On the geometric relationship between deformation microstructures in zircon and the kinematic framework of the shear zone

Kovaleva, Elizaveta; Klötzli, Urs; Habler, Gerlinde

doi:10.1016/j.lithos.2016.07.001

Cited by 12 publications

(24 citation statements)

References 73 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4f). Rotation of the lattice reaches 7 • with respect to the undeformed lattice (Kovaleva et al, 2016), indicating that this vermicular zircon grain predated shearing and ductile deformation.…”

Section: (C-e) Enlarged Bse (Left) and CL (Right) Images Of The Arementioning

confidence: 94%

Interpretation of zircon coronae textures from metapelitic granulites of the Ivrea–Verbano Zone, northern Italy: two-stage decomposition of Fe–Ti oxides

Kovaleva¹,

Austrheim²,

Klötzli³

2017

Solid Earth

Self Cite

View full text Add to dashboard Cite

Abstract. In this study, we report the occurrence of zircon coronae textures in metapelitic granulites of the IvreaVerbano Zone. Unusual zircon textures are spatially associated with Fe-Ti oxides and occur as (1) vermicular-shaped aggregates 50-200 µm long and 5-20 µm thick and as (2) zircon coronae and fine-grained chains, hundreds of micrometers long and ≤ 1 µm thick, spatially associated with the larger zircon grains. Formation of such textures is a result of zircon precipitation during cooling after peak metamorphic conditions, which involved: (1) decomposition of Zr-rich ilmenite to Zr-bearing rutile, and formation of the vermicular-shaped zircon during retrograde metamorphism and hydration; and (2) recrystallization of Zr-bearing rutile to Zr-depleted rutile intergrown with quartz, and precipitation of the submicron-thick zircon coronae during further exhumation and cooling. We also observed hat-shaped grains that are composed of preexisting zircon overgrown by zircon coronae during stage (2). Formation of vermicular zircon (1) preceded ductile and brittle deformation of the host rock, as vermicular zircon is found both plastically and cataclastically deformed. Formation of thin zircon coronae (2) was coeval with, or immediately after, brittle deformation as coronae are found to fill fractures in the host rock. The latter is evidence of local, fluid-aided mobility of Zr. This study demonstrates that metamorphic zircon can nucleate and grow as a result of hydration reactions and mineral breakdown during cooling after granulite-facies metamorphism. Zircon coronae textures indicate metamorphic reactions in the host rock and establish the direction of the reaction front.

show abstract

Section: (C-e) Enlarged Bse (Left) and CL (Right) Images Of The Arementioning

confidence: 94%

Interpretation of zircon coronae textures from metapelitic granulites of the Ivrea–Verbano Zone, northern Italy: two-stage decomposition of Fe–Ti oxides

Kovaleva¹,

Austrheim²,

Klötzli³

2017

Solid Earth

Self Cite

View full text Add to dashboard Cite

show abstract

“…The most commonly reported slips systems are {100}<010> or {001}<100> (Reddy 231 et al, 2007;Nemchin et al, 2009;Reddy et al, 2009;Timms and Reddy, 2009;232 Kaczmarek et al, 2011;Piazolo et al, 2012;Timms et al, 2012b;MacDonald et al, 233 2013;Cavosie et al, 2015a;Kovaleva et al, 2015;Kovaleva et al, 2016). 234…”

