Abstract
The mining district of Nefza-Sejnane (Tunisia) encloses numerous ores and raw material deposits, all formed in relation with successive Fe-rich fluids of meteoric and/or hydrothermal origins. Here, for the first time in Tunisia, (U-Th)/He ages were obtained on supergene goethite from various localities/deposits of the district highlight direct dating of significant weathering episodes during late Tortonian and late Pleistocene. These weathering events are most likely associated with favorable conditions that combine (i) wet climate displaying sufficient meteoric water/fluid; and (ii) regional exhumation, due to large-scale vertical lithospheric movements enhancing the percolation of fluids. Matched with previous works, these results refine the stratigraphic frame for the polymetallic mineralization and clay deposits in the district, confirming the influence of meteoric fluids circulation during the late Cenozoic. As a consequence of the new (U-Th)/He data, we moreover propose a taxonomic and stratigraphic revision of the well-known mammalian fauna from the Fe-rich Douahria locality, suggesting an early Tortonian age for the fossils, i.e., prior to the first episode of meteoric event in the area.
Highlights
Well-crystallized goethite with botryoidal texture (Figure 3A,B) that formed during the pedogenesis affecting the Tamra Formation [4]
Tamra and Boukchiba goethite is better than the 10% error estimated to account for He the present data. diffusion
The new (U-Th)/He ages obtained on goethite in the mineralized and vertebratebearing sediments of the Nefza-Sejnane district (Tunisia) highlight that:
Summary
Licensee MDPI, Basel, Switzerland.Attribution (CC BY) license (https://creativecommons.org/licenses/by/ 4.0/).The mining district of Nefza-Sejnane contains numerous ores and raw material deposits, including the Zn–Pb mineralization of Sidi Driss, the vertebrate-bearing Douahria basin that hosts a SEDEX deposit [1], the halloysite-bearing iron deposit of Tamra Formation [2,3,4,5], the Fe-LREE-U enriched breccia of Oued Belif [5], and kaolinitic clays of the late Oligocene Numidian Flysch Formation [6,7]; (Figures 1 and 2). From the Miocene onwards, these deposits experienced successive circulations of Fe-rich fluids of mixed meteoric and hydrothermal origins. The hydrothermal activity resulted from a relatively high geothermal gradient and Miocene magmatic rocks of the area [8]. Using geochemical
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