Fruttstock-Gruppe (mittelvariszische Intrusiva)

Representation and status

Color CMYK

(0%,50%,48%,14%)

Color RGB

R: 220 G: 110 B: 115

Rank

lithostratigraphic Group

Validity

Unit is in Use

Nomenclature

Deutsch

Fruttstock-Gruppe (mittelvariszische Intrusiva)

Français

Groupe du Fruttstock

Italiano

Gruppo del Fruttstock

English

Fruttstock Group

Origin of the Name

Fruttstock (UR), Silenen

Historical Variants

Group B (Schaltegger 1994), Düssi-Fruttstock-Brunni-Komplex (Spillmann et al. 2011), Middle Variscan plutonic rocks = Fruttstock Group (Berger et al. 2017)

Hierarchy and sequence

Subordinate units

• Voralp-Granit
• Brunni-Granit
• Munt-Dado-Granit
• Bugnei-Granodiorit
• Düssi-Diorit
• Schöllenen-Diorit
• Rossplatten-Diorit
• Dammagletscher-Diorit
• Bristenstock-Syenit

Units at roof

• Haslital-Gruppe (spät- bis postvariszische Intrusiva)

Age

Age at top

• Middle Pennsylvanian

Age at base

• Middle Pennsylvanian

Dating Method

312-306 Ma (Schaltegger 1994)

Palaenography and tectonic

• Variscan plutonic rocks of the Helvetic

Paleogeography

European continental plate

Tectonic unit (resp. main category)

• Aar

References

Definition

Berger Alfons, Mercolli Ivan, Herwegh Marco, Gnos Edwin (2017) : Geological Map of the Aar Massif, Tavetsch and Gotthard Nappes. Geological Special Map 1:100'000, Explanatory Notes 129

p.40: The plutonic rocks of the Fruttstock Group represent a calc-alkaline suite dominated by diorites and granodiorites of Moscovian age (Fig. 4, “Group B” of SCHALTEGGER 1994). This group outcrops mainly in the eastern part of the Aar Massif. Local mutual contact relationships indicate an older age with respect to the Haslital Group (GNOS 1988, LABHART & RENNER 2012). U/Pb dating on zircon have confirmed these age relationships. SCHALTEGGER (1994) reported an age interval between 312– 306 Ma for these intrusions (Fig. 4, Tab. 2). SCHALTEGGERet al.(1991) discussed the high-K calc-alkaline rocks of the Fruttstock Group and interpreted them as the product of intense fractional crystallisation and crustal contamination in primary melts of an enriched subcontinental mantle.