Plutone della Bregaglia
Representation and status
- Index
- Ber
- Color RGB
- R: 241 G: 237 B: 239
- Rank
- lithostratigraphic Group
- Validity
- Unit is in Use
- Status
- informal term
- Status discussion
Nomenclature
- Deutsch
- Bregaglia-Pluton
- Français
- Pluton de la Bregaglia
- Italiano
- Plutone della Bregaglia
- English
- Bregaglia Pluton
- Origin of the Name
- Historical Variants
-
Granite der Valle della Mera = Granite der Bassa Valle della Mera (Wenk 1956), batolite bregagliotta = Massiccio Bregagliotto (Godenzi 1963), Bergeller Intrusion = tertiäre synorogene granitoide Intrusiva des Bergell (Bucher-Nurminen 1970), Zone Giubasco-Jorio-Sorico-Monte Bassetta-Val Masino-Monte Sissone = Zone Jorio-Sissone = Serizzo-Zug (Wenk 1982), Bregaglia-Iorio Intrusive (Trommsdorf & Nivergelt 1986), plutone di Val Màsino-Bregaglia-Iorio (Sciesa 1991), plutoniti di Bregaglia (Dal Piaz et al. 1992a), intrusion de la Bregaglia (Mayerat Demarne 1994), Masino-Bregaglia igneous body (Hansmann 1996), Plutone Val Masino-Bregaglia (Spalla et al. 1998), Complesso di Bregaglia (Wenk 2012), Bregaglia intrusion = Bregaglia-Intrusionskörper = intrusion de la Bregaglia (TK500)
Hierarchy and sequence
Age
- Age at top
-
- Oligocene
- Age at base
-
- Oligocene
- Dating Method
-
32-30 Ma
Geography
- Geographical extent
- Massiccio intrusivo compresso fra le Valli Bregaglia, Masino e Malenco.
- Type area
- Val Bregaglia (GR)
Palaenography and tectonic
- Tectonic unit (resp. main category)
- Kind of protolith
-
- plutonic
- Conditions of formation
-
Hansmann 1996 S.422: Field evidence defines the following magmatic sequence in the MB area:
(i) Andesitic-basaltic dikes that crosscut the Alpine fohation in the neighbouring units (Nievergelt and Dietrich, 1977) show a contact metamorphic overprint in the MB aureole (Gautschi and Montrasio, 1978).These were interpreted as precursors of the main intrusions on geochemical grounds (Diethelm, 1989; von Blanckenburg et al., 1992).
(ii) Gabbros and hornblendites occur as variously-sized inclusions only in the tonahte and are interpreted as early magmatic differentiates (Diethelm, 1985,1989).
(iii) The two main intrusions, the tonalite ("Serizzo") and the granodiorite ("Serizzo Ghiandone" in the older Italian hteräture). These are in-contact along a complex transition zone (Moticska, 1970; Reusser. 1987) but age relationships of the two are ambiguous in the western part of the main igneous body. The tonalite is considered to be older (e.g. Cornelius, 1928; Bucher-Nurminen, 1977; Berger and Giere, 1995). Field evidence in support of this hypothesis is given by a small granodioritic stock intruding the tonahte in the Val Sissone (Montrasio and Trommsdorff, 1983; Berger and Giere, 1995).
(iv) Lamprophyric dikes of calc-alkaline and shoshonitic compositions are present in the granodiorite with variable degrees of disintegration from undisturbed dikes through disrupted dikes and swarms of inclusions to isolated inclusions. These dikes intruded the granodioritic magma prior to its complete sohdification (Diethelm, 1989).
(v) The youngest major intrusion in the area is represented by a garnet-bearing two-mica-leucogranite, the Novate Granite. Pegmatites, leucocratic inicro-granjtes and aplites are widespread in the whole MB region. Some of these dikes radiate from the Novate intrusion. Among the several generations of leucocratic dikes (e.g. Moticska, 1970), Reusser (1987) distinguished pre- and post granodioritic types, therefore only some of the dikes can actually be associated with the Novate intrusion.
-
Aplite di Zocca
- Name Origin
- Rank
- lithostratigraphic unit
- Status
- local name (informal)
- In short
-
Filoni aplitici e pegmatitici.
-
Microgranito del Monte Rosso
- Rank
- lithostratigraphic unit
- Status
- local name (informal)
-
Granodiorite dell'Alpe Cameraccio
- Name Origin
- Rank
- lithostratigraphic Formation
- Status
- local name (informal)
- In short
- Granodiorite massicco a grana fine, senza megacristalli.
-
Minestronite
- Rank
- petrographic facies
- Status
- incorrect name (though informally used)
- In short
- Brecce di gabbri, di serzzo e di rocce incassanti, cementate da ghiandone.
-
Granodiorite della Bregaglia (ghiandone)
- Rank
- lithostratigraphic Formation
- Status
- informal term
- Nomenclatorial Remarks
- <p>Ghiandone auct.</p>
- In short
-
Porphyrischer («klotziger») Granodioritischer Kern der Bergell-Intrusion.
- Age
- early Oligocene
-
Granodiorite della Val Màsino
- Name Origin
- Status
- valid formal name
- Nomenclatorial Remarks
- ghiandone auct., Bergellergranit, Disgraziagranit [sic]
- In short
- Granodiorite con porfiroblasti di K-feldspato, talora orientati, da la parte centrale ed orientale del plutone della Val-Màsino-Bregaglia-Iorio.
- Age
- early Oligocene
-
Melirolo-Augengneis
- Name Origin
-
Melirolo (TI), Val Morobbia
- Status
- informal term
- In short
- Granodiorite ad orneblenda, con "occhi" di plagioclasio. Südliche Randfazies des Iorio-Tonalites.
-
Tonalite della Bregaglia (serizzo)
- Rank
- lithostratigraphic Formation
- Status
- informal term
- Nomenclatorial Remarks
- serizzo auct., Hornblendegneiss (Théobald 1866 S.254), Syenit (Théobald 1866 S.256), gneiss anfibolico (porphiroide) (Melzi 1893 S.110)
- In short
- Tonalitische (quarzdioritische) Hülle der Bergell-Intrusion, die von der Bergell-Granodiorit intrudiert und vergneist wurde.
- Age
- early Oligocene
-
Quarzdiorite del Monte Bassetta
- Name Origin
- Status
- valid formal name
- Nomenclatorial Remarks
- serizzo auct., Bergell-Tonalit, Masino-Tonalit
- In short
- Diorite quarzosa epidotica, orientata, con passagi a tonaliti o gabbri al bordo meridionale e sud-orientale del plutone di Val Màsino-Bregaglia-Iorio.
- Age
- early Oligocene
-
Tonalite di Sòrico
- Name Origin
- Status
- local name (informal)
- In short
- Tonaliti e dioriti epidotiche, simili al serizzo, ma più laminate, con frequenti inclusi basici e di rocce incassanti.
-
Tonalite di San Iorio
- Name Origin
- Status
- local name (informal)
- Nomenclatorial Remarks
- Horneblendegneiss auct.