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description Publicationkeyboard_double_arrow_right Article , Other literature type 2018Embargo end date: 01 Jan 2018 Switzerland, Italy EnglishPublisher:Copernicus Publications Giuntoli, Francesco; Lanari, Pierre; Burn, Marco; Kunz, Barbara Eva; Engi, Martin;doi: 10.7892/boris.129160
Subducted continental terranes commonly comprise an assembly of subunits that reflect the different tectono-metamorphic histories they experienced in the subduction zone. Our challenge is to unravel how, when, and in which part of the subduction zone these subunits were juxtaposed. Petrochronology offers powerful tools to decipher pressure–temperature–time (P–T–t) histories of metamorphic rocks that preserve a record of several stages of transformation. A major issue is that the driving forces for re-equilibration at high pressure are not well understood. For example, continental granulite terrains subducted to mantle depths frequently show only partial and localized eclogitization. The Sesia Zone (NW Italy) is exceptional because it comprises several continental subunits in which eclogitic rocks predominate and high-pressure (HP) assemblages almost completely replaced the Permian granulite protoliths. This field-based study comprises both main complexes of the Sesia terrane, covering some of the recently recognized tectonic subunits involved in its assembly; hence our data constrain the HP tectonics that formed the Sesia Zone. We used a petrochronological approach consisting of petrographic and microstructural analysis linked with thermodynamic modelling and U–Th–Pb age dating to reconstruct the P–T–t trajectories of these tectonic subunits. Our study documents when and under what conditions re-equilibration took place. Results constrain the main stages of mineral growth and deformation, associated with fluid influx that occurred in the subduction channel. In the Internal Complex (IC), pulses of fluid percolated at eclogite facies conditions between 77 and 55 Ma with the HP conditions reaching ∼ 2 GPa and 600–670 °C. By contrast, the External Complex (EC) records a lower pressure peak of ∼ 0.8 GPa for 500 °C at ∼ 63 Ma. The juxtaposition of the two complexes occurred during exhumation, probably at ∼ 0.8 GPa and 350 °C; the timing is constrained between 46 and 38 Ma. Mean vertical exhumation velocities are constrained between 0.9 and 5.1 mm year−1 for the IC, up to its juxtaposition with the EC. Exhumation to the surface occurred before 32 Ma, as constrained by the overlying Biella Volcanic Suite, at a mean vertical velocity between 1.6 and 4 mm year−1. These findings constrain the processes responsible for the assembly and exhumation of HP continental subunits, thus adding to our understanding of how continental terranes behave during subduction.
CORE (RIOXX-UK Aggre... arrow_drop_down CORE (RIOXX-UK Aggregator)Article . 2018Full-Text: http://oro.open.ac.uk/54801/1/54801.pdfData sources: CORE (RIOXX-UK Aggregator)Bern Open Repository and Information System (BORIS)Article . 2018 . Peer-reviewedData sources: Bern Open Repository and Information System (BORIS)add ClaimPlease grant OpenAIRE to access and update your ORCID works.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.This Research product is the result of merged Research products in OpenAIRE.
