Hostname: page-component-78c5997874-t5tsf Total loading time: 0 Render date: 2024-11-10T12:34:10.220Z Has data issue: false hasContentIssue false
  • English
  • Français

Bimodal magmatism as a consequence of the post-collisional readjustment of the thickened Variscan continental lithosphere (Aiguilles Rouges-Mont Blanc Massifs, Western Alps)

Published online by Cambridge University Press:  03 November 2011

François Bussy ,
Jean Hernandez  and
Jürgen Von Raumer
François Bussy
Affiliation:
François Bussy, Earth Sciences Department, Royal Ontario Museum, Toronto, Canada; and IMP-BFSH2, UNIL, CH-1015 Lausanne,Switzerland e-mail: francois.bussy@imp.unil.ch
Jean Hernandez
Affiliation:
Jean Hernandez, IMP-BFSH2, UNIL, CH-1015 Lausanne,Switzerland e-mail: jean.hernandez@imp.unil.ch
Jürgen Von Raumer
Affiliation:
Jürgen Von Raumer, Institut de Minéralogie, Pérolles Université, CH-1700 Fribourg,Switzerland e-mail: juergen.vonraumer@unifr.ch
Get access Rights & Permissions [Opens in a new window]

Abstract

High Precision U-Pb zircon and monazite dating in the Aiguilles Rouges–Mont Blanc area allowed discrimination of three short-lived bimodal magmatic pulses: the early 332 Ma Mg–K Pormenaz monzonite and associated 331 Ma peraluminous Montées Pélissier monzogranite; the 307 Ma cordierite-bearing peraluminous Vallorcine and Fully intrusions; and the 303 Fe-K Mont Blanc syenogranite. All intruded syntectonically along major-scale transcurrent faults at a time when the substratum was experiencing tectonic exhumation, active erosion recorded in detrital basins and isothermal decompression melting dated at 327-320 Ma. Mantle activity and magma mixing are evidenced in all plutons by coeval mafic enclaves, stocks and synplutonic dykes. Both crustal and mantle sources evolve through time, pointing to an increasingly warm continental crust and juvenile asthenospheric mantle sources. This overall tectono-magmatic evolution is interpreted in a scenario of post-collisional restoration to normal size of a thickened continental lithosphere. The latter re-equilibrates through delamination and/or erosion of its mantle root and tectonic exhumation/erosion in an overall extensional regime. Extension is related to either gravitational collapse or back-arc extension of a distant subduction zone.

Keywords

Acid-basicexhumationextensiongranitemigmatitessyntectonic intrusionU-Pb datingzircon
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 91 , Issue 1-2: Fourth Hutton Symposium: The Origin of Granites and Related Rocks , 2000 , pp. 221 - 233
Copyright
Copyright © Royal Society of Edinburgh 2000

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Barbarin, B. 1996. Genesis of two main types of peraluminous granitoids. Geology 24, 295–8.Google Scholar
Bonin, B., Brändlein, P., Bussy, F., Desmons, J., Eggenberger, U., Finger, F., Graf, K., Marro, C., Mercolli, F., Obcrhänsli, R., Ploquin, A., von, Quadt A., von, Raumer J., Schaltegger, U., Steyrer, H. P., Visonà, D.& Vivier, G., 1993. Late Variscan magmatic evolution of the Alpine Basement. In von, Raumer J. F.& Neubauer, F. (eds) Pre-Mesozoic Geology in the Alps, 171–201. Berlin: Springer.Google Scholar
Bonin, B., Azzouni-Sekkal, A., Bussy, F.& Ferrag, S. 1998. Alkalicalcic to alkaline post-collision granite magmatism: petrologic constraints and geodynamic settings. Lithos 45, 45–70.Google Scholar
Bovay, P. 1988. Pétrographie et géochimie d'une association de roches acides et basiques, Massif cristallin de Fully (Valais). Unpublished Diploma work, Lausanne.Google Scholar
Brändlein, P. 1991. Petrographische und geochemische Characteristika des Vallorcine-Granits, Aiguilles Rouges-Massiv (Westalpen, Schweiz). Unpublished Ph.D. Thesis, Erlangen.Google Scholar
