Sources, Timing, Environmental and Tectonic Implications of Epigenetic Mineralization Along the Arabian-African Plate Boundary

The formation of divergent plate boundaries involves the opening of continental basins and uplift of plate margins accompanied by seawater ingression and the reorganization of surface and groundwater drainage systems. These processes drive water-rock reactions, resulting in the deposition of epigenetic minerals in the country rock adjacent to the plate boundary. Here, we study the isotopic geochemical record of epigenetic dolomite and ferric-oxide minerals that occur along tectonic lines in the Negev (southern Israel), which border the Cenozoic rift system that developed between the African and Arabian plates. The observed ranges of new and published O, C, Sr, Mo, Fe, and Pb isotope compositions indicate mixing between the country rock, seawater and deep-seated groundwater source-solutions. We suggest that mineralization occurred as brines migrated from their marine source, mixed with groundwater in a deep siliciclastic aquifer environment, and subsequently upwelled along tectonic lines and reacted with the overlying carbonate rocks. Relative and U-Pb dating of epigenetic minerals suggest that mineralization occurred at 31.4 ± 4.6 Ma in the central Negev sites and at 46 ± 12 Ma and again at 14.5 ± 2.3 Ma in the northeast Negev. The younger two ages overlap the timing of pre- Red Sea Rift doming of northeastern Africa and Arabia, driven by the Afar Plume, and lateral-movement along the Dead Sea Transform (DST), respectively. We associate the youngest mineralization event with a time-interval in which the DST already hosted a marine lagoon, while the transform's western margin has remained a low relief landscape.