The postglacial climate history of Gondwana represents the most prominent climate amelioration in the Phanerozoic, ranging from severe icehouse conditions in the Late Carboniferous (Pennsylvanian) to ...extreme hothouse conditions in the Early Triassic. Here we report new sedimentological and palynological data from a 350m thick coal-bearing succession intersected by borehole 945L_0022, drilled in the eastern Tete Province of Mozambique, which documents southwestern Gondwana’s Permian postglacial climate amelioration. Palynofacies data further support the environmental reconstructions interpreted from the sedimentary succession. Changes in the palynomorph assemblage document a shift from cold, to cool-temperate, to warm-temperate climatic conditions. This climate signature corresponds with observations from other depositional environments elsewhere in southern Africa, and thus enables correlation on a regional to interregional scale. Thick lacustrine deposits are described within the lower coal-bearing succession, reflecting the final glacial retreat, with melt waters supplying fresh water to the incipient lacustrine system. Lakes as characteristic postglacial sedimentary sinks are excellent palaeoclimate archives and the high Total Organic Carbon content of these fine-grained clastic sediments also makes them potential source rock targets for oil and gas.
The coal in Mozambique's Tete province has been known about for a long time, as the artist/explorer Thomas Baines first captured onto canvass a coal outcrop on the banks of the Zambezi in the late ...1850s. The first geological works in the Tete province referred to the studies of coal occurrence, and were undertaken by Richard Thornton (1859), a geologist on the Zambezi expedition under Dr David Livingstone and Guyot. However, most of the recent exploration has been conducted to ascertain the economic potential of the coal resources within the region. The majority of these resources are located within remnants of the Ecca Group of rocks, of the Karoo Supergroup, in the Zambezi graben of the Tete province of Mozambique. The coalfield consists of various sub-basins and is considered the largest undeveloped coal province in the world. Amongst others, it forms host to the well publicised Moatize metallurgical and thermal coal deposit, reported to contain 2.4Gt of coal and located within the Moatize sub-basin.
In late 2004, a consortium of companies headed by Brazilian iron-ore miner, Vale, won the right to develop the Moatize coal deposit. Other companies which tendered for this right were BHP Billiton, Rio Tinto and Anglo American. Vale is partnered in this project with American Metals and Coal International (AMCI), a North American coal producer, which owns 5% of the consortium. The consortium bid $122.8M for the rights to explore and develop the coal deposit.
The allocation of the tender award to Vale opened the way for smaller investors, such as the Zambezi Energy Corporation (ZEC) who decided in late 2004 to develop a number of projects within licence blocks in the Zambezi graben. Investment within the region has accelerated rapidly over the last couple of years and the region has seen a number of developments. During this time the authors have helped to develop the potential of new coal resources and have modified the traditional coal resource estimation techniques, such that they can be used for reporting coal resources according to the terminology and guidelines given in the JORC (the Joint Ore Reserves Committee) code (JORC, 2004).
The paper describes the complexities of the underlying regional and local resource geology and describes the challenges of producing resource estimates to international standards, such as JORC.
► An active coal exploration case study. ► Application of JORC International Standards to developing coal resources. ► Analytical data exposed that has not yet been made public. ► Development of a workflow to analyse coal resources using computer modelling systems in mining.
The detailed palynostratigraphic study of four boreholes in the Muarádzi sub-basin, Moatize-Minjova Coal Basin (MMCB) southeast of Moatize, allowed the assignment of relative ages to the ...stratigraphic units. Three assemblages were studied in detail and are assigned to the Lopingian. Assemblage L1 is characterized by the rich occurrence of Guttulapollenites and Weylandites. Assemblage L2 is defined on the first occurrence (FO) of abundant Thymospora pseudothiessenii together with Indotriradites niger, Kraeuselisporites spp., Polypodiisporites mutabilis and Polypodiidites sp. Assemblage L3 is characterized by the first occurrence of Osmundacidites senectus together with the taxa described from the previous assemblages. Palynological correlation with other Karoo basins is discussed and three distinct palynostratigraphic events emerge based on the FO and abundance of key taxa (as for instance, FO of G. hannonicus, T. pseudothiensenii and O. senectus). A close palynological correlation between Mozambique (Moatize-Minjova Basin), Tanzania (Selous Basin), Zambia (mid-Zambezi Basin) and Madagascar palynoevents is established. This major region can be assigned to the northern Karoo-aged basins of south-central Africa and the palynoevents can be correlated with Lopingian assemblages of Pakistan, India and some basins of East Antarctica. The southern Karoo-aged basins of south-central Africa, including South Africa and Zimbabwe, show different Lopingian palynoevents and a direct correlation is demanding. These palynological data may open new perspectives for coal exploration in the MMCB as the coal deposits show a wider stratigraphic distribution, reaching until the latest Lopingian.
•Detailed palynostratigraphy of late Permian in Karoo succession of Mozambique•Palynological events through the Karoo central Gondwana paleobiogeographic basins•New data opens new perspectives for coal exploration.
