Fluid-present deformation aids chemical modification of chromite: Insights from chromites from Golyamo Kamenyane, SE Bulgaria

Satsukawa, Takako; Piazolo, Sandra; Gonzáléz-Jiménez, José María; Colás, Vanessa; Griffin, William L.; O’Reilly, Suzanne Y.; Gervilla, Fernando; Fanlo, Isabel; Kerestedjian, Thomas

doi:10.1016/j.lithos.2015.04.020

Cited by 34 publications

(20 citation statements)

References 74 publications

(106 reference statements)

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“…EBSD mapping reveals that crystal-plastic deformation has resulted in continuous crystal bending and formation of well-developed subgrain boundaries in the interstitial olivines ( Figs 2c , S2 ). In these grains, these subgrain boundaries allow determination of the activated slip system utilizing the orientation of the misorientation axis, as defined by the lattice dispersion paths, and orientations of the subgrain boundary trace 17 18 19 20 21 22 23 24 25 26 27 28 29 . The small size of the olivine inclusions precludes quantitative substructure analysis.…”

Section: Resultsmentioning

confidence: 99%

“…1a ), indicates that grain growth occurred after the transition from the orthorhombic HPP-chromite to cubic chromite. Grain growth occurs by grain boundary migration between pre-existing grains, allowing readjustment of mineral compositions in the “swept” area to one in equilibrium in the prevailing PT conditions, while maintaining crystallographic near-continuity with the core 29 30 31 32 33 . The grain-size difference between the enclosed and interstitial olivine grains is consistent with the evidence for grain boundary migration, because grain boundaries can readily migrate across small grains but can be pinned by larger grains 34 35 36 37 38 39 .…”

Section: Significance and Discussionmentioning

confidence: 99%

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Messengers from the deep: Fossil wadsleyite-chromite microstructures from the Mantle Transition Zone

Satsukawa

Griffin

Piazolo

et al. 2015

Sci Rep

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Investigations of the Mantle Transition Zone (MTZ; 410–660 km deep) by deformation experiments and geophysical methods suggest that the MTZ has distinct rheological properties, but their exact cause is still unclear due to the lack of natural samples. Here we present the first direct evidence for crystal-plastic deformation by dislocation creep in the MTZ using a chromitite from the Luobusa peridotite (E. Tibet). Chromite grains show exsolution of diopside and SiO2, suggesting previous equilibration in the MTZ. Electron backscattered diffraction (EBSD) analysis reveals that olivine grains co-existing with exsolved phases inside chromite grains and occurring on chromite grain boundaries have a single pronounced crystallographic preferred orientation (CPO). This suggests that olivine preserves the CPO of a high-pressure polymorph (wadsleyite) before the high-pressure polymorph of chromite began to invert and exsolve. Chromite also shows a significant CPO. Thus, the fine-grained high-pressure phases were deformed by dislocation creep in the MTZ. Grain growth in inverted chromite produced an equilibrated microstructure during exhumation to the surface, masking at first sight its MTZ deformation history. These unique observations provide a window into the deep Earth, and constraints for interpreting geophysical signals and their geodynamic implications in a geologically robust context.

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Section: Resultsmentioning

confidence: 99%

Section: Significance and Discussionmentioning

confidence: 99%

Messengers from the deep: Fossil wadsleyite-chromite microstructures from the Mantle Transition Zone

Satsukawa

Griffin

Piazolo

et al. 2015

Sci Rep

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“…Heterogeneous microfabrics observed in gold (Fig. 4H) may be formed in other minerals such as zircon (Piazolo et al 2012), and chromite (Satsukawa et al 2015) in response to local high degrees of deformation at grain edges. The physical impact of hard material against the detrital gold particle induces locally high dislocation densities (e.g., Piazolo et al 2012).…”

