The P–T path of eclogites in the St. Cyr klippe, Yukon, Canada: Permian metamorphism of a coherent high-pressure unit in an accreted terrane of the North American Cordillera

Petrie, Meredith Blair; Massonne, Hans‐Joachim; Gilotti, Jane A.; McClelland, William C.; Staal, Cees van

doi:10.1127/ejm/2016/0028-2576

Cited by 17 publications

(13 citation statements)

References 62 publications

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“…For example, breakdown of chlorite and lawsonite can release water and oxygen (e.g., Ferrando, Frezzotti, Petrelli, & Compagnoni, 2009;Groppo & Castelli, 2010), which tend to leave the system. The incorporation of Fe 3+ will influence the P-T field of minerals such as clinopyroxene, amphibole, and epidote (Diener & Powell, 2010;Petrie, Massonne, Gilotti, McClelland, & Van Staal, 2016;White, Powell, Holland, & Worley, 2000), thus a reasonable estimation of the true Fe 3+ content in the bulk rock is important. A small amount of K is mainly hosted by mica, and to a lesser extent by amphibole and feldspar; therefore, K 2 O is retained in the calculations.…”

Section: Analytical Resultsmentioning

confidence: 99%

Partial melting due to breakdown of an epidote‐group mineral during exhumation of ultrahigh‐pressure eclogite: An example from the North‐East Greenland Caledonides

Cao

Gilotti

Massonne

et al. 2018

Journal Metamorphic Geology

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In the North‐East Greenland Caledonides, P–T conditions and textures are consistent with partial melting of ultrahigh‐pressure (UHP) eclogite during exhumation. The eclogite contains a peak assemblage of garnet, omphacite, kyanite, coesite, rutile, and clinozoisite; in addition, phengite is inferred to have been present at peak conditions. An isochemical phase equilibrium diagram, along with garnet isopleths, constrains peak P–T conditions to be subsolidus at 3.4 GPa and 940°C. Zr‐in‐rutile thermometry on inclusions in garnet yields values of ~820°C at 3.4 GPa. In the eclogite, plagioclase may exhibit cuspate textures against surrounding omphacite and has low dihedral angles in plagioclase–clinopyroxene–garnet aggregates, features that are consistent with former melt–solid–solid boundaries and crystallized melt pockets. Graphic intergrowths of plagioclase and amphibole are present in the matrix. Small euhedral neoblasts of garnet against plagioclase are interpreted as formed from a peritectic reaction during partial melting. Polymineralic inclusions of albite+K‐feldspar and clinopyroxene+quartz±kyanite±plagioclase in large anhedral garnet display plagioclase cusps pointing into the host, which are interpreted as crystallized melt pockets. These textures, along with the mineral composition, suggest partial melting of the eclogite by reactions involving phengite and, to a large extent, an epidote‐group mineral. Calculated and experimentally determined phase relations from the literature reveal that partial melting occurred on the exhumation path, at pressures below the coesite to quartz transition. A calculated P–T phase diagram for a former melt‐bearing domain shows that the formation of the peritectic garnet rim occurred at 1.4 GPa and 900°C, with an assemblage of clinopyroxene, amphibole, and plagioclase equilibrated at 1.3 GPa and 720°C. Isochemical phase equilibrium modelling of a symplectite of clinopyroxene, plagioclase, and amphibole after omphacite, combined with the mineral composition, yields a P–T range at 1.0–1. 6 GPa, 680–1,000°C. The assemblage of amphibole and plagioclase is estimated to reach equilibrium at 717–732°C, calculated by amphibole–plagioclase thermometry for the former melt‐bearing domain and symplectite respectively. The results of this study demonstrate that partial melt formed in the UHP eclogite through breakdown of an epidote‐group mineral with minor involvement of phengite during exhumation from peak pressure; melt was subsequently crystallized on the cooling path.

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Section: Analytical Resultsmentioning

confidence: 99%

Partial melting due to breakdown of an epidote‐group mineral during exhumation of ultrahigh‐pressure eclogite: An example from the North‐East Greenland Caledonides

Cao

Gilotti

Massonne

et al. 2018

Journal Metamorphic Geology

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“…Previous studies recorded amphibolite-to eclogite-facies metamorphism in YTT during the mid-Permian-Middle Triassic and the latest Triassic-Early Jurassic (Fig. 10A) (e.g., Berman et al, 2007;Petrie et al, 2016;Staples et al, 2016;Clark, 2017;Gilotti et al, 2017;Morneau et al, 2017). Minimum temperature estimates for D2 deformation (~540-440 °C) are greater than or approximately equal to the closure temperature for Ar loss in muscovite (380-450 °C, Harrison et al, 2009).…”

