Khalid Tarawneh

New K-Ar ages of basalts from the Harrat Ash Shaam volcanic field in Jordan: Implications for the span and duration of the upper-mantle upwelling beneath the western Arabian plate

The volcanism in the western Arabian plate extends from the Red Sea through the Harrat Ash Shaam system to western Syria, as far north as the Bitlis suture in the Taurides. The Harrat Ash Shaam volcanic system in Jordan consists of northwest-trending dikes and a volcanic field that together encompass a width of 220 km. In terms of width, direction, and age of the main volcanic phases, the system is similar to the Red Sea dike belt. About 130 new K-Ar age determinations show that the ages of the Harrat Ash Shaam system (dikes and flows) range from Oligocene to Quaternary. However, there is a distinct gap in the ages between ∼22 and 13 Ma. This gap coincides with an apparent decrease in volcanism in the Red Sea region from around 20 to 12 Ma. We interpret this 9 m.y. gap as a quiescent period interrupting the volcanic activity in the region and suggest that from ∼22 to 13 Ma, tectonic activity in the Arabian plate was mainly restricted to the Red Sea region. A renewal of volcanism along the western margins of the Arabian plate at 13 Ma was very likely associated with the sinistral movement along the north-trending Dead Sea transform. This renewal of volcanism and tectonic activity may reflect the emergence of upper-mantle upwelling beneath the western Arabian plate at that time.

Anatomy of the Dead Sea Transform from lithospheric to microscopic scale

Fault zones are the locations where motion of tectonic plates, often associated with earthquakes, is accommodated. Despite a rapid increase in the understanding of faults in the last decades, our knowledge of their geometry, petrophysical properties, and controlling processes remains incomplete. The central questions addressed here in our study of the Dead Sea Transform (DST) in the Middle East are as follows: (1) What are the structure and kinematics of a large fault zone? (2) What controls its structure and kinematics? (3) How does the DST compare to other plate boundary fault zones? The DST has accommodated a total of 105 km of left-lateral transform motion between the African and Arabian plates since early Miocene (similar to 20 Ma). The DST segment between the Dead Sea and the Red Sea, called the Arava/Araba Fault (AF), is studied here using a multidisciplinary and multiscale approach from the mu m to the plate tectonic scale. We observe that under the DST a narrow, subvertical zone cuts through crust and lithosphere. First, from west to east the crustal thickness increases smoothly from 26 to 39 km, and a subhorizontal lower crustal reflector is detected east of the AF. Second, several faults exist in the upper crust in a 40 km wide zone centered on the AF, but none have kilometer-size zones of decreased seismic velocities or zones of high electrical conductivities in the upper crust expected for large damage zones. Third, the AF is the main branch of the DST system, even though it has accommodated only a part (up to 60 km) of the overall 105 km of sinistral plate motion. Fourth, the AF acts as a barrier to fluids to a depth of 4 km, and the lithology changes abruptly across it. Fifth, in the top few hundred meters of the AF a locally transpressional regime is observed in a 100-300 m wide zone of deformed and displaced material, bordered by subparallel faults forming a positive flower structure. Other segments of the AF have a transtensional character with small pull-aparts along them. The damage zones of the individual faults are only 5-20 m wide at this depth range. Sixth, two areas on the AF show mesoscale to microscale faulting and veining in limestone sequences with faulting depths between 2 and 5 km. Seventh, fluids in the AF are carried downward into the fault zone. Only a minor fraction of fluids is derived from ascending hydrothermal fluids. However, we found that on the kilometer scale the AF does not act as an important fluid conduit. Most of these findings are corroborated using thermomechanical modeling where shear deformation in the upper crust is localized in one or two major faults; at larger depth, shear deformation occurs in a 20-40 km wide zone with a mechanically weak decoupling zone extending subvertically through the entire lithosphere.

Evaluating the potential of sediments in Ziqlab Reservoir (northwest Jordan) for soil replacement and amendment

Abstract Surface sediments of Ziqlab Reservoir, northwest Jordan, were evaluated to characterize trace element distributions and sources related to various physicochemical variables. Trace element distribution is determined by texture, parent material in the catchment, and anthropogenic activities. The suitability of reservoir sediment for replacing or amending soil was assessed by comparing sediment characteristics to natural soils. Results suggest that the sandy facies can be used as artificial soils, whereas clayey facies can be utilized as fertilizer for poor quality soils in Jordan. The fine-grained sediment fraction is associated with (1) high abundance of clay minerals with high cation exchange capacity and available micronutrients; (2) occurrence of kaolinite, montmorillonite–illite, vermiculite, and smectite; and (3) optimal pH values for availability of most micronutrients. Among the trace elements measured, total nickel and cadmium slightly exceeded recommended safe levels for soils, but the high concentrations may decline when sediments are exposed to air. If removal of the bottom sediments of Ziqlab Reservoir becomes economically feasible, it would extend the reservoir lifespan, improve water quality, compensate for soil scarcity in some regions, and enhance soil productivity.