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<p>K–Ar dating of fine-grained fractions from metasedimentary rocks is a powerful tool for reconstructing the tectono-thermal evolution across the brittle–ductile transition. In particular, it enables the identification of white mica growth episodes, which, in deformed rocks, can be linked with tectono-metamorphic events. In southern Patagonia, poly-deformed Carboniferous slates are unconformably overlain by Upper Jurassic volcanic rocks, revealing a hiatus of 180–160 My in the geologic record. Therefore, constraining the timescales of pre-Jurassic orogenic construction in southern Patagonia is crucial for establishing correlations with neighboring regions (e.g., northern Patagonia, the Deseado Massif, and the Antarctic Peninsula), although geochronological data remain scarce. To address this issue, we conducted a study combining K–Ar dating in metasedimentary rocks with illite crystallographic characterization obtained through X-ray diffraction analysis. The results presented here allow us to identify two main stages of fold–thrust belt activity: a first stage during the Permian (290–260&#xa0;Ma), followed by a second one during the Late Triassic (230–215&#xa0;Ma). These deformation stages are interpreted in the framework of a two-stage, polyphase deformation, corresponding to the late Paleozoic Gondwanide and early Mesozoic Chonide orogenies, respectively, both of which are part of the broader geodynamic framework of the Terra Australis Orogen.</p> Graphical abstract <p></p>

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White mica K–Ar geochronology reveals late Paleozoic–early Mesozoic tectono-thermal evolution of southern Patagonia (South America)

  • 期刊论文

  • 发表日期：

    2026年5月14日

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  • Rodrigo J. Suárez,
  • Klaus Wemmer,
  • Mathias Hueck,
  • Sebastián Oriolo,
  • Pablo D. González,
  • Claudia B. Zaffarana,
  • Matías Ghiglione,
  • Miguel Ramos,
  • Juan Albano

摘要

K–Ar dating of fine-grained fractions from metasedimentary rocks is a powerful tool for reconstructing the tectono-thermal evolution across the brittle–ductile transition. In particular, it enables the identification of white mica growth episodes, which, in deformed rocks, can be linked with tectono-metamorphic events. In southern Patagonia, poly-deformed Carboniferous slates are unconformably overlain by Upper Jurassic volcanic rocks, revealing a hiatus of 180–160 My in the geologic record. Therefore, constraining the timescales of pre-Jurassic orogenic construction in southern Patagonia is crucial for establishing correlations with neighboring regions (e.g., northern Patagonia, the Deseado Massif, and the Antarctic Peninsula), although geochronological data remain scarce. To address this issue, we conducted a study combining K–Ar dating in metasedimentary rocks with illite crystallographic characterization obtained through X-ray diffraction analysis. The results presented here allow us to identify two main stages of fold–thrust belt activity: a first stage during the Permian (290–260 Ma), followed by a second one during the Late Triassic (230–215 Ma). These deformation stages are interpreted in the framework of a two-stage, polyphase deformation, corresponding to the late Paleozoic Gondwanide and early Mesozoic Chonide orogenies, respectively, both of which are part of the broader geodynamic framework of the Terra Australis Orogen.

Graphical abstract