Brändlein, P., Nollau, G., Sharp, Z.& von, Raumer J., 1994. Petrography and geochemistry of the Vallorcinc granite (Aiguilles Rouges massif, Western Alps). Schweizerische Mineralogische und Petrographische Mitteilungen 74, 227–43.Google Scholar
Burg, J.P., Van, Den Dricssche J.& Brun, J.P. 1994. Syn- to post-thickening extension in the Variscan belt of Western Europe: modes and structural consequences. Géologie de la France 3, 33–51.Google Scholar
Bussy, F. 1990. Pétrogenèse des enclaves microgrenues associèes aux granitoïdes calc-alcalins: example des massifs varisque du Mont Blanc (Alpes occidentales) et miocène du Monte Capanne (He d'Elbe, Italic). Ph.D. Thesis, Mémoires de Géologie (Lausanne) 7.Google Scholar
Bussy, F., Schaltegger, U.& Marro, C. 1989. The age of the Mont Blanc granite (Western Alps): a heterogeneous isotopic system dated by Rb–Sr whole rock determinations on its microgranular enclaves. Schweizerische Mineralogische und Petrographische Mitteilungen 69, 3–13.Google Scholar
Bussy, F., Klemens, W. P., Krogh, T. E.& Schwerdtner, W. M. 1995. Tectonic and metamorphic events in the westernmost Grenville Province, central Ontario: new results from high-precision U—Pb zircon geochronology. Canadian Journal of Earth Sciences 32, 660–71.10.1139/e95-055Google Scholar
Bussy, F., Venturini, G., Hunziker, J.& Martinotti, G. 1998. U–Pb ages of magmatic rocks of the Western Austroalpine Dent-Blanche-Sesia Unit. Schweizerische Mineralogische und Petrographische Mitteilungen 78, 163–8.Google Scholar
Bussy, F.& Cadoppi, P. 1996. U–Pb zircon dating of granitoids from the Dora-Maira massif (western Italian Alps). Schweizerische Mineralogische und Petrographische Mitteilungen 76, 217–33.Google Scholar
Bussy, F.& Hernandez, J., 1997. Short-lived bimodal magmatism at 307 Ma in the Mont Blanc/Aiguilles Rouges area: a combination of decompression melting, basaltic underplating and crustal fracturing. Abstract, Quaderni Geodinamica Alpina e Quaternaria, Milano 4, 22. Milan: C.N.R.I.Google Scholar
Bussy, F.& Von, Raumer J. 1993. U–Pb dating of Palaeozoic events in the Mont Blanc crystalline massif, Western Alps. Terra abtracts EUG7, Strasbourg: 382–3.Google Scholar
Capuzzo, N.& Bussy, F. 1999. Volcanic Input in a Late Paleozoic Tectono-Sedimentary Basin: The Salvan-Dorénaz Basin (Southwestern Switzerland-Eastern France). EUG10, Strasbourg. Terra Abstracts 11, 297.Google Scholar
Cocherie, A.& Rossi, P. 1995. Respective roles of source composition and melting conditions in the high-K content of some magmas: geochemical constraints. In The origin of granites and related rocks, 3rd Hutton Symposium, Abstracts. U. S. Geological Survey Circular 1129, 36–7.Google Scholar
Dahl, P. S. 1997. A crystal-chemical basis for Pb retention and fissiontrack annealing systematics in U-bearing minerals, with implications for geochronology. Earth and Planetary Science Letters 150, 277–90.Google Scholar
Debon, F., Guerrot, C., Ménot, R.P., Vivier, G.& Cocherie, A. 1998. Late Variscan granites of the Belledonne massif (French western Alps): a lower Visean magnesian plutonism. Schweizerische Mineralogische und Petrographische Mitteilungen 78, 67–85.Google Scholar
Debon, F.& Lemmet, M. 1999. Evolution of Mg/Fe ratios in late Variscan plutonic rocks from the External Crystalline Massifs of the Alps (France, Italy, Switzerland). Journal of Petrology 40, 1151–85.Google Scholar
Délitroz, D.& Fellay, R. 1997. Etude géologique et minéralogique de la région de Pormenaz (Haute Savoie, France). Unpublished diploma work, Lausanne.Google Scholar
Dobmeier, C. 1996. Die variskische Entwicklung des südwestlichen Aiguilles Rouges-Massives (Westalpen, Frankreich). Ph.D. Thesis, Mémoires de Géologic Lausanne 29.Google Scholar