Section: Post-depositional Modification: Hypogene Environmentmentioning

confidence: 99%

Chemical and physical heterogeneity within native gold: implications for the design of gold particle studies

et al. 2021

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Studies of populations of gold particles are becoming increasingly common; however, interpretation of compositional data may not be straightforward. Natural gold is rarely homogenous. Alloy heterogeneity is present as microfabrics formed either during primary mineralization or by modification of pre-existing alloys by chemical and physical drivers during subsequent residence in either hypogene or surficial environments. In electron-probe-microanalysis (EPMA)-based studies, the combination of Cu, Hg, and Pd values and mineral inclusion suites may be diagnostic for source style of mineralization, but Ag alone is rarely sufficient. Gold characterization studies by laser-ablation-ICP mass spectrometry linked to both quadrupole and Time-of-Flight (ToF-MS) systems show that only Ag, Cu, and Hg form homogenous alloys with Au sufficiently often to act as generic discriminants. Where present, other elements are commonly distributed highly heterogeneously at the micron or submicron scale, either as mineral inclusions or in highly localized, but low concentrations. Drawing upon our own data derived from individual inspection and analyses of approximately 40,000 gold particles from 526 placer and in situ localities worldwide, we show that adequate characterization of gold from a specific locality normally requires study of a minimum of 150 particles via a two-stage approach comprising spatial characterization of compositional heterogeneity, plus crystallographic orientation mapping, that informs subsequent targeted acquisition of quantitative compositional data by EPMA and/or laser-ablation ICP-MS methods. Such data provide the platform to review current understanding of the genesis of gold particle characteristics, elevating future compositional studies from empirical descriptions to process-focused interpretations.

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“…Due to the importance of characterizing both the former partial melt network and the subgrain boundaries present within deformed quartz grains, we utilize a combined approach informed by previous optical microstructural studies that provide insight into locations of former melt that help determine melt‐producing reactions (e.g., Holness et al., 2011; Holness & Sawyer, 2008; Kriegsman & Álvarez‐Valero, 2010; Sawyer, 2001), and studies that add in analysis of compositional and orientation data (e.g., Hasalova et al., 2008; Negrini et al., 2014; Yakymchuk & Godin, 2012). We employ a combined electron backscatter diffraction (EBSD) and energy dispersive X‐ray spectroscopy (EDS) mapping method, which has recently been documented as a powerful approach to solving complex microstructural problems, with studies that reveal chemical changes, including enhanced diffusion associated with deformation (Kovaleva et al., 2017; Massey et al., 2011; Satsukawa et al., 2015; Whitney & Seaton, 2010), conditions of deformation (Hanna et al., 2015; Linckens et al., 2015; Lindgren et al., 2011; McNamara et al., 2016; Vukmanovic et al., 2013), and rheology (Czaplińska et al., 2015; Lund et al., 2006). The proliferation of scanning electron microscopes (SEMs) with EBSD capabilities now allows more opportunities to unravel complex microstructural problems using this enhanced composition and orientation mapping approach.…”

Section: Introductionmentioning

confidence: 99%

Subgrain Boundaries as Sites of Melt Generation and Pathways for Melt Flow: Implications for Rheology From Combined Chemical and Quantitative Orientation Analysis

Levine

Rahl

2021

JGR Solid Earth

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Partial melting influences important Earth processes, including the generation of crustal-forming melts and the softening of the lower crust or mantle, impacting the structure of the continents and tectonic plates. Both melt generation/extraction and rheologic weakening are known to be influenced by several factors, but two important parameters are the nature and evolution of the melt network in a partially molten rock. For example, the permeability of melt varies not just with melt fraction but also with grain size (von Bar-

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Fluid-present deformation aids chemical modification of chromite: Insights from chromites from Golyamo Kamenyane, SE Bulgaria

Cited by 34 publications

References 74 publications

Messengers from the deep: Fossil wadsleyite-chromite microstructures from the Mantle Transition Zone

Messengers from the deep: Fossil wadsleyite-chromite microstructures from the Mantle Transition Zone

Chemical and physical heterogeneity within native gold: implications for the design of gold particle studies

Subgrain Boundaries as Sites of Melt Generation and Pathways for Melt Flow: Implications for Rheology From Combined Chemical and Quantitative Orientation Analysis

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