Borel-Gneiskomplex

Representation and status

Index

P-B

Color CMYK

(12%,0%,15%,35%)

Color RGB

R: 145 G: 165 B: 140

Rank

lithostratigraphic Formation

Validity

Unit is in Use

Status

informal term

Nomenclature

Deutsch

Borel-Gneiskomplex

Français

Complexe gneissique du Piz Borel

Italiano

Complesso gneissico del Piz Borel

English

Borel Gneiss Complex

Origin of the Name

Fuorcla Borel (GR), Tujetsch

Historical Variants

Borelzone (Huber 1943), Borel zone (Beffa 1993), Zone des Piz Borel = Piz Borel zone (Mercolli et al. 1994), Borel-Zone (Labhart & Renner 2012), Borel Gneiss Complex (Berger et al. 2017)

Description

Description

... und Metaquarzit?

Hierarchy and sequence

Superordinate unit

• Streifengneis-Komplex

Age

Age at top

• Paleozoic

Age at base

• Paleozoic

Geography

Geographical extent

E-W trending slice extending from Pizzo Centrale to Passo del Lucomagno, and possibly continuing to the Rappental.

Palaenography and tectonic

• Middle Paleozoic Clastic Rocks

Tectonic unit (resp. main category)

• Gotthard

Kind of protolith

• sedimentary
• volcanic

Metamorphism

polycyclic (Alpine and Variscan)

Metamorphic facies

• greenschist facies (epizone)
• amphibolite facies

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.70: The Borel, Tenelin, Laiets and Giubine Gneiss Complexes constitute four thin, concordant intercalations of garnet-mica schist, hornblende-garnet-mica schist (“Hornblendegarbenschiefer”), calcite-bearing mica schist, amphibolite and quartzite within the units of the polycyclic metamorphic basement. While the Borel and Tenelin Gneiss Complexes form two coherent bands, which can be followed from the Pizzo Centrale area to the Lukmanierpass, the Laiets Gneiss Complex splits into three branches east of the Cristallina Granodiorite (VÖGELI et al. 2013). HUBER (1943) described the petrography and structures of the Borel and Tenelin Gneiss Complexes, whereas WINTERHALTER (1930) treated those of the Laiets Gneiss Complex. HAFNER (1958) and STEIGER (1962) mapped and described a “Giubine-Serie” from the Val Bedretto to the Lukmanierpass. MERCOLLI et al. (1994) outlined the lithological differences in the “Giubine-Serie” and proposed to split it into two branches. Following these authors, the western branch (from Val Bedretto to the region of the Lago della Sella), consisting of migmatitic gneisses, was assigned to the Paradis Gneiss Complex. In contrast, the eastern branch (from the Piz Giübin to the Pizzo dell’Uomo) comprises metasedimentary garnet-mica schist similar to that of the Tenelin and Borel Gneiss Complexes (STEIGER 1962). Therefore, the eastern branch is reported on the map sheet as the Giubine Gneiss Complex, representing a part of the Val Rondadura Group.
OBERHOLZER (1955) described a suite of discontinuous quartzite layers of a few metres thickness in the “Streifengneis” Complex west of the Rotondo Granite. These layers can be followed over a length of few kilometres and could probably represent a western continuation (at least geometrically) of the Borel and Tenelin Gneiss Complexes (MERCOLLI et al.1994). These quartzite layers are not depicted on the present map sheet.