Granulites and charnockites of the Gruf Complex: Evidence for Permian ultra-high temperature metamorphism in the Central Alps

Galli, Andrea; Bayon, Benjamin Le; Schmidt, Max W.; Burg, Jean‐Pierre; Caddick, Mark J.; Reusser, Éric

doi:10.1016/j.lithos.2010.08.003

Cited by 56 publications

(108 citation statements)

References 105 publications

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“…Highpressure rocks known from the adjacent Adula nappe are absent in the Gruf complex. Rare sapphirine-bearing granulites, discovered by Cornelius (1916) and Wenk et al (1974) only in the form of loose blocks in Val Codera, in fact form schlieren within charnockites and residual enclaves, both within migmatitic orthogneisses and charnockites (Galli et al 2011). Granulites and charnockites formed under ultra-high temperature conditions of T = 920-940°C and P = 8.5-9.5 kbar (Galli et al 2011).…”

Section: Geological Settingmentioning

confidence: 96%

“…Rare sapphirine-bearing granulites, discovered by Cornelius (1916) and Wenk et al (1974) only in the form of loose blocks in Val Codera, in fact form schlieren within charnockites and residual enclaves, both within migmatitic orthogneisses and charnockites (Galli et al 2011). Granulites and charnockites formed under ultra-high temperature conditions of T = 920-940°C and P = 8.5-9.5 kbar (Galli et al 2011). Droop and Bucher-Nurminen (1984), and Schmitz et al (2009) suggested an Alpine age for the granulites, whereas Huber (1999), Burri et al (2005) and Galli et al (2011) envisaged a pre-Alpine age.…”

Section: Geological Settingmentioning

confidence: 96%

“…Granulites and charnockites formed under ultra-high temperature conditions of T = 920-940°C and P = 8.5-9.5 kbar (Galli et al 2011). Droop and Bucher-Nurminen (1984), and Schmitz et al (2009) suggested an Alpine age for the granulites, whereas Huber (1999), Burri et al (2005) and Galli et al (2011) envisaged a pre-Alpine age. Subsequently, the charnockites have been dated at 282-260 Ma (U-Pb on zircon) placing granulite facies conditions in the Permian (Galli et al 2012).…”

Section: Geological Settingmentioning

confidence: 99%

“…The occurrence of high grade metamorphic rocks such as sapphirine-bearing granulites and charnockites (Cornelius 1916;Wenk et al 1974;Galli et al 2011) and widespread migmatisation (Berger et al 1996;Davidson et al 1996) make the Gruf complex unique within the Central Alps. It is crucial to understand such rocks in modern orogenic systems and, from a more regional point of view, these distinct rocks need to be integrated into the tectonometamorphic evolution of the Lepontine Alps.…”

Section: Introductionmentioning

confidence: 99%

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Tectonometamorphic history of the Gruf complex (Central Alps): exhumation of a granulite–migmatite complex with the Bergell pluton

et al. 2013

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We describe field occurrences of sapphirinebearing granulites, charnockites and migmatites in the Gruf complex, Central Alps and present a new geological map and a structural analysis of the entire Gruf complex for the first time. We have carried out an accurate analysis of the relationships between granulite facies metamorphism, migmatisation and deformation within the complex, in relation to the intrusion of the Bergell pluton. Granulites and charnockites display fabrics different from those defined by the regional foliation and lineation, which are, typically for migmatites, disordered on the mesoscale. On a regional scale, strike variations are also related to the structural complexity of migmatites within which no major antiform could be identified. Irregular interfingering of subparallel leucosome veins and back-veining along the contact between the Gruf migmatites and the Bergell tonalite are evidence for contemporaneous emplacement and crystallisation at about 740°C and 6.5-7.5 kbar in Oligocene times (ca 30 Ma). Metamorphic conditions in the charnockites and granulites ([920°C for 8.5-9.5 kbar) largely exceed these regional metamorphic conditions and are dated at 282-260 Ma. We propose that the ascending Bergell pluton entrained the polymetamorphic, granulitic lower crust enclosed within the peripheral migmatitic Gruf complex.

