To understand the main processes that occur in the uppermantle (i.e. sub solidus recrystallization and magmaticcrystallization as well as metasomatism), one of the fundamentalsteps is an accurate textural characterization of natural xenoliths.Texture, as well as composition and mineralogy, reflects thetemperature, pressure, stress conditions, melting and/orcontamination events undergone during, or more commonlybefore, the entrapment in the host magma (Pearson et al., 2003).For these reasons, studying the distribution of glass pockets andveins, as well as the texture of silicate, oxide and sulphide phasesin mantle xenoliths has great importance in the study of mantlemetasomatism (Coltorti et al., 2000; Hughes et al., 2016; Lenazet al., 2017; Blanks et al., 2020).We performed an investigatory multi-scale 3D texturalanalysis through X-ray computed microtomography (micro-CT)on three mantle xenoliths from different geodynamic settings(i.e. mobile belt zone, pericraton, oceanic hotspot). These havebeen selected to represent different, variably complex, internalstructures, composed by grains of different phases, fractures,possible fluids and voids of different sizes. We used an approachstructured in increasing steps of resolution, starting withconventional X-ray micro-CT imaging (voxel size: 30 μm) andmoving on to phase-contrast synchrotron-based X-ray micro-CTto reach a voxel size of 0.9 μm.We tested the effectiveness of micro-tomographic imaging ontextural characterization of xenoliths, comparing the results withthe observation of conventional thin sections in opticalmicroscopy. 3D models obtained allow us to collect severaltextural information that were impossible to determine in a 2Dclassification. For example, we identified: spinel layering in onesample (MG10x), presence of gas vesicles in glass of xenolithBi4, and silicic glass scattered through sample FN38. Moreover,high-density volumes were detected in nodules MG10x and Bi4,showing no relation with the spinel layering in the first one and apreferential concentration along fractures in the latter one.
Some examples of X-ray micro-computed tomography applied to mantle petrology.
MARCO VENIERPrimo
;LUCA ZIBERNASecondo
;FEDERICO BERNARDINI;DAVIDE LENAZPenultimo
;ANGELO DE MINUltimo
2021-01-01
Abstract
To understand the main processes that occur in the uppermantle (i.e. sub solidus recrystallization and magmaticcrystallization as well as metasomatism), one of the fundamentalsteps is an accurate textural characterization of natural xenoliths.Texture, as well as composition and mineralogy, reflects thetemperature, pressure, stress conditions, melting and/orcontamination events undergone during, or more commonlybefore, the entrapment in the host magma (Pearson et al., 2003).For these reasons, studying the distribution of glass pockets andveins, as well as the texture of silicate, oxide and sulphide phasesin mantle xenoliths has great importance in the study of mantlemetasomatism (Coltorti et al., 2000; Hughes et al., 2016; Lenazet al., 2017; Blanks et al., 2020).We performed an investigatory multi-scale 3D texturalanalysis through X-ray computed microtomography (micro-CT)on three mantle xenoliths from different geodynamic settings(i.e. mobile belt zone, pericraton, oceanic hotspot). These havebeen selected to represent different, variably complex, internalstructures, composed by grains of different phases, fractures,possible fluids and voids of different sizes. We used an approachstructured in increasing steps of resolution, starting withconventional X-ray micro-CT imaging (voxel size: 30 μm) andmoving on to phase-contrast synchrotron-based X-ray micro-CTto reach a voxel size of 0.9 μm.We tested the effectiveness of micro-tomographic imaging ontextural characterization of xenoliths, comparing the results withthe observation of conventional thin sections in opticalmicroscopy. 3D models obtained allow us to collect severaltextural information that were impossible to determine in a 2Dclassification. For example, we identified: spinel layering in onesample (MG10x), presence of gas vesicles in glass of xenolithBi4, and silicic glass scattered through sample FN38. Moreover,high-density volumes were detected in nodules MG10x and Bi4,showing no relation with the spinel layering in the first one and apreferential concentration along fractures in the latter one.File | Dimensione | Formato | |
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