Browsing by Author "Elisaimon, Elisante"

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    A gis-aided aerogeophysical, geological and geochemical investigation of late archaean granitites in the Musoma-Mara greenstone belt, north east Tanzania
    (University of Dar es Salaam, 2008) Elisaimon, Elisante
    The Musoma Mara Greenstone Belt (MMGB) is intruded by syn-to-post orogenic suites of granitoids which range in composition from Tonalite Trondhjemite Granodiorites (TTG) to granite. High resolution aerogeophysical survey by the Geological Survey of Tanzania in 2003 has provided aeromagnetic and radiometric data that were used in this study to classify various granitoids existing in the MMGB. Based on the analysis and interpretation made on airborne radiometric and magnetic data as well as previous geological maps, a geophysical interpretation map was obtained. This map broadly categorized the MMGB granitoids into two types, the first granitoid type is characterized by high contents of K, U and Th and magnetic intensity < 33997 nT. The second granitoid type is characterized by high K relative to U and Th, and magnetic intensity >33997 nT. The aerogeophysical interpretation map was used as a base map for ground follow-up whereby the granite types were sampled accordingly for geochemical analysis. The two granitoid types identified on the basis of geophysical data can further be subdivided into three types based on geochemical data i.e. biotite granites, calcic granites and TTG. The more abundant biotite and calcic granites correspond to the aerogeophysical high K, U and Th contents whereas the TTG correspond to the high K relative to U and Th concentrations. On the basis of compositional similarity with the northern MMGB high-K and Na-rich granitoids, that were previously studied by Manya et al (2007a, b), the biotite and calcic granites are inferred to have been generated by partial melting of pre-existing materials including TTG and intermediate to felsic volcanic rocks whereas the TTGs were generated by partial melting of hydrous basaltic crust that had been metamorphosed to garnet amphibolite.