scholarly journals Brittle Deformation During Eclogitization of Early Paleozoic Blueschist

2020 ◽  
Vol 8 ◽  
Author(s):  
Michał Bukała ◽  
Christopher J. Barnes ◽  
Pauline Jeanneret ◽  
Károly Hidas ◽  
Stanisław Mazur ◽  
...  
Keyword(s):  
Electron Backscatter Diffraction ◽  
Fluid Pressure ◽  
Chemical Mapping ◽  
Brittle Deformation ◽  
X Ray ◽  
Metasedimentary Rocks ◽  
Dehydration Reactions ◽  
Computed Microtomography ◽  
Migration Pathways ◽  
Polyphase Inclusions

The Tsäkkok Lens of the Scandinavian Caledonides represents the outermost Baltican margin that was subducted in late Cambrian/Early Ordovician time during closure of the Iapetus Ocean. The lens predominantly consists of metasedimentary rocks hosting eclogite bodies that preserve brittle deformation on the μm-to-m scale. Here, we present a multidisciplinary approach that reveals fracturing related to dehydration and eclogitization of blueschists. Evidence for dehydration is provided by relic glaucophane and polyphase inclusions in garnet consisting of clinozoisite + quartz ± kyanite ± paragonite that are interpreted as lawsonite pseudomorphs. X-Ray chemical mapping of garnet shows a network of microchannels that propagate outward from polyphase inclusions. These microchannels are healed by garnet with elevated Mg relative to the surrounding garnet. Electron backscatter diffraction mapping revealed that Mg-rich microchannels are also delimited by low angle (<3°) boundaries. X-ray computed microtomography demonstrates that some garnet is transected by up to 300 μm wide microfractures that are sealed by omphacite ± quartz ± phengite. Locally, mesofractures sealed either by garnet- or omphacite-dominated veins transect through the eclogites. The interstices within the garnet veins are filled with omphacite + quartz + rutile + glaucophane ± phengite. In contrast, omphacite veins are predominantly composed of omphacite with minor apatite + quartz. Omphacite grains are elongated along [001] crystal axis and are preferably oriented orthogonal to the vein walls, indicating crystallization during fracture dilation. Conventional geothermobarometry using omphacite, phengite and garnet adjacent to fractures, provides pressure-temperature conditions of 2.47 ± 0.32 GPa and 620 ± 60°C for eclogites. The same method applied to a mesoscale garnet vein yields 2.42 ± 0.32 GPa at 635 ± 60°C. Zirconium-in-rutile thermometry applied to the same garnet vein provides a temperature of ∼620°C. Altogether, the microchannels, microfractures and mesofractures represent migration pathways for fluids that were produced during glaucophane and lawsonite breakdown. The microfractures are likely precursors of the mesoscale fractures. These dehydration reactions indicate that high pore-fluid pressure was a crucial factor for fracturing. Brittle failure of the eclogites thus represents a mechanism for fluid-escape in high-pressure conditions. These features may be directly associated with seismic events in a cold subduction regime.

Brittle deformation during eclogitization: a perspective from a cold, early Paleozoic subduction zone

2021 ◽  
Author(s):  
Michał Bukała ◽  
Christopher Barnes ◽  
Iwona Klonowska ◽  
Károly Hidas ◽  
Kathrin Fassmer ◽  
...  
Keyword(s):  
Fluid Pressure ◽  
Early Paleozoic ◽  
Brittle Deformation ◽  
National Agency ◽  
Academic Exchange ◽  
Icp Ms ◽  
Dehydration Reactions ◽  
Trace Element Profiles ◽  
Migration Pathways ◽  
Polyphase Inclusions

<p>The Tsäkkok Lens (northern Scandinavian Caledonides) represents the outermost part of the rifted passive Baltica margin and consists of sediments and pillow basalts of MORB affinity that were metamorphosed under eclogite facies conditions. Fieldwork and further multidisciplinary analytical approach (including e.g. X-ray and EBSD mapping, and μ-CT imaging) revealed that eclogites record brittle deformation on the μm-to-m scale. This deformation is expressed as a set of microfractures (single-grain rupture) and mesofractures (sealed by garnet- and omphacite-veins). Phase equilibrium thermodynamic modeling of phengite-bearing and phengite-free eclogites performed in NCKFMMnASHT and NCFMMnASHT systems predict profuse dehydration related to lawsonite and amphibole breakdown at ~2.35 GPa and ~600°C, close to the peak conditions of ~2.55 GPa and ~640°C. These estimates are in line with conventional thermobarometry and Zr-in-rutile thermometry results. The evidence for dehydration is also provided by the  occurrence of relic glaucophane in matrix and polyphase inclusions in garnet consisting of clinozoisite + quartz ± kyanite ± paragonite that are interpreted as pseudomorphs after lawsonite. Dehydration reactions were responsible for producing fluid, which facilitated brittle fracturing of the eclogites at HP conditions due to increased pore-fluid pressure (also promoted by the volume changes during eclogitization) on the microscale. Altogether, micro- and mesofracturing acted as migration pathways for released fluid, whereas the microfractures are likely precursors of the mesoscale fractures. Garnet-WR Lu-Hf geochronology provided ages of 487.7 ± 4.6, 486.2 ± 3.2, and 484.6 ± 4.5 Ma. LA-ICP-MS trace element profiles of garnet revealed a well-pronounced peak of Lu content in the garnet cores that decreased towards the rims, indicating these dates represent the age of prograde metamorphism. Therefore, the early Paleozoic Tsäkkok Lens eclogites constitute the oldest documented natural example of HP brittle deformation during eclogitization of blueschist.</p><p>Research funded by NCN project no. 2019/33/N/ST10/01479 (M. Bukała) and no. 2014/14/E/ST10/00321 (J. Majka), as well as the Polish National Agency for the Academic Exchange scholarship no. PPN/IWA/2018/1/00046/U/0001 given to M. Bukała.</p>

