Mineralization and fluid inclusion characteristics of Pb-Zn-Fe-Ba (Cu, F, Sr) ore-deposits in northern east of Algeria

Abstract

The northern east of Algeria represents the most important metallogenic zone for Pb-Zn-Fe-Ba (Cu, F, Sr) ore-deposits. The mineral association consists of galena, sphalerite, barite, and celestite with gray copper, pyrite, chalcopyrite, and marcasite associated with a carbonate (dolomite and calcite) matrix. Quartz, siderite, fluorite, and oxidation products like hematite, limonite, magnetite, smithsonite, and hydrozincite are also abundant. The ore-bodies are hosted in carbonate sedimentary rocks of lower Cretaceous, from Hauterivian to Aptian. Mineralization is mainly in vein fillings in fractures and in epigenetic lenticular or strata-bound ores. Most of the ore-bodies are structurally controlled by NE-SW-, NW-SE-, and E-W-trending faults, localized along the margins of subsiding sedimentary basins and diapiric zones, either inside hinges or on the flanks of anticlinal structures. Micro-thermometric data from sphalerite, dolomite, fluorite, quartz, calcite, and barite samples show relatively high temperatures, varying between 90 and 160°C. Salinity is variable, generally with high values (between 10 and 29.92 wt% NaCl equiv). These results combined to geological and metallogenic observations suggest an epigenetic origin for these mineral deposits. The saline fluids responsible for mineralization are related to basin fluids (formation water), which are classified as Mississippi Valley type (MVT), diluted locally by meteoric water. Eutectic temperatures measured in the fluid inclusions indicate an H2O-NaCl-CaCl2 system. The presence and variability of Na+ and Ca++ in the aqueous solutions suggest interaction with host rocks (contamination by dissolution respectively of Triassic gypsum and carbonate formations).