In the Sesia-Lanzo Zone, Western Alps, the Rocca Canavese Thrust Sheets (RCT) subunit is characte... more In the Sesia-Lanzo Zone, Western Alps, the Rocca Canavese Thrust Sheets (RCT) subunit is characterized by a mixture of mantle- and crust-derived lithologies, such as metapelites, metagranitoids, metabasics, and serpentinized mantle slices with sizes ranging from meters to hundreds of meters. Structural and metamorphic history suggests that the RCT rocks experienced a complex evolution. In particular, two different peak conditions were obtained for the metabasics, representing different tectono-metamorphic units (TMUs), namely, D1a under eclogite facies conditions and D1b under lawsonite-blueschist-facies conditions. The two TMUs were coupled during the syn-D2 exhumation stage under epidote-blueschist-facies conditions. The different rocks and metamorphic evolutions and the abundance of serpentinites in the tectonic mixture suggest a possible subduction-related mélange origin for the RCT. To verify whether a subduction-related mélange can record tectono-metamorphic histories similar ...
Multiscale structural analysis was carried out to explore the sequence of superposed pre-Alpine c... more Multiscale structural analysis was carried out to explore the sequence of superposed pre-Alpine chloritoid–staurolite–andalusite metamorphic assemblages in the polydeformed Variscan basement of the upper Val Camonica, in the central Southalpine domain. The dominant fabric in the upper Val Camonica basement is the late-Variscan S2 foliation, marked by greenschist facies minerals and truncated by the base of Permian siliciclastic sequences. The intersection with the sedimentary strata defines a Permianage limit on the pre-Alpine tectonometamorphic evolution and exhumation of the Variscan basement. The detailed structural survey revealed that the older S1 foliation was locally preserved in low-strained domains. S1 is a composite fabric resulting from combining S1a and S1b: in the metapelites, S1a was supported by chloritoid, garnet, and biotite and developed before S1b, which was marked by staurolite, garnet, and biotite. S1a and S1b developed at intermediate pressure amphibolite facie...
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
In the Southern Steep Belt, Italian Central Alps, relicts of the pre-Alpine continental crust are... more In the Southern Steep Belt, Italian Central Alps, relicts of the pre-Alpine continental crust are preserved. Between Valtellina and Val Camonica, a poly-metamorphic rock association occurs, which belongs to the Austroalpine units and includes two classically subdivided units: the Languard-Campo nappe (LCN) and the Tonale Series (TS). The outcropping rocks are low to medium grade muscovite, biotite and minor staurolite-bearing gneisses and micaschists, which include interlayered garnet-and biotite-bearing amphibolites, marbles, quartzites and pegmatites, as well as sillimanite-bearing gneisses and micaschists. Permian intrusives (granitoids, diorites and minor gabbros) emplaced in the metamorphic rocks. We performed a detailed structural, petrological and geochronological analysis focusing on the two main lithotypes, namely, staurolite-bearing micaschists and sillimanitebearing paragneisses, to reconstruct the Variscan and Permian-Triassic his
We develop a two-dimensional thermo-mechanical numerical model in which the formation of oceanic ... more We develop a two-dimensional thermo-mechanical numerical model in which the formation of oceanic crust and serpentinite due to the hydration of the uprising mantle peridotite has been implemented, with the aim of discussing the behaviour of the lithosphere of the Alps and Northern Apennines during the transition from continental rifting to ocean spreading of the Alpine Tethys. The predictions of the model are compared with natural data related to the Permian–Triassic high-temperature – low-pressure (HT-LP) metamorphism affecting the continental lithosphere and data from the JurassicP–Tevolution of the oceanic lithosphere from the Alps and the Northern Apennines. Our analysis indicates that a thinned continental crust, an ocean–continent transition zone and an oceanic lithosphere characterize the final structure of the system in a poor magma rift pre-Alpine configuration. We also find that mantle serpentinization starts before crustal break-up and that denudation occurs before ocean ...
