Brittle fracturing and fracture healing of zircon: An integrated cathodoluminescence, EBSD, U-Th-Pb, and REE study

Rimsa, Andrius; Whitehouse, Martin J.; Johansson, Leif; Piazolo, Sandra

doi:10.2138/am.2007.2458

Cited by 50 publications

(22 citation statements)

References 51 publications

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“…Formation of the new grains occurs due to progressive subgrain rotation recrystallization, or as a result of cataclastic behavior due to high strain rates at comparatively low temperatures. A similar process occurring in zircon grains was described and discussed in detail by Rimsa et al (2007). In this case, traces of former fractures and/or (sub)grain boundaries are clearly shown as bright CL domains and are often decorated by inclusions or pores (Fig.…”

Section: Distortion Type (Iii)supporting

confidence: 65%

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Finite lattice distortion patterns in plastically deformed zircon grains

et al. 2014

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Abstract. This study examines finite deformation patterns of zircon grains from high-temperature natural shear zones. Various zircon-bearing rocks were collected in the Western Tauern Window, eastern Alps, where they were deformed under amphibolite facies conditions, and in the Ivrea-Verbano Zone (IVZ), southern Alps, where deformation is related with granulite-facies metamorphism. Among the sampled rocks are granitic orthogneisses, metalamprophyres and paragneisses, all of which are strongly deformed.The investigated zircon grains ranging from 10 to 50 µm were studied in situ using a combination of scanning electron microscope (SEM) techniques, backscattered electron (BSE) imaging, forward-scattered electron (FSE) imaging, cathodoluminescence (CL) imaging, and crystallographic orientation mapping by electron backscatter diffraction (EBSD), as well as micro-Raman spectroscopy. Energy-dispersive X-ray spectrometry (EDS) was applied to host phases.Microstructural analysis of crystal-plastically deformed zircon grains was based on high-resolution EBSD maps. Three general types of finite lattice distortion patterns were detected: type (I) is defined by gradual bending of the zircon lattice with orientation changes of about 0.6-1.8 • per micrometer without subgrain boundary formation. Cumulative grain-internal orientation variations range from 7 to 25 • within single grains. Type (II) represents local gradual bending of the crystal lattice accompanied by the formation of subgrain boundaries that have concentric semicircular shapes in 2-D sections. Cumulative grain-internal orientation variations range from 15 to 40 • within single grains. Type (III) is characterized by formation of subgrains separated by a welldefined subgrain boundary network, where subgrain boundaries show a characteristic angular closed contour. The cumulative orientation variation within a single grain ranges from 3 to 10 • . Types (I) and (II) predominate in granulite facies rocks, whereas type (III) is restricted to the amphibolite facies rocks. The difference in distortion patterns is controlled by strain rate and by ratio between dislocation formation and dislocation motion rates, conditioned by the amount of differential stress.Investigated microstructures demonstrate that misorientation axes are usually parallel to the < 001 > and < 100 > crystallographic directions; dominant slips are < 010 > { 001 }, < 010 > { 100 } and < 001 > { 010 }, whereas in some grains cross-slip takes place. This study demonstrates that activation of energetically preferable slip systems is facilitated if zircon grain is decoupled from the host matrix and/or hosted by a soft phase.

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Section: Distortion Type (Iii)supporting

confidence: 65%

“…(Fig. 8); Rimsa et al (2007). misorientation (more than 10 • ), whereas type (III) shows continuous low-angle boundary networks (less than 10 • misorientation).…”

Section: (?)mentioning

confidence: 97%

Finite lattice distortion patterns in plastically deformed zircon grains

et al. 2014

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“…The fracturing causes an instantaneous drop in fluid pressure, which in turn triggers precipitation, resulting in almost simultaneous crack-sealing (Ramsay 1980;Ladeira and Price 1981). This network closely resembles the fine-scale healed fractures in zircons described by Rimsa et al (2007), who favoured hydraulic fracturing as the most probable mechanism.…”

Section: Signatures Unrelated To Grain Boundary Migrationsupporting

confidence: 60%

The recognition of multiple magmatic events and pre-existing deformation zones in metamorphic rocks as illustrated by CL signatures and numerical modelling: examples from the Ballachulish contact aureole, Scotland

Bergman

Piazolo

2011

Int J Earth Sci (Geol Rundsch)

