The 3D quantitative lattice and shape preferred orientation of a mylonitised metagranite from Monte Rosa (Western Alps): Combining neutron diffraction texture analysis and synchrotron X-ray microtomography

Abstract

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. a b s t r a c tTwo complementary 3D techniques, neutron diffraction and synchrotron X-ray microtomography (SXRmCT), were used to compare the Shape and Lattice Preferred Orientations of a mylonitised metagranite from the Monte Rosa unit (Western Alps, Italy). The goal of using these techniques was to obtain two different orientation distribution functions. Although the two functions describe relatively independent characteristics of the rock fabric, nonetheless they also exhibit close relationships to macroscopic fabrics and may be complementarily used to quantify rock fabrics and microstructures, thereby highlighting 3D features that cannot be obtained with either technique, if used independently. We describe an approach that can be potentially useful in various disciplines, e.g., structural geology, rock mechanics, tectonics and geophysics, when a complete data set of preferred orientations and size distribution is needed. Micas display a strong orthorhombic symmetry between mesoscopic lineation and microscopic SPO and LPO, whereas quartz and feldspars are characterised by a monoclinic symmetry between mesoscopic lineation and LPO. These observations suggest a rheological decoupling between the weak phase mica layers and the stronger quartz þ feldspar layers. This mechanical decoupling occurred during the Alpine subduction-collision, when the Monte Rosa unit was part of the Insubric Line system and accommodated large vertical strain.

Integrating X-Ray Computed Tomography With Chemical Imaging to Quantify Mineral Re-crystallization From Granulite to Eclogite Metamorphism in the Western Italian Alps (Sesia-Lanzo Zone)

“…Phase-contrast X-ray µ-CT measurements based on synchrotron and microfocus X-ray sources applied in the Earth science domain represent a powerful tool for the nondestructive characterization of the internal microstructures and the mineral phases separation thanks to their different density and/or chemical composition (Polacci et al, 2010;Zandomeneghi et al, 2010;Baker et al, 2012;Cnudde and Boone, 2013). Through virtual slicing of the sample volume and applying image processing and analysis 3D tools, it is possible to achieve a quantitative shape preferred orientation (SPO) analysis by means of the extraction of geometrical, morphological, and orientation parameters (Voltolini et al, 2011;Zucali et al, 2014b).…”

Crystallographic and Seismic Anisotropies of Calcite at Different Depths: A Study Using Quantitative Texture Analysis by Neutron Diffraction

“…The samples were cut in cubes of ≈ 1cm edge ( In order to evaluate the Crystallographic Preferred Orientation (CPO) of the samples we used the non-disruptive method of the Quantitative Texture Analysis (QTA) by neutron diffraction, successfully applied on various types of rocks and synthetic materials: in monomineralic quartzites [20], marbles [17], limestones [21], dunite [22] or glaucophanite [23], in poly-phasic rocks, as amphibolite [24,25], quartz-feldspatic mylonitic orthogneisses and gabbros [26,27], subacqueous lavas [28] or sandstones [29].…”

3‐D microstructure of olivine in complex geological materials reconstructed by correlative X‐ray ‐CT and EBSD analyses

“…, ), as well as in fragments of mylonitised metagranites (Zucali et al. , ) up to ca . 0.25 cm 3 in size.…”

“…However, routine 3-D FIB-EBSD is difficult to apply on low-conductive Earth materials, and the maximum observable volume is currently up to about 10 6 µm 3 (Burnett et al, 2016 and references therein), which is at least six orders of magnitude smaller than that required for the characterisation of the microstructure of natural rocks composed of cm-sized to mm-sized crystals. To acquire mineral CPO with information on the 3-D SPO in larger samples, high-energy synchrotron X-rays and neutron diffraction were applied in shale and schist (Wenk et al, 2010), as well as in fragments of mylonitised metagranites (Zucali et al, 2014) up to ca. 0.25 cm 3 in size.…”