The volcano-clastic sequence of Trompia Valley, which caps the Tre Valli Bresciane Variscan basem... more The volcano-clastic sequence of Trompia Valley, which caps the Tre Valli Bresciane Variscan basement (TVB), comprises the Dosso dei Galli Conglomerate (DGC), the oldest deposit containing up to metre-sized metamorphic pebbles. This Lower Permian formation of the Trompia Basin was fed by the erosion products of the Variscan chain. We used microstructural and mineral chemical data on metamorphic pebbles of the DGC to infer a quantitative tectono-thermal evolution of the eroded pre-Permian basement and to compare them with those of TVB and the surrounding Southalpine basement units (tectonometamorphic units = TMUs). Metapelitic and metaintrusive pebbles record a polyphase metamorphism with two metamorphic re-equilibrations: the first under epidote amphibolite facies (M1, T max ÀP T max) and the second under greenschist facies (M2) conditions. Rock types and metamorphic data largely match those of TVB basement unit. The structural and metamorphic records in the pebbles are pre-Permian, and the conglomerate matrix is non-metamorphic. The DGC deposition age (283 ± 1-280.5 ± 2 Ma) constrains the minimal exhumation age of its basement source. The lack of staurolite bearing assemblages in metamorphic pebbles suggests that the DGC basement source was already exhumed to shallow structural levels (greenschist facies conditions) before the thermal equilibration consequent upon continental crust thickening induced by the Variscan collision.
Rodingiti eclogitizzate nella zona Zermatt-Saas: ricostruzione della loro evoluzione dalle relazi... more Rodingiti eclogitizzate nella zona Zermatt-Saas: ricostruzione della loro evoluzione dalle relazioni deformazione-metamorfismo. Un'area dell'alta Valtournenche è stata selezionata per la ricostruzione della storia deformativa e metamorfica di dicchi e boudin rodingitici incassati nelle meta-ofioliti di HP della zona Zermatt-Saas. A questo scopo nuovi dati meso-e micro-strutturali sono presentati per ricostruire le relazioni tra deformazione e metamorfismo nelle rodingiti e tra queste rocce e le serpentiniti incassanti. Le evidenze raccolte sinora suggeriscono che l'interazione metasomatica durante la subduzione è stata molto limitata e che alcune delle tessiture sono interpretabili come ricristallizzazione delle rodingiti in condizioni di alta pressione e bassa temperatura.
ABSTRACT supplemental to "Superposed syn-metamorphic structures of the Alpine and pr... more ABSTRACT supplemental to "Superposed syn-metamorphic structures of the Alpine and pre-Alpine convergent cycles in the Southalpine basement of the Orobic Alps (Northern Italy)"
The interaction between fabric gradients and reaction rate as a tool for individuating volumes ca... more The interaction between fabric gradients and reaction rate as a tool for individuating volumes carrying the longest «rock memory» is discussed through some examples from continental units of the Alpine chain. Here quality P-T-d-t paths have been inferred using a sampling strategy based on reconstruction of the metamorphic evolution, supported by a regionally valid deformation history and on the choice of sites for investigations on compositional variations, where mineral growth and sequences of overprinting fabrics are known. The examples show that correlation between degree of fabric evolution and progress of metamorphic transformation is positive and influence of strain partitioning on tectono-thermal rock memory must be taken into account during P-T-d-t reconstruction to avoid errors in determining the sequence of P-T re-equilibration steps and to obtain clustered P-T estimates relative to each step. RIASSUNTO.-L'interazione tra i gradienti di fabric e la velocità di reazione, utilizzata come strumento di individuazione di volumi di roccia caratterizzati dalla «memoria» più lunga, è discussa con alcuni esempi dalle unità continentali della catena Alpina. La qualità dei percorsi P-T-d-t è stata attribuita utilizzando una strategia di campionamento basata sulla ricostruzione della evoluzione metamorfica, supportata da una storia deformativa valida a scala regionale e sulla scelta di siti di analisi composizionali solo dove è nota la sequenza dei fabric sovrapposti e della crescita di minerali. Gli esempi mostrano che la correlazione tra grado di evoluzione del fabric e progresso della trasformazione metamorfica è positiva e che l'influenza della ripartizione della deformazione sulla memoria tettonotermica delle rocce deve essere tenuta in considerazione durante la ricostruzione dei percorsi P-T-d-t, per evitare errori nel determinare la sequenza degli stadi di riequilibrazione P-T e ottenere stime P-T coerenti, relativamente ad ogni stadio.
