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Pegmatites are considered the most differentiated rocks on Earth. They are mainly acidic rocks rich in quartz, feldspars, micas, and other accessory minerals that may be of economic interest. The pegmatites of Sidi Bou Othmane are a good example and have never been the object of any geological studies. The present work is, therefore, to show for the first time the geophysical, petrographic, geodynamic, and metallogenic features of these rocks. Based on field investigation three generations of pegmatite dykes have been observed. The area of Sidi Bou Othmane is a sector where pegmatites outcrop in the form of N-S-, NNE-SSW-, NE-SW-, and E-W-oriented decimetric to decametric dykes. These dykes are generally deformed (folded, fractured, schistose, and altered) and exhibit pre-, syn- and post-tectonic signatures. The fieldwork has revealed the relationships and chronology between the different dykes of pegmatite at Sidi Bou Othmane. The N-S; NNE-SSW direction is the oldest pegmatite dykes and is cross-cut by the E-W direction, which in itself is cross-cut by the N40 pegmatite dykes. The geophysical observation, using the electrical resistivity method, shows that the pegmatitic dykes extend at a depth of 24–28 m, and bring out an anomaly which can be the signature of the magmatic intrusion from a depth of 13 m. The mineralogy of collected samples shows a granitic composition. Feldspar is the most abundant mineral, followed by quartz, micas, tourmaline, and accessory minerals, such as garnet, zircon, apatite, cassiterite, and columbo-tantalite. The mineralogical study, completed by X-ray diffraction and microscopic observation, shows three facies’ varieties: (a) quartz, illite, and muscovite; (b) quartz, illite, albite, and muscovite; and (c) quartz, albite, muscovite, microcline, and clinochlore. We have classified this pegmatite in the Li-Cs-Ta (LCT) family, which is enriched in Li, Cs, and Ta. Petrographic observations and geochemical characteristics of these pegmatites enabled us to categorize them as lithium rare-element pegmatites (REL-LCT).

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Unveiling the Geophysical and Petrographic Signatures of Sidi Bou Othmane Pegmatites (Central Jebilet): A Preliminary Study on Their Geodynamic and Metallogenic Features

  • 会议论文

  • 发表日期：

    2025年

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  • Amina Wafik,
  • Nouamane El Aouad,
  • Wissale Aba Sidi,
  • Abdelali Fadil

摘要

Pegmatites are considered the most differentiated rocks on Earth. They are mainly acidic rocks rich in quartz, feldspars, micas, and other accessory minerals that may be of economic interest. The pegmatites of Sidi Bou Othmane are a good example and have never been the object of any geological studies. The present work is, therefore, to show for the first time the geophysical, petrographic, geodynamic, and metallogenic features of these rocks. Based on field investigation three generations of pegmatite dykes have been observed. The area of Sidi Bou Othmane is a sector where pegmatites outcrop in the form of N-S-, NNE-SSW-, NE-SW-, and E-W-oriented decimetric to decametric dykes. These dykes are generally deformed (folded, fractured, schistose, and altered) and exhibit pre-, syn- and post-tectonic signatures. The fieldwork has revealed the relationships and chronology between the different dykes of pegmatite at Sidi Bou Othmane. The N-S; NNE-SSW direction is the oldest pegmatite dykes and is cross-cut by the E-W direction, which in itself is cross-cut by the N40 pegmatite dykes. The geophysical observation, using the electrical resistivity method, shows that the pegmatitic dykes extend at a depth of 24–28 m, and bring out an anomaly which can be the signature of the magmatic intrusion from a depth of 13 m. The mineralogy of collected samples shows a granitic composition. Feldspar is the most abundant mineral, followed by quartz, micas, tourmaline, and accessory minerals, such as garnet, zircon, apatite, cassiterite, and columbo-tantalite. The mineralogical study, completed by X-ray diffraction and microscopic observation, shows three facies’ varieties: (a) quartz, illite, and muscovite; (b) quartz, illite, albite, and muscovite; and (c) quartz, albite, muscovite, microcline, and clinochlore. We have classified this pegmatite in the Li-Cs-Ta (LCT) family, which is enriched in Li, Cs, and Ta. Petrographic observations and geochemical characteristics of these pegmatites enabled us to categorize them as lithium rare-element pegmatites (REL-LCT).