Bergell Pluton, Central Alps


Mechanisms and timescales of pluton emplacement

Publications: Samperton et al., 2015, Samperton et al., 2017

K-feldspar megacrysts entrained in a mafic enclave, Forno region

Recently deglaciated exposure is sufficiently fresh that oxidation of exposed pyrite is still ongoing.

Dense clot of K-feldspar megacrysts, Forno region

Strongly foliated amphibolite xenoliths near the roof of the Bergell pluton, Forno region

Amphibolite xenolith with calc-silicate affinities (note epidote and calcite veins) near the roof of the Bergell pluton, Forno region

Extensive exposure of the megacrystic K-feldspar granodiorite facies of the Bergell Pluton near Albigna

The spire of Piz. Badile, glacially carved out of Bergell granodiorite, Sciora region

A large mafic enclave cut and offset by an aplite dike, Sciora region

Mafic enclave diced by two small magmatic shear zones, Sciora region

Nearly hexagonal mafic enclave, Sciora region

Dust rises from an active rockfall on Piz. Cengalo, Sciora region

An aplite “schlieren-dike” offset across a magmatic shear zone in the transitional “übergangszone” facies of the Bergell pluton, Sciora region

Heterogeneous enclave swarm in the Bergell übergangszone, Sciora region

Poikilitic garnet and tourmaline crystals in a pegmatite dike, Sciora region

Large mafic enclave swarm in the Bergell übergangszone, Sciora region

K-feldspar megacryst entrained and partially resorbed within mafic enclave, Sciora region

Deformed mafic enclaves in an enclave swarm, übergangszone, Sciora region

Ultramafic xenoliths in Bergell granodiorite, altered to anthophyllite and biotite, Sciora region

Dense K-feldspar megacryst clot with biotite-rich interstices, Gianetti region. Ruler is set to 1m for scale.

Large aplite dike, Gianetti region. One of many striking roughly ~240 throughout the Bergell pluton. Kyle Samperton for scale.

Close-packed K-feldspar megacryst clot offset by otherwise-invisible magmatic shear zone, Gianetti region. Note marked concentration of biotite at margin.

Detail of megacryst clot, Gianetti region

Altered ultramafic xenolith, progresively retrograded to chlorite (center) and biotite (rim). Allievi region.

Discordant magmatic contact cut by composite aplite-pegmatite dike, Kima region

Bergell tonalite scattered with ultramafic talus fallen from Monte Disgrazia

Deformed quartz veins following a classic conjugate fracture pair, Ponti region

Discordant contact revealed by strong magmatic fabrics, Ponti region

Sharp contact of Bergell tonalite with shear zone at roof of pluton, Ponti region

Calc-silicate boudin in marble country rock near the roof of the Bergell pluton, Ponti region