Serpentinization, a hydrothermal alteration of ultramafic rocks (e.g. peridotite, pyroxenite), mainly occurs in two geological settings on the Earth: i) ocean floor, mid-ocean ridges; ii) subduction zones. Serpentinization greatly modifies the physical, mechanical, and chemical properties of ultramafic rock, which can be partially or totally serpentinized. Serpentinization is accompanied by abundant veining marked by different generations of vein-filling serpentine, which induces a decrease in density. Serpentine veins in hydrated peridotite are particularly abundant and display a vast and complex variety of textures and morphologies. This variety reflects numerous mechanisms of vein formation and fluid conditions recorded by various serpentine mineral assemblages (Andréani et al., 2007). It is worth remembering that the dominant type of serpentine infill is the fibrous one (e.g. chrysotile, protoserpentine, polygonal serpentines). Vein infill typologies are conventionally studied by using optical and scanning electron microscopy (SEM), which only allow two-dimensional (2D) imaging of samples. In this work we present results obtained by the application of high-resolution X-ray computed microtomography which provided a realistic visualization of the 3D shapes and orientations of veins that can be quantified through the extraction of parameters such as volume fraction, size distributions, orientation and connectivity. Furthermore, the phase-contrast mode allowed to detect the crystals with chemical composition different from the serpentinite group minerals (e.g., magnetite). We have investigated the serpentine vein infill, which crosscuts massive serpentinite bodies cropping out in the Gimigliano-Mount Reventino Unit (Calabria, Southern-Italy) (Bloise et al., 2016). Obtained data allowed to evaluate i) the geometric interface between serpentine-fibrous infill veins and the matrix; ii) the percentage of serpentinization; iii) the percentage of fibrous minerals in massive serpentinite rocks.
X-ray tomographic microscopy study of serpentine veins in massive serpentinite
PUNTURO, Rosalda AnnaSecondo
Membro del Collaboration Group
;Vaccaro C.Ultimo
Membro del Collaboration Group
2018
Abstract
Serpentinization, a hydrothermal alteration of ultramafic rocks (e.g. peridotite, pyroxenite), mainly occurs in two geological settings on the Earth: i) ocean floor, mid-ocean ridges; ii) subduction zones. Serpentinization greatly modifies the physical, mechanical, and chemical properties of ultramafic rock, which can be partially or totally serpentinized. Serpentinization is accompanied by abundant veining marked by different generations of vein-filling serpentine, which induces a decrease in density. Serpentine veins in hydrated peridotite are particularly abundant and display a vast and complex variety of textures and morphologies. This variety reflects numerous mechanisms of vein formation and fluid conditions recorded by various serpentine mineral assemblages (Andréani et al., 2007). It is worth remembering that the dominant type of serpentine infill is the fibrous one (e.g. chrysotile, protoserpentine, polygonal serpentines). Vein infill typologies are conventionally studied by using optical and scanning electron microscopy (SEM), which only allow two-dimensional (2D) imaging of samples. In this work we present results obtained by the application of high-resolution X-ray computed microtomography which provided a realistic visualization of the 3D shapes and orientations of veins that can be quantified through the extraction of parameters such as volume fraction, size distributions, orientation and connectivity. Furthermore, the phase-contrast mode allowed to detect the crystals with chemical composition different from the serpentinite group minerals (e.g., magnetite). We have investigated the serpentine vein infill, which crosscuts massive serpentinite bodies cropping out in the Gimigliano-Mount Reventino Unit (Calabria, Southern-Italy) (Bloise et al., 2016). Obtained data allowed to evaluate i) the geometric interface between serpentine-fibrous infill veins and the matrix; ii) the percentage of serpentinization; iii) the percentage of fibrous minerals in massive serpentinite rocks.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
