Arne Solli

Devonian, orogen-parallel, opposed extension in the Central Norwegian Caledonides

Late orogenic, Early to Middle Devonian extension in the Scandinavian Caledonides was unidirectional in western Norway. New data from two detachment zones (Hoybakken and Kollstraumen) north of the More-Trondelag Fault Complex show that bidirectional, opposed, orogen-parallel extension dominated in this region. At this time, the fault complex acted as a transfer zone for the Hoybakken detachment. Extension and uplift in central Norway triggered significant magmatic activity, in contrast to the lack of granite intrusions during exhumation of western Norway.

A major synmetamorphic Early Devonian thrust and extensional fault system in the Mid Norway Caledonides: relevance to exhumation of HP and UHP rocks

Abstract The study of complex orogenic belts commonly begins in the frontal regions with well-defined tectonostratigraphy, and relatively simple structure and metamorphism, and proceeds into the progressively more complex hinterland, which nevertheless may contain the best geochronological record of the most intense orogenic events. The northern part of the Western Gneiss Region in the hinterland of the Scandian orogen contains a robust U–Pb zircon geochronological framework on rocks subjected to high-pressure (HP) and ultra-high-pressure (UHP) metamorphism that has implications for tectonic development both there and towards the foreland. HP and UHP eclogite crystallization occurred at 415–410 Ma (Early Devonian, Lochkovian to Pragian), followed by pegmatite crystallization at c. 395 Ma (Late Emsian) during exhumation and return to amphibolite-facies conditions, thus limiting the process to 15–20 myr. The nature and sequence of events are much more complex than in the foreland, causing difficulty in correlation, yet the combined tectonics in the two regions provides the necessary context to explain, for example, how rocks were subjected to deep-seated, high-temperature metamorphism and then exhumed to shallower levels. Here, we suggest how a recently recognized extensional detachment fault and a recently recognized out-of-sequence thrust might be linked to the timing of HP metamorphism and later exhumation. The postulated Agdenes extensional detachment in its footwall has basement gneisses containing Mesoproterozoic igneous titanite fully reset at 395 Ma, as well as Devonian pegmatites, and in the hanging wall Ordovician to Early Silurian granitoids of the Støren Nappe containing igneous titanite barely influenced by Devonian recrystallization and no evidence of post-Ordovician melts. This implies removal of a significant crustal section on a large-scale detachment. Rocks both above and below are overprinted by the same late, subhorizontal, sinistral ductile extensional fabric, obscuring any fabrics produced during development of the detachment itself. Eastern Trollheimen escaped the late, strong, subhorizontal overprint, and shows: (1) early emplacement of thrust nappes of Lower and Middle Allochthons over Baltican basement and its Late Neoproterozoic quartzite cover; (2) major, SE-directed, recumbent folding of the entire thrust-imbricated sequence; and (3) major, out-of-sequence, SE-directed thrusting (Storli Thrust), for an 80 km minimum transport across-strike, of the recumbent-folded sequence over deeper, less deformed, lower basement gneisses and unconformable Neoproterozoic quartzite cover. The upper basement contains boudins of eclogite and garnet-corona gabbro lacking in the lower basement. Similar basement imbrications occurred in the Tømmerås window, the Skarddøra Antiform, the Mullfjället Antiform and the Grong–Olden Culmination, up to 240 km NE of Trollheimen, as well as in the Reksdalshesten antiform 100 km west, all within the postulated minimum 400×180 km area of the Agdenes detachment.

Household and family during urbanization and industrialization: efforts to shed new light on an old debate

Household and family during urbanization and industrialization: efforts to shed new light on an old debate Paul Puschmann & Arne Solli a Research Foundation Flanders (FWO), Brussels, Belgium b KU Leuven, Family and Population Studies (FaPOS), Centre for Sociological Research, Leuven, Belgium c Department of Archaeology, History, Cultural Studies and Religion, University of Bergen, Bergen, Norway Published online: 05 Feb 2014.

