[en] Combining geological mapping and petrological, structural and geophysical (gravity and seismic) data already available for the late Proterozoic Rogaland Igneous Complex of Norway allows the 3D shape of the Bjerkreim-Sokndal layered intrusion to be modelled as a thick cumulate series capped by massive granitic rocks. Using the latter data, along with the spectacular convergent linear flow pattern that covers both the cumulates and the felsic rocks of this chamber, evidence is presented to show that the granitic material was down-dragged through the sinking of its high-density mafic floor into lower density anorthosites and granulitic gneisses. This example illustrates that downward gravity-driven flows of rocks were active, in addition to upward flows, in the building of the early crust up to late-Proterozoic times, helping to explain the geochemical and structural complexities of the old crust.
Disciplines :
Physical, chemical, mathematical & earth Sciences: Multidisciplinary, general & others
Author, co-author :
Bolle, Olivier ; Université de Liège - ULiège > Département de géologie
Trindade, Ricardo I.F.
Bouchez, Jean-Luc
Duchesne, Jean-Clair ; Université de Liège - ULiège > Département de Géologie > Pétrologie et Géochimie endogènes
Language :
English
Title :
Imaging downward granitic magma transport in the Rogaland Igneous Complex, SW norway
Améglio L., Vigneresse J.L., Bouchez J.L. (1997) Granite pluton geometry and emplacement mode inferred from combined fabric and gravity data. Granite from Segregation of Melts to Emplacement Fabrics , (J.L. Bouchez, et al., eds), Kluwer, Dordrecht; 199-214.
Aswhal L.D. Anorthosites, Springer. Berlin; 1993.
Barnichon J.D., Havenith H., Hoffer B. (1999) The deformation of the Egersund-Ogna anorthosite massif. South Norway: Finite-element modelling of diapirism. Tectonophysics 303:109-130.
Bolle O., Diot H., Duchesne J.C. (2000) Magnetic fabric and deformation in charnockitic igneous rocks of the Bjerkreim-Sokndal layered intrusion (Rogaland, Southwest Norway). J. Struct. Geol 22:647-667.
Borradaile J.G., Henry B. (1997) Tectonic applications of magnetic susceptibility and its anisotropy. Earth Sci. Rev 42:49-93.
Bouchez J.L. (1997) Granite is never isotropic: An introduction to AMS studies in granitic rocks. Granite: From Segregation of Melts to Emplacement Fabrics , (J.L. Bouchez et al., eds). Kluwer, Dodrecht; 95-112.
Bouchez J.L. (2000) Magnetic susceptibility anisotropy and fabrics in granites. C.R. Acad. Sci. Paris , Earth Planet. Sci; 330:1-14.
Bouchez J.L., Ceuleneer G., Nicolas A. (1998) Olivine and quartz-rich tectonites related to intra-occanic thrusting. Fault-Related Rocks. A Photographic Atlas , (A.W. Snoke et al., eds), Princeton University Press, Princeton, NJ; 244-245.
Bouhallier H., Chardon D., Choukroune P. (1995) Strain patterns in Archaean dome and basin structures: The Dharwar craton (Karnataka, South India). Earth Planet. Sci. Lett 135:57-75.
Collins W.J., van Kranendonk M.J., Teyssier C. (1998) Partial convective overturn of Archean crust in the East Pilbara Craton, Western Australia: Driving mechanisms and tectonic implications. J. Struct. Geol 20:1405-1424.
Deemer S., Hurich C. (1997) Seismic image of the basal portion of the Bjerkreim-Sokndal layered intrusion. Geology 25:1107-1110.
Dixon J.M., Summers J.M. (1983) Patterns of total and incremental strain in subsiding troughs: Experimental centrifuge models of inter-diapir synclines. Can. J. Earth Sci 20:1843-1861.
Duchesne J.C., Wilmart E. (1997) Igneous charnockites and related rocks from the Bjerkreim-Sokndal layered intrusion (Southwest Norway): A jotunite (hypersthene monzodiorite)-derived A-type granitoid suite. J. Petrol 38:337-369.
Duchesne J.C., Maquil R., Demaiffe D. (1985) The Rogaland anorthosites: Facts and speculations. The Deep Proterozoic Crust in the North Atlantic Provinces , (A.C. Tobi and J.L.R. Touret, eds), Reidel, Dordrecht; 449-476.
Duchesne J.C., Liégeois J.P., Van der Auwera J., Longhi J. (1999) The crustal tongue melting model and the origin of massive anorthosites. Terra Nova 11:100-105.
Falkum T. (1982) Geologisk kart over Norge, berggrunnskart Mandal, map scale 1:250,000. Norges geol. Unders, Bergen; .
Fram M.S., Longhi J. (1992) Phase equilibra of dikes associated with Proterozoic anorthosite complexes. Am. Min 77:605-616.
Glazner A.F., Miller D.M. (1997) Late-stage sinking of plutons. Geology 25:1099-1102.
Grégoire V., Darrozes J., Gaillot P. (1998) Magnetite grain shape fabric and distribution anisotropy vs. rock magnetic fabric: A three-dimensional case study. J. Struct. Geol 7:937-944.
Longhi J., Fram M.S., Van der Auwera J., Montieth J.N. (1993) Pressure effects, kinetics, and rheology of anorthositic and related magmas. Am. Miner 78:1016-1030.
Longhi J., Van der Auwera J., Fram M.S., Duchesne J.C. (1999) Some phase equilibrium constraints on the origin of Proterozoic anorthosites and related rocks. J. Petrol 40:339-362.
Maquil R., Duchesne J.C. (1984) Géothermométrie par les pyroxènes et mise en place du massif anorthositique d'Egersund-Ogna (Rogaland, Norvège méridionale). Ann. Soc. Géol. Belg 107:27-49.
Michot J., Michot P. (1969) The problem of the anorthosites: The South-Rogaland igneous complex (Southwestern Norway). Origin of the Anorthosites and Related Rocks , (Y.W. Isachsen, ed.). N.Y. State Mus. Sci. Serv. Mem; 18:399-410.
Paludan J., Hansen U.B., Olesen N.O. (1994) Structural evolution of the Precambrian Bjerkreim-Sokndal intrusion, South Norway. Norsk Geol. Tidsskr 74:185-198.
Petford N., Cruden A.R., McCaffrey K.J., Vigneresse J.L. (2000) Granite magma formation, transport and emplacement in the Earth's crust. Nature 408:669-673.
Schumacher J.C., Westphal M. (2001) Thermal modelling of the metamorphism of the Rogaland granulites. GEODE Field Workshop 8-12th July 2001 on Ilmenite Deposits in the Rogaland Anorthosite Province, S. Norway , (A. Korneliussen, ed.). Norges geol. unders. Rep., 2001; 42:127-128.
Smithson S.B., Ramberg I.B. (1979) Gravity interpretation of the Egersund anorthosite complex, Norway: Its petrological and geothermal significance. Bull. Geol. Soc. Am 90:199-204.
Ramberg H. Gravity, Deformation and the Earth's Crust, Academic Press, London; 1981.
Schärer U., Wilmart E., Duchesne J.C. (1996) The short duration and anorogenic character of anorthosite magmatism: U-Pb dating of the Rogaland Complex, Norway. Earth Planet. Sci. Lett 139:335-350.
Wilmart E., Duchesne J.C. (1987) Geothermobarometry of igneous and metamorphic rocks around the Āna-Sira anorthosite massif: Implications for the depth of emplacement of the South Norwegian anorthosites. Norsk Geol. Tidsskr 67:185-196.