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For further information contact us at helpdesk@openaire.euAccess Routesgold 0 citations 0 popularity Average influence Average impulse Average Powered by BIP!download 63download downloads 63 Powered bymore_vert CORE (RIOXX-UK Aggre... arrow_drop_down CORE (RIOXX-UK Aggregator)Article . 2018Full-Text: http://oro.open.ac.uk/54801/1/54801.pdfData sources: CORE (RIOXX-UK Aggregator)Bern Open Repository and Information System (BORIS)Article . 2018 . Peer-reviewedData sources: Bern Open Repository and Information System (BORIS)add ClaimPlease grant OpenAIRE to access and update your ORCID works.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.All Research productsarrow_drop_down <script type="text/javascript"> <!-- document.write('<div id="oa_widget"></div>'); document.write('<script type="text/javascript" src="https://www.openaire.eu/index.php?option=com_openaire&view=widget&format=raw&projectId=10.7892/boris.129160&type=result"></script>'); --> </script>
For further information contact us at helpdesk@openaire.eudescription Publicationkeyboard_double_arrow_right Article , Other literature type 2018Embargo end date: 01 Jan 2018 Italy, Switzerland EnglishPublisher:Copernicus Publications Authors: F. Giuntoli; P. Lanari; M. Engi;F. Giuntoli; P. Lanari; M. Engi;doi: 10.7892/boris.129161
Contiguous continental high-pressure terranes in orogens offer insight into deep recycling and transformation processes that occur in subduction zones. These remain poorly understood, and currently debated ideas need testing. The approach we chose is to investigate, in detail, the record in suitable rock samples that preserve textures and robust mineral assemblages that withstood overprinting during exhumation. We document complex garnet zoning in eclogitic mica schists from the Sesia Zone (western Italian Alps). These retain evidence of two orogenic cycles and provide detailed insight into resorption, growth, and diffusion processes induced by fluid pulses in high-pressure conditions. We analysed local textures and garnet compositional patterns, which turned out remarkably complex. By combining these with thermodynamic modelling, we could unravel and quantify repeated fluid–rock interaction processes. Garnet shows low-Ca porphyroclastic cores that were stable under (Permian) granulite facies conditions. The series of rims that surround these cores provide insight into the subsequent evolution: the first garnet rim that surrounds the pre-Alpine granulite facies core in one sample indicates that pre-Alpine amphibolite facies metamorphism followed the granulite facies event. In all samples documented, cores show lobate edges and preserve inner fractures, which are sealed by high-Ca garnet that reflects high-pressure Alpine conditions. These observations suggest that during early stages of subduction, before hydration of the granulites, brittle failure of garnet occurred, indicating high strain rates that may be due to seismic failure. Several Alpine rims show conspicuous textures indicative of interaction with hydrous fluid: (a) resorption-dominated textures produced lobate edges, at the expense of the outer part of the granulite core; (b) peninsulas and atoll garnet are the result of replacement reactions; and (c) spatially limited resorption and enhanced transport of elements due to the fluid phase are evident along brittle fractures and in their immediate proximity. Thermodynamic modelling shows that all of these Alpine rims formed under eclogite facies conditions. Structurally controlled samples allow these fluid–garnet interaction phenomena to be traced across a portion of the Sesia Zone, with a general decrease in fluid–garnet interaction observed towards the external, structurally lower parts of the terrane. Replacement of the Permian HT assemblages by hydrate-rich Alpine assemblages can reach nearly 100 % of the rock volume. Since we found no clear relationship between discrete deformation structures (e.g. shear zones) observed in the field and the fluid pulses that triggered the transformation to eclogite facies assemblages, we conclude that disperse fluid flow was responsible for the hydration.
Solid Earth arrow_drop_down Bern Open Repository and Information System (BORIS)Article . 2018 . Peer-reviewedData sources: Bern Open Repository and Information System (BORIS)add ClaimPlease grant OpenAIRE to access and update your ORCID works.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.All Research productsarrow_drop_down <script type="text/javascript"> <!-- document.write('<div id="oa_widget"></div>'); document.write('<script type="text/javascript" src="https://www.openaire.eu/index.php?option=com_openaire&view=widget&format=raw&projectId=10.7892/boris.129161&type=result"></script>'); --> </script>
For further information contact us at helpdesk@openaire.euAccess Routesgold 0 citations 0 popularity Average influence Average impulse Average Powered by BIP!more_vert Solid Earth arrow_drop_down Bern Open Repository and Information System (BORIS)Article . 2018 . Peer-reviewedData sources: Bern Open Repository and Information System (BORIS)add ClaimPlease grant OpenAIRE to access and update your ORCID works.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.All Research productsarrow_drop_down <script type="text/javascript"> <!-- document.write('<div id="oa_widget"></div>'); document.write('<script type="text/javascript" src="https://www.openaire.eu/index.php?option=com_openaire&view=widget&format=raw&projectId=10.7892/boris.129161&type=result"></script>'); --> </script>
For further information contact us at helpdesk@openaire.eudescription Publicationkeyboard_double_arrow_right Article , Conference object 2018 Italy EnglishCapraro, Luca; Ferretti, Patrizia; Macrì, Patrizia; Scarponi, Daniele; Fornaciari, Eliana; Xian, Feng; Zhou, Weijian; Kong, Xianghui; Boschi, Vanessa;handle: 10278/3710893
The 10Be/9Be ratio is acknowledged as an effective tool for establishing the stratigraphic position of paleomagnetic excur-sions. Still, our data suggest that, in particular depositional settings, the interplay between climate, sedimentation and oceanography may jeopardize a realistic depiction of the natural 10Be/9Be record.