Dobmeier, C. 1998. Variscan P-T-deformation paths from the southwestern Aiguilles Rouges massif (External massif, western Alps) and their implication for its tectonic evolution. Geologische Rundschau 87, 107–23.Google Scholar
Dobmeier, C., Pfeifer, H. P.& Von, Raumer J. F. 1999. The newly defined ‘Greenstone Unit’ of the Aiguilles Rouges massif (western Alps); remnant of an early Palaeozoic oceanic island-arc? Schweizerische Mineralogische und Petrographische Mitteilungen 79, 263–76.Google Scholar
Dobmeier, C.& Von, Raumer J. F. 1995. Significance of latest-Variscan and Alpine deformation for the evolution of Montagne de Pormenaz (South-western Aiguilles Rouges massif, Western Alps). Eclogae Geologicae Helvetiae 88, 267–279.Google Scholar
Faure, M. 1995. Late orogenic Carboniferous extensions in the Variscan French Massif Central. Tectonics 14, 132–53.Google Scholar
Faure, M., Leloix, C.& Roig, J. Y. 1997. L'évolution polycyclique de la chaînc hereynienne. Bulletin de la Société Géologique de France 168, 695–705.Google Scholar
Gerdes, A., Wörner, G.& Finger, F. 1998a. Large chemical variations in the Variscan Rastenberg pluton caused by mixing enriched mantle magmas with crustal melts. Abstract, Acta Universitatis Carolinae, Geologica 42, 256.Google Scholar
Gerdes, A., Wörner, G.& Henk, A. 1998b. Thermal and geochemical evidence for granite generation and HT-LP metamorphism by crustal stacking and radiogenic heating (The Variscan Southern Bohemian masif). Abstract, Acta Universitatis Carolinae, Geologica 42, 254.Google Scholar
Guillot, S.& Ménot, R. P. 1999. Nappe stacking and first evidence of Late Variscan extension in the Belledonne Massif (External Crystalline Massifs, French Alps). Geodynamica Acta 12, 97–111.10.1080/09853111.1999.11105334Google Scholar
Hermann, J., Müntener, O., Trommsdorff, V., Hansmann, W.& Picardo, G.B. 1997. Fossil crust-to-mantle transition, Val Malenco (Italian Alps). Journal of Geophysical Research 102, 20123–32.Google Scholar
Holdaway, M. J. 1971. Stability of andalusite and the aluminium silicate phase diagram. American Journal of Science 271, 97–131.Google Scholar
Holub, F. V. 1977. Petrology of inclusions as a key to petrogenesis of the durbachitic rocks from Czecheslovakia. Tschermaks Mineralogische und Petrographische Mitteilungen 24, 133–50.10.1007/BF01158191Google Scholar
Janoušek, V., Rogers, G.& Bowes, D.R. 1995. Sr–Nd isotopic constraints on the petrogenesis of the Central Bohemian Pluton, Czech Republic. Geologische Rundschau 84, 520–34.Google Scholar
Kerrich, R., Allison, I., Barnett, R. L., Moss, S.& Starkey, J. 1980. Microstructural and chemical transformations accompanying deformation of granite in a shear zone at Miéville, Switzerland; with implications for stress corrosion cracking and superplastic flow. Contributions to Mineralogy and Petrology 73, 221–42.Google Scholar
Krogh, T. E. 1973. A low-contamination method for hydrothermal decomposition of zircon and extraction of U and Pb for isotopic age determinations. Geochemica et Cosmochimica Acta 37, 485–94.Google Scholar
Krogh, T. E. 1982. Improved accuracy of U–Pb zircon ages by the creation of more concordant systems using an air abrasion technique. Geochimica et Cosmochimica Acta 46, 637–49.Google Scholar
Krummenacher, D. 1959. Le cristallin de la région de Fully (Valais). Schweizerische Mineralogische und Petrographische Mitteilungen 39, 151–266.Google Scholar
Laurent, R. 1967. Etude géologique et pétrographiquc de l'extrémité méridionale du massif des Aiguilles Rouges (Haute Savoie, France). Ph.D. Thesis, No 1434, University of Geneva.Google Scholar