Section: Timing Constraints and Tectonic Significance Of The Yrsz: A mentioning

confidence: 86%

“…262 Ma suggests that YTT underwent lithospheric extension at that time, synchronous with emplacement of the Sulphur Creek suite (Johnston et al, 2007;Parsons et al, 2018;van Staal et al, 2018). If D2 deformation initiated during Late Permian-Middle Triassic metamorphism (e.g., Creaser et al, 1997;Villeneuve et al, 2003;Staples, 2014;Petrie et al, 2016;Gilotti et al, 2017), then the available constraints suggest that top-ESE shearing on the YRSZ occurred during lithospheric extension ( Fig. 10A).…”

Section: Timing Constraints and Tectonic Significance Of The Yrsz: A mentioning

confidence: 99%

“…Polyphase amphibolite-to eclogite-facies metamorphism recorded by the YTT continental basement occurred during the mid-Permian to Middle Triassic, latest Triassic-Early Jurassic, and Late Jurassic-Early Cretaceous (e.g., Dusel-Bacon et al, 1995;Creaser et al, 1997;Berman et al, 2007;Staples, 2014;Petrie et al, 2016;Staples et al, 2016;Clark, 2017;Gilotti et al, 2017;Morneau et al, 2017). Each of these metamorphic events was followed by rapid cooling (e.g., Dusel-Bacon et al, 2002;Knight et al, 2013;Staples et al, 2016;Parsons et al, 2018).…”

Section: Regional Geology: the Yukon-tanana Terranementioning

confidence: 99%

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Structural evolution of a crustal-scale shear zone through a decreasing temperature regime: The Yukon River shear zone, Yukon-Tanana terrane, Northern Cordillera

et al. 2018

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We present the first detailed structural analysis of the Yukon River shear zone (YRSZ), which forms an important structural break within the Yukon-Tanana terrane of the Northern Cordillera in Yukon (Canada). The YRSZ is a NW-SE-striking shear zone that juxtaposes Mississippian orthogneiss hanging-wall rocks (Simpson Range suite) against preLate Devonian metasedimentary footwall rocks (Snowcap assemblage). Field and microstructural analyses, including quartz c-axis fabric investigation, indicate that the YRSZ initiated as a top-ESE mid-crustal shear zone active through a temperature range of ≥650-500 °C to ~540-440 °C. Constraints from the footwall associated with top-ESE shearing on the YRSZ at mid-crustal conditions record a decrease in deformation temperature toward the shear zone, coincident with a transition from coaxial to non-coaxial deformation and an increase in fabric intensity, strain rate, and differential stress estimates. Collectively, these spatial trends represent a classic example of a narrowing shear zone that progressively localizes and intensifies deformation as ambient temperature decreases. U-Pb zircon geochronometry of a deformed Permian orthogneiss from within the YRSZ combined with previously published thermochronometry bracket the timing of top-ESE mid-crustal shearing between 259 ± 2 Ma and 176-168 Ma, either during Late Permian-Middle Triassic metamorphism and lithospheric extension or latest Triassic-Early Jurassic metamorphism and crustal thickening. The YRSZ was subsequently reactivated as a top-WNW upper-crustal thrust fault zone during or after Early to Middle Jurassic cooling and exhumation at 176-168 Ma. This top-WNW thrusting within the YRSZ may be responsible for structural separation of Late Triassic and Early Jurassic plutonic rocks in the hanging wall of the YRSZ from Permian plutonic rocks in its footwall.

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“…Erdmer et al (1998), Berman et al (2007), Mihalynuk et al (2006), Devine et al (2006) Middle to late Permian (ca. 270-250) Greenschist -Amphibolite; Eclogite Subduction and collision with Laurentia Petrie et al (2016), Creaser et al (1997), Philippot et al (2001), Beranek and Mortensen (2011) Middle Triassic (ca. 240 Ma) Hornblende Hornfels -Upper Amphibolite Intra-arc shortening or extension Berman et al (2007), Gaidies et al (2020) Early Jurassic (ca.…”

Section: Sample Locationsmentioning

confidence: 99%

The Early Jurassic Metamorphic History of the Yukon-Tanana Terrane of Northwestern British Columbia: Insights from a New Inverse Garnet Fractionation Modelling Technique

Dyer¹

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The P–T path of eclogites in the St. Cyr klippe, Yukon, Canada: Permian metamorphism of a coherent high-pressure unit in an accreted terrane of the North American Cordillera

Cited by 17 publications

References 62 publications

Partial melting due to breakdown of an epidote‐group mineral during exhumation of ultrahigh‐pressure eclogite: An example from the North‐East Greenland Caledonides

Partial melting due to breakdown of an epidote‐group mineral during exhumation of ultrahigh‐pressure eclogite: An example from the North‐East Greenland Caledonides

Structural evolution of a crustal-scale shear zone through a decreasing temperature regime: The Yukon River shear zone, Yukon-Tanana terrane, Northern Cordillera

The Early Jurassic Metamorphic History of the Yukon-Tanana Terrane of Northwestern British Columbia: Insights from a New Inverse Garnet Fractionation Modelling Technique

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