add ClaimPlease grant OpenAIRE to access and update your ORCID works.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.All Research productsarrow_drop_down <script type="text/javascript"> <!-- document.write('<div id="oa_widget"></div>'); document.write('<script type="text/javascript" src="https://www.openaire.eu/index.php?option=com_openaire&view=widget&format=raw&projectId=10278/3710893&type=result"></script>'); --> </script>
For further information contact us at helpdesk@openaire.eu0 citations 0 popularity Average influence Average impulse Average Powered by BIP!more_vert add ClaimPlease grant OpenAIRE to access and update your ORCID works.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.All Research productsarrow_drop_down <script type="text/javascript"> <!-- document.write('<div id="oa_widget"></div>'); document.write('<script type="text/javascript" src="https://www.openaire.eu/index.php?option=com_openaire&view=widget&format=raw&projectId=10278/3710893&type=result"></script>'); --> </script>
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description Publicationkeyboard_double_arrow_right Article , Other literature type 2018Embargo end date: 01 Jan 2018 Switzerland, Italy EnglishPublisher:Copernicus Publications Giuntoli, Francesco; Lanari, Pierre; Burn, Marco; Kunz, Barbara Eva; Engi, Martin;doi: 10.7892/boris.129160
Subducted continental terranes commonly comprise an assembly of subunits that reflect the different tectono-metamorphic histories they experienced in the subduction zone. Our challenge is to unravel how, when, and in which part of the subduction zone these subunits were juxtaposed. Petrochronology offers powerful tools to decipher pressure–temperature–time (P–T–t) histories of metamorphic rocks that preserve a record of several stages of transformation. A major issue is that the driving forces for re-equilibration at high pressure are not well understood. For example, continental granulite terrains subducted to mantle depths frequently show only partial and localized eclogitization. The Sesia Zone (NW Italy) is exceptional because it comprises several continental subunits in which eclogitic rocks predominate and high-pressure (HP) assemblages almost completely replaced the Permian granulite protoliths. This field-based study comprises both main complexes of the Sesia terrane, covering some of the recently recognized tectonic subunits involved in its assembly; hence our data constrain the HP tectonics that formed the Sesia Zone. We used a petrochronological approach consisting of petrographic and microstructural analysis linked with thermodynamic modelling and U–Th–Pb age dating to reconstruct the P–T–t trajectories of these tectonic subunits. Our study documents when and under what conditions re-equilibration took place. Results constrain the main stages of mineral growth and deformation, associated with fluid influx that occurred in the subduction channel. In the Internal Complex (IC), pulses of fluid percolated at eclogite facies conditions between 77 and 55 Ma with the HP conditions reaching ∼ 2 GPa and 600–670 °C. By contrast, the External Complex (EC) records a lower pressure peak of ∼ 0.8 GPa for 500 °C at ∼ 63 Ma. The juxtaposition of the two complexes occurred during exhumation, probably at ∼ 0.8 GPa and 350 °C; the timing is constrained between 46 and 38 Ma. Mean vertical exhumation velocities are constrained between 0.9 and 5.1 mm year−1 for the IC, up to its juxtaposition with the EC. Exhumation to the surface occurred before 32 Ma, as constrained by the overlying Biella Volcanic Suite, at a mean vertical velocity between 1.6 and 4 mm year−1. These findings constrain the processes responsible for the assembly and exhumation of HP continental subunits, thus adding to our understanding of how continental terranes behave during subduction.
