Direccao Nacional de Geologia
Direccao Nacional de Geologia
Macheyeki A.S.,Geological Survey of Tanzania |
Mdala H.,Geological Survey of Malawi |
Chapola L.S.,The Catholic University of Malawi |
Manhica V.J.,National Directorate of Geology |
And 14 more authors.
Journal of African Earth Sciences | Year: 2015
The East African Rift System (EARS) has natural hazards - earthquakes, volcanic eruptions, and landslides along the faulted margins, and in response to ground shaking. Strong damaging earthquakes have been occurring in the region along the EARS throughout historical time, example being the 7.4 (Ms) of December 1910. The most recent damaging earthquake is the Karonga earthquake in Malawi, which occurred on 19th December, 2009 with a magnitude of 6.2 (Ms). The earthquake claimed four lives and destroyed over 5000 houses. In its effort to improve seismic hazard assessment in the region, Eastern and Southern Africa Seismological Working Group (ESARSWG) under the sponsorship of the International Program on Physical Sciences (IPPS) carried out a study on active fault mapping in the region. The fieldwork employed geological and geophysical techniques. The geophysical techniques employed are ground magnetic, seismic refraction and resistivity surveys but are reported elsewhere. This article gives findings from geological techniques. The geological techniques aimed primarily at mapping of active faults in the area in order to delineate presence or absence of fault segments. Results show that the Karonga fault (the Karonga fault here referred to as the fault that ruptured to the surface following the 6th-19th December 2009 earthquake events in the Karonga area) is about 9. km long and dominated by dip slip faulting with dextral and insignificant sinistral components and it is made up of 3-4 segments of length 2-3. km. The segments are characterized by both left and right steps.Although field mapping show only 9. km of surface rupture, maximum vertical offset of about 43. cm imply that the surface rupture was in little excess of 14. km that corresponds with Mw = 6.4. We recommend the use or integration of multidisciplinary techniques in order to better understand the fault history, mechanism and other behavior of the fault/s for better urban planning in the area. © 2014 Elsevier Ltd.
Emmel B.,University of Bergen |
Kumar R.,University of Bergen |
Ueda K.,University of Bergen |
Jacobs J.,University of Bergen |
And 3 more authors.
Tectonics | Year: 2011
In this paper, we present a conceptual model to describe the post-Pan-African (<∼500 Ma) basement cooling pattern for NE Mozambique. The cooling history is derived from combined low-temperature thermochronological dating methods comprising titanite, zircon and apatite fission track data. After Pan-African orogenesis (∼620-530 Ma) the Precambrian basement was subject to extensional tectonics and a relatively slow Lower Ordovician to Recent cooling with rates of ∼2.2°C to 0.1°C Myr-1. Basement rock cooling was mainly a response to Late Paleozoic to Mesozoic rifting between northern Mozambique and East Gondwana during the opening of the Rovuma and Mozambique sedimentary basins. Meanwhile, different dynamic margin and basin types evolved along the eastern and southern continental margins of NE Mozambique. During the Late Carboniferous-Triassic an intracontinental rift opened between NE Mozambique and East Antarctica, and the fastest denudation was focused along the present southern continental margin. Since the Middle Jurassic, tectonic denudation along the Rovuma margin was localized in a narrow zone, some 30 km wide, associated with erosion along strike-slip faults. In contrast, the Jurassic-Cretaceous opening and ocean crust formation in the Mozambique Basin were accompanied with an unusually uniform Late Cretaceous cooling pattern over a large area (∼150,000 km2) of the basin hinterland. This pattern can be explained by isostatic and erosional response to magmatic underplating or differential stretching, whereby the old Pan-African lithospheric structure appears to have important controls on later events. Copyright 2011 by the American Geophysical Union.
Borodin P.,Russian Academy of Sciences |
Brenes J.,Instituto Costarricense Of Electricidad |
Daudi E.,Direccao Nacional de Geologia |
Efendi N.,Meteorological and Geophysical Agency |
And 15 more authors.
Data Science Journal | Year: 2011
Good magnetic observatories are needed more than ever for global modeling and navigation. Magnetic satellite missions, once said to be the death of ground based observations, are now demanding quality data from fixed observations points on the Earth.
