Browsing by Author "Kebede, Wubegzier"

Now showing 1 - 1 of 1
  • No Thumbnail Available
    Item
    Geology, Geochemistry and Genesis of Ula Ulo Nickel Deposit, Adola Belt, Southern Ethiopia
    (Addis Ababa University, 2018-05-30) Kebede, Wubegzier; Getaneh, Worash (PhD); Alene, Mulugeta (PhD)
    The study area is located in the Neoproterozic metavolcano-sedimentary assemblages of Megado belt within Adola belt of southern Ethiopia. Nickel mineralization is hosted and confined by serpentinites. The country rocks are tremolite talc schist and talc tremolite schists. Geochemistry of the host rock and country rocks is studied. All units shows LILE Enrichment (Ba/Yb)n is 2.92 (serpentinite), 1.2(talc schist), 3.84 (tremolite schist) and 3.2 (amphibolite). Because these LILEs are fluid mobile and easily assimilated from the subducting slab as compared HFSEs. REEt calculated as serpentinite (0.7 – 1.84 ppm), talc schist (2.69 ppm) and tremolite schist (2.79) while amphibolite has REEt (6.18). (La/Yb) c.n values are serpentinite (4.2), talc schist (6.6), tremolite schist (3.7) and amphibolite (8.1). Slight enrichment of LILE and LREE and depletion of HFSE and HREE for both serpentinite, talc tremolite schist and amphibolite is due to assimilation and dehydration of subducting slab. Magmatic evolution undergone without amphibole intervention and plagioclase crystallization. Both ultramafic and mafic rocks are crystallized from similar origin. The geochemical signature of both the mafic and ultramafic rocks is similar to alkaline thoeliitic and island arc thoeliitic bonnieite. Tectonic discrimination shows island arc boninite andesite affinity. Meta sedimentary rocks are also common in the study area. These are quartzite, meta psmmite and graphite schist. Both metavolcanic and metasedimentary rocks are metamorphosed to greenschist facies. Because the mineral assemblages are antigorite, lizardite, talc, tremolite, actinolite, chlorite, epidote, sericite and hornblende. The rocks are aligned NS and dips towards 700 towards W. The deposit is zoned into two. These are oxide zone and saprolite zone. Oxide zone is upper portion of the lateritic column while saprolite covers the lower part. The occurrence of the mineralization in these zones is variable. Inferred resources estimation is done for these zones separately. The source of the Ni is serpentinites. The metal is leached from oxide zone and serpentinites and precipitated in the saprolite as garnierites. The mineralogy of these garnierites is studied. Both serpentine-like and talc-like garnierites are observed. Other ore minerals observed are chromite and magnetite. The genesis is formulated based on geochemical and mineralogical characteristic of garnierites. The deposit model is ultramafic hosted lateritic nickel deposit hosted. Ore body Morphology, extent, mineralogy and geochemistry are studied and explained.