Mineral Mozambique Introduction

Mozambique  mining equipment

Mozambique mining equipment

About two-third of Mozambique, including the inland areas in the north are underlain by igneous and metamorphic rocks of Archean to Neoproterozoic age. Phanerozoic terrains are found south of the Zambezi valley and along the coastal belt in the northeast.

Archean and Paleoproterozoic terrains are an extension of the Zimbabwe Craton and its supracrustal, but also include granitoids, gneisses and migmatites of the Barue Complex. Two main orogenies are recognised, the lumide belt (1800-1350 Ma) in the northwest and the Ubiquitous Mozambique Belt (1100-850 Ma), with evidence of extensive migmatisa-tion and granitisation as well as various granitoids and supracrustals; together these terrains constitute about 90% of the Precambrian rocks of Mozambique. The Neoproterozoic Cycle (800-410 Ala) is marked by the the formation of the small platform basins, as well as the influence of the Pan-African (Katangan) orogeny in the northwest, and by the emplacement of monzonites, syenites, granites and pegmatites. Carboniferous to upper Jurassic rifting associated with sedimentation and widespread igneous activity led to numerous intercratonic Karroo basins, followed by Post-Karroo continental deposits and vol-canics, as well as Meso-Cenozoic continental and marine deposits, and a thick Plioctocine and Quaternary cover.

The economic mineral potential is largely untapped. Gold has been produced from the Archean Manica Greenstone Belt and various alluvial occurrences; large BIF deposits are also known in this terrain. Numerous pegmatite fields host important deposits of tantalum-niobium, rare earths and semi-precious stones. In addition, heavy-mineral sands, graphite, flourite, apatite, bauxite, dimension stone, various clays, sands, refractory minerals, limestone, coal and natural gas form the bulk of the mineral endowment of the country.

Geological Mapping

After national independence, the government of Mozambique launched an increased geological study for mineral exploration and geological mapping in the country which resulted in identification of several new mineral deposits. However, in 1983 when the civil war intensified the geological mapping and mineral exploration fieldworks were forced to be reduced to a large extent. In 1999 the government relaunched extensive geological studies over the large parts of the country, in order to increase the geological information availability and archiving it systematically for publishing and promotional purposes. During this period the National Directorate of Geology undertook the following activities:

Geological mapping of Niassa and Manica Greenstone Belts

- From 1999 up to 2000: Ngoo, Cobue and Lupilichi in Niassa Province;

- From 2002 up to 2003: sheets 1437 and 1438 in Niassa-Nampula Provinces; and about 25,000 Km2, which covered the districts of Cuamba, Metarica, Muoco, Nipepe, Ribaue, Iapala, Malema and Mutuali;

Geological prospection in selected areas

- In 1999, the field work covering 280 km2 was directed to exploring ornamental stones in Gorongosa area and two types of rocks with economic interest were identified:

  • Granito negro (olivinic gabbro and dolorito) in Mfumo Domba, Monte Ndemera, Monte Nhade areas;
  • Granito roseo (granular granite and granitoides) in Serra Carabina and Serra da Gorongosa areas.

- In 2000, the field work in Espungabera area was carried out and 297 km2 was covered with promising areas of granito negros:

  • Basalto de Chinica, Monte Cibeche, Corneana de Rio Caja, Chirarue, Monte Chicono, Basalto do Monte Mangala.
  • Xisto Ardosio, sources of thermal water in Vira-Vira and Regulo Wilson zone.

- In 2002, Tete Province was explored covering 499 km2 with:

  • Granitos (negro, castanho) with economic interest in Nhatipissa, Ratoneira,Nhambia, Txisita, Buzimuana, Moatize Catema; along Tete-Songo in Cahora Bassa region.

- In 2003 the fieldwork was undertaken in Cahora Bassa and Changara Districts and granites were identified in Maroeira, Nditi, Cahora Bassa,Kadzipande and Thaka areas.

Development of Geological Infrastructure Project

Geological mapping project with the aim of improving the existing geological information and acquiring new information using different methodologies is underway at present. This project has the following geological mapping tasks (see Fig 2):

  • Comprehensive re-mapping of areas underlain by Precambrian rocks (Areas A, B, C, and D) at a scale of 1:250,000 and selected 1:50,000 map sheets.
  • Revision of the geology of the Phanerozoic rocks (Area C)
  • Introduction of contemporary, systematic lithos-tratigraphic classification
  • Production of modern geological map coverage and explanations in digital format
Mozambique Geological Mapping

Mozambique Geological Mapping

Geological mapping of Area A

Between 2003 and 2004 a consortium of three European companies namely the Norconsult, Norway Geological Survey and British Geological Survey, performed the geological mapping and covered 31 map sheets in Niassa and Cabo Delgado Province.

Geological mapping of Area B

The Geological Survey of Finland (GTK), ITC and Gondwana consortium undertook the geological mapping of 24 map sheets in Tete Province and parts of Manica, Sofala and Zambezia provinces.

Geological mapping of Area C

The mapping of the southern region of Mozambique was done by GTK, ITC and Gondwana from 2003 up to 2005 covering 29 map sheets.

Geological mapping of Area D

The South African Council for Geoscience (CGS) and the National Directorate of Geology of Mozambique (DNG) undertook the geological mapping of 12 map sheets in Nampula, Zambezia and Tete Provinces from 2001 to 2004.

Aeromagnetic and Radiometric Survey

The historical geophysical data set, from early 1970′s, covering the northern part of Mozambique was conducted by CGG of France. The survey included total magnetic field and total count radiometrics.

