Combined microstructural, mineral chemical, X-ray maps, and X-ray single-crystal diffraction analyses are used to reveal the rheological behaviour of individual grains of magmatic allanite relicts hosted in variably deformed metagranitoids at Lago della Vecchia (inner part of the Sesia-Lanzo Zone, Western Alps, Europe), which experienced high pressure and low temperature metamorphism during the Alpine subduction. X-ray single crystal diffraction shows that none of the allanite crystals, irrespective of the strain state of the host rock, record any evidence of plastic deformation (i.e., intracrystalline deformation), as indicated by the shape of the Bragg diffraction spots, the atomic site positions, and their displacement around the centre of gravity. On the contrary, strong plastic deformation affected matrix minerals, such as quartz, white mica, and feldspar of the hosting rocks, during the development of the Alpine eclogitic- and blueschist-facies metamorphism. Despite the strain-free atomic structures of allanite, different patterns of chemical zoning, as a function of strain accumulated in the rock matrix, are observed. Since allanite occurs in magmatic and metamorphic rocks and it is stable at high pressure and low temperature conditions, we infer that allanite could behave as one of the main carriers of light-rare-earth-elements into the mantle wedge during subduction of continental crust. In particular, the release of light-rare-earth-elements from allanite, under high pressure conditions in subduction zones, is facilitated by high strain accumulated in the host rock.

Strain partitioning in host rock controls LREE release from allanite-(Ce) in subduction zones / L. Corti, D. Zanoni, G.D. Gatta, M. Zucali. - In: MINERALOGICAL MAGAZINE. - ISSN 1471-8022. - (2020). [Epub ahead of print]

Strain partitioning in host rock controls LREE release from allanite-(Ce) in subduction zones

L. Corti
Primo
Writing – Review & Editing
;
D. Zanoni
Secondo
Membro del Collaboration Group
;
G.D. Gatta
Penultimo
Membro del Collaboration Group
;
M. Zucali
Ultimo
Membro del Collaboration Group
2020

Abstract

Combined microstructural, mineral chemical, X-ray maps, and X-ray single-crystal diffraction analyses are used to reveal the rheological behaviour of individual grains of magmatic allanite relicts hosted in variably deformed metagranitoids at Lago della Vecchia (inner part of the Sesia-Lanzo Zone, Western Alps, Europe), which experienced high pressure and low temperature metamorphism during the Alpine subduction. X-ray single crystal diffraction shows that none of the allanite crystals, irrespective of the strain state of the host rock, record any evidence of plastic deformation (i.e., intracrystalline deformation), as indicated by the shape of the Bragg diffraction spots, the atomic site positions, and their displacement around the centre of gravity. On the contrary, strong plastic deformation affected matrix minerals, such as quartz, white mica, and feldspar of the hosting rocks, during the development of the Alpine eclogitic- and blueschist-facies metamorphism. Despite the strain-free atomic structures of allanite, different patterns of chemical zoning, as a function of strain accumulated in the rock matrix, are observed. Since allanite occurs in magmatic and metamorphic rocks and it is stable at high pressure and low temperature conditions, we infer that allanite could behave as one of the main carriers of light-rare-earth-elements into the mantle wedge during subduction of continental crust. In particular, the release of light-rare-earth-elements from allanite, under high pressure conditions in subduction zones, is facilitated by high strain accumulated in the host rock.
Mineral rheology; Sesia-Lanzo Zone; Strain partitioning; Single-crystal X-ray diffraction; LREE release; Chemical imaging
Settore GEO/03 - Geologia Strutturale
Settore GEO/09 - Georisorse Miner.Appl.Mineral.-Petrogr.per l'amb.e i Beni Cul
22-gen-2020
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/706077
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