In the Sesia-Lanzo Zone, Western Alps, the Rocca Canavese Thrust Sheets (RCT) subunit is characte... more In the Sesia-Lanzo Zone, Western Alps, the Rocca Canavese Thrust Sheets (RCT) subunit is characterized by a mixture of mantle- and crust-derived lithologies, such as metapelites, metagranitoids, metabasics, and serpentinized mantle slices with sizes ranging from meters to hundreds of meters. Structural and metamorphic history suggests that the RCT rocks experienced a complex evolution. In particular, two different peak conditions were obtained for the metabasics, representing different tectono-metamorphic units (TMUs), namely, D1a under eclogite facies conditions and D1b under lawsonite-blueschist-facies conditions. The two TMUs were coupled during the syn-D2 exhumation stage under epidote-blueschist-facies conditions. The different rocks and metamorphic evolutions and the abundance of serpentinites in the tectonic mixture suggest a possible subduction-related mélange origin for the RCT. To verify whether a subduction-related mélange can record tectono-metamorphic histories similar ...
Multiscale structural analysis was carried out to explore the sequence of superposed pre-Alpine c... more Multiscale structural analysis was carried out to explore the sequence of superposed pre-Alpine chloritoid–staurolite–andalusite metamorphic assemblages in the polydeformed Variscan basement of the upper Val Camonica, in the central Southalpine domain. The dominant fabric in the upper Val Camonica basement is the late-Variscan S2 foliation, marked by greenschist facies minerals and truncated by the base of Permian siliciclastic sequences. The intersection with the sedimentary strata defines a Permianage limit on the pre-Alpine tectonometamorphic evolution and exhumation of the Variscan basement. The detailed structural survey revealed that the older S1 foliation was locally preserved in low-strained domains. S1 is a composite fabric resulting from combining S1a and S1b: in the metapelites, S1a was supported by chloritoid, garnet, and biotite and developed before S1b, which was marked by staurolite, garnet, and biotite. S1a and S1b developed at intermediate pressure amphibolite facie...
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
In the Southern Steep Belt, Italian Central Alps, relicts of the pre-Alpine continental crust are... more In the Southern Steep Belt, Italian Central Alps, relicts of the pre-Alpine continental crust are preserved. Between Valtellina and Val Camonica, a poly-metamorphic rock association occurs, which belongs to the Austroalpine units and includes two classically subdivided units: the Languard-Campo nappe (LCN) and the Tonale Series (TS). The outcropping rocks are low to medium grade muscovite, biotite and minor staurolite-bearing gneisses and micaschists, which include interlayered garnet-and biotite-bearing amphibolites, marbles, quartzites and pegmatites, as well as sillimanite-bearing gneisses and micaschists. Permian intrusives (granitoids, diorites and minor gabbros) emplaced in the metamorphic rocks. We performed a detailed structural, petrological and geochronological analysis focusing on the two main lithotypes, namely, staurolite-bearing micaschists and sillimanitebearing paragneisses, to reconstruct the Variscan and Permian-Triassic his
We develop a two-dimensional thermo-mechanical numerical model in which the formation of oceanic ... more We develop a two-dimensional thermo-mechanical numerical model in which the formation of oceanic crust and serpentinite due to the hydration of the uprising mantle peridotite has been implemented, with the aim of discussing the behaviour of the lithosphere of the Alps and Northern Apennines during the transition from continental rifting to ocean spreading of the Alpine Tethys. The predictions of the model are compared with natural data related to the Permian–Triassic high-temperature – low-pressure (HT-LP) metamorphism affecting the continental lithosphere and data from the JurassicP–Tevolution of the oceanic lithosphere from the Alps and the Northern Apennines. Our analysis indicates that a thinned continental crust, an ocean–continent transition zone and an oceanic lithosphere characterize the final structure of the system in a poor magma rift pre-Alpine configuration. We also find that mantle serpentinization starts before crustal break-up and that denudation occurs before ocean ...