Solid solution between potassic-obertiite and potassic-fluoro-magnesio-arfvedsonite in a silica-rich lamproite from northeastern Mozambique

A fine-grained dike rock was collected during regional geologic mapping in the Xixano region, northeastern Mozambique. Observation in thin section and SEM and EMP analyses showed a fine-grained igneous texture dominated by optically unusual zoned amphibole and Fe 3+ -bearing low sanidine, with Sr-bearing fluorapatite, rutile, Sr-bearing barite, a silica mineral, hematite and zircon. The mineralogy and major element data indicate an unusual high-silica lamproite. The amphibole is concentrically zoned and pleochroic from pale brown to pale greenish blue, with common abnormal blue and brown interference colours, indicative of high dispersion commonly associated with Fe 3+ . Results of 29 EMP analyses, including two traverses across zoning, were formulated in different modes. The most satisfactory formulae were obtained assuming high Fe 3+ /(Fe 2+ + Fe 3+ ) ratios and significant oxo component (O 2− at the O(3) site substituting for (OH, F)). The most Ti-rich core composition approximates: K Na 2 (Mg 3 Fe 2+ 0.5 Fe 3+ 1 Ti 0.5 ) Si 8 O 22 (F 1 O 1 ), and can be classified as 1:1 solid solution between potassic-obertiite and potassic-fluoro-magnesio-arfvedsonite. Zoning toward the rims increases the potassic-fluoro-magnesio-arfvedsonite component up to K Na 2 (Mg 3.5 Fe 3+ 1.5 ) Si 8 O 22 (F 1 (OH) 0.5 O 0.5 ).

Dynamic Metasomatism: Stable Isotopes, Fluid Evolution, and Deformation of Albitite and Scapolite Metagabbro (Bamble Lithotectonic Domain, South Norway)

New stable isotopic data from mineral separates of albite, scapolite, amphibole, quartz, and calcite of metasomatic rocks (Bamble lithotectonic domain) give increased knowledge on fluid type, source, and evolution duringmetamorphism. Albite from a variety of albitites givesδ18OSMOW values of 5.1–11.1‰,while quartz fromclinopyroxene-bearing albitite gives 11.5–11.6‰. δ 18OSMOW values for calcite samples varies between 3.4 and 12.4‰ and shows more consistent δC values of −4.6 to −6.0‰. Amphibole from scapolite metagabbro yields a δ18OSMOW value of 4.3 to 6.7‰and δDSMOW value of−84 to−50‰,while the scapolite gives δ 18OSMOW values in the range of 7.4 to 10.6‰.These results support the interpretation that the originalmagmatic rocks weremetasomatised by seawater solutions with a possible involvement from magmatic fluids. Scapolitisation and albitisation led to contrasting chemical evolution with respect to elements like P, Ti, V, Fe, and halogens. The halogens deposited as Cl-scapolite were dissolved by albitisation fluid and reused as a ligand for metal transport. Many of the metal deposits in the Bamble lithotectonic domain, including Fe-ores, rutile, and apatite deposits formed during metasomatism. Brittle to ductile deformation concurrent with metasomatic infiltration illustrates the dynamics and importance of metasomatic processes during crustal evolution.

Chemostratigraphic constraints on the time of deposition of carbonate rocks in the Karasjok Greenstone Belt, northern Norway

The time of deposition of the rocks of the Karasjok Greenstone Belt, the most continuous and longest, linear Precambrian terrane in northern Norway, remains poorly dated. The belt is composed of several volcanic and sedimentary formations including a continuous unit of calcite and dolomite marbles. Most rocks have been strongly deformed and altered under amphibolite-facies metamorphism. Carbon isotope chemostratigraphy has been applied to provide an apparent depositional age of carbonate units and associated sedimentary and volcanic rocks. Thirty-eight samples representing marbles in four different locations in the northern part of the belt show high δCcarb values, hence recording the Palaeoproterozoic Lomagundi–Jatuli isotopic event. The least-altered δCcarb values suggest the presence of two isotopically different assemblages (+8 to +9‰ and +12 to +14‰) whose apparent time of deposition can be constrained between 2220 and 2140 Ma, and between 2220 and 2110 Ma, respectively.