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The combination of cathodoluminescence (CL) analysis, temperature and temperature-time calculations, and microstructural numerical modelling offers the possibility to derive the time-resolved evolution of a metamorphic rock. This combination of techniques is applied to a natural laboratory, namely the Ballachulish contact aureole, Scotland. Analysis of the Appin Quartzite reveals that the aureole was produced by two distinct magmatic events and infiltrated by associated fluids. Developing microstructures allow us to divide the aureole into three distinct regions. Region A (0-400 m, 663°C \ T max \ 714°C) exhibits a three-stage grain boundary migration (GBM) evolution associated with heating, fluid I and fluid II. GBM in region B (400-700 m, 630°C \ T max \ 663°C) is associated with fluid II only. Region C ([700 m of contact, T max \ 630°C) is characterised by healed intragranular cracks. The combination of CL signature analysis and numerical modelling enables us to recognise whether grain size increase occurred mainly by surface energy-driven grain growth (GG) or strain-induced grain boundary migration (SIGBM). GG and SIGBM result in either straight bands strongly associated with present-day boundaries or highly curved irregular bands that often fill entire grains, respectively. At a temperature of *620°C, evidence for GBM is observed in the initially dry, largely undeformed quartzite samples. At this temperature, evidence for GG is sparse, whereas at *663°C, CL signatures typical for GG are commonplace. The grain boundary network approached energy equilibrium in samples that were at least 5 ka above 620°C.

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“…10 Ma or younger zircons). Despite differences in crystallization mechanisms, the hydrothermally‐precipitated and hydrothermally‐altered zircons share common characteristics as they are LREE‐enriched and have flatter chondrite‐normalized LREE patterns (low [Sm/La] N ) than magmatic zircon, as well as smaller Ce anomalies (Ce/Ce*) than magmatic zircon (Cavosie, Valley, & Wilde, ; Geisler et al, ; Hoskin, ; Pelleter et al, ; Pettke, Audetat, Schaltegger, & Heinrich, ; Rimsa, Whitehouse, Johansson, & Piazolo, ; Xia, Zheng, & Hu, ). In particular, the LREE are enriched by about two orders of magnitude.…”

Section: Discussionmentioning

confidence: 99%

Multistage tectono‐magmatic evolution of the central Urumieh–Dokhtar magmatic arc, south Ardestan, Iran: Insights from zircon geochronology and geochemistry

et al. 2018

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Combining high‐spatial resolution geochronology and geochemistry of zircon provides constraints on the geodynamic evolution of the Zagros orogen. This study underlines the significance of hitherto unknown magmatic/geological events in the central Urumieh–Dokhtar magmatic arc (UDMA) of Iran at ca. 35–22 and 10 Ma. Recently reported U–Pb zircon ages of 25–24 Ma for the granodioritic rocks from the south Ardestan area were interpreted to constrain the crystallization age. Newly determined U–Pb zircon ages of ca. 35 to 22 Ma from south Ardestan gabbroic to granitic rocks and related dikes indicate that the melt evolution continued from the Oligocene into Early Miocene time. In addition, a ca. 10 Ma U–Pb age for the zircons from a south Ardestan diorite provides evidence for a so far unknown, igneous episode. Representing the youngest magmatic stage recognized in the central part of the UDMA, the 10 Ma age is interpreted to document magmatic activity related to the Arabia–Eurasia collision, as recognized elsewhere in the Zagros orogen. South Ardestan zircons with geochemical signatures indicating continental affinity likely recrystallized in the course of a major event (asthenospheric mantle melt formation) that has affected crustal rocks. The significant lower LREEs of these zircons compared to hydrothermal zircons, moderate Th/U (>0.4), and high (Sm/La)N (>10) ratios associated with low [La] (<1 ppm) suggest that these crystals have an igneous origin and are not related to hydrothermal or metamorphic processes. These findings bear important implications for the geodynamic evolution of the Zagros orogen and support a model suggesting that magmatic activity still affected the UDMA in Late Miocene time.

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Brittle fracturing and fracture healing of zircon: An integrated cathodoluminescence, EBSD, U-Th-Pb, and REE study

Cited by 50 publications

References 51 publications

Finite lattice distortion patterns in plastically deformed zircon grains

Finite lattice distortion patterns in plastically deformed zircon grains

The recognition of multiple magmatic events and pre-existing deformation zones in metamorphic rocks as illustrated by CL signatures and numerical modelling: examples from the Ballachulish contact aureole, Scotland

Multistage tectono‐magmatic evolution of the central Urumieh–Dokhtar magmatic arc, south Ardestan, Iran: Insights from zircon geochronology and geochemistry

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