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Full-Text Articles in Geology

Studies On Benthic Denitrification In The Chwaka Bay Mangrove Sediments, Zanzibar, Sm Mahommed, Rw Johnstone Nov 2002

Studies On Benthic Denitrification In The Chwaka Bay Mangrove Sediments, Zanzibar, Sm Mahommed, Rw Johnstone

Tanzania Journal of Science

Denitrification was measured at three sites in a narrow tidal creek in the Chwaka mangrove ecosystem. Denitrification arising from water column nitrate (Dw) was low (< 0.1μM Nm-2h-1) and there was little spatial and seasonal variation in Dw rates in the creek. Coupled nitrification-denitrification (Dn) was found to be low, but within the range measured in other mangrove sediments. Average values ranged from 0.01 to 0.45 μM Nm-2h-1 and showed strong spatial variations. The low denitrifcation rates observed in the creek were possibly as a result of the low availability of NO3 and high C:N values of the organic matter in the sediment. Spatial variations in denitrification rates were due to variations in concentration levels of organic matter and possibly to disproportionate competition for inorganic nitrogen between denitrifiers and benthic autotrophs among sites. There were no seasonal differences in denitrification rates. Results from the present study suggest that sediment denitrification does not play a major role as a sink for N in this ecosystem

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Interpretation Of Refelction Seismic Data From The Usangu Basin, East African Rift System, Ei Mbede Nov 2002

Interpretation Of Refelction Seismic Data From The Usangu Basin, East African Rift System, Ei Mbede

Tanzania Journal of Science

Reflection seismic data collected by AMOCO Tanzania Oil Company in the 80s, are herin used to correlate the main Usangu Basin parameters to those estimated from outcrop, gravity and aeromagnetic data. The seismic data are further used to constrain the geometry of crustal extension in this south-western sector of the East African Rift System (EARS) in Tanzania. Three distinct sedimentary packages on top of the basement reflector are interpreted and correlated to the Permo-Carboniferous Karoo rocks, the Jurassic/Cretaceous and Miocene Red Sandstone Group and Miocene to recent Lake Beds in the adjacent Rukwa basin, where the ages of the sedimentary …

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Tectonic Setting Of Gabbroic Rocks In The Western Part Of The Lupa Gold Field, South-West Tanzania, Sr Mnali Nov 2002

Tectonic Setting Of Gabbroic Rocks In The Western Part Of The Lupa Gold Field, South-West Tanzania, Sr Mnali

Tanzania Journal of Science

There is a pronounced occurrence of gabbroic rocks in the western part of the Lupa gold field, SW Tanzania. These rocks occur in the peripheral part around the Saza-Chuya granodiorite with which it makes a gradiational, unchilled contact. The rocks have been altered or metamorphosed to low-grade greenschist facies as indicated by the presence of secondary epidote, penninite, chlorite, sericite and calcite. The majority of major-element oxides show scattered variation trends against immobile elements such as Zr, indicating some degree of element mobility during post-crystallization processes of alteration or metamorphism. Major-trace-element data show that the gabbroic rocks in the study …

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The Polarising Effects In Sintered Kaolin, Fm D'Ujanga, Y Kaahwa, L Atteraas Nov 2002

The Polarising Effects In Sintered Kaolin, Fm D'Ujanga, Y Kaahwa, L Atteraas

Tanzania Journal of Science

The polarizing effects in sintered kaolin samples were analysed in terms of the sample density (or porosity) using direct current (dc) techniques. More porous samples exhibited higher polarizing effects than the less porous ones. The conduction carriers in kaolin samples at room temperature were found to be mainly electrons, with ionic conduction being enhanced by the moisture content with the pores. The influence of the uniaxial pressure and particle-size on the compacted and sintered density of the ceramic have been studied, and a density-pressure relationship before- and after-sintering conditions obtained

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The Emplacement Age Of Gabbroic Rocks And Associated Granitoids Of The Liganga-Msanyo Complex, South Eastern Tanzania, M. A. H. Maboko Dec 2001