Lorenz, V.& Nicholls, I.A. 1984. Plate and intraplate processes of Hercynian Europe during the Late Paleozoic. Tectonophysics 107, 25–56.Google Scholar
Ludwig, K. 1999. Isoplot/Ex. A Geochronological Toolkit for Microsoft Excel. Berkeley, CA: Berkeley Geochronology Center, Special Publication 1a.Google Scholar
Marro, C. 1988. Organisation géochimique et intrusion du granite du Mont Blanc et de deux leucogranites. Schweizerische Mineralogische und Petrographische Mitteilungen 68, 521–29.Google Scholar
Ménard, G.& Molnar, P. 1988. Collapse of a Hercynian Tibetan Plateau into a Late Paleozoic European Basin and Range province. Nature 334, 235–7.Google Scholar
Paquette, J. L., Ménot, R. P.& Peucat, J.. 1989. REE, Sm–Nd and U–pb zircon study of eclogites from the Alpine External massifs (Western Alps): evidence for crustal contamination. Earth and Planetary Science Letters 96, 181–198.Google Scholar
Patño-Douce, A. E.& Harris, N. 1998. Experimental constraints on Himalayan anatexis. Journal of Petrology 39, 689–710.Google Scholar
Pin, C.& Vielzeuf, D. 1983. Granulites and related rocks in Variscan Median Europe: a dualistic interpretation. Tectonophysics 93, 47–74.Google Scholar
Pupin, J.P. 1980. Zircon and granite petrology. Contributions to Mineralogy and Petrology 73, 207–20.Google Scholar
Pupin, J.P. 1988. Granites as indicators in paleogeodynamics. Rendiconti della Societa Italiana di Mineralogia e Petrologia 43, 237–62.Google Scholar
Rey, P., Burg, J. P.& Casey, M. 1997. The Scandinavian Caledonides and their relationship to the Variscan belt. In Burg, J.P.& Ford, M. (eds) Orogeny through Time, Geological Society Special Publications 121, 179–200. London: Geological Society Google Scholar
Rock, N. M. S. 1991. Lamprophyres, Glasgow: Blackie.Google Scholar
Rossi, P.& Cocherie, A. 1995. A belt of high-K plutonic rocks related to crustal extension: evidence from the European Variscan. In The Origin of Granites and Related Rocks 3rd Hutton Symposium, Abstracts. U. S. Geological Survey Circular 1129, 128–9.Google Scholar
Schaltegger, U. 1994. Unravelling the pre-Mcsozoic history of Aar and Gotthard massifs (Central Alps) by isotopic dating—a review. Schweizerische Mineralogische und Petrographische Mitteilungen 74, 41–52.Google Scholar
Schaltegger, U. 1997. Magma pulses in the Central Variscan belt: episodic melt generation and emplacement during lithospheric thinning. Terra Nova 9, 242–5.Google Scholar
Schaltegger, U, Schneider, J. L., Maurin, J. C.& Corfu, F. 1996. Precise U–Pb chronometry of 345-340 Ma old magmatism related to synconvergence extension in the Southern Vosges (Central Variscan Belt). Earth and Planetary Science Letters 144, 403–419.Google Scholar
Schaltegger, U., Fanning, C. M., Günther, D., Maurin, J. C., Schulmann, K.& Gebauer, D. 1999. Growth, annealing and recrystallization of zircon and preservation of monazite in highgrade metamorphism: conventional and in-situ isotope, cathodoluminescence and microchemical evidence. Contributions to Mineralogy and Petrology 134, 186–201.Google Scholar
Schaltegger, U.& Corfu, F. 1992. The age and source of Late Hercynian magmatism in the Central Alps: evidence from precise U–Pb ages and initial Hf isotopes. Contributions to Mineralogy and Petrology 111, 329–344.Google Scholar
Schaltegger, U.& Corfu, F. 1995. Late Variscan ‘Basin and Range’ magmatism and tectonics in the Central Alps: evidence from U–Pb geochronology. Geodynamica Acta 8, 82–98.Google Scholar
Schärer, U. 1984. The effect of initial 230Th disequilibrium on young U–Pb ages: the Makalu case, Himalaya. Earth and Planetary Science Letters 67, 191–204.10.1016/0012-821X(84)90114-6Google Scholar