Determination of reservoir rock residual water using X-ray computed microtomography

2018 ◽  
pp. 38-42 ◽  
Author(s):  
I.V. Yazynina ◽  
◽  
E.V. Shelyago ◽  
A.A. Abrosimov ◽  
N.E. Grachev ◽  
...  
Keyword(s):  
Reservoir Rock ◽  
Residual Water ◽  
X Ray ◽  
Computed Microtomography ◽  
X Ray Computed

Acoustic emission and X-ray computed microtomography characterization of damage accumulation in a woven Cf/SiC composite

2019 ◽  
Vol 155 ◽  
pp. 109748
Author(s):  
Yudong Xue ◽  
Qinglei Wang ◽  
Jianbao Hu ◽  
Haijun Zhou ◽  
Qingliang Shan ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Damage Accumulation ◽  
X Ray ◽  
Computed Microtomography ◽  
X Ray Computed

scholarly journals Stable and Metastable Phase Equilibria Involving the Cu6Sn5 Intermetallic

2021 ◽  
Author(s):  
A. Leineweber ◽  
M. Löffler ◽  
S. Martin
Keyword(s):  
Phase Equilibria ◽  
Electron Backscatter Diffraction ◽  
Metastable Phase ◽  
Stable Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Heat Treated ◽  
Ordered Phases ◽  
Backscatter Diffraction ◽  
Kinetics Of

Abstract Cu6Sn5 intermetallic occurs in the form of differently ordered phases η, η′ and η′′. In solder joints, this intermetallic can undergo changes in composition and the state of order without or while interacting with excess Cu and excess Sn in the system, potentially giving rise to detrimental changes in the mechanical properties of the solder. In order to study such processes in fundamental detail and to get more detailed information about the metastable and stable phase equilibria, model alloys consisting of Cu3Sn + Cu6Sn5 as well as Cu6Sn5 + Sn-rich melt were heat treated. Powder x-ray diffraction and scanning electron microscopy supplemented by electron backscatter diffraction were used to investigate the structural and microstructural changes. It was shown that Sn-poor η can increase its Sn content by Cu3Sn precipitation at grain boundaries or by uptake of Sn from the Sn-rich melt. From the kinetics of the former process at 513 K and the grain size of the η phase, we obtained an interdiffusion coefficient in η of (3 ± 1) × 10−16 m2 s−1. Comparison of this value with literature data implies that this value reflects pure volume (inter)diffusion, while Cu6Sn5 growth at low temperature is typically strongly influenced by grain-boundary diffusion. These investigations also confirm that η′′ forming below a composition-dependent transus temperature gradually enriches in Sn content, confirming that Sn-poor η′′ is metastable against decomposition into Cu3Sn and more Sn-rich η or (at lower temperatures) η′. Graphic Abstract

scholarly journals Evaluation of the Antimicrobial Protection of Pharmaceutical Kaolin and Talc Modified with Copper and Zinc

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1173
Author(s):  
Fotini Martsouka ◽  
Konstantinos Papagiannopoulos ◽  
Sophia Hatziantoniou ◽  
Martin Barlog ◽  
Giorgos Lagiopoulos ◽  
...  
Keyword(s):  
Cation Exchange ◽  
Photoelectron Spectroscopy ◽  
Antimicrobial Properties ◽  
Exchange Capacity ◽  
Elevated Concentration ◽  
Chemical Mapping ◽  
Exchange Method ◽  
X Ray ◽  
Copper And Zinc ◽  
Antimicrobial Protection

