Browsing by Author "Emmanuel, Venance"

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    The occurrence of Ruangwa tsavorite deposits withing the pan-african Neoproterozoic metamorphic mozambique belt(nmmb), south eastern Tanzania
    (University of Dar es Salaam,, 2012) Emmanuel, Venance
    The rocks at Ruangwa vanadium grossular deposits have been studied having their lithological and geochemical attributes been discussed. The geometrical model of the area is as well constructed. The rock sequence in this area consists of high grade metamorphic rocks predominantly the graphitic gneisses which are intercalated with layers of impure marble and calcsilicates, metapegmatites and metagabbros. These rocks are then crosscut by tsavorite-bearing quartz veins together with the overlapping younger sediments. The lithostratigraphic column is established and the target areas of tsavorite development clearly identified which is both lithologically and structurally controlled and hosted either in quartz veins or disseminated in metasomatized zones of graphitic gneisses and metagabbros. Ruangwa tsavorite presents geochemicaly two types which include the vanadium-chromium and manganese-rich varieties occurring in quartz veins and metaggabbro respectively. The green garnets are vanadian-chromian grossular type representing the grossular end member composition in a range between 91.75 and 93.40 wt. % and the manganoan as 56 wt. %. Petrographic characteristics of these rocks are also discussed noting a consistent association of quartz, graphite, feldspar and/or phlogopite with green grossular garnet in graphitic gneisses. The whole rock chemistry shows diversified rock types with dominance of metapelitic chemical affinity, rocks rich in silica and alumina. Thegeochemistry of these rock assemblages is found to form the basis for the developed tsavorites in Ruangwa area. The oxygen isotope composition (per mil, %o) for the tsavorite is established forming a distinct range of between 9.5 and 11± 0.3%0 and is combined with the V/Cr and Mn0 compositions to assign its locality print. 1