Name : ______________
Department : Geological Engineering
Faculty : Mineral Resources Technology
Title of Programme : Msc (Geological Engineering)
Duration : Full Time (Three Years)
Expected Year of Completion : _____________
Petrographical and Geochemical Classification of Manganese Carbonates and Their Correlation with Specific Gravity at Pit C Of Ghana Manganese Company, Nsuta
Statement of Problem
Specific gravity was used to complement the estimation of iron content of the rock Red Mountain Formation of Silurian age in Alabama (Sheldon, 1964). This method was also employed by Costin et al. (2015) at Postmasburg Manganese Field. Rongkhapimonpong et al. (2016) examined mineralised characteristics of rocks from Chatree gold deposit, Central Thailand and found five types of quartz textures related to high grade gold mineralisation.
There is widespread distribution of Manganese ores in Paleoproterozoic Birimian of Ghana. They are found in the Nangodi Belt and Lawra Belt in the northern part of Ghana and Ashanti Belt in the southern part of Ghana (Kesse, 1976). The supergroup hosts the Nsuta manganese deposit in a greenschist facies metamorphic volcano-sedimentary succession which developed along the east of the West African craton (Nyame, 1998; Nyame et al., 2003; Beukes, 2006). According to Kesse (1985), the deposits mainly contain oxide (chiefly pyrolusite and psilomelane) at the upper deposition layer and carbonate (rhodochrosite) at the primary layer. There are thick stratiform manganese carbonate ore beds which occur in a unit of carbonaceous phyllite and metagreywacke that are sandwiched in a very thick succession of meta1avas (Nyame, 1998; Nyame et al., 2003). The Manganese bearing rocks of Nsuta took place in five structurally delineated areas known as hills A-E which conforms to the regional strike of Birimian strata (Service, 1943). The Hill D North and South deposit forms part of a double folded synclinal structure which has been the main production area at Nsuta in recent years Nyame et al. (2003). Currently, the Ghana Manganese Company (GMC) Limited has its mining operations concentrated at Pit C (Amegbey and Afum, 2015).
The manganese carbonate bed at Nsuta is interbedded with fine-grained black carbonaceous shale that grades into a succession of greywacke and shale with abundant manganese oxide minerals in solution channels such as fractures and cavities within silicate gangue (Nyame et al., 1995). Macroscopically, the intraclast of the four manganese–carbonate related ores displays graded bedding, subangular to subrounded less than a millimetre and matrix-supported fabric with microconcretionary carbonates, quartz, muscovite and subordinate pyrite (Nyame, 2008). The ore bed along the north-eastern strike length is homogeneous and very fine-grained to microcrystalline but the structurally complex appears significantly altered and recrystallised (Van Bart, 2001). Veins and coarsely recrystallised pink carbonate patches appear undeformed and post-date cleavage and low-grade regional metamorphism (Nyame and Beukes, 2006). The host phyllite consists of microcrystalline and microconcretionary carbonate minerals in a matrix of very fine-grained carbonates, quartz, muscovite, pyrite, rutile and subordinate spessartine and occasional tourmaline. In some microconcretions, microbands of Mn dolomite and carbonates of a magnesite-rhodochrosite solid solution are present (Nyame and Beukes, 2006). This manganese carbonate ore is of higher grade than the fine-grained sedimentary ores and is especially abundant in Hill D South (Tetteh, 2010). The manganese element is second to iron in abundance in the earth crust with deposits grouped into three broad genetic types; hydrothermal, sedimentary and superficial (Roy, 1968). At Vizianagram – Visakhapatnam Manganese Belt, India, the variation in the trend of amounts of major oxides in the kodurites major oxides show several trends with increase of both Mn and Fe and vice versa (Siddique and Shaif, 2015).
According to Kesse (1976), the general stratigraphy of the Nsuta deposit consists of a basal greenstone unit followed successively upwards by argillaceous rocks and tuffs, manganese carbonates, argillaceous rocks and tuffs which, in turn, is overlain by greenstone. The manganese carbonates have a specific gravity of 2.77, oxides have 2.80, metatuffs have 2.82, volcanic ash has 2.89 and the carbonates have the highest specific gravity of 3.40 (Agbeno et al., 1993). Currently, super high grade 30 % Mn, high grades (28 % to 29.9 % Mn), medium grades (22 % to 27.9 % Mn) and low grades (18 % to 21.9 % Mn) are produced (Amankwah and Ali, 2013). The highest specific gravity correlates with high grade manganese carbonate (Beukes et al., 2006). Petrographical together with geochemical classification of manganese carbonates correlated with specific gravity have not been studied at Ghana Manganese company, Nsuta. Therefore, this research seeks to conduct these analyses to help in exploration of the ore. This can be used in further search of manganese deposits in the Birimian and on similar deposits in the world.
The objectives of this thesis are:
- To study the petrography, mineralogy and microtextures of the different types of manganese carbonate ores at the Pit C of Nsuta Mine,
- To geochemically classify the manganese carbonates respect to grade,
- To determine the specific gravity of the various types of manganese carbonate ores, and
- To correlate field observations, microscopic analyses and specific gravities with respect to the grades of the Mn carbonates.
By the end of this thesis, it is expected that:
- Petrology, mineralogy and microtextures of the carbonate ore would be ascertained
- Geochemical classification of the manganese carbonate ore with respect to grade would be identified
- Specific gravity of the various type of carbonate ores would be determined
- Correlation between field observations, microscopic analyses and specific gravities with respect to the grades of the Mn carbonates would be deduced.
