Au-Pd Mineralization and Ore-Forming Fluids of the Bleida Far West Deposit (Anti-Atlas, Morocco)

The Au-Pd mineralization of the Bleida Far West deposit, which is represented by an unusual association of palladium gold and minerals of the Pd-Bi-Se system, as well as silvery gold and minerals of the Pd-Bi-Te system, is investigated. The deposit is localized in the Neoproterozoic volcanic rocks of the Central Anti-Atlas (Morocco). The chemical analysis of minerals was carried out at the Center for Collective Use of Multielement and Isotopic Studies of the Siberian Branch of the Russian Academy of Sciences (Novosibirsk, Russia) using the method of electron-probe microanalysis (EPMA). Fluid inclusions were by means of using cryometry and homogenization using a THMSG-600 microthermochamber. The composition of the gas phase and the solid phases of the inclusions were determined by Raman spectroscopy. The qualitative chemical composition of fluid-inclusion salts was determined by the EPMA method. It is suggested that palladium gold and minerals of the Pd-Bi-Se system were formed under conditions close to the conditions of formation of Au-Pd infiltration deposits in Brazil, while silvery gold and minerals of the Pd-Bi-Te system may have been formed under conditions that are similar, but not identical, to the formation conditions of Au-Pd low-temperature mineralization in porphyry deposits. According to the study of fluid inclusions in quartz and calcite, Au-Pd mineralization took place at temperatures from 384 to 75 degrees C with the participation of homogeneous or heterophasic CaCl2-NaCl highly saline hydrothermal solutions at a depth of 2.8-2.7 km. Minerals of the Pd-Bi-Se system previously unknown in Bleida Far West ores were found in association with native gold: oosterboschite (Pd, Cu)(7)Se-5, paladsite (Pd17Se15), padmaite PdBiSe, native Se, and unnamed phases Pd3BiSe and (Au,Ag)Se, as well as a number of unidentified phases-Pd2BiSe, Pd3BiSe, Pd4BiSe, and Pd5BiSe.