Grantham G.H.,Council for Geoscience |
Grantham G.H.,Japan National Institute of Polar Research |
Macey P.H.,Council for Geoscience |
Horie K.,Japan National Institute of Polar Research |
And 6 more authors.
Precambrian Research | Year: 2013
Reconstructions of Gondwana place Dronning Maud Land, Antarctica (DML) adjacent to N. Mozambique prior to fragmentation. The Monapo Complex outlier klippen overlying the Nampula Terrane in N. Mozambique has been correlated with rocks in eastern and central DML. Metamorphic assemblages and P-T conditions from the two areas are compared as well the timing of metamorphism. Granulite grade assemblages preserved in the Monapo Complex suggest P-T conditions of ~900. °C and >10. kb. Textures vary with reactions typical of isothermal decompression, isobaric cooling and hydration being recognized but also include equilibrium assemblages. P-T estimates from four samples suggest initial inversion of high pressure assemblages from at least ~10. kb and ~900. °C to mid-crustal levels where near isobaric cooling and hydration at between ~4-7. kb and 550-700. °C is recognized. Granulite grade assemblages from Balchenfjella in eastern Sør Rondane, DML suggest initial P-T conditions of ~900. °C and >10. kb. Textures vary with reactions typical of decompression, cooling and hydration being recognized but also include equilibrium assemblages. P-T estimates from four samples suggest initial inversion of high pressure assemblages from at least ~10. kb and ~900. °C to mid-crustal levels where retrogression at between ~6-7. kb and 600-700. °C is recognized.SHRIMP zircon data from six samples from eastern Sør Rondane show episodic zircon growth over a period from ~630. Ma to ~530. Ma with five metamorphic pulses being defined. Undeformed granitic intrusions with ages of ~550. Ma intrude Sør Rondane. SHRIMP zircon data from samples from alkaline intrusions and mafic granulites in the Monapo Complex yield crystallization and metamorphic ages of ~635. Ma and 570-590. Ma respectively. The complex is intruded by granitic veins with ages of ~550. Ma.The similarities in metamorphic mineral assemblages, P-T estimates and zircon geochronology data indicate a common geological history between Sør Rondane and the Monapo Complex of northern Mozambique. This common history is interpreted to result from both areas being part of a mega-nappe structure which was emplaced in a transpressional setting involving collision between N. Gondwana (comprising rocks of the East African Orogeny) and south Gondwana (comprising the Nampula Terrane of northern Mozambique and the Maud Province of western Dronning Maud Land) along the Damara-Zambesi-Lurio-CDML collision boundary.Other erosional remnants of this nappe include the Mugeba Complex in northern Mozambique, the Kataragama klippe in Sri Lanka, the Urungwe klippe in Zimbabwe, the Masosa Suite and Mavhuradohna Complex in western Mozambique and NE Zimbabwe. © 2012 Elsevier B.V.
