Detailed mineralogy and geochemistry of manganese oxyhydroxide deposits of the Tizi-n-Isdid district

The Tizi-n-Isdid manganese deposit, located between the Central Anti-Atlas and the Ounein High Atlas in Morocco, represents a significant stratiform Mn occurrence with low-to-medium ore grades (8–32 wt.% Mn). The mineralization occurs within reddish-brown claystones at the base of the Taroudant Group (Tabia Member), beneath the Tamjout dolomite, and is assigned a Lower Cambrian age (529–541 Ma) (AFLLA et al., 2025). It extends over about 6 km north–south, exhibiting stratiform to lenticular geometry with three facies: massive (F1), banded (F2, dominant), and brecciated (F3).

Mineralogical and geochemical analyses, including new X-ray diffraction data from 14 samples, refine the paragenetic and genetic model (Aflla et al., 2025). The ore assemblage is dominated by braunite (Mn²⁺Mn³⁺₆SiO₁₂), associated with piemontite, hollandite-group minerals, jacobsite, rhodochrosite, and kutnohorite, while pyrolusite represents a secondary oxidation phase. The gangue mainly consists of quartz, calcite, and minor barite, with muscovite and illite in the altered host rock.

Geochemical correlations between Al₂O₃–Zr (r = 0.66), Fe₂O₃–Zr (r = 0.89), and TiO₂–Zr (r = 0.85) indicate a mafic terrigenous contribution. Co/Ni ratios > 1 and REE data showing HREE enrichment, positive Eu and Ce anomalies, and weak ∑LREE/∑HREE correlation (r = 0.30) suggest a marine hydrothermal Sedex-type system. The paragenetic sequence includes four stages: (1) pre-ore silicification, (2) Mn mineralization with silicification, (3) carbonatation, and (4) late Mn oxidation.

These results indicate syn-sedimentary hydrothermal activity related to rift-associated faulting rather than direct volcanism. The Tizi-n-Isdid deposit provides a representative model for stratiform manganese mineralization within the Ouarzazate Manganese Field.