<p>Pb–Zn–Ba–Sr–F mineralization hosted by the Albian–Aptian carbonates of Hameimat North and Hameimat South massifs is an example of many peridiapiric deposits of the ‘Diapir Zone’ of the Eastern Saharan Atlas, Algeria. In this area, the mineralization develops either at the contact between the Triassic diapiric evaporite bodies and the Creatceous sedimentary cover or along the tectonic faults and karstic cavities within these Albian–Aptian often reef limestones. At Hameimat massifs, the mineralization consists of abundant barite and galena, and minor sphalerite, celestine and fluorite. Gangue minerals are composed of calcite, dolomite and rare quartz. Stable S, C and O isotope analyses were caried out on sulphur-bearing phases and gangue carbonates to shed more light on the genesis and the nature of the mineralizing fluids. Sulphur isotopic data from the Triassic gypsum (δ³⁴S_V−CDT), which range from + 13.4 to + 15.1‰, are similar to those obtained from regional Triassic evaporites, and are consistent with the values of Triassic seawater sulphates worldwide. Sulphur of the barite and celestine minerals display higher δ³⁴S_V−CDT values, varying between + 18 and + 24‰, whereas sulphide phases (galena and sphalerite) exhibit lower δ³⁴S values (between − 2.2 and + 10.4‰) than those of the Triassic sulphates. This most likely points to the derivation of sulphide-derived sulphur from Triassic sulphates through thermochemical sulphate reduction, a process supported by existing fluid inclusion data. The C and O isotopic compositions of the host carbonates (δ¹³C_V−PDB = + 0.2 to + 4.7‰; δ¹⁸O_V−SMOW = + 20.6 to + 23.1‰) reflect an inorganic carbon source and oxygen derived from fluid-rock interactions. Combined isotopic and metallographic evidence indicates that the ore-forming fluids originated from deep-seated brines. The ore isotopic signatures resemble those obtained on the Mississippi Valley-type deposits.</p>