Abstract
The basement lithostratigraphy within the Middle Penninic domain in Wallis, Switzerland (formerly the Grand St. Bernard nappe), is described in order to try to produce reconstruction of the pre-Alpine history. The combined effect of pervasive Alpine deformation and metamorphism (mainly Tertiary greenschist facies overprint) as well as the lack of biostratigraphic and radiometric data make this attempt difficult.
Polymetamorphic basements, affected successively by pre-Alpine metamorphism(s) and by Alpine metamorphism, are distinguished from monometamorphic basements, that apparently were only subject to this latter disturbance. The Pontis and Siviez-Mischabel nappes comprise both poly- and mono-metamorphic units while the rocks of the “Zone Houillère” and the Mont Fort nappe do not seem to have suffered Pre-Alpine metamorphism.
Upper Proterozoic to lower Palaeozoic(?) siliciclastic meta-sediments of the polymetamorphic basement form a thick coarse-grained series overlaid by a dominantly pelitic series. Carbonate rocks (skarns, marbles) do not exist. A wide variety of magmatites (calc-alkaline granitoids, pyroxenites, felsic and mafic volcanites) are presumed to have been generated in different geodynamic environments from upper Proterozoic to lower Palaeozoic time.
Two metamorphic preserved windows allow a partial reconstitution of the pre-Alpine metamorphic history: (1) outcrops of eclogites and retroeclogites (Siviez-Mischabel nappe), usually associated with banded amphibolites, show HP mineral assemblages (pyrope-rich almandine and omphacite) which are overprinted by an amphibolite-facies event (syn-Variscan?); (2) the most internal part of the Ruitor zone (Pontis nappe) is essentially composed of garnet-staurolite micaschists and aluminum silicate-bearing schists (andalusite-sillimanite). Textures and mineral chemistry support a possible evolution in staurolite-almandine subfacies and P-T estimates lead to a polyphase metamorphic trajectory, retrograde in pressure (10→2.5 kb) and thermally prograde (470→580 °C). Correlation with Variscan climax is likely, even if radiometric data is still lacking.
Post-metamorphic late Carboniferous to Early Triassic fluviatil deposits form a thick sequence within the “Zone Houillère” and other parallel grabens(?). The most southern pull-apart(?) basin that is filled up with a thick volcano-sedimentary series (Carboniferous(?) Early Triassic) is largely incorporated into the Mont Fort nappe. Permian gabbros and subalkaline granitoids form sills and laccoliths intruding both poly- and mono-metamorphic basements.
The major uncertainties still concern: (1) the precise age of all rocks and series, except those belonging to the “Zone Houillère”; (2) the initial nature of the polymetamorphic magmatites and the geodynamic context during their ascent; (3) the age and the geodynamic meaning of the different pre-Alpine metamorphic events (HP, HT), especially the age of Variscan(?) paroxysm (amphibolite-facies).
