Mechanical anisotropies and mechanisms of mafic magma ascent in the middle continental crust: The Sondalo magmatic system (N Italy)

Petri, Benoît; Skrzypek, Etienne; Mohn, Geoffroy; Mateeva, Tsvetomila; Robion, Philippe; Schulmann, Karel; Manatschal, Giänreto; Müntener, Othmar

doi:10.1130/b31693.1

Cited by 6 publications

(2 citation statements)

References 118 publications

(150 reference statements)

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“…These metasediments are intruded by a Permian gabbroic pluton emplaced at 4-6 kbar (Sondalo mafic complex, point 3; Petri et al, 2016). Importantly, the center of the Campo unit is devoid of any significant post-Permian deformation (see Petri et al, 2018). The overlying Grosina unit is made of amphibolite-facies orthogneiss and metasediments of unknown age showing a gently NW-dipping foliation cross cut by numerous greenschist facies extensional shear zones (Fig.…”

Section: Necking Zone: the Campo -Grosina Sectionmentioning

confidence: 99%

Thinning mechanisms of heterogeneous continental lithosphere

Petri

Duretz

Mohn

et al. 2019

Earth and Planetary Science Letters

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Section: Necking Zone: the Campo -Grosina Sectionmentioning

confidence: 99%

Thinning mechanisms of heterogeneous continental lithosphere

Petri

Duretz

Mohn

et al. 2019

Earth and Planetary Science Letters

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“…The fabric development can be described semi-quantitatively in the field (foliation, lineation), but proper quantification requires more rigorous methods (Higgins, 2006). To date, quantitative fabric studies involve electron backscatter diffraction (EBSD; Prior et al, 1999) measurements for CPO determination (e.g., Bascou et al, 2001) and magnetic fabric measurements, such as anisotropy of both magnetic susceptibility (AMS) and anhysteretic remanent magnetization (AARM) (Borradaile and Jackson, 2010;Hirt and Almqvist, 2012); AMS and AARM depend on both CPO and SPO (for ferromagnetic minerals) of the magnetic minerals of rocks (Petri et al, 2018). Obtaining the three dimensional SPO is however time-consuming because it requires either serial sectioning or grinding of samples and image analysis (e.g., Bryon et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

3D rock fabric analysis using micro-tomography: An introduction to the open-source TomoFab MATLAB code

Petri

Almqvist

Pistone

2020

Computers & Geosciences

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The study of rock fabric properties (orientation, planar, linear, anisotropy) is key to unravelling the geological processes that generated them. With advancements in data acquisition and treatment, X-ray micro-computed tomography (μXCT) represents a powerful method to analyse the shape preferred orientation (SPO) of rockforming elements, including minerals, aggregates, and pores, in the three-dimensional space. After reconstruction and segmentation of μXCT images, we developed a novel protocol to construct and analyse the fabric tensor, a second-rank symmetric tensor constructed using the orientation and the length of the three characteristic axes of each grain (simplified to a best fit ellipsoid). The analysis of the fabric tensor permits calculation of mean principal directions and associated confidence ellipses, and quantifies the degree of anisotropy (P 0 ) and the shape (T) of the fabric ellipsoid by eigenvalue and eigenvector analysis.We implement this method in the TomoFab open-source MATLAB package. The code integrates a graphical user interface (GUI) that allows the visualisation of the full set of ellipsoid orientation, shape, and size. Density plots and contouring can be utilised to identify fabrics graphically, and a full set of fabric parameters can be calculated based on the analysis of the fabric tensor and/or the analysis of each principal direction orientation tensor.We demonstrate the versatility of TomoFab with synthetic datasets and a field-and laboratory-based investigation of a sample presenting a magmatic foliation and lineation, collected in the Mafic Complex within the lower crustal section of the Ivrea-Verbano Zone (North Italy). In the light of these developments, we stress that μXCT represents a pertinent tool for rock fabric analysis to characterise the SPO of rock components. This approach can be performed parallel or complementary to other rock fabric quantification methods (e.g., AMS, EBSD) and applied to various rock types.

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