Mineralogy, Geochemistry and Genesis of Mekane Selam Iron Occurrence in Tewa Area, Northern Ethiopia.
No Thumbnail Available
Date
2020-10-02
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
Iron is the fourth abundant metal in Earth’s crust and its ore minerals are concentrated as hematite, goethite, magnetite, siderite, illmenite and other sulfides. The Mekane Selam iron mineralization is part of the Northwestern plateau that bounded by Axum–Adigrat and Ambo lineaments of the N and SW. Mineralogy, geochemistry and genesis studies are main objective of this work. Geologic field work and mapping, X-ray diffraction, ore petrographic study of ore, geochemical analysis of host rock were applied methodologies. XRD and ore microscopic study reveals hematite, goethite, magnetite, kaolinite anatase and quartz are the principal ore minerals and associated gangue phases of ore while quartz and feldspars are petrographic composition of the host. Chemical analysis of major constituent show significant enrichment of SiO2, Al2O3 in the host and Fe2O3 in the ore with strong depletion of K2O, Na2O, MnO, MgO, CaO and P2O5. High value of CIA (88.46-99.44) with depleted content of K2O and Na2O suggests the area is subjected to intensive weathering process. Chondurite-normalized REE pattern show enrichment in LREE and relatively smooth pattern of HREE. The pattern is consistent with the characteristics of upper continental crust, protholith of sediments and weathered terrestrial is iron source. Positive Ce and negative Eu anomalies of analyzed samples suggest iron reprecipitation is occurring in weathered (supergene) oxidation leaching of REE. It indicates digenetic alteration and the absence of hydrothermal fluid inputs during mineralization. Concentrated detrital derived elements of Zr, Al and Nb with the oolithc textures of ore samples are the characteristic of digenetic modification in iron formation. The XRD results of goethite, hematite and kaolinites minerals indicate the genesis of Mekane Selam iron occurrence is laterite. SiO2-Fe2O3-Al2O3 ternary plot of ore and host rock samples show the ore is altered to hematite due to low–strong degree of lateritization while the host rock is as a result of kaolinization to kaolinite. Field observation and exposure measurement, mineralogical and geochemical data analysis suggests the iron occurrence of the area is classified as an indicated resource. Surface weathering, REE leaching, transportation and other physico-chemical conditions enrich iron. The digenesis and sediment recrystallization are significant iron ore formation and modification of the area.
Description
Keywords
Iron ore, Genesis, Geologic setting, Laterite, Continental Crust, Geochemical, Mineralogy