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References
Allimann M (1987) La nappe du Mont Fort dans le Val d’Hérens. Bull Soc Vaudoise Sci Nat 78: 431–444
Allimann M (1989) Les brèches de la région d’Evolène (Nappe du Mont Fort, Valais, Suisse). Schweiz Mineral Petrogr Mitt 69: 237–250
Argand E (1909) L’exploration géologique des Alpes pennines centrales. Bull Soc Vaudoise Sci Nat 45: 217–276
Argand E (1911) Sur la tectonique de la grande zone permohouillère des Alpes occidentales. Eclogae Geol Helv 11: 747–751
Arthaud F, Matte P (1977) Late Paleozoic strike-slip faulting in Southern Europe and Northern Africa: result of a right-lateral shear zone between the Appalachians and the Urals. Geol Soc Am Bull 88: 1305–1320
Bearth P (1963) Contribution à la subdivision tectonique et stratigraphique du Cristallin de la nappe du Grand-StBernard dans le Valais ( Suisse ). Livre Mém Prof Paul Fallot Soc Géol Fr Mém hs tome II: 407–418
Bearth P (1964) Geologischer Atlas der Schweiz 1:25’000, Blatt 43: Randa mit Erläuterungen. Schweiz Geol Komm
Bearth P (1973) Geologischer Atlas der Schweiz 1: 25’000, Blatt 61: Simplon mit Erläuterungen. Schweiz Geol Komm
Bearth P (1980) Geologischer Atlas der Schweiz 1:25’000, Blatt 71: St. Niklaus mit Erläuterungen. Schweiz Geol Komm
Bocquet J (1974) Il metamorfismo prealpino nella Vanoise (Savoia) e altri settori dello zoccolo brianzones. Mem Soc Geol Ital 3: 271–284
Burri M (1975) Sur les structures de la zone houillère dans les vallées des Drances (Vs). Eclogae Geol Helv 68: 285–299
Burri M (1979) Les formations valaisannes dans la région de Visp. Eclogae Geol Helv 72: 789–802
Burri M (1983 a) Description géologique du front du Saint Bernard dans les vallées de Bagnes et d’Entremont (Valais). Bull Lab Géol Univ Lausanne 270: 1–88
Burri M (1983 b) Le front du Grand St-Bernard du val d’Hérens au val d’Aoste. Eclogae Geol Helv 76: 469–490
Burri M, Jemelin L (1983) Notice explicative de la feuille Sem-brancher (Feuille 77 de l’Atlas). Atlas géologique de la Suisse 1.25’000. Comm Géol Suisse
Caby R (1968) Contribution à l’étude structurale des Alpes occidentales: subdivisions stratigraphiques et structures de la zone du Grand-Saint-Bernard dans la partie sud du Val d’Aoste (Italie). Géol Alp 44: 95–111
Caby R (1974) Gneiss permo-carbonifères d’origine granitique et volcanique dans la zone houillère et la zone du Grand-Saint-Bernard en Val d’Aoste (Italie). Géol Alp 50: 39–44
Chessex R Les métabasites de l’unité du Métailler (nappe du Mont Fort, Valais). Arch Sci Genève (in prep)
Chessex R Les métabasites de l’unité du Métailler (nappe du Mont Fort, Valais). Arch Sci Genève (in prep)
Coleman RG, Lee DE, Beatty LB, Brannock WW (1965) Eclogites and eclogites: Their Differences and Similarities. Geol Soc Am Bull 76: 483–508
Desmons J, Fabre J (1988) Contribution à la connaissance pétrographique du Mont Pourri ( Savoie, France); conséquences structurales. Géol Alp 64: 13–26
Desmons J, Ploquin A (1989) Chimisme du Briançonnais-Grand Saint-Bernard Anté-Mésozoïque (Alpes Occidentales): une vue synoptique. Géol Alp 65: 1–31
Eikenberg J, Köppel V, Labhart T, Signer P (1989) U-Pb, U-Xe and U-Kr systematics of a greenschist facies metamorphic uranium mineralization of the Siviez-Mischabel nappe ( Valais, Switzerland). Schweiz Mineral Petrogr Mitt 69: 331–344
