Project

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Shearing, fluid-rock interaction and rheology of a deep crustal section of the Scandinavian Caledonides: the COSC-1 drill core

Applicant Giuntoli Francesco
Number 168722
Funding scheme Early Postdoc.Mobility
Research institution Department of Earth Sciences The Open University
Institution of higher education Institution abroad - IACH
Main discipline Geology
Start/End 01.08.2016 - 31.01.2018
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All Disciplines (2)

Discipline
Geology
Geochronology

Keywords (5)

Mineral reactions; Fluid-rock interaction; Shear zone; Rheology lower crust; Microstructures

Lay Summary (Italian)

Lead
Deformazione, interazione fluido-roccia e reologia di una sezione crostale profonda delle Caledonidi Scandinave: la carota del COSC-1In sintesiLe catene orogeniche fossili sono archivi naturali per lo studio dei processi di deformazione che occorrono nella crosta profonda. Nelle Caledonidi Scandinave sono esposte sezioni crostali medio-profonde grazie a un’intensa erosione perpetuata nel corso di centinaia di milioni di anni. In questo contesto, le zone di deformazione fossili fungono da siti ideali per collegare la testimonianza geologica con la tettonica attiva.
Lay summary

Soggetto e obiettivo

L’Orogenesi Collisionale nelle Caledonidi Scandinave (COSC) è uno dei pochi progetti di perforazione continentale presenti al mondo. Il nostro progetto si avvarrà dei campioni provenienti dalla sezione crostale profonda 2.5 km, campionata durante la realizzazione del pozzo COSC-1.

Lo scopo di questo progetto è di analizzare come la deformazione è distribuita nella crosta continentale profonda e di capire la connessione esistente tra i processi di deformazione, le reazioni mineralogiche e la reologia. Saranno ricostruite le condizioni pressione-temperatura e tempo nelle quali le zone di deformazione agivano ed i meccanismi di deformazione responsabili per il loro sviluppo. Inoltre sarà testata l’ipotesi che la partizione della deformazione rifletta la distribuzione di zone in cui il fluido è presente o assente.

Contesto socio-scientifico

Il nostro progetto permetterà la ricostruzione di un profilo di deformazione nella crosta profonda e porterà nuove conoscenze nel ruolo che hanno i fluidi nel favorire e localizzare le reazioni mineralogiche ed i processi di deformazione.

Quantificare i meccanismi grazie ai quali la crosta terrestre si deforma e si rompe è fondamentale per capire come, quando e dove grandi terremoti nucleano e si propagano lungo le maggiori zone di faglia.

 

Direct link to Lay Summary Last update: 06.06.2016

Responsible applicant and co-applicants

Publications

Publication
Protracted shearing at midcrustal conditions during large‐scale thrusting in the Scandinavian Caledonides.
GiuntoliFrancesco, MenegonLuca, WarrenClare J., DarlingJames, AndersonMark W. (2020), Protracted shearing at midcrustal conditions during large‐scale thrusting in the Scandinavian Caledonides., in Tectonics, 39, 1-31.

Collaboration

Group / person Country
Types of collaboration
Dr James Darling's research group, Portsmouth Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure
- Exchange of personnel
Dr Jaroslaw Majka's research group, Uppsala University Sweden (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Exchange of personnel

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
TSG and MSG Joint Conference Talk given at a conference Mineral replacement reactions during viscous creep of amphibolites in the middle crust. 04.01.2018 Plymouth, Great Britain and Northern Ireland Giuntoli Francesco;
Invited speaker to conferences geosciences Rennes Individual talk UNRAVELLING THE METAMORPHIC AND DEFORMATIVE HISTORY OF SUBDUCTED CRUST 27.10.2017 Rennes, France Giuntoli Francesco;
4th European Geosciences Union Summer School – Structural analysis of crystalline rocks, South Tyrol, Italy. Poster Fracturing, fluid transport and dissolution-precipitation creep in amphibolites (COSC-1 borehole, Scandinavian Caledonides) 25.08.2017 South Tyrol, Italy Giuntoli Francesco;
European Geosciences Union General Assembly 2017 Poster Dissolution-precipitation creep at mid-crustal levels of the Scandian Caledonides: the COSC-1 case study 23.04.2017 Wien, Austria Giuntoli Francesco;
Metamorphic Studies Group meeting Talk given at a conference Dissolution-precipitation creep at mid-crustal levels of the Scandian Caledonides: the COSC-1 case study 15.03.2017 Oxford, Great Britain and Northern Ireland Giuntoli Francesco;
Invited speaker to Seminar Series by Geologiska Sektionen Talk given at a conference Assembly of continental fragments during subduction at HP 11.01.2017 Uppsala, Sweden Giuntoli Francesco;


Abstract

The thermo-mechanical properties of the lower continental crust exert a fundamental control on the structure of orogenic belts, and on the amount and style of shortening during continental collision. The mechanics of lower crustal deformation is typically constrained by geodynamic models, laboratory experiments, and geophysical data. It is increasingly clear that anhydrous lower crustal rocks are mechanically strong and can survive metastably during subduction-exhumation cycles. Infiltration of fluids (partial melt, water) appears to be a necessary condition for weakening and deformation in the lower crust to occur. However, the precise quantification of the how fluid-rock interaction and deformation mechanisms are linked in the lower crust is still elusive, yet these links are critical for providing insights to the rheological structure and strength evolution of the deep portions of the crust.The aim of this project is therefore to investigate deformation microstructures and mineral reactions in lower crustal rocks along strain gradients. I will test the hypothesis that the partitioning of deformation and metamorphism at the shear zone scale reflects the distribution of water-deficient and water-present domains. Fossil collisional orogens are natural archives for studying the deformation processes occurring in the deep crust, and natural lower crustal shear zones provide ideal locations for linking the geological record to active tectonics. By virtue of the deep erosional level, the internal parts of the Scandinavian Caledonides expose middle and lower crustal sections involved in subduction-exhumation history and nappe stacking. This project proposes to use the unique opportunity of the continuous COSC-1 drill section (Scandinavian Caledonides) to analyse the distribution of strain and to infer the links between deformation processes and rheology. The methods used to attain these aims will include light- and scanning electron microscopy (to describe the microstructures), electron backscatter diffraction analysis (to determine the deformation mechanisms and to derive the rheological parameters), Fourier transform infrared spectroscopy (to measure water in nominally anhydrous minerals), electron microprobe analysis (to compute pressure and temperature of the mineral assemblages) and radiometric age dating (to link ages to these metamorphic and deformative processes and potentially determine the rates at which these processes proceed and operate).
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