Non-sulfide Zn deposits in the Moroccan High Atlas

Abstract

International audienceWe have investigated six Zn non-sulfide ore deposits (also called " calamines ") from the Moroccan High Atlas, in order to understand processes and timing of their formation. Structural field observations have revealed a genetic link between regional faulting and cavities filled by ores. Based on our mineralogical investigation, we propose the following stages: 1) formation of the protore sulfides, 2) early supergene weathering with formation of Zn-Pb-bearing carbonates and iron oxi-hydroxides and 3) late supergene weathering with deposition of Zn-carbonates and silicates. Direct replacement of primary sulfides is the dominant process. A complementary rock magnetism study shows similar horizontal magnetic fabrics for calamines and internal sediments. Isolated high temperature components are of primary origin and the paleomagnetic directions of calamines and internal sediments are compatible. The calculated poles are consistent with the last 30 Ma of the Apparent Polar Wander Path (APWP) of Africa. These promising results pave the way for an efficient method to constrain the age of Zn supergene deposits