Escher A (1988) Structure de la nappe du Grand Saint-Bernard entre le val de Bagnes et les Mischabel. Rapp Géol Sery Hydrol Geol Natl Berne 7: 1–26
Escher A, Masson H, Steck A (1988) Coupes géologiques des Alpes occidentales suisses. Rapp Géol Sery Hydrol Geol Natl Berne 2: 1–11
Fabre J (1987) Evénements tectoniques et sédimentaires préalpins dans la zone briançonnaise (Zone Houillère) des Alpes occidentales. In: Sassi FP, Bourrouilh R (eds) IGCP Proj 5 Newslett 7, Padova, Bordeaux, pp 143–147
Fabre J, Schade J, Baudin T, Desmons J, Mercier D, Perrucio-Parison MD (1987) Relics of pre-Mesozoic events in the Briançon zone (northern French Alps). In: Flügel HW, Sassi FP, Grecula P (eds) Pre-Variscan and Variscan events in the Alpine-Mediterranean mountain belts. Mineralia slovaca Monogr, Alfa, Bratislava, pp 183–208
Frisch W, Ménot RP, Neubauer F, von Raumer JF (1990) Correlation and evolution of the Alpine basement. Schweiz Mineral Petrogr Mitt 70: 265–285
Gebauer D, Quadt A, Compston W, Williams IS, Grünefelder M (1988) Archean zircons in a retrograded Caledonian eclogite of the Gotthard Massif ( Central Alps, Switzerland). Schweiz Mineral Petrogr Mitt 68: 485–490
Gebauer D, Quadt A, Compston W, Williams IS, Grünefelder M (1988) Archean zircons in a retrograded Caledonian eclogite of the Gotthard Massif ( Central Alps, Switzerland). Schweiz Mineral Petrogr Mitt 68: 485–490
Gouffon Y (1992) Géologie de la “nappe” du Grand St-Bernard entre la Doire Baltée et la frontière suisse (Vallée d’Aoste, Italie). Mém Géo112:147 pp Lausanne
Holdaway MJ, Dutrow BL, Hinton RW (1988) Devonian and Carboniferous metamorphism in west-central Maine: The muscovite-almandine geobarometer and the staurolite problem revisited. Am Mineral 73: 20–47
Jäckli R (1950) Geologische Untersuchungen in der Stirnzone der Mischabeldecke zwischen Réchy, Val d’Anniviers und Visp (Wallis). Eclogae Geol Helv 43: 31–93
Jeanbourquin P, Burri M (1989) La zone de Sion-Courmayeur dans la région du Simplon. Rapp Géol Sery Hydrol Geol Natl Berne 11: 1–35
Jongmans WJ (1960) Die Karbonflora der Schweiz. Beitr Geol Karte Schweiz NF 108, 97 pp
Lombard A (1942) Excursion à la mine de Chandoline près de Sion. Eclogae Geol Heiv 35: 158–159
Lombard A (1949) La formation et la mise en place des anthracites du Valais. Ann Mines Paris 138: 3–14
Liegois JP, Duchesne JC (1981) The Lac Cornu retrograded eclogites (Aiguilles Rouges massif, Western Alps, France): evidence of crustal origin and metasomatic alteration. Lithos 14: 35–48
Loeschke J (1989) Lower Paleozoic volcanism of the Eastern Alps and its geodynamic implications. Geol Rundsch 78: 599–616
Maggetti M, Galetti G (1988) Evolution of the Silvretta eclogites: metamorphic and magmatic events. Schweiz Mineral Petrogr Mitt 68: 467–484
Manby GB, Thiedig F (1988) Petrology of eclogites from Saualpe, Austria. Schweiz Mineral Petrogr Mitt 68: 441–466
Marthaler M (1984) Géologie des unités penniques entre le val d’Anniviers et le val de Tourtemagne (Valais, Suisse). Eclogae Geol Helv 77: 395–448
Meschede M (1986) A method of discriminating between different types of mid-ocean ridge basalts and continental tholeiites with the Nb-Zr-Y diagram. Chem Geol 56: 207–218
Monié P (1990) Preservation of Hercynian 40Ar/39Ar ages through high-pressure low-temperature alpine metamorphism in the Western Alps. Eur J Mineral 2: 343–361
