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Gardner J, Wallis D, Hansen LN, Wheeler J. Weighted Burgers Vector analysis of orientation fields from high-angular resolution electron backscatter diffraction. Ultramicroscopy 2024; 257:113893. [PMID: 38056396 DOI: 10.1016/j.ultramic.2023.113893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 10/31/2023] [Accepted: 11/23/2023] [Indexed: 12/08/2023]
Abstract
The Weighted Burgers Vector (WBV) method can extract information about dislocation types and densities present in distorted crystalline materials from electron backscatter diffraction (EBSD) maps, using no assumptions about which slip systems might be present. Furthermore, high-angular resolution EBSD (HR-EBSD) uses a cross-correlation procedure to increase the angular precision of EBSD measurements by an order of magnitude compared to conventional EBSD. However, the WBV technique has not previously been applied to HR-EBSD data and therefore it remains unclear as to which low-angle substructures can be reliably characterised by WBV analysis of conventional EBSD data and which require additional HR-EBSD processing. To establish some practical examples that can be used to guide future data-acquisition strategies, we compare the output of the WBV method when applied to conventional EBSD data and HR-EBSD data collected from the most common minerals in Earth's lower crust (plagioclase feldspar) and upper mantle (olivine). The results demonstrate that HR-EBSD and WBV processing are complementary techniques. The increase in angular precision achieved with HR-EBSD processing allows low-angle (on the order of 0.1°) structures, which are obscured by noise in conventional EBSD data, to be analyzed quantitatively using the WBV method. Combining the WBV and HR-EBSD methods increases the precision of calculated WBV directions, which is essential when using information about active slip systems to infer likely deformation mechanisms from naturally deformed microstructures. This increase in precision is particularly important for low-symmetry crystals, such as plagioclase, that have a wide range of available slip systems that vary in relative activity with changing pressure, temperature and differential stress. Because WBV directions are calculated using no assumptions about which slip systems may be present, combining this technique with HR-EBSD to refine the precision of lattice orientation gradients is ideal for investigating complex natural materials with unknown deformation histories.
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Affiliation(s)
- Joe Gardner
- Department of Earth, Ocean and Ecological Sciences, University of Liverpool, UK.
| | - David Wallis
- Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK
| | - Lars N Hansen
- Department of Earth and Environmental Sciences, University of Minnesota-Twin Cities, Minneapolis, MN 55455, USA
| | - John Wheeler
- Department of Earth, Ocean and Ecological Sciences, University of Liverpool, UK
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2
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Khudhur FWK, MacDonald JM, Daly L, Macente A, Spruženiece L, Griffin S, Wilson C. Microstructural analysis of slag properties associated with calcite precipitation due to passive CO 2 mineralization. Micron 2023; 174:103532. [PMID: 37683551 DOI: 10.1016/j.micron.2023.103532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 08/21/2023] [Accepted: 08/28/2023] [Indexed: 09/10/2023]
Abstract
CO2 mineralization in slag has gained significant attention since it occurs with minimal human intervention and energy input. While the amount of theoretical CO2 that can be captured within slag has been quantified based on slag composition in several studies, the microstructural and mineralogical effects of slag on its ability to capture CO2 have not been fully addressed. In this work, the CO2 uptake within legacy slag samples is analyzed through microstructural characterization. Slag samples were collected from the former Ravenscraig steelmaking site in Lanarkshire, Scotland. The collected samples were studied using X-ray Computed Tomography (XCT) to understand the distribution and geometry of pore space, as well as with scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) to visualize the distribution of elements within the studied samples. Electron backscatter diffraction (EBSD) was used to study the minerals distribution. The samples were also characterized through X-ray diffraction (XRD) and X-ray fluorescence (XRF), and the amount of captured CO2 was quantified using thermogravimetric analysis (TGA). Our results demonstrate that CO2 uptake occurs to the extent of ∼9-30 g CO2/ kg slag. The studied samples are porous in nature, with pore space occupying up to ∼30% of their volumes, and they are dominated by åkermanite-gehlenite minerals which interact with the atmospheric CO2 slowly at ambient conditions. EDS and EBSD results illustrate that the precipitated carbonate in slag is calcite, and that the precipitation of calcite is accompanied by the formation of a Si-O-rich layer. The provided analysis concludes that the porous microstructure as well as the minerals distribution in slag should be considered in forecasting and designing large-scale solutions for passive CO2 mineralization in slag.
