The lithosphere of the East African Rift and Plateau (Afar-Ethiopia-Turkana) : insights from Integrated 3-D density modelling

The area encompassing the Eastern branch of the East African Rift System (EARS: Afar-Ethiopia-Turkana) and associated plateaux is an ideal region to investigate extension and magmatism associated with rupturing continental lithosphere. Ethiopia covers an important part of the EARS. It contains the major section of the ca. 5000 km Afro-Arabian rift and includes the transition between the Arabo-Nubian-Shield and the Mozambique Belt. A compilation of over 45000 onshore and offshore gravity stations covering the EARS and adjacent regions (Eastern Sudan, Red Sea and Gulf of Aden margins) has been made and forms the major data set upon which this study is based. The database is re-evaluated and re- processed using consistent procedures and has an estimated Bouguer gravity error of 1.5-4.5 x10-5m/s2. An attempt has been made to fill data gaps by merging the terrestrial data with GRACE satellite data. A regional 3D density model is developed using the GIS functionalities of a potential field-modelling program (IGMAS) and integrates seismic constraints with information from isostatic models, global seismic tomography, geological, geochemical, petrological and experimental results. Thirty parallel east-west sections through the EARS are modelled to a depth of 150 km. The 3D density structure reproduces the Bouguer gravity anomaly with a high accuracy (standard deviation of 16x10-5 m/s2). Misfits are attributed to errors in the gravity database and unconsidered structures. Analysis of the new gravity database and 3D modelling offers new information on the EARS, namely the isostatic state of the region, crust and upper mantle structures, basement and optimised Moho maps, quantification of modelled units and estimation of rigidity, among others. Based on the present data and new additional data sets, short and long-term scientific goals can be identified. Some of the most important are: further rigidity calculations using the 3D density model, joint modelling of gravity and magnetic data in selected areas, updating of the gravity network in Ethiopia, heat flow measurements in the Main Ethiopian rift and adjacent plateau, and integrated geoscientific experiments in the broadly-rifted region of southern Ethiopia

Effective fluoride adsorption by aluminum oxide modified clays: Ethiopian bentonite vs commercial montmorillonite

This study focuses on the chemical modification of Ethiopian bentonite and commercial montmorillonite with aluminum oxi-hydroxide (AO) for the purpose of defluoridation from aqueous solution. The chemical modification was achieved by preparing AO-modified adsorbents at different pH values. The adsorbent materials were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and point of zero charge (PZC). From the modified adsorbents, AO-Mont at pH 5 (AO-Mont 5) showed a slight shift of d001 at 2θ = 7.5ºreflection toward the lower angle 2θ = 7.0ºas a result of the Al2O3 insertion into interlayer space. The elemental composition from XRF further showed the increment of Al content accompanied with a decrease in the exchangeable cations in the modified samples and higher content of Al was observed in AO-Mont 5. In addition, the PZC initially 8.5 and 2.5 for raw bentonite and montmorillonite clays were increased to 10 and 8.5 in AO-Bent 5 and AO-Mont 5, respectively. Adsorption of fluoride on these modified adsorbents was studied as a function of preparation pH, contact time, solution pH and co-existing anions. AO-Mont prepared at pH 5, which contained higher content of Al resulted better fluoride removal performance. AO-Bent 5 and AO-Mont 5 have shown five and nine fold increase in fluoride removal capacity, respectively as compared to their respective unmodified clays. The experimental data fitted well with Freundlich adsorption isotherm model which indicated that the surface of the adsorbent is heterogeneous and adsorption of fluoride followed a multilayer sorption. Hence AO-modified Bent and Mont adsorbents prepared at pH 5 can be considered as potential adsorbents for defluoridation from drinking water.The authors would like to acknowledge the National Science Foundation (NSF) and USAID PEER grant [AID-OAA-A-1100012] for financial support. MD acknowledges the Ethiopian Institute of Water Resources, Addis Abeba University and Swiss Federal Institute of Aquatic Science and Technology (Eawag) for financial and technical support.Peer Reviewe

Estimates of Cancer Incidence in Ethiopia in 2015 Using Population-Based Registry Data

Purpose Noncommunicable diseases, prominently cancer, have become the second leading cause of death in the adult population of Ethiopia. A population-based cancer registry has been used in Addis Ababa (the capital city) since 2011. Availability of up-to-date estimates on cancer incidence is important in guiding the national cancer control program in Ethiopia. Methods We obtained primary data on 8,539 patients from the Addis Ababa population-based cancer registry and supplemented by data on 1,648 cancer cases collected from six Ethiopian regions. We estimated the number of the commonest forms of cancer diagnosed among males and females in Ethiopia and computed crude and age-standardized incidence rates. Results For 2015 in Ethiopia, we estimated that 21,563 (95% CI, 17,416 to 25,660) and 42,722 (95% CI, 37,412 to 48,040) incident cancer cases were diagnosed in males and females, respectively. The most common adult cancers were: cancers of the breast and cervix, colorectal cancer, non-Hodgkin lymphoma, leukemia, and cancers of the prostate, thyroid, lung, stomach, and liver. Leukemia was the leading cancer diagnosis in the pediatric age group (age 0 to 14 years). Breast cancer was by far the commonest cancer, constituting 33% of the cancers in women and 23% of all cancers identified from the Addis Ababa cancer registry. It was also the commonest cancer in four of the six Ethiopian regions included in the analysis. Colorectal cancer and non-Hodgkin lymphoma were the commonest malignancies in men. Conclusion Cancer, and more prominently breast cancer, poses a substantial public health threat in Ethiopia. The fight against cancer calls for expansion of population-based registry sites to improve quantifying the cancer burden in Ethiopia and requires both increased investment and application of existing cancer control knowledge across all segments of the Ethiopian population

Alternative beneficiation of tantalite and removal of radioactive oxides from Ethiopian Kenticha pegmatite–spodumene ores

The beneficiation methods for Ethiopian Kenticha pegmatite–spodumene ores were assessed through mineralogical and quantitative analyses with X-ray diffraction (XRD) and energy-dispersive X-ray fluorescence (EDXRF). The tantalite in the upper zone of the Kenticha pegmatite–spodumene deposit is 58.7wt% higher than that in the inner zone. XRD analysis revealed that the upper zone is dominated by manganocolumbite, whereas the inner zone is predominantly tantalite-Mn. Repeated cleaning and beneficiation of the upper-zone ore resulted in concentrate compositions of 57.34wt% of Ta 2 O 5 and 5.41wt% of Nb 2 O 5 . Washing the tantalite concentrates using 1vol% KOH and 1 M H 2 SO 4 led to the removal of thorium and uranium radioactive oxides from the concentrate. The findings of this study suggest that the beneficiation and alkaline washing of Kenticha pegmatite–spodumene ores produce a high-grade export-quality tantalite concentrate with negligible radioactive oxides