Section: Thermodynamic Calculation Of the Zircon Dissociation Reactionmentioning

confidence: 99%

A pressure-temperature phase diagram for zircon at extreme conditions

Timms

Erickson

Pearce

et al. 2017

Earth-Science Reviews

143

145

View full text Add to dashboard Cite

Hypervelocity impact processes are uniquely capable of generating shock metamorphism, which causes mineralogical transformations and deformation that register pressure (P) and temperature (T) conditions far beyond even the most extreme conditions created by terrestrial tectonics. The mineral zircon (ZrSiO 4) responds to 26 shock deformation is various ways, including crystal-plasticity, twinning, 27 polymorphism (e.g., transformation to the isochemical mineral reidite), formation of 28 granular texture, and dissociation to ZrO 2 + SiO 2 , which provide robust 29 thermobarometers that record different extreme conditions. The importance of 30 understanding these material processes is twofold. First, these processes can mobilize 31 and redistribute trace elements, and thus be accompanied by variable degrees of 32 resetting of the U-Pb system, which is significant for the use of zircon as a 33 geochronometer. Second, some features described herein form exclusively during 34 shock events and are diagnostic criteria that can be used to confirm the hypervelocity 35 origin of suspected impact structures. We present new P-T diagrams showing the 36 phase relations of ZrSiO 4 polymorphs and associated dissociation products under extreme conditions using available empirical and theoretical constraints. We present case studies to illustrate zircon microstructures formed in extreme environments, and present electron backscatter diffraction data for grains from three impact structures (Mistastin Lake of Canada, Ries of Germany, and Acraman of Australia) that preserve different minerals and microstructures associated with different shock conditions. For each locality, we demonstrate how systematic crystallographic orientation relationships within and between minerals can be used in conjunction with the new phase diagrams to constrain the P-T history. We outline a conceptual framework for a zircon-based approach to 'extreme thermobarometry' that incorporates both direct observation of high-P and high-T phases, as well as inferences for the former existence of phases from orientation relationships in recrystallised products, a concept we refer to here as 'phase heritage'. This new approach can be used to unravel the pressure-temperature history of zircon-bearing samples that have experienced extreme conditions, such as rocks that originated in the Earth's mantle, and those shocked during impact events on Earth and other planetary bodies.

show abstract

“…4f, black arrow). Rotation of the lattice on this tip reaches 7° with respect to the undeformed lattice (Kovaleva et al, 2016). This observation indicates that zircon vermicular grains preexisted not only brittle deformation of the host rock, but also shearing and ductile deformation.…”

mentioning

confidence: 76%

“…Such shapes are the result of zircon being exposed to various crustal conditions, from impact events to hydrothermal reactions (e.g., Corfu et al, 2003 and references therein). Contrary to the common opinion that zircon behaves extremely robust and inert, its behavior in various metamorphic conditions and during deformation events can be highly variable (e.g., Reddy et al, 2007;Kohn et al, 2015;Kovaleva et al, 2015Kovaleva et al, , 2016, even 35 under low metamorphic grades (e.g., Dempster et al, 2008), especially in the presence of fluid. Mineral-fluid interaction can result in very "unusual" zircon textures.…”

mentioning

confidence: 76%

Interpretation of zircon corona textures from metapelitic granulites of Ivrea-Verbano Zone, Northern Italy: Two-stage decomposition of Fe-Ti oxides

Kovaleva¹,

Austrheim²,

Klötzli³

2016

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. In this study we report the occurrence of zircon corona textures in metapelitic granulites of the Ivrea-Verbano Zone. Unusual zircon textures are spatially associated with Fe-Ti oxides and occur as (1) vermicular-shaped aggregates 50–200 µm long and 5–20 µm thick, and as (2) zircon coronas and fine-grain chains, hundreds of µm long and ≤ 1 µm thick, spatially associated with (1). Formation of such textures is a result of mineral-fluid reactions, which occurred in two stages and involved: (1) decomposition of ilmenite to Zr-rich rutile and vermicular-shaped zircon during peak metamorphism and initial cooling stage, and (2) recrystallization of Zr-rich rutile to Zr-depleted rutile and submicron-thick zircon coronas during further exhumation and cooling. We also observed hat-shaped grains that are composed of preexisting zircon overgrown by zircon coronas during stage (2). Hat-shaped grains have a flat surface towards the oxide phase, which indicates partial dissolution of preexisting zircon grain. Formation of vermicular zircon (1) preceded ductile and brittle deformation of the host rock, as vermicular zircon is found both plastically- and cataclastically-deformed. Formation of thin zircon coronas (2) was coeval with or soon after the brittle deformation, as coronas occasionally fill fractures in the host rock. Occurrences of zircon coronas has important implications in fundamental studies regarding metamorphism, metasomatism and element transport in the Earth’s crust. We demonstrate that metamorphic zircon can nucleate and grow as a result of hydration reactions at the cooling stage after granulite-facies metamorphism, and reflects stages of rock evolution. Zircon corona textures are the tool for indicating metamorphic and metasomatic reactions in the host rock, and establish the directions of the reaction front.

show abstract

On the geometric relationship between deformation microstructures in zircon and the kinematic framework of the shear zone

Cited by 12 publications

References 73 publications

Interpretation of zircon coronae textures from metapelitic granulites of the Ivrea–Verbano Zone, northern Italy: two-stage decomposition of Fe–Ti oxides

Interpretation of zircon coronae textures from metapelitic granulites of the Ivrea–Verbano Zone, northern Italy: two-stage decomposition of Fe–Ti oxides

A pressure-temperature phase diagram for zircon at extreme conditions

Interpretation of zircon corona textures from metapelitic granulites of Ivrea-Verbano Zone, Northern Italy: Two-stage decomposition of Fe-Ti oxides

Contact Info

Product

Resources

About