Granite de Vallorcine

Representation and status

Color CMYK

(0%,48%,56%,6%)

Color RGB

R: 240 G: 125 B: 105

Rank

lithostratigraphic Formation

Validity

Unit is in Use

Status

informal term

Nomenclature

Deutsch

Vallorcine-Granit

Français

Granite de Vallorcine

Italiano

Granito di Vallorcine

English

Vallorcine Granite

Origin of the Name

Vallorcine (France)

Historical Variants

granite de Valorcine (Necker 1828), granite de Valorsine (Delesse 1850), Valorsine-Granit = Granit bei Poyaz (Gerlach 1871), Valorsine-Granit = Granit der Barberine (Studer 1872), granite de Vallorcine (Corbin & Oulianoff 1931, Dhellemmes 1955, Krummenacher 1959), Vallorcine-Granit (Labhart & Rybach 1972), Vallorcine anatectic granite (Bussy et al. 2000, Capuzzo et al. 2003); mylonite: Reinhard & Preiswerk 1927

Links

Synonyms

Granite des Aiguilles Rouges

Mylonite de Miéville

Hierarchy and sequence

Superordinate unit

• Mittelvariszische Intrusiva

Subordinate units

• Mylonite de Miéville

Lower boundary

Contact intrusif dans le Complexe gneissique du Brévent visible dans la région de Vallorcine (Dhellemmes 1955).

Age

Age at top

• Late Carboniferous (= Pennsylvanian)

Age at base

• Late Carboniferous (= Pennsylvanian)

Dating Method

307 +/-2 Ma (U/PB on zircon and monazite ; Bussy et al. 2000), 306.5 +/-1.5 Ma

Geography

Geographical extent

Etroite bande s'étendant d'Argentière (vallée de Chamonix) à Vernayaz (plaine du Rhône), sur le flanc SE de la partie septentrionale du massif des Aiguilles Rouges.

Type area

vallée de Vallorcine

Reference profiles

• carrière de Miéville
  Coordinates
  • (568270 / 110960)
  Note
  • différents stades de mylonitisation sont observables

Palaenography and tectonic

• Variscan plutonic rocks of the Helvetic

Tectonic unit (resp. main category)

• Aiguilles Rouges :
  massif des Aiguilles Rouges

Kind of protolith

• plutonic

Metamorphism

monocyclic

Metamorphic facies

• greenschist facies (epizone)

Note on metamorphism

contact SE intensément mylonitisé

References

Definition

Necker Louis Albert (1828) : Mémoire sur la vallée de Valorsine. Mém. Soc. phys. hist. nat. Genève IV 209

«Granite à feldspath blanc dominant, à quartz gris, à mica noir, dont les feuillets sont irrégulièrement disséminés dans toute la masse. De grands cristaux de feldspath donnent à ce granite la structure porphyrique». (Necker 1828 p.209)

Definition

Bussy François, von Raumer Jürgen, Capuzzo Nicola (2001) : Mont-Blanc, Aiguilles-Rouges massifs (External Massifs) - an example of polyorogenic evolution. Fieldtrip Guide 1, 53-84, Univ. Lausanne

p. 67: Located in the northern part of the Aiguilles- Rouges massif (stop 1A and 1G1), the Vallorcine granite is a 15-km-long by 1-km thick sheet-like pluton (see fig. 23), which intruded at 306.5 ± 1.5 Ma along a steeply dipping, NE-SW trending, dextral strike-slip shear zone (Brändlein 1991; Brändlein et al. 1994). Syntectonic intrusion is inferred on the basis of structural analysis, which documents long-lasting strike-slip shearing both in the country rocks (pre- and post-intrusion fabrics) and in the granite. The latter developed an early NE-SW trending magmatic flow structure, evolving locally into a post-solidus foliation. The Vallorcine granite was subsequently affected along its SE contact by an intense low-T ductile shearing leading to the well-known “Miéville ultramylonite” (Kerrich et al. 1980) of Late Variscan age (but reworked during the Alpine orogeny). Alpine relief provides a 2000 m-high natural cross-section through the pluton. The lowermost facies is a biotite-rich monzogranite hosting numerous enclaves up to 30 cm in size; including gneiss xenoliths from the country rocks, hornfelses, micaceous restites with sillimanite and hercynite, early cordierite-bearing leucogranite blocks and mafic microgranular enclaves. The upper facies is finer-grained with less biotite and almost no enclaves, pointing to an enclave unmixing process during upward motion of the magma. Aplitic and subvolcanic dykes are concentrated within the wall rocks of the upper contact. The Vallorcine intrusion is a typical S-type granite, as confirmed by zircon typology, stable isotopes (Brändlein et al. 1994) and the presence of Al-rich minerals (cordierite, muscovite, andalusite, etc.).

Important Publications

Necker Louis Albert (1828) : Mémoire sur la vallée de Valorsine. Mém. Soc. phys. hist. nat. Genève IV 209

Delesse A. (1850) : Analyse du granite de Valorsine. Bull. Soc. geol. Fr. (2) VII, 424

Labhart Toni P., Rybach L. (1972) : Der Vallorcine-Granit und seine radiometrischen Anomalien. Schweiz. Min. Petr. Mitt. 52/3, 571-574

Material and varia