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Section: Geological Settingmentioning

confidence: 96%

Section: Geological Settingmentioning

confidence: 96%

Section: Geological Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Tectonometamorphic history of the Gruf complex (Central Alps): exhumation of a granulite–migmatite complex with the Bergell pluton

et al. 2013

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“…Significantly older examples of comparably shortlived G-UHT metamorphism associated with the rapid transfer of heat promoted by extension and magmatic underplating may include the Palaeozoic (272 ± 4 Ma) Gruf Complex, within the Alps (Galli et al, 2011), which underwent UHT for less than 5 Myr, and, in the light of the most recent geochronology, the Palaeoproterozoic (1900 ± 6 Ma) South Harris Complex of Scotland (Baba et al, 2012).…”

Section: Fast Granulites and Short Lived Uhtmentioning

confidence: 99%

A matter of time: The importance of the duration of UHT metamorphism

Harley

2016

Journal of Mineralogical and Petrological Sciences

142

110

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The duration of granulite (G) and ultra-high temperature (UHT) conditions in regional metamorphism is critical to arguments regarding the tectonic settings of granulites and their relationships to Supercontinent assembly. Analysis of zircon geochronology integrated with trace element (REE) constraints on the timing of zircon growth or modification and evidence for metamorphic temperatures from Ti-in-zircon reveals that zircon can form episodically at or near the metamorphic peak in long-lived UHT granulites. This reflects the segregation, transfer and stagnation or trapping of melts which leads to local melt-rock interactions that promotes zircon crystallisation. In contrast, although rutile can retain UHT information in short duration ('fast') G-UHT terrains it is afflicted by Zr loss in long duration ('slow') terrains and yields temperatures significantly lower than those preserved by zircons formed in the same G-UHT events. An assessment of the age-duration evidence from several well-documented G-UHT terrains reveals that most are 'slow', having durations of UHT, Δt 900 , in the range 30-100 Myr. Some UHT terrains previously considered to be short-lived (Δt 900 < 10 Myr) have longer durations of UHT in the light of recent geochronology and hence are also classed as 'slow'. Of the models proposed to account for UHT metamorphism, the 'large hot orogen' (LHO) model for collisional orogeny provides the best setting for the formation of such 'slow' UHT granulites. LHO models can account not only for the P-T paths, which can range from UHT with near-isothermal decompression (UHT-ITD) through to decompression-cooling and UHT followed by near-isobaric cooling (UHT-IBC), but also for residence times under UHT conditions. The Napier Complex, the Earth's premier UHT terrain, probably formed as trapped deep crust in the hot underbelly of a late-Archaean LHO. Shorter duration UHT and near-UHT granulites also exist, mostly with Δt 900 less than 10 Myr. A number of these are likely to have formed as a consequence of severe lithospheric thinning and crustal extension accompanied by voluminous magmatism, which could occur in arc and back-arc settings affected by subduction roll-back or, as advocated by previous workers, continental arcs undergoing extension. However, attaining long-lived UHT conditions in these settings is unlikely unless the crust has inherently high radioactive heat production in addition to the transient heat added during extension and magmatism.

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The Alps and Their Siblings

Neukirchen¹

2022

The Formation of Mountains

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Granulites and charnockites of the Gruf Complex: Evidence for Permian ultra-high temperature metamorphism in the Central Alps

Cited by 56 publications

References 105 publications

Tectonometamorphic history of the Gruf complex (Central Alps): exhumation of a granulite–migmatite complex with the Bergell pluton

Tectonometamorphic history of the Gruf complex (Central Alps): exhumation of a granulite–migmatite complex with the Bergell pluton

A matter of time: The importance of the duration of UHT metamorphism

The Alps and Their Siblings

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