Uranium isotopes and trace element distributions in atmospheric dust mineral phases from the Sahara-Arabia Desert Belt

Abstract

Atmospheric dust plays a key role in shaping global climate by affecting the radiative budget, modulating precipitation, and serving as an important source of limiting nutrients to the oceans. At present, the primary source of atmospheric dust in the world is the Sahara-Arabia Desert Belt (SADB). However, the mineralogical constituents of dust are highly variable and can be divided into several phases. Moreover, the chemistry of these phases changes from source to sink, over unknown time periods, due to chemical and physical weathering.

Here, we report (²³⁴U/²³⁸U) ratios and trace element concentrations in five sequentially leached phases of 18 dust samples collected in the Gulf of Aqaba, northern Red Sea, between 2013 and 2019. The sampling site is located between the Sahara and the Arabia Deserts, and exposed to frequent dust storms, whose source is identified through air mass back trajectories. The sequential leaching steps, successfully extracted the water labile, Ca‑carbonates, FeMn oxides, Mg‑carbonates and silicate phases. The geochemical fingerprint and (²³⁴U/²³⁸U) ratios are used to identify sources and interaction between samples and phases.

This is the first report of the uranium isotopic composition of atmospheric dust from the eastern SADB. Coupled with trace element abundances, we characterize the end member compositions of each mineral phase, their provenance and transport time (i.e., comminution age). The latter spans over the last ∼200 kyrs for most samples, and longer (350–410 kyrs) for samples from the northern Arabian Peninsula. These results emphasize the fundamentally different sources and histories of dust across the SADB.