Métamonzonite de Pormenaz

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Darstellung und Status

Farbe CMYK
(0%,51%,49%,16%)
Farbe RGB
R: 215 G: 105 B: 110
Rang
lithostratigraphische Formation
Gebrauch
Element ist in Gebrauch
Status
informeller Begriff

Nomenklatur

Deutsch
Pormenaz-Metamonzonit
Français
Métamonzonite de Pormenaz
Italiano
Metamonzonite di Pormenaz
English
Pormenaz Metamonzonite
Herkunft des Namens

Hameau/alpage de Pormenaz (France)

Historische Varianten

granite de Pormenaz (Dhellemmes 1955), Granite diffus de Pormenaz (Pairis et al. 1992), Pormenaz monzonite = Pormenaz granite (Bussy et al. 1997, Capuzzo et al. 2003)

Beschreibung

Beschreibung

gneiss et des micaschistes biotitiques fortement mylonitisés et rétromorphosés

Hierarchie und Abfolge

Übergeordnete Einheit

Alter

Alter Top
  • Viséen
Alter Basis
  • Viséen
Datierungsmethode

332 +/-2 Ma (U/Pb on zircon and monazite ; Bussy et al. 1997, Bussy et al. 2000)

Geografie

Geographische Verbreitung
Bande N-S de 500 m de large entre le chalet du Fer (rive gauche de la Diosaz) et les chalets de Chavanne (flanc SW de la Pointe Noire de Pormenaz).
Typusregion
Montagne de Pormenaz (France)

Paläogeografie und Tektonik

Tektonische Einheit (bzw. Überbegriff)
Herkunftstyp
  • plutonisch

Referenzen

Neubearbeitung
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.66: The Pormenaz monzonite is a 1.4 by 2.5 km porphyritic funnelshaped mass in vertical cross section, which intruded amphibolite-facies metamorphic rocks and lower Carboniferous metagraywackes (Délitroz & Fellay 1997). The shape and internal structures of the intrusion suggest a syntectonic emplacement of the magma and post-crystallization mylonitic deformations along a long-lasting dextral transpressive fault. The main facies is a porphyritic to equigranular monzonite with large pink or white K-feldspar megacrysts (up to 4 cm) in a dark graygreen amphibole-rich matrix. Euhedral crystals of brown sphene are clearly visible on hand specimen. Plurimetric bodies of durbachites (Holub 1977; Rock 1991) are found as dark green, equigranular, magmatic enclaves. The Pormenaz monzonite is characterized by high to very high concentrations in LILE like K, Rb, Ba, Sr, in Mg and transition elements like Cr, Ni, and V, and in incompatible elements like LREE, Zr and Th. Conversely, Ca is relatively low in this range of SiO2 content. REE are strongly fractionated without substantial Eu anomaly. The durbachitic enclaves have the same chemical characteristics as the monzonites, reminiscent of lamprophyres.

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