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<p>Metasedimentary rocks consisting of layered metapelites, quartzites, and calc-silicates in the northwestern Gyeonggi Massif underwent metamorphism and deformation during the Permian–Triassic. As a result, they provide insights into a subduction- and exhumation-related collisional orogeny. However, the metamorphic pressure–temperature–time (<i>P–T</i>–<i>t</i>) paths of the metapelites and calc-silicates remain poorly constrained. Based on petrographic observations, <i>P–T</i>–<i>X</i><sub>CO2</sub> (CO<sub>2</sub>/[CO<sub>2</sub> + H<sub>2</sub>O]) modeling, and detrital zircon U–Pb ages, the estimated peak metamorphic <i>P–T</i> conditions of the garnet-biotite schist, kyanite-staurolite-garnet schist, and scapolite-diopside calc-silicate rocks were 7.7–9.2 kbar/560–575&#xa0;°C, 7.0–9.0 kbar/625–670&#xa0;°C, and 6.2–7.5 kbar/550–575&#xa0;°C (at <i>X</i><sub>CO2</sub> = 0.05), respectively, during the Middle Triassic (244–239&#xa0;Ma). Subsequently, both the metapelites and calc-silicates underwent retrograde metamorphism at ~ 4 kbar and ~ 500&#xa0;°C. The metapelites and calc-silicates in the northwestern Gyeonggi Massif underwent a clockwise <i>P–T</i>–<i>t</i> path under amphibolite- and greenschist-facies conditions, accompanied by shearing and folding during the Permian–Triassic collisional orogeny. This evolution is almost identical to that experienced by the Neoproterozoic–Devonian metasedimentary rocks in the Hongseong–Imjingang Belt.</p>

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The pressure–temperature–time path of metasedimentary rocks during the Permian–Triassic collisional orogeny along the northwestern margin of the Gyeonggi Massif, South Korea

  • 期刊论文

  • 发表日期：

    2025年2月17日

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  • Jeongmin Lee,
  • Hyeong Soo Kim

摘要

Metasedimentary rocks consisting of layered metapelites, quartzites, and calc-silicates in the northwestern Gyeonggi Massif underwent metamorphism and deformation during the Permian–Triassic. As a result, they provide insights into a subduction- and exhumation-related collisional orogeny. However, the metamorphic pressure–temperature–time (P–T–t) paths of the metapelites and calc-silicates remain poorly constrained. Based on petrographic observations, P–T–XCO2 (CO2/[CO2 + H2O]) modeling, and detrital zircon U–Pb ages, the estimated peak metamorphic P–T conditions of the garnet-biotite schist, kyanite-staurolite-garnet schist, and scapolite-diopside calc-silicate rocks were 7.7–9.2 kbar/560–575 °C, 7.0–9.0 kbar/625–670 °C, and 6.2–7.5 kbar/550–575 °C (at XCO2 = 0.05), respectively, during the Middle Triassic (244–239 Ma). Subsequently, both the metapelites and calc-silicates underwent retrograde metamorphism at ~ 4 kbar and ~ 500 °C. The metapelites and calc-silicates in the northwestern Gyeonggi Massif underwent a clockwise P–T–t path under amphibolite- and greenschist-facies conditions, accompanied by shearing and folding during the Permian–Triassic collisional orogeny. This evolution is almost identical to that experienced by the Neoproterozoic–Devonian metasedimentary rocks in the Hongseong–Imjingang Belt.