Copper-enriched syngenetic dolostones as a source for epigenetic copper mineralization in sandstones and shales (Timna, Israel)

The Lower Cambrian Timna Formation in southern Israel was deposited during a short marine episode within a thick clastic sequence. Its upper part consists of bedded sandy dolomites (dolomitic lithofacies) that change laterally into manganese sandstones (sandy lithofacies) which host large parts of the copper mineralization in the area. Both lithofacies are overlain by a thin shale bed. Field and petrographic relationships suggest that the sandy lithofacies is residual, and resulted from the dissolution of part of the dolomitic lithofacies by subsurface, epigenetic "karstification' processes, which probably began during the Miocene. The main copper deposit is, however, hosted by the sandy lithofacies and the overlying shales. It includes (in descending order of abundance) copper silicates, carbonates, phosphates, chlorides, and sulphates, which occur as irregular veins, nodules, and impregnations. Data on the copper mineralization in the sandy lithofacies fit well with an epigenetic model wherein the copper source rocks were the same sandy dolomites that contained the paratacamite-djurleite mineralization and that generally had a high copper content. -from Authors