The Emplacement Age Of Gabbroic Rocks And Associated Granitoids Of The Liganga-Msanyo Complex, South Eastern Tanzania, M. A. H. Maboko

Tanzania Journal of Science

The Msanyo Gabbro and the associated Mdando granitoids, which intrude Paleoproterozoic high-grade metamorphic rocks of the Ubendian Belt in southern Tanzania, yield imprecise Sm-Nd whole rock isochron ages of 1608±134 Ma (ε (Nd) = 2.1) and 1642±100 Ma (ε (Nd) = 1.6), respectively. These ages are indistinguishable at the 95% confidence level, indicating that the two rock suites were intruded at the same time. A more precise estimate of the time of emplacement is provided by a 5-point mineral isochron age of 1505±42 obtained from one of the gabbro samples. Calculated initial ε (Nd) values and mean crustal residence ages …

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Tectonic Setting And Uplift Analysis Of The Pangani Rift Basin In Northern Tanzania Using Apatite Fission Track Thermochronology, E. I. Mbede Dec 2001

Tectonic Setting And Uplift Analysis Of The Pangani Rift Basin In Northern Tanzania Using Apatite Fission Track Thermochronology, E. I. Mbede

Tanzania Journal of Science

Thirty four new Apatite Fission Track (AFT) ages and 32 track length distributions from samples of basement rocks flanking the Pangani rift, East African Rift System (EARS) are presented, in an attempt to elucidate the uplift and erosion of the rift flanks. The ages fall in the range of 207±15 to 48±4 Ma, spanning from Early Jurassic to Early Tertiary. These ages are much younger than the last termal event in the Mozambique belt that form the basement complex and are interpreted to represent the most recent tectonic events. Track length (TL) distributions suggest that uplift and erosion of the …

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Subsidence History Of The Rukwa Rift In South West Tanzania Analysed From Ivuna Well, E I Mbede Dec 2000

Subsidence History Of The Rukwa Rift In South West Tanzania Analysed From Ivuna Well, E I Mbede

Tanzania Journal of Science

The variation in subsidence rate during rift basin development is a good indication for the Geodynamic history of a sedimentary basin. The sedimentary section of Ivuna Well is herein used to explain the structural evolution of Rukwa Basin within the Western Rift of the East African Rift System. The sedimentary record of Ivuna Well is extracted from published information. The effects of sedimentary load, corrected for compaction and variation in water depth, and lake-level have been removed to obtain the "tectonic subsidence." Curves show two phases of accelerated subsidence related to the fault controlled rifting phases: The Karoo rifting and …

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Theoretical Evaluation Of Selective Radiation–Absorbing Surface, K.R. O’Shea Jul 1975

Theoretical Evaluation Of Selective Radiation–Absorbing Surface, K.R. O’Shea

Tanzania Journal of Science

An algol computer program is described, by means of which the spectral reflectivity for any angle of incidence may be calculated for a surface consisting of up to two thin absorbing films on a bulk substrate. The values of optical constant, n and k, for the materials used and also the thickness of the films, are the only data required. Calculated reflectivities have been shown to be consistent with experimental results.

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The Separation And Analysis Of Titanium And Iron In The Mineral Ilmenite, Adolf M Mulokozi Jan 1975

The Separation And Analysis Of Titanium And Iron In The Mineral Ilmenite, Adolf M Mulokozi

Tanzania Journal of Science

Since the location of extensive *ilmenite-bearing beach sands in Australia, and now in Tanzania, the separation and analysis of the mineral has become more important than ever. This is particularly because ilmenite has now become the principal source of rutile, an important product in the manufacture of pigments and ceramic materials. Ion exchange separation using a mixture of HCI and HF is described in the literature. The method has serious limitations especially when the use of glassware cannot be avoided. The author has successfully applied exclusively HCI solution for the anion exchange separation. The mineral was first brought in solution …

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