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<p>Calcareous rocks of the southern Jabal Akhdar Dome (JAD), Oman, have experienced multiple geological processes, yet maximum overprinting temperatures were previously estimated below ~250&#xa0;°C. Our discovery of wollastonite-carrying metalimestone layers and veins indicates localized heating exceeding these conditions. Structural, petrographical, geochemical analyses (XRF), and thermodynamic modelling were employed to investigate the respective metasomatic event. Wollastonite is associated with NW-striking faults and vein systems within Jurassic to Lower Cretaceous strata, which likely formed during late Eocene–early Miocene doming of the JAD and/or Arabia–India shortening. Wollastonite and dolomite occur as isolated grains and clusters, concentrated in layers between sterile strata. Evidence for hydrothermal fluid flow from a localized source (intrusion) includes: (i) wollastonite also present in veins and (ii) positive correlations between wollastonite and typical hydrothermal elements, such as Fe, Pb, and Zn. Thermodynamic modelling indicates formation temperatures of 380–420&#xa0;°C and requires Si-rich fluids. Collectively, these observations point to an unexposed, previously unrecognized intrusion, revealing a new aspect of the geological and magmatic evolution of the JAD.</p> Graphical abstract <p>The simplified model (not to scale) on the right shows the proposed intrusion in the limestones, a possible contact metamorphicwollastonite-rich aureole, and the locations of outcropping wollastonite emplacement within limestone layers and veins. Themicroscope image on the left displays the fabric of the limestone with some euhedral wollastonite crystals.</p> <p></p>

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Metasomatism on Jabal Akhdar (Sultanate of Oman): evidence for post-obduction intrusion-related fluids in platform carbonates

  • 期刊论文

  • 发表日期：

    2025年10月31日

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  • Bernhard Pracejus,
  • Andreas Scharf,
  • Frank Mattern

摘要

Calcareous rocks of the southern Jabal Akhdar Dome (JAD), Oman, have experienced multiple geological processes, yet maximum overprinting temperatures were previously estimated below ~250 °C. Our discovery of wollastonite-carrying metalimestone layers and veins indicates localized heating exceeding these conditions. Structural, petrographical, geochemical analyses (XRF), and thermodynamic modelling were employed to investigate the respective metasomatic event. Wollastonite is associated with NW-striking faults and vein systems within Jurassic to Lower Cretaceous strata, which likely formed during late Eocene–early Miocene doming of the JAD and/or Arabia–India shortening. Wollastonite and dolomite occur as isolated grains and clusters, concentrated in layers between sterile strata. Evidence for hydrothermal fluid flow from a localized source (intrusion) includes: (i) wollastonite also present in veins and (ii) positive correlations between wollastonite and typical hydrothermal elements, such as Fe, Pb, and Zn. Thermodynamic modelling indicates formation temperatures of 380–420 °C and requires Si-rich fluids. Collectively, these observations point to an unexposed, previously unrecognized intrusion, revealing a new aspect of the geological and magmatic evolution of the JAD.

Graphical abstract

The simplified model (not to scale) on the right shows the proposed intrusion in the limestones, a possible contact metamorphicwollastonite-rich aureole, and the locations of outcropping wollastonite emplacement within limestone layers and veins. Themicroscope image on the left displays the fabric of the limestone with some euhedral wollastonite crystals.