An evaluation of the feasible development of geothermal energy in Mozambique is proposed based on some thermal springs geochemical characterization in the Tete region. Chemical and isotopic data ...suggest that the springs have a meteoric origin and do not show connection with any active magmatic system. The proposed circulation model suggests high depths infiltration of meteoric waters along faults and fractures in a system characterised by discrete permeability and reservoir temperature between 90 and 120 °C. These results, jointly with low salinity fluids and corrosive components absence suggest that the geothermal system may be conveniently exploited for direct and indirect uses.
The family Bunyaviridae has more than 530 members that are distributed among five genera or remain to be classified. The genus Orthobunyavirus is the most diverse bunyaviral genus with more than 220 ...viruses that have been assigned to more than 18 serogroups based on serological cross-reactions and limited molecular-biological characterization. Sequence information for all three orthobunyaviral genome segments is only available for viruses belonging to the Bunyamwera, Bwamba/Pongola, California encephalitis, Gamboa, Group C, Mapputta, Nyando, and Simbu serogroups. Here we present coding-complete sequences for all three genome segments of 15 orthobunyaviruses belonging to the Anopheles A, Capim, Guamá, Kongool, Tete, and Turlock serogroups, and of two unclassified bunyaviruses previously not known to be orthobunyaviruses (Tataguine and Witwatersrand viruses). Using those sequence data, we established the most comprehensive phylogeny of the Orthobunyavirus genus to date, now covering 15 serogroups. Our results emphasize the high genetic diversity of orthobunyaviruses and reveal that the presence of the small nonstructural protein (NSs)-encoding open reading frame is not as common in orthobunyavirus genomes as previously thought.
The Moatize-Minjova Basin is a Karoo-aged rift basin located in the Tete Province of central Mozambique along the present-day Zambezi River valley. In this basin the Permian Moatize and Matinde ...formations consist of interbedded carbonaceous mudstones and sandstones with coal seams. The thermal history has been determined using rock samples from two coal exploration boreholes (ca. 500 m depth) to constrain the burial and exhumation history of the basin. Organic maturation levels were determined using vitrinite reflectance and spore fluorescence/colour. Ages and rates of tectonic uplift and denudation have been assessed by apatite fission track analysis. The thermal history was modelled by inverse modelling of the fission track and vitrinite reflectance data. The Moatize Formation attained a coal rank of bituminous coals with low to medium volatiles (1.3–1.7%Rr). Organic maturation levels increase in a linear fashion downhole in the two boreholes, indicating that burial was the main process controlling peak temperature maturation. Calculated palaeogeothermal gradients range from 59 °C/km to 40 °C/km. According to the models, peak burial temperatures were attained shortly (3–10 Ma) after deposition. Apatite fission track ages 146 to 84 Ma (Cretaceous) are younger than the stratigraphic age. Thermal modelling indicates two episodes of cooling and exhumation: a first period of rapid cooling between 240 and 230 Ma (Middle – Upper Triassic boundary) implying 2500–3000 m of denudation; and a second period, also of rapid cooling, from 6 Ma (late Miocene) onwards implying 1000–1500 m of denudation. The first episode is related to the main compressional deformation event within the Cape Fold Belt in South Africa, which transferred stress northwards on pre-existing transtensional fault systems within the Karoo rift basins, causing tectonic inversion and uplift. During the Mesozoic and most of the Cenozoic the basin is characterized by very slow cooling. The second period of fast cooling and denudation during the Pliocene was likely related to the southward propagation of the East African Rift System into Mozambique.
•VR yields low to medium bituminous coal rank values related to burial.•Peak temperature is reached shortly after deposition, at 240 Ma.•Estimated palaeogeothermal gradients range between 40 and 59 °C/km.•Two cooling phases are identified during the Middle Triassic and Late Neogene.
The surface nuclear magnetic resonance (SNMR) method is a geophysical method designed for non-invasive groundwater investigations. Inversion of experimental data provides the spatial distribution of ...the water content in the subsurface. However, SNMR inversion is ill-posed and admits many solutions because of the imaging equation properties that are compounded by experimental error. SNMR data sets are conveniently presented as complex numbers, thus possessing phase and amplitude components. Subsurface electroconductive formations and fluctuations of the Earth's magnetic field cause non-negligible phase shifts. Consequently, the forward modelling of the SNMR signal generated by 3-D water saturated formations is achieved in the complex domain. Nevertheless, in many cases, phase measurements are less reliable than amplitude measurements and water content rendering cannot be carried out using the complex SNMR signal. This problem is resolved by performing inversion using complex forward modelling whose resulting signal amplitude is used for comparison with the data. Along with water content boundaries ranging from 0 to 1, this property turns the linear initial value inversion problem into a non-linear one. In such a situation, the comprehensive analysis of inversion uncertainties is achieved by performing a solution space exploration based on a Monte Carlo approach. An adapted Metropolis–Hastings algorithm has been used on SNMR 3-D data sets to perform such an exploration. Computing time depends on the problem dimensions. With a standard laptop computer about 10 hr were necessary for the inversion of our field data set. The resulting model collection is used to calculate the probability density functions of the water content. From there, it is possible to estimate the uncertainty of the water content imagery. Using both synthetic and experimental data, we show that our routine provides robust estimates of the spatial distribution of the water content for the SNMR 3-D initial amplitude inversion.
PDF