Schulz, B.& Von, Raumer J. F. 1993. Syndeformational uplift of Variscan high pressure rocks (Val Bérard, Aiguilles Rouges, Western Alps. Zeitschrift der Deutschen Geologischen Gesellschaft 144, 104–20.Google Scholar
Stacey, J. S.& Kramers, J. D. 1975. Approximation of terrestrial lead isotope evolution by a two-stage model. Earth and Planetary Science Letters 6, 15–25.Google Scholar
Stampfli, G. M. 1996. The Intra-Alpine terrain: a Paleotcthyan remnant in the Alpine Variscides. Elogue Geologicae Helvetiae 89, 13–42.Google Scholar
Stampfli, G. M., Mosar, J., Favre, P., Pillevuit, A.& Vannay, J. C. 2000. Permo-Mesozoic evolution of the western Tethyan realm: the Neotethys/East-Mediterranean connection. In Cavazza, W., Robertson, A. H. F. R. & Ziegler, P. A. (eds) Peritethyan rift/ wrench basins and passive margins IGCP 369. Bulletin du Museum National d'Histoire Naturelle Paris (in press).Google Scholar
Thompson, A. B. 1990. Heat, fluids, and melting in the granulite facies. In Vielzeuf, D.& Vidal, P. (eds) Granulites and crustal evolution, 35–57. Dordrecht: Kluwer.Google Scholar
Thompson, A. B.& Connolly, J. A. D. 1995. Melting of the continental crust: some thermal and petrological constraints on anatexis in continental collision zones and other tectonic settings. Journal of Geophysical Research 100, 15565–79.Google Scholar
Vavra, G.& Schaltegger, U. 1999. Post-granulite facies monazite growth and rejuvenation during Permian to Lower Jurassic thermal and fluid events in the Ivrea zone (Southern Alps). Contributions to Mineralogy and Petrology 134, 403–14.10.1007/s004100050493Google Scholar
Vielzeuf, D.& Pin, C. 1989. Geodynamic implications of granulitic rocks in the Hercynian Belt. In Daly, J. S., Cliff, R. A.& Yardley, B. W. D. (eds) Evolution of Metamorphic Belts, Geological Society Special Publications 43, 343–8. London: Geological Society.Google Scholar
Von, Blanckenburg F.& Davies, J. H. 1995. Slab breakoff: a model for syncollisional magmatism and tectonics in the Alps. Tectonics 14, 120–31.Google Scholar
Von, Raumer J. F. 1998. The Palaeozoic evolution in the Alps: from Gondwana to Pangea. Geologische Rundschau 87, 407–35.Google Scholar
Von, Raumer J. F., Galetti, G., Oberhänsli, R.& Pfeifer, H. R. 1990. Amphibolites from Lac d'Emosson/ Aiguilles Rouges (Switzerland): Tholeiitic basalts at a transition zone between continental and oceanic crust. Schweizerische Mineralogische und Petrographische Mitteilungen 70, 419–35.Google Scholar
Von, Raumer J., Bussy, F.& Sharp, Z. D. 1996. Lac Cornu revisited: the evolution from lower to upper crust (Aiguilles Rouges Massif, Western Alps). Schweizerische Mineralogische und Petrographische Mitteilungen 76, 120–1.Google Scholar
Von, Raumer J. F., Abrecht, J., Bussy, F., Lombardo, B., Ménot, R. P.& Schaltegger, U. 1999a. The Palaeozoic metamorphic evolution of the Alpine External Massifs. Schweizerische Mineralogische und Petrographische Mitteilungen 79, 5–22.Google Scholar
Von, Raumer F., Bussy, F.& Stampfli, G. 1999b. The peri-Gondwanan origin of pre-Mesozoic basement units in the Alps, EUG10, Strasbourg. Terra Abstracts 11, 88.Google Scholar
Von, Raumer J.& Neubauer, F. 1993. Late Precambrian and Palaeozoic Evolution of the Alpine Basement—an overview, In Von, Raumer J. F.& Neubauer, F. (eds) The pre-Mesozoic geology in the Alps, 625–39. Heidelberg: Springer.Google Scholar
Von, Raumer J. F.& Schwander, H. W. 1985. Garnet evolution in pre-Variscan pelitic rocks from the Lake Emosson area, Aiguilles Rouges Massif, Western Alps, Journal of Metamorphic Geology 3, 467–79.Google Scholar
Wirsing, A. 1997. Die Orthogneise des oberen Val Bérard (Aiguilles Rouges Massiv, Westalpen, Frankreich). Unpublished Ph.D. Thesis, Fribourg.Google Scholar