CORE (RIOXX-UK Aggre... arrow_drop_down CORE (RIOXX-UK Aggregator)Article . 2018Full-Text: http://oro.open.ac.uk/54801/1/54801.pdfData sources: CORE (RIOXX-UK Aggregator)Bern Open Repository and Information System (BORIS)Article . 2018 . Peer-reviewedData sources: Bern Open Repository and Information System (BORIS)add ClaimPlease grant OpenAIRE to access and update your ORCID works.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.All Research productsarrow_drop_down <script type="text/javascript"> <!-- document.write('<div id="oa_widget"></div>'); document.write('<script type="text/javascript" src="https://www.openaire.eu/index.php?option=com_openaire&view=widget&format=raw&projectId=10.7892/boris.129160&type=result"></script>'); --> </script>
For further information contact us at helpdesk@openaire.euAccess Routesgold 0 citations 0 popularity Average influence Average impulse Average Powered by BIP!download 63download downloads 63 Powered bymore_vert CORE (RIOXX-UK Aggre... arrow_drop_down CORE (RIOXX-UK Aggregator)Article . 2018Full-Text: http://oro.open.ac.uk/54801/1/54801.pdfData sources: CORE (RIOXX-UK Aggregator)Bern Open Repository and Information System (BORIS)Article . 2018 . Peer-reviewedData sources: Bern Open Repository and Information System (BORIS)add ClaimPlease grant OpenAIRE to access and update your ORCID works.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.All Research productsarrow_drop_down <script type="text/javascript"> <!-- document.write('<div id="oa_widget"></div>'); document.write('<script type="text/javascript" src="https://www.openaire.eu/index.php?option=com_openaire&view=widget&format=raw&projectId=10.7892/boris.129160&type=result"></script>'); --> </script>
For further information contact us at helpdesk@openaire.eudescription Publicationkeyboard_double_arrow_right Article , Other literature type 2018Embargo end date: 01 Jan 2018 Italy, Switzerland EnglishPublisher:Copernicus Publications Authors: F. Giuntoli; P. Lanari; M. Engi;F. Giuntoli; P. Lanari; M. Engi;doi: 10.7892/boris.129161
Contiguous continental high-pressure terranes in orogens offer insight into deep recycling and transformation processes that occur in subduction zones. These remain poorly understood, and currently debated ideas need testing. The approach we chose is to investigate, in detail, the record in suitable rock samples that preserve textures and robust mineral assemblages that withstood overprinting during exhumation. We document complex garnet zoning in eclogitic mica schists from the Sesia Zone (western Italian Alps). These retain evidence of two orogenic cycles and provide detailed insight into resorption, growth, and diffusion processes induced by fluid pulses in high-pressure conditions. We analysed local textures and garnet compositional patterns, which turned out remarkably complex. By combining these with thermodynamic modelling, we could unravel and quantify repeated fluid–rock interaction processes. Garnet shows low-Ca porphyroclastic cores that were stable under (Permian) granulite facies conditions. The series of rims that surround these cores provide insight into the subsequent evolution: the first garnet rim that surrounds the pre-Alpine granulite facies core in one sample indicates that pre-Alpine amphibolite facies metamorphism followed the granulite facies event. In all samples documented, cores show lobate edges and preserve inner fractures, which are sealed by high-Ca garnet that reflects high-pressure Alpine conditions. These observations suggest that during early stages of subduction, before hydration of the granulites, brittle failure of garnet occurred, indicating high strain rates that may be due to seismic failure. Several Alpine rims show conspicuous textures indicative of interaction with hydrous fluid: (a) resorption-dominated textures produced lobate edges, at the expense of the outer part of the granulite core; (b) peninsulas and atoll garnet are the result of replacement reactions; and (c) spatially limited resorption and enhanced transport of elements due to the fluid phase are evident along brittle fractures and in their immediate proximity. Thermodynamic modelling shows that all of these Alpine rims formed under eclogite facies conditions. Structurally controlled samples allow these fluid–garnet interaction phenomena to be traced across a portion of the Sesia Zone, with a general decrease in fluid–garnet interaction observed towards the external, structurally lower parts of the terrane. Replacement of the Permian HT assemblages by hydrate-rich Alpine assemblages can reach nearly 100 % of the rock volume. Since we found no clear relationship between discrete deformation structures (e.g. shear zones) observed in the field and the fluid pulses that triggered the transformation to eclogite facies assemblages, we conclude that disperse fluid flow was responsible for the hydration.
