Mineralogical and Geochemical Characterization of Clay and Lacustrine Deposits of Lake Ashenge Basin, Northern Ethiopia: Implication for Industrial Applications

The paper tries to characterize and evaluate clay, lacustrine and diatomaceous earth deposits of Lake Ashenge basin, near Koram, northern Ethiopia and comment on its industrial implications. The country rocks are dominantly basalts and basaltic agglomerates overlain by minor amounts of rhyolite and ignimbrite. Sedimentary deposits, clays and associated sediments include 1) intercalations of lacustrine diatomaceous earth, other lacustrine and clays with channel deposits (gravel, pebbly sand and silt); 2) intercalations of diatomaceous earth, peat and clays with channel deposits exposed; and 3) intercalations of clay with channel deposits. X-ray diffractometer analysis of clay samples indicates kaolinite as a dominant clay mineral among others. On the basis of the abundance of different minerals, the clays are subdivided into four groups, 1) Kaolinite (K), 2) Microcline-Kaolinite (MK), 3) Muscovite-Kaolinite (MuK), and 4) Muscovite-Microcline-Kaolinite (MuMK). Other minor mineral phases include quartz, vermiculite, low-high albite, calcite and calcite magnesia. Diatomaceous clays are almost free from kaolinite. Kaolinite, being the dominant clay mineral varies from 6% in light brown to 77% in light grey clays. Al 2 O 3 and SiO 2 dominate the clay geochemistry among other oxides and based on the Al 2 O 3 content, the kaolinite variety is subdivided into high Al 2 O 3 (16-21 wt %) and low Al 2 O 3 (8-13 wt%) types. Higher Al 2 O 3 and similar SiO 2 and Fe 2 O 3 values in clays compared to the source basaltic rocks are related to the topography, mineralogy and climatic conditions that exist in the area. Compared to the low grade kaolinite type (about 56*10 6 tones), diatomaceous earth variety (77.3*10 5 tones) is relatively of good quality with high SiO 2 content. Keywords : Clay and lacustrine deposits, Kaolinite, Diatomite, Lake Ashenge, Tigray, Ethiopia