The volcano-clastic sequence of Trompia Valley, which caps the Tre Valli Bresciane Variscan basem... more The volcano-clastic sequence of Trompia Valley, which caps the Tre Valli Bresciane Variscan basement (TVB), comprises the Dosso dei Galli Conglomerate (DGC), the oldest deposit containing up to metre-sized metamorphic pebbles. This Lower Permian formation of the Trompia Basin was fed by the erosion products of the Variscan chain. We used microstructural and mineral chemical data on metamorphic pebbles of the DGC to infer a quantitative tectono-thermal evolution of the eroded pre-Permian basement and to compare them with those of TVB and the surrounding Southalpine basement units (tectonometamorphic units = TMUs). Metapelitic and metaintrusive pebbles record a polyphase metamorphism with two metamorphic re-equilibrations: the first under epidote amphibolite facies (M1, T max ÀP T max) and the second under greenschist facies (M2) conditions. Rock types and metamorphic data largely match those of TVB basement unit. The structural and metamorphic records in the pebbles are pre-Permian, and the conglomerate matrix is non-metamorphic. The DGC deposition age (283 ± 1-280.5 ± 2 Ma) constrains the minimal exhumation age of its basement source. The lack of staurolite bearing assemblages in metamorphic pebbles suggests that the DGC basement source was already exhumed to shallow structural levels (greenschist facies conditions) before the thermal equilibration consequent upon continental crust thickening induced by the Variscan collision.
Rodingiti eclogitizzate nella zona Zermatt-Saas: ricostruzione della loro evoluzione dalle relazi... more Rodingiti eclogitizzate nella zona Zermatt-Saas: ricostruzione della loro evoluzione dalle relazioni deformazione-metamorfismo. Un'area dell'alta Valtournenche è stata selezionata per la ricostruzione della storia deformativa e metamorfica di dicchi e boudin rodingitici incassati nelle meta-ofioliti di HP della zona Zermatt-Saas. A questo scopo nuovi dati meso-e micro-strutturali sono presentati per ricostruire le relazioni tra deformazione e metamorfismo nelle rodingiti e tra queste rocce e le serpentiniti incassanti. Le evidenze raccolte sinora suggeriscono che l'interazione metasomatica durante la subduzione è stata molto limitata e che alcune delle tessiture sono interpretabili come ricristallizzazione delle rodingiti in condizioni di alta pressione e bassa temperatura.
ABSTRACT supplemental to "Superposed syn-metamorphic structures of the Alpine and pr... more ABSTRACT supplemental to "Superposed syn-metamorphic structures of the Alpine and pre-Alpine convergent cycles in the Southalpine basement of the Orobic Alps (Northern Italy)"
The interaction between fabric gradients and reaction rate as a tool for individuating volumes ca... more The interaction between fabric gradients and reaction rate as a tool for individuating volumes carrying the longest «rock memory» is discussed through some examples from continental units of the Alpine chain. Here quality P-T-d-t paths have been inferred using a sampling strategy based on reconstruction of the metamorphic evolution, supported by a regionally valid deformation history and on the choice of sites for investigations on compositional variations, where mineral growth and sequences of overprinting fabrics are known. The examples show that correlation between degree of fabric evolution and progress of metamorphic transformation is positive and influence of strain partitioning on tectono-thermal rock memory must be taken into account during P-T-d-t reconstruction to avoid errors in determining the sequence of P-T re-equilibration steps and to obtain clustered P-T estimates relative to each step. RIASSUNTO.-L'interazione tra i gradienti di fabric e la velocità di reazione, utilizzata come strumento di individuazione di volumi di roccia caratterizzati dalla «memoria» più lunga, è discussa con alcuni esempi dalle unità continentali della catena Alpina. La qualità dei percorsi P-T-d-t è stata attribuita utilizzando una strategia di campionamento basata sulla ricostruzione della evoluzione metamorfica, supportata da una storia deformativa valida a scala regionale e sulla scelta di siti di analisi composizionali solo dove è nota la sequenza dei fabric sovrapposti e della crescita di minerali. Gli esempi mostrano che la correlazione tra grado di evoluzione del fabric e progresso della trasformazione metamorfica è positiva e che l'influenza della ripartizione della deformazione sulla memoria tettonotermica delle rocce deve essere tenuta in considerazione durante la ricostruzione dei percorsi P-T-d-t, per evitare errori nel determinare la sequenza degli stadi di riequilibrazione P-T e ottenere stime P-T coerenti, relativamente ad ogni stadio.
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