Solid Earth arrow_drop_down Bern Open Repository and Information System (BORIS)Article . 2018 . Peer-reviewedData sources: Bern Open Repository and Information System (BORIS)add ClaimPlease grant OpenAIRE to access and update your ORCID works.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.All Research productsarrow_drop_down <script type="text/javascript"> <!-- document.write('<div id="oa_widget"></div>'); document.write('<script type="text/javascript" src="https://www.openaire.eu/index.php?option=com_openaire&view=widget&format=raw&projectId=10.7892/boris.129161&type=result"></script>'); --> </script>
For further information contact us at helpdesk@openaire.euAccess Routesgold 0 citations 0 popularity Average influence Average impulse Average Powered by BIP!more_vert Solid Earth arrow_drop_down Bern Open Repository and Information System (BORIS)Article . 2018 . Peer-reviewedData sources: Bern Open Repository and Information System (BORIS)add ClaimPlease grant OpenAIRE to access and update your ORCID works.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.All Research productsarrow_drop_down <script type="text/javascript"> <!-- document.write('<div id="oa_widget"></div>'); document.write('<script type="text/javascript" src="https://www.openaire.eu/index.php?option=com_openaire&view=widget&format=raw&projectId=10.7892/boris.129161&type=result"></script>'); --> </script>
For further information contact us at helpdesk@openaire.eudescription Publicationkeyboard_double_arrow_right Article , Conference object 2018 Italy EnglishCapraro, Luca; Ferretti, Patrizia; Macrì, Patrizia; Scarponi, Daniele; Fornaciari, Eliana; Xian, Feng; Zhou, Weijian; Kong, Xianghui; Boschi, Vanessa;handle: 10278/3710893
The 10Be/9Be ratio is acknowledged as an effective tool for establishing the stratigraphic position of paleomagnetic excur-sions. Still, our data suggest that, in particular depositional settings, the interplay between climate, sedimentation and oceanography may jeopardize a realistic depiction of the natural 10Be/9Be record.
add ClaimPlease grant OpenAIRE to access and update your ORCID works.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.All Research productsarrow_drop_down <script type="text/javascript"> <!-- document.write('<div id="oa_widget"></div>'); document.write('<script type="text/javascript" src="https://www.openaire.eu/index.php?option=com_openaire&view=widget&format=raw&projectId=10278/3710893&type=result"></script>'); --> </script>
For further information contact us at helpdesk@openaire.eu0 citations 0 popularity Average influence Average impulse Average Powered by BIP!more_vert add ClaimPlease grant OpenAIRE to access and update your ORCID works.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.This Research product is the result of merged Research products in OpenAIRE.
You have already added works in your ORCID record related to the merged Research product.All Research productsarrow_drop_down <script type="text/javascript"> <!-- document.write('<div id="oa_widget"></div>'); document.write('<script type="text/javascript" src="https://www.openaire.eu/index.php?option=com_openaire&view=widget&format=raw&projectId=10278/3710893&type=result"></script>'); --> </script>
For further information contact us at helpdesk@openaire.eu