Discovery of heavy mineral sand in Djiboutian coastline (Obock area, SE Afar rift)

• Heavy mineral sand deposits discovered in the coastline of the SE Afar Rift (Obock, Djibouti). • Madrepore, sand dune and alluvial deposits characterize the Obock coastline. • Concentration of titanium dioxide and iron oxide are 23.9 % and 53.9 % respectively. • Djibouti black sands contain both light and heavy minerals. • Chromite, Ilmenite, and Titanomagnetite were present in the magnetic fraction of the heavy mineral sands. In this paper, we present the first study of black sand deposits collected along the coastline of the Obock area, which is located in the North East part of Djibouti (SE Afar Rif). This area consists mainly of uplifted madrepores, sand dunes and alluvial deposits. Geochemical studies were carried out using techniques such as X-ray fluorescence (XRF) to quantify the heavy mineral sands. Electron microprobe and X-ray diffraction (XRD) techniques were used to identify minerals. Mineral sands have been identified in coastal backshore deposits, containing light minerals (calcite, aragonite, quartz, anorthite, augite, microcline, albite, enstatite, nontronite and diopside) and heavy minerals (hematite, ilmenite, chromite and magnetite). In general, titanium dioxide (TiO 2 ) and iron oxide (Fe 2 O 3 ) are found in the backshore, with averages of TiO 2 (23.9 %) and Fe 2 O 3 (53.9 %) in the total of heavy mineral fraction. Although, titanomagnetite is not widely exploited in the world due of the treatment to enrich ores with Fe and Ti, the presence of ilmenite and vanadium as trace elements in the subsurface and in titanomagnetite respectively, even at very low grades may potentially justify further of the lateral extent and depth geochemical and drilling investigations in order to upgrade the concentration of titanium oxide in the Obock coastal sands.