. Wikstrom, A. 1987 Magmatic diapirism of granites in south-eastern Sweden Revista Brasileira de Geosciencias 17, in print. Wikstrom, A., Aaro, S. 1986 The Finspang augen gneiss massif. Geology, geophysics and relationship to postorogenic granites Sveriges geologiska undersokning C. 813, pp. 1-39, Kresten P., 1986 The granites of the Vastervik area south-eastern Sweden. Sveriges geologiska undersokning C. 814, pp. 1-35

The Breven dolerite dike in the eastern part of south central Sweden has been remapped. A large central part of the dike is occupied by a red granophyre, most probably a late differentiate of the dolerite. To the east of the major dike there is a hybrid dolerite-breccia with xenoliths of granophyre showing different stages of assimilation. The latter dike has a width of around 100 m and a length of at least 8 km. These observations suggest several pulses of dolerite in the dike system. Key Words: Breven doleritecompositional variationsgranophyrefault relationshipshybrid doleritegranophyre xenolithssouth central SwedenN5856 N5856 E1542 E1542

A Rb-Sr whole rock isochron for the Finspång augen gneiss, south central Sweden, yields an age of 1834 ± 21 Ma which is compared with intrusive ages for similar rocks in the neighbourhood. The augen gneiss is interpreted as an outer ‘skin’ surrounding younger granite intrusions.

"Post-granitoid basic plutonics in the Småland—Värmland belt." Geologiska Föreningen i Stockholm Förhandlingar, 107(3), pp. 183–184