Mullen ED (1983) MnO/TiO2/P2O5: a minor element discriminant for basaltic rocks of oceanic environments and its implications for petrogenesis. Earth Planet Sci Lett 62: 53–62
Müller R (1982) Die tektonische Erforschung der Penninischen Alpen. Eclogae Geol Helv 75: 447–479
Oulianoff N (1957) La zone du Carbonifère entre Isérables et Bramois (vallée du Rhône). Eclogae Geol Helv 50: 482–491
Oulianoff N, Trümpy R (1958) Atlas géologique de la Suisse 1: 25’000, Feuille 33: Grand St. Bernard (avec notice explicative). Comm Géol Suisse
Paquette JL, Ménot RP, Peucat JJ (1989) REE, Sm-Nd and U-Pb zircon study of eclogites from the Alpine External Massifs ( Western Alps ): Evidence for crustal contamination. Earth Planet Sci Lett 96: 181–198
Pearce JA (1980) Geochemical evidence for the genesis and eruptive setting of lavas from Tethyan ophiolites. In: Panayiotou A (ed) Proc Int Ophiolite Symp Cyprus 1979, Rep of Cyprus Geol Sury Dep Nicosia, pp 261–272
Pearce JA, Cann JR (1973) Tectonic setting of basic volcanic rocks determined using trace elements analysis. Earth Planet Sci Lett 19: 290–300
Pearce JA; Norry MJ (1979) Petrogenetic implications of Ti, Zr, Y and Nb variations in volcanic rocks. Contrib Mineral Petrol 69: 33–47
Pfeifer HR, Colombi A, Ganguin J (1989) Zermatt-Saas and Antrona Zone: a petrographic and geochemical comparison of polyphase-metamorphic ophiolites of the West-Central Alps. Schweiz Mineral Petrogr Mitt 69: 33–47
Pin C, Peucat JJ (1986) Ages des épisodes de métamorphisme paléozoïques dans le Massif central et le Massif armoricain. Bull Soc Géol Fr II (3): 461–469
Pupin JP (1980) Zircon and granite petrology. Contrib Mineral Petrol 75: 207–220
Rahn M (1991) Eclogites from the Minugrat, Siviez-Mischabel nappe (Valais, Switzerland). Schweiz Mineral Petrogr Mitt 71: 415–426
von Raumer JF (1983) Die Metapelite von Emosson (Aiguilles Rouges Massiv) als Beispiel spätkaledonisch-frühvariszi scher Metamorphose im Altkristallin des helvetischen Bereichs. Schweiz Mineral Petrogr Mitt 63: 421–455
von Raumer JF (1987) Les massifs du Mont Blanc et des Aiguilles Rouges: Témoins de la formation de croûte varisque dans les Alpes occidentales. Géol Alp 63: 7–24
Sartori M (1990) L’unité du Barrhorn (Zone Pennique, Valais, Suisse). Mém Géol Lausanne, 6: 156 pp
Sartori M, Thélin P (1987) Les schistes oeillés de Barneuza (Nappe de Siviez-Mischabel, Valais, Suisse). Schweiz Mineral Petrogr Mitt 67: 229–256
Sartori M, Bugnon PC, Frey M, Ganguin J, Masson H, Steck A, Thélin P (1989) Compte-rendu de l’excursion commune de la SSMP et de la SGS le long du profil Rawil-Zermatt 9/10/11 octobre 1988. Schweiz Mineral Petrogr Mitt 69: 261–281
Schaer JP (1959 a) Géologie de la partie septentrionale de l’Eventail de Bagnes. Arch Sci Genève 12: 473–620
Schaer JP (1959 a) Géologie de la partie septentrionale de l’Eventail de Bagnes. Arch Sci Genève 12: 473–620
Stampfli GM, Marthaler M (1990) Divergent and convergent margins in the North-Western Alps: confrontation to actualistic models. Geodin Acta Paris 4: 159–184
Staub W (1927) ZurTektonik des Gebirges zwischen Turtmanntal und Simplonpass. Eclogae Geol Hely 20: 247–252
Staub W (1934) Kleintektonik und Oberflächengestalt auf Westseite des Vispertales. Eclogae Geol Heiv 27: 517–519
Stille P (1980) On the genesis of the amphibolites and hornblendefelses in the Berisal Complex ( Simplon, Italy-Switzerland). Mem Inst Geol Univ Padova, tome XXXIV: 205–246
