Clastic dikes of the Hatrurim basin (western flank of the Dead Sea) as natural analogues of alkaline concretes: Mineralogy, solution chemistry, and durability

This study shows that the mineral assemblages from clastic dikes in areas adjacent to the Dead Sea graben may be considered as natural analogues of alkaline concretes. The main infilling material of the clastic dikes is composed of well-sorted and well-rounded quartz sand. The cement of these hard rocks contains hydroxylapophyllite, tacharanite, calcium silicate hydrates, opal, calcite, and zeolite-like phases, which is indicative of a similarity of the natural cementation processes and industrial alkaline concrete production from quartz sands and industrial alkaline cements. The quartz grains exhibit a variety of reaction textures reflecting the interaction with alkaline solutions (opal and calcium hydrosilicate overgrowths; full replacement with apophyllite or thomsonite + apophyllite). The physicochemical analysis and reconstruction of the chemical composition of peralkaline Ca, Na, and K solutions that formed these assemblages reveal that the solutions evolved toward a more stable composition of zeolite-like phases, which are more resistant to long-term chemical weathering and atmospheric corrosion. The 40 Ar/ 39 Ar age of 6.2 ± 0.7 Ma obtained for apophyllite provides conclusive evidence for the high corrosion resistance of the assemblages consisting of apophyllite and zeolite-like phases.