Journal Article

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

Ryb, U., Erel, Y., Avni, Y., Stern, D., Matthews, A.

2022

Overview

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. Plain Language Summary Stages in the breakup of continental plates are accompanied and recorded by the formation of mineral deposits by water‐rock reactions. We studied dolomite and iron mineralization occurrences along tectonic lines between the Red Sea Rift and its Dead Sea Transform (DST) segments of the Cenozoic rift system between the African and Arabian plates. We combine new and published isotope compositions of O, C, Sr, Mo, Fe, and Pb to identify the sources and timing of mineralization. We demonstrate that the mineralization occurred as seawater migrated through the subsurface, mixed with continental groundwater, and upwelled through tectonic lines to interact with carbonate country rocks. Age constraints based on geological observations and absolute U‐Pb dating suggest three mineralization events at 46 ± 12, 31.4 ± 4.6, and 14.5 ± 2.3 Ma. The two younger events correspond to the timing of pre Red Sea Rift doming of northeastern Africa and Arabia driven by the Afar Plume, and DST. We associate the youngest age with the presence of a lagoon in the DST. The results of this study demonstrate that marine ingression into the DST preceded significant surface uplift of the transform's western margin. Key Points Mineral deposits along the African‐Arabian plate‐margins formed by mixing between country rocks, seawater, and continental groundwater U‐Pb dating indicate three phases of mineralization that overlap intervals of Red Sea Rift and Dead Sea Transform (DST) activities Marine ingression into the DST preceded surface uplift of the transform's western margin

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Aquifers / Brines / Carbonate rocks / Carbonates / Cenozoic / Cenozoic Era / Dolomite / Dolostone / Drainage systems / Epigenetics / Groundwater / Iron / Isotope composition / Isotopes / Lagoons / Mineral deposits / Mineralization / Minerals / Oxide minerals / Plate boundaries / plate boundary / Plate margins / Plates / Seawater / stable isotopes / Uplift / U‐Pb dating / water rock reactions