Stille P, Oberhänsli R (1987) Petrology and Alpine metamorphic evolution of the metabasic and ultrabasic rocks in the Berisal crystalline complex. Lithos 20: 169–180
Stille P, Tatsumoto M (1985) Precambrian tholeiitic-dacitic rock-suites and Cambrian ultramafic rocks in the Pennine nappe system of the Alps: Evidence from Sm-Nd isotopes and rare earth elements. Contrib Mineral Petrol 89: 184–192
Thélin P (1983) Les gneiss oeillés de la nappe du Grand Saint-Bernard: essai d’évaluation des critères susceptibles d’en préciser l’hérédité pré-métamorphique (Alpes valaisannes). Thèse, Univ Lausanne, 483 pp
Thélin P (1987) Nature originelle des gneiss oeillés de Randa. Bull Lab Géol Univ Lausanne 290: 1–75
Thélin P (1989) Essai de chronologie magmatico-métamorphique dans le socle de la nappe du Grand Saint-Bernard: quelques points de repère. Schweiz Mineral Petrogr Mitt 69: 193–204
Thélin P (1992) Les métapélites du Mont Mort: une fenêtre métamorphique (nappe des Pontis, Valais). Bull Soc Vaudoise Sci Nat 82: 97–116
Thélin P, Ayrton S (1983) Cadre évolutif des événements magmatico-métamorphiques du socle anté-triasique dans le domaine pennique ( Valais ). Schweiz Mineral Petrogr Mitt 63: 393–420
Thélin, P, Sartori M. Lengeler R, Schaerer JP (1990) Eclogites of Paleozoic or early Alpine age in the basement of the Penninic Siviez-Mischabel nappe, Wallis, Switzerland. Lithos 25: 71–88
Trümpy R (1966) Considérations générales sur le “Verrucano des Alpes suisses”. In: Tongiorgi M, Rau A (eds) Atti del symposium sul Verrucano, Pisa 1965. Soc Tosc Sci Nat Pisa, pp 212–232
Trümpy R, Dösseger R (1972) Permian of Switzerland. In: Cuvillier J, Schürman P (eds) Rotliegend, essays of European Lower Permian. Int Sediment Petrogr Ser, Leiden, Brill, XV: 189–215
The Pre-Alpine Basement of the Briançonnais (Wallis, Vallet JM (1948) Sur la nature “des orthogneiss” de Thion ( Val d’Hérens, Valais). Arch Sci Genève 1: 409–412
Vallet JM (1950) Etude géologique et pétrographique de la partie inférieure du Val d’Hérens et du Val d’Hérémence (Valais). Schweiz Mineral Petrogr Mitt 30: 322–476
Wegmann E (1923) Zur Geologie der St-Bernard Decke im Val d’Hérens. Bull Soc Neuchâtel Sci Nat 47: 3–63
Wegmann E (1923) Zur Geologie der St-Bernard Decke im Val d’Hérens. Bull Soc Neuchâtel Sci Nat 47: 3–63
Wegmann E (1923) Zur Geologie der St-Bernard Decke im Val d’Hérens. Bull Soc Neuchâtel Sci Nat 47: 3–63
Wust GH, Baehni LA (1986) The distinctive tectonometamorphic evolution of two basement complexes belonging to the Grand-Saint-Bernard Nappe ( Val de Bagnes, Valais). Schweiz Mineral Petrogr Mitt 66: 53–71
Ziegler PA (1984) Caledonian and Hercynian crustal consolidation of Western and Central Europe — a working hypothesis. Geol Mijnbouw 63: 93–108
Zingg MA (1989) Die Siviez-Mischabel-Decke: Entstehung und Entwicklung eines Altkristallins. Schweiz Mineral Petrogr Mitt 69: 130
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Thélin, P., Sartori, M., Burri, M., Gouffon, Y., Chessex, R. (1993). The Pre-Alpine Basement of the Briançonnais (Wallis, Switzerland). In: von Raumer, J.F., Neubauer, F. (eds) Pre-Mesozoic Geology in the Alps. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-84640-3_17
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