Methods To Be Used
- Field mapping and sampling,
- Petrographic and geochemical analyses,
- Specific gravity measurements,
- Excel correlation of the various parameters determined.
Facilities To Be Used
- Library and Internet facilities at Ghana Manganese Company, Nsuta and the University of Mines and Technology (UMaT), Tarkwa.
- LEICA DM750P and LEICA DM2700P polarising microscopes at the Petrology Laboratory at the Department of Geological Engineering, and scanning electron microscope at the Environmental and Safety Laboratory at UMaT, Tarkwa XRF machine at the ALS, Canada.
- Pycnometer at the Geotechnical Laboratory at UMaT,
_______________ _______________ _____________________
Name: Name: Name:
(Student) (Supervisor) (Head of Department)
- Agbeno, S. K., Mireku-Gyimah, D. and Ziegler K. M. (1993), “Improving blast performance by adjustment of drilling pattern at Ghana National Manganese Corporation”, Transaction of the Institution of Mining and Metallurgy Section A, No. 102, pp. A197-A200.
- Ali, M. and Amankwah, R. K. (2013), “Recovery of Nsutite from tailings material of Ghana Manganese Company (GMC) Limited Mine, Nsuta”, Ghana Mining Journal, Vol. 14, 65pp.
- Amegbey, N. and Afum, B. O. (2014), “Atmospheric pollutants diffusion Studies”, Unpublished Report, Ghana Manganese Company, Tarkwa, 48 pp.
- Beukes, N. J., and Gutzmer, J. (2008), “Origin and paleoenvironmental significance of major iron formations at the Archaean-Paleo proterozoic boundary”, Reviews in Economic Geology, Vol. 15, pp.5-47.
- Costin, G., Fairey, B., Tsikos, H., & Gucsik, A. (2015), “Tokyoite, As-rich tokyoite, and noelbensonite: New occurrences from the Postmasburg Manganese Field, Northern Cape Province, South Africa”, The Canadian Mineralogist, Vol. 53, pp. 981–990.
- Kesse, G. O. (1976), “The manganese ore deposits of Ghana”, Ghana Geological Survey Bulletin, No. 44, 97 pp.
- Kesse, G. O. (1985), “The Mineral and Rock Resources of Ghana”, A. A Balkema, Rotterdam, 610 pp.
- Nyame, F. K. (2008), “Petrography and geochemistry of intraclastic manganese-carbonates from the ~2.2 Ga, Nsuta deposit of Ghana: Significance for manganese sedimentation in the Palaeoproterozoic of West Africa”, Journal of African Earth Sciences, Vol. 50, pp. 133 – 147.
- Nyame, F. K. and Beukes, N. J. (2006), The genetic significance of carbon and oxygen isotopic variations in Mn-bearing carbonates from the Paleo-Proterozoic (∼2.2 Ga) Nsuta deposit in the Birimian of Ghana Carbonates Evaporites, Vol. 21, pp. 21–32.
- Nyame, F. K., Beukes, N. J., Kase, K. and Yamamoto, M. (2003), “Compositional variations in manganese carbonate micronodules from the Lower Proterozoic Nsuta deposit, Ghana: product of authigenic precipitation or post-formational diagenesis”, Sedimentary Geology, Vol. 154, pp. 159-175.
- Nyame, F. K., Kase, K. and Yamamoto, M. (1998), “Spessartine garnets in a manganiferous carbonate formation from Nsuta, Ghana”, Resource Geology, Vol. 48, pp. 13-22.
- Nyame, F. K., Kase, K. and Yamamoto, M., (1995), “Occurrence and composition of manganese oxide minerals from the Nsuta manganese deposit, Western Ghana”, Okayama University Earth Science Report, Vol. 2, pp. 71 – 80.
- Rongkhapimonpong, P., Sutthirat, C. and Lunwongsa, W. (2016), “Vein Textures and Chemistry of Ore Minerals Associated with High Grade Gold Mineralisation from A East Pit, Chatree Gold Deposit, Central Thailand”, Bulletin of Earth Sciences of Thailand, Vol. 7, No. 1, pp. 42-56.
- Roy, S. (1968), “Mineralogy of the different genetic types of manganese deposits”, Economic Geology, Vol. 63, pp. 760 – 786.
- Service, H. (1943), “The Geology of the Nsuta Manganese Ore Deposits”, Gold Coast Geological Survey Memoir, Vol. 5, 32 pp.
- Sheldon, B. (1964), “Piezomagnetic effect at the time of local earthquakes”, Springer, Vol. 202, No. 4934, pp. 790- 791.
- Siddiquie, F. N. and Shaif, M. (2015), “Geochemistry of Major Oxides in Host Rocks in Vizianagarm Manganese Ores Belt (A.P.), India”, International Journal of Geosciences, Vol. 6, pp. 350 – 372.
- Tetteh, G. M. (2010), Geology and mineralization of the Paleoproterozoic Nsuta manganese deposit in the Birimian of Ghana, PhD Thesis (Unpublished), University of Ghana, Legon, 186 pp.
- Van Bart, A, (2001), Structure, stratigraphy and sedimentology of the Paleoproterozoic Nsuta Manganese Deposit, Ghana, MSc Thesis (Unpublished), Rand Afrikaans University, Johannesburg, 110 pp.