Moabi N.G.,Central Regions Unit |
Grantham G.H.,Central Regions Unit |
Roberts J.,University of Pretoria |
le Roux P.,University of Cape Town |
Matola R.,Direccao Nacional de Geologia
Journal of African Earth Sciences | Year: 2014
Whole rock major and trace element chemistry as well as radiogenic isotope data from the Espungabera Formation of central Mozambique are compared with published data from the Umkondo Formation lavas in SE Zimbabwe and Straumsnutane Formation lavas in western Dronning Maud Land, Antarctica. These formations form part of the ~1100. Ma Umkondo Igneous Province in southern Africa and are now preserved on the Grunehogna (in Antarctica) and Zimbabwe (in Zimbabwe) Cratons.The chemical data indicate that the Espungabera Formation lavas are dominantly tholeiitic and basaltic to basaltic andesitic in composition. The Espungabera lavas are dominated by plagioclase, clinopyroxene and Fe-Ti oxides. Metamorphic mineral assemblages indicate the lavas have been metamorphosed under mid-greenschist facies on a retrograde path to prehnite-pumpellyite facies conditions. The decrease in FeOt with increasing MgO content in the Espungabera lavas and the slight decrease in TiO2 with increasing MgO indicates fractionation of Fe-Ti oxides. The lavas are characterised by negative Nb anomalies; enriched LILE's and high 87Sr/86Sr isotopic ratios. The 87Sr/86Sr data calculated at 1100Ma suggest contamination by continental crust during the petrogenesis of the lavas. The Espungabera volcanics have negative εNd values (-2.83 to -3.49) also suggesting that the magma was contaminated by older crust.Comparison of the chemical data from the Espungabera Formation with data from the Umkondo Group basalts from SE Zimbabwe and the Straumsnutane Formation lavas from Dronning Maud Land, Antarctica shows that they are similar. These similarities, along with similarities in the available geochronological data suggest that these rocks are comagmatic. Both units are also geochemically similar to some rock units that form part of the Umkondo Large Igneous Province (i.e. Zimbabwe basalts that were regarded as Umkondo basalts by Munyanyiwa (1999), Waterberg sills, Umkondo sills and Type III Mutare and Guruve dykes identified by Ward (2002)), and therefore we conclude that the Espungabera lavas in Mozambique also form part of the Umkondo Igneous Province.The craton-based tholeiitic Umkondo Igneous Province is broadly coeval with tonalitic calc-alkaline and granitic gneisses in the Nampula and Maud Terranes in Mozambique and Antarctica respectively, immediately east of the Kalahari Craton in a reconstructed Gondwana. These data can be interpreted to indicate that the Espungabera and Straumsnutane lavas form part of a back-arc complex, west of a volcanic arc/subduction zone along the eastern margin of the Kalahari Craton at ~1100. Ma. © 2014 Elsevier Ltd.
Eberle D.G.,Council for Geoscience |
Daudi E.X.F.,Direccao Nacional de Geologia |
Muiuane E.A.,Eduardo Mondlane University |
Nyabeze P.,Council for Geoscience |
Pontavida A.M.,Direccao Nacional de Geologia
Journal of African Earth Sciences | Year: 2012
The National Geology Directorate of Mozambique (DNG) and Maputo-based Eduardo-Mondlane University (UEM) entered a joint venture with the South African Council for Geoscience (CGS) to conduct a case study over the meso-Proterozoic Alto Ligonha pegmatite field in the Zambézia Province of northeastern Mozambique to support the local exploration and mining sectors. Rare-metal minerals, i.e. tantalum and niobium, as well as rare-earth minerals have been mined in the Alto Ligonha pegmatite field since decades, but due to the civil war (1977-1992) production nearly ceased. The Government now strives to promote mining in the region as contribution to poverty alleviation. This study was undertaken to facilitate the extraction of geological information from the high resolution airborne magnetic and radiometric data sets recently acquired through a World Bank funded survey and mapping project. The aim was to generate a value-added map from the airborne geophysical data that is easier to read and use by the exploration and mining industries than mere airborne geophysical grid data or maps. As a first step towards clustering, thorium (Th) and potassium (K) concentrations were determined from the airborne geophysical data as well as apparent magnetic susceptibility and first vertical magnetic gradient data. These four datasets were projected onto a 100. m spaced regular grid to assemble 850,000 four-element (multivariate) sample vectors over the study area. Classification of the sample vectors using crisp clustering based upon the Euclidian distance between sample and class centre provided a (pseudo-) geology map or value-added map, respectively, displaying the spatial distribution of six different classes in the study area. To learn the quality of sample allocation, the degree of membership of each sample vector was determined using a-posterior discriminant analysis. Geophysical ground truth control was essential to allocate geology/geophysical attributes to the six classes. The highest probability to meet pegmatite bodies is in close vicinity to (magnetic) amphibole schist occurring in areas where depletion of potassium as indication of metasomatic processes is evident from the airborne radiometric data. Clustering has proven to be a fast and effective method to compile value-added maps from multivariate geophysical datasets. Experience made in the Alto Ligonha pegmatite field encourages adopting this new methodology for mapping other parts of the Mozambique Fold Belt. © 2011 Elsevier Ltd.