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Affiliation(s)
- Faisal W K Khudhur
- School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
| | - John M MacDonald
- School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK
| | - Luke Daly
- School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK; Australian Centre for Microscopy and Microanalysis, University of Sydney, Sydney 2006, NSW, Australia; Department of Materials, University of Oxford, Oxford OX1 3PH, UK
| | - Alice Macente
- School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK; Department of Civil and Environmental Engineering, University of Strathclyde, Glasgow G1 1XJ, UK; School of Civil Engineering, University of Leeds, Leeds LS2 9JT, UK
| | - Liene Spruženiece
- School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK; Geoanalytical Electron Microscopy and Spectroscopy (GEMS) Laboratory, University of Glasgow, Glasgow G12 8QQ, UK
| | - Sammy Griffin
- School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK
| | - Claire Wilson
- School of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK
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Zhang Y, Cai Y, Qu Y, Wang Q, Gu L, Li G. Two-stage fluid pathways generated by volume expansion reactions: insights from the replacement of pyrite by chalcopyrite. Sci Rep 2020; 10:19993. [PMID: 33203897 PMCID: PMC7673132 DOI: 10.1038/s41598-020-76813-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 10/13/2020] [Indexed: 11/17/2022] Open
Abstract
Volume expansion reactions involved in mineral–fluid interactions are linked to a number of geological processes, including silicate weathering, retrograde metamorphism, and mineralization. However, the effect of volume expansion on replacement reactions remains unclear. Here, we demonstrate that reactions associated with volume expansion during the replacement of pyrite by chalcopyrite involve two competing processes. The reaction is initially augmented because of the development of reaction-induced fractures in the pyrite. However, these fractures are subsequently filled by compacted products, which ultimately disrupts the contact and interaction between bulk fluids and the pristine pyrite surface. These competing processes indicate that replacement reactions are both augmented and inhibited by volume expansion reactions during pyrite replacement.
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Affiliation(s)
- Yang Zhang
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, 163 Xianlin Avenue, Nanjing, 210023, China
| | - Yuanfeng Cai
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, 163 Xianlin Avenue, Nanjing, 210023, China.
| | - Yang Qu
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, 163 Xianlin Avenue, Nanjing, 210023, China
| | - Qin Wang
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, 163 Xianlin Avenue, Nanjing, 210023, China
| | - Lixin Gu
- Electron Microscopy Laboratory, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China
| | - Gaojun Li
- MOE Key Laboratory of Surficial Geochemistry, School of Earth Sciences and Engineering, Nanjing University, 163 Xianlin Avenue, Nanjing, 210023, China
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Feedback between high-pressure genesis of abiotic methane and strain localization in subducted carbonate rocks. Sci Rep 2020; 10:9848. [PMID: 32555339 PMCID: PMC7300122 DOI: 10.1038/s41598-020-66640-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 05/08/2020] [Indexed: 11/08/2022] Open
Abstract
Fluid-rock interactions exert key control over rock rheology and strain localization. Redox may significantly affect the reaction pathways and, thereby, the mechanical properties of the rock. This effect may become critical in volatile-rich, redox sensitive rocks such as carbonate-rich lithologies, the breakdown of which can significantly modify the net volume change of fluid-mediated reactions. Subduction focus the largest recycling of crustal carbonates and the most intense seismic activity on Earth. Nevertheless, the feedbacks between deep carbon mobilization and deformation remain poorly investigated. We present quantitative microstructural results from natural samples and thermodynamic modeling indicating that percolation of reducing fluids exerts strong control on the mobilization of carbon and on strain localization in subducted carbonate rocks. Fluid-mediated carbonate reduction progressed from discrete domains unaffected by ductile deformation into localized shear zones deforming via diffusion creep, dissolution-precipitation creep and grain boundary sliding. Grain-size reduction and creep cavitation along localized shear zones enhanced fluid-carbonate interactions and fluid channelization. These results indicate that reduction of carbonate rocks can exert an important positive feedback on strain localization and fluid channelization, with potential implications on seismic activity and transport of deep hydrocarbon-bearing fluids.
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Mineral dissolution and reprecipitation mediated by an amorphous phase. Nat Commun 2018; 9:1637. [PMID: 29691391 PMCID: PMC5915427 DOI: 10.1038/s41467-018-03944-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 03/23/2018] [Indexed: 11/08/2022] Open
Abstract
Fluid-mediated mineral dissolution and reprecipitation processes are the most common mineral reaction mechanism in the solid Earth and are fundamental for the Earth's internal dynamics. Element exchange during such mineral reactions is commonly thought to occur via aqueous solutions with the mineral solubility in the coexisting fluid being a rate limiting factor. Here we show in high-pressure/low temperature rocks that element transfer during mineral dissolution and reprecipitation can occur in an alkali-Al-Si-rich amorphous material that forms directly by depolymerization of the crystal lattice and is thermodynamically decoupled from aqueous solutions. Depolymerization starts along grain boundaries and crystal lattice defects that serve as element exchange pathways and are sites of porosity formation. The resulting amorphous material occupies large volumes in an interconnected porosity network. Precipitation of product minerals occurs directly by repolymerization of the amorphous material at the product surface. This mechanism allows for significantly higher element transport and mineral reaction rates than aqueous solutions with major implications for the role of mineral reactions in the dynamic Earth.
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