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<p>The present study focuses on characterizing the different types of alteration, and the nature and origin of the fluids responsible for the deposition of Pb-Zn-Ba ores of three representative deposits in the Diapir Zone of northeastern Algeria. Petrographic and mineralogical data from the Ain Mimoun, Mesloula and Hameimat Nord ore deposits reveal two main phases of dolomitization: a replacement phase and a dolomitic cementation phase. The dolomitization process is accompanied by later ankeritization, locally followed by episodes of silicification and calcitization. These alterations gradually decrease with increasing distance from the Pb-Zn-Ba ore bodies towards the fresh host rocks. The studied hydrothermal carbonate minerals show high Sr contents in calcite III and ankerite from Ain Mimoun (619.66–1327.8 ppm) and Hameimat Nord (781.36–1116.3 ppm), indicating an Sr-enriched mineralizing fluid that locally deposited gangue celestite (SrSO₄) in these deposits. The enrichment in Zn, Cu, and Pb observed in ankerite samples from Ain Mimoun and calcite from Mesloula reflects the Zn-, Cu- and Pb-enriched fluids that deposited base-metal mineralization (galena, sphalerite and tennantite) in these localities. The δ¹³C values of the whole rock limestones in the three sites suggest a marine origin for carbon; whereas δ¹⁸O values (+ 24.2‰ to + 27.3‰) fall within to the isotopic composition range of the fresh Aptian-Albien facies in all the diapir zone of Algeria and Tunisia. The range of δ¹³C values observed in the hydrothermal calcite, dolomite and ankerite (varying between − 4 and + 4‰) remain within the range of marine carbonates, while the moderately low δ¹⁸O values (+ 18 to 24‰) compared to the host limestones reflect the influence of hydrothermal fluids, which are characterized by markedly low δ¹⁸O values (between + 9 and + 13‰), with the lowest values recoded in earliest hydrothermal carbonate minerals formed (dolomite), then ankerite and finally calcite showing the highest values. This study highlights the relevance of the present multidisciplinary approach in determining the origin, nature, and evolution of the fluids involved in the observed hydrothermal alterations in the MVT-like peridiapiric ore deposits of Eastern Saharan Atlas.</p>

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Hydrothermal alteration features of the peridiapiric Pb-Zn-Ba deposits of Northeastern Algeria: Geochemical approach and stable C- and O-isotope study

  • 期刊论文

  • 发表日期：

    2026年3月4日

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  • Houssem Metrouni,
  • Rabah Laouar,
  • Rabah Zedam,
  • Salah Bouhlel,
  • Ali Tlili

摘要

The present study focuses on characterizing the different types of alteration, and the nature and origin of the fluids responsible for the deposition of Pb-Zn-Ba ores of three representative deposits in the Diapir Zone of northeastern Algeria. Petrographic and mineralogical data from the Ain Mimoun, Mesloula and Hameimat Nord ore deposits reveal two main phases of dolomitization: a replacement phase and a dolomitic cementation phase. The dolomitization process is accompanied by later ankeritization, locally followed by episodes of silicification and calcitization. These alterations gradually decrease with increasing distance from the Pb-Zn-Ba ore bodies towards the fresh host rocks. The studied hydrothermal carbonate minerals show high Sr contents in calcite III and ankerite from Ain Mimoun (619.66–1327.8 ppm) and Hameimat Nord (781.36–1116.3 ppm), indicating an Sr-enriched mineralizing fluid that locally deposited gangue celestite (SrSO₄) in these deposits. The enrichment in Zn, Cu, and Pb observed in ankerite samples from Ain Mimoun and calcite from Mesloula reflects the Zn-, Cu- and Pb-enriched fluids that deposited base-metal mineralization (galena, sphalerite and tennantite) in these localities. The δ¹³C values of the whole rock limestones in the three sites suggest a marine origin for carbon; whereas δ¹⁸O values (+ 24.2‰ to + 27.3‰) fall within to the isotopic composition range of the fresh Aptian-Albien facies in all the diapir zone of Algeria and Tunisia. The range of δ¹³C values observed in the hydrothermal calcite, dolomite and ankerite (varying between − 4 and + 4‰) remain within the range of marine carbonates, while the moderately low δ¹⁸O values (+ 18 to 24‰) compared to the host limestones reflect the influence of hydrothermal fluids, which are characterized by markedly low δ¹⁸O values (between + 9 and + 13‰), with the lowest values recoded in earliest hydrothermal carbonate minerals formed (dolomite), then ankerite and finally calcite showing the highest values. This study highlights the relevance of the present multidisciplinary approach in determining the origin, nature, and evolution of the fluids involved in the observed hydrothermal alterations in the MVT-like peridiapiric ore deposits of Eastern Saharan Atlas.