Chemical and mineralogical variations at the transition from subaqueous to subaerial rift-related freshwater limestones along the Dead Sea Transform Fault, NW Jordan

The Dead Sea Transform Fault, creating one of the most prominent rift basins on Earth, provoked freshwater limestones to develop in five stages: (I) 45 to 26 ka, (II) 26 to 15 ka, (III) 15 to 12 ka, (IV) 12 to 5 ka, (V) 5000 to 1500. Stages I and II represent periods of subaqueous limestone formation and stages III to V sedimentation of carbonate in a subaerial depositional regime. Kutnahorite, barite, halite, sylvite and kainite reflect the environmental conditions of the limestones caused by oxidising, slightly acidic to strongly alkaline fluids. The mineral succession reflects the solubility products of the minerals involved, coupled with an uplift-induced detrital runoff and a hydrothermal activity (temperatures 40-70 degrees C), leading to "white smokers". Si, Fe, Y, V and Zr are representative of the detrital input, S, Sr, F and Ba of newly-formed minerals in the freshwater limestones and negative Yb anomalies are interpreted as an evidence for hydrothermal activity. The C isotopes suggest mixed sources of the mineralising fluids. The crystal morphology of the minerals is controlled by the presence of cations heavier than Ca2+ and organic compounds. The Ba-Mn-bearing calcareous rocks evolved in subaqueous to subaerial depositional environments under hypogene through supergene conditions.