Six pharmaceutical pastes were prepared using chemically modified kaolin and talc powders. Tests were conducted to determine their structural and chemical characteristics as well as their antimicrobial protection, thus rendering them suitable for cosmetic and pharmaceutical uses. Kaolin and talc were treated chemically via the cation exchange method to load the clay particles with copper and zinc ions, two cations well known for their antimicrobial properties. Mineralogical analyses were conducted by using X-ray diffraction (XRD) before and after the modification, confirming the mineralogical purity of the samples. Scanning electron microscopy was also used in conjunction with energy dispersed spectroscopy (SEM-EDS) to obtain chemical mapping images, revealing the dispersion of the added metals upon the clay minerals surfaces. Moreover, chemical analysis has been performed (XRF) to validate the enrichment of the clays with each metal utilizing the cation exchange capacity. All modified samples showed the expected elevated concentration in copper or zinc in comparison to their unmodified versions. From the X-ray photoelectron spectroscopy (XPS), the chemical state of the samples’ surfaces was investigated, revealing the presence of salt compounds and indicating the oxidation state of adsorbed metals. Finally, the resistance of pastes in microbial growth when challenged with bacteria, molds, and yeasts was assessed. The evaluation is based on the European Pharmacopeia (EP) criteria.

scholarly journals Pervasive fluid-rock interaction in subducted oceanic crust revealed by oxygen isotope zoning in garnet

2021 ◽  
Vol 176 (7) ◽  
Author(s):  
Thomas Bovay ◽  
Daniela Rubatto ◽  
Pierre Lanari
Keyword(s):  
Oxygen Isotope ◽  
Western Alps ◽  
Large Contribution ◽  
Chemical Mapping ◽  
Rock Interaction ◽  
Rock Density ◽  
Chemical Zoning ◽  
Dehydration Reactions ◽  
Subducted Oceanic Crust ◽  
Eclogite Facies

AbstractDehydration reactions in the subducting slab liberate fluids causing major changes in rock density, volume and permeability. Although it is well known that the fluids can migrate and interact with the surrounding rocks, fluid pathways remain challenging to track and the consequences of fluid-rock interaction processes are often overlooked. In this study, we investigate pervasive fluid-rock interaction in a sequence of schists and mafic felses exposed in the Theodul Glacier Unit (TGU), Western Alps. This unit is embedded within metaophiolites of the Zermatt-Saas Zone and reached eclogite-facies conditions during Alpine convergence. Chemical mapping and in situ oxygen isotope analyses of garnet from the schists reveal a sharp chemical zoning between a xenomorphic core and a euhedral rim, associated to a drop of ~ 8‰ in δ18O. Thermodynamic and δ18O models show that the large amount of low δ18O H2O required to change the reactive bulk δ18O composition cannot be produced by dehydration of the mafic fels from the TGU only, and requires a large contribution of the surrounding serpentinites. The calculated time-integrated fluid flux across the TGU rocks is 1.1 × 105 cm3/cm2, which is above the open-system behaviour threshold and argues for pervasive fluid flow at kilometre-scale under high-pressure conditions. The transient rock volume variations caused by lawsonite breakdown is identified as a possible trigger for the pervasive fluid influx. The calculated schist permeability at eclogite-facies conditions (~ 2 × 10–20 m2) is comparable to the permeability determined experimentally for blueschist and serpentinites.

scholarly journals Micro-Fabric Analyzer (MFA): A New Semiautomated ArcGIS-Based Edge Detector for Quantitative Microstructural Analysis of Rock Thin-Sections

2021 ◽  
Vol 10 (2) ◽  
pp. 51 ◽  
Author(s):  
Roberto Visalli ◽  
Gaetano Ortolano ◽  
Gaston Godard ◽  
Rosolino Cirrincione
Keyword(s):  
Physical Properties ◽  
Electron Backscatter Diffraction ◽  
Microstructural Analysis ◽  
Image Features ◽  
Elemental Distribution ◽  
Edge Detector ◽  
Sandstone Sample ◽  
Thin Sections ◽  
X Ray ◽  
Distribution Maps

Micro-Fabric Analyzer (MFA) is a new GIS-based tool for the quantitative extrapolation of rock microstructural features that takes advantage both of the characteristics of the X-ray images and the optical image features. Most of the previously developed edge mineral grain detectors are uniquely based on the physical properties of the X-ray-, electron-, or optical-derived images; not permitting the exploitation of the specific physical properties of each image type at the same time. More advanced techniques, such as 3D microtomography, permit the reconstruction of tridimensional models of mineral fabric arrays, even though adjacent mineral grain boundaries with the same atomic density are often not detectable. Only electron backscatter diffraction (EBSD) allows providing high-performing grain boundary detection that is crystallographically differentiated per mineral phase, even though it is relatively expensive and can be executed only in duly equipped microanalytical laboratories by suitably trained users. Instead, the MFA toolbox allows quantifying fabric parameters subdivided per mineral type starting from a crossed-polarizers high-resolution RGB image, which is useful for identifying the edges of the individual grains characterizing rock fabrics. Then, this image is integrated with a set of micro-X-ray maps, which are useful for the quantitative extrapolation of elemental distribution maps. In addition, all this is achieved by means of low-cost and easy-to-use equipment. We applied the tool on amphibolite, mylonitic-paragneiss, and -tonalite samples to extrapolate the particle fabric on different metamorphic rock types, as well as on the same sandstone sample used for another edge detector, which is useful for comparing the obtained results.

Sign in / Sign up

Export Citation Format

Share Document