The second set of airborne geophysical data covering the central zone, which included gamma-ray spectrometry measurements (TC,Th, U, K) was conducted by Hunting Geophysics between 1982 and 83. The data is available at the National Directorate of Geology in digital format.

As part of the geological infrastructure development project, regional and detail aeromagnetic and radiometric surveys were conducted bv FUGRO on selected areas. The survey details for the regional survey, flown in 2003/04, were as follows:

  • Line spacing and trend of 1,000 meters at 90°, with gradiometer;
  • Tie line spacing and trend of 10,000 meters at 180°, with gradiometer;
  • Sensor clearance: magnetic and radiometric at 100 meters;
  • Data recorded: magnetic total field horizontal gra-diometry and Gamma Ray Spectrometry;
  • Data sampling: magnetic and radiometric at 8.5 meters (0.1 sec)

Detailed airborne survey for total magnetic and gamma-ray spectrometric data was acquired in 2004/05 on 6 selected areas. Survey details were as follows

  • Line spacing and trend of 300 meters at 90°, with gradiometer
  • Tie line spacing and trend of 3 000 meters at 000°, with gradiometer
  • Sensor clearance: magnetic and radiometric at 80 meters
  • Data recorded: magnetic total field horizontal gradiometry and Gamma Ray Spectrometry
  • Data sampling: magnetic 7 meters (0.1 sec) and radiometric at 70 meters (0.1 sec)

The digital gridded data set is available at DNG and consists of the following individual data grids in GEOSOFT format, gridded at 250m cell size:

  • Total field magnetic, reduced to the pole magnetic, calculated vertical gradient, calculated horizontal gradient, analytical signal, IGRF corrected magnetic;
  • Potassium %, equivalent uranium ppm, equivalent thorium ppm, natural air absorbed rate, uranium/thorium ratio, uranium/potassium ratio, thorium/potassium ratio, digital terrain model;
  • Line data (Magnetic): Line Number, GPS time, fiducial, date, flight, aircraft registration, GPS latitude/longitude in WGS84 , X / Y co-ordinates in UTM, magnetic raw, residual diurnal correction, magnetic levelled, radar altitude, barometric altitude, terrain elevation and
  • Line data (Radiometric): Line Number, GPS time, fiducial, date, flight, aircraft registration, interpolated latitude/longitude in WGS84, Interpolated X/Y co-ordinate in UTM, raw total count, raw potassium, raw uranium, raw thorium, processed potassium, processed uranium, processed thorium, radar altitude, barometric altitude, terrain elevation, temperature.

Geochemical surveys

The first significant geochemical exploration work was carried out by Borches. From 1970 to 1974 geochemical exploration was conducted on a broader scale, mostly by Portuguese and French teams, and by the end of 1974 about 19% of the country had been surveyed at the reconnaissance and regional levels mostly for base metals.

Most of the major geochemical surveys carried out at this period were executed by private companies with technical assistance of geologists from the National Institute of Geology of Mozambique. About 270,000 km2 or 34% of the country was surveyed using various geochemical sampling methods.

Most of the geochemical data was available only as hard copy maps and data tables. Original heterogeneous data (methodology, elements, missing results) had to be gathered in order to establish the use of existing information. Maps had to be scanned, georef-erenced and digitized which involved considerable amount of manual work. In these surveys only base metals have been analysed bv AAS. Gold was not analysed. New surveys with multi-element analysis generally cover only small areas.

During the GEODESA project of SEAMIC in 1998 and 1999, different digital data sets of Manica, Tete and Zambezia Provinces were digitized, which included the following:

  • The sample locations including the assay (Cu, Co, Ni, Zn) of Mavita-Gogoi area in Manica Province;
  • Generation of Mineral Occurrence data set from the same map (commodity, type of mineralization, location and commodity number);
  • Digitalization of sample location points from Regional reconnaissance and follow up geochemical maps and join assay data (Cu, Co, Ni, Zn, Pb) scanned to MS Excel;
  • The UNDP Geochemical maps (Cu, Co, Ni, Pb, Cr, Mo, Zn) of Tete province namely Monte Caperimbeua, Rio Maue, Cadzomba, Metengobalame, Macungua, Cacomue, Dezenza, Chitipi, Capitaciria, Namadende, Domue and Furancungo have been digitised and the data are available;
  • The data set from Zambezia Province done by Aquater (20 elements) was converted to MS Excel format which can be imported into any G1S package;
  • Under Greenstone Belt project (Lupiliche-Metangula, Niassa province) – Geological, geochemical, stream sediment samples, rock samples and ternary maps at a scale 1:50,000 have been produced and digitized.

As part of Mineral Resource Management Capacity Building Project, Geochemical and Industrial Mineral Surveys (GIM) were started in March 2005 by a consortium of GTK and Gondwana Ltd. The survey is expected to be completed by the end of 2007.

As part of Mineral Resource Management Capacity Building Project, Geochemical and Industrial Mineral Surveys (GIM) were started in March 2005 by a consortium of GTK and Gondwana Ltd. The survey is expected to be completed by the end of 2007.

The project was divided into three phases:

Phase I: Compilation and synthesis of existing data (info of earlier geochemical surveys, available samples (including reanalysis), design of GDB, training, GIS)

  • Scanning of the maps (map mosaics)
  • Georeferencing
  • On-the-screen digitizing (data tables):1)sample points, 2)calculating the coordinates (UTM/ WGS 84/Zone 36S – metric system)
  • adding the analytical data into data tables
  • the Survey Information Table (SIT); METADATA
  • the Analysis Data Tables (ADT) containing the actual analytical and coordinate data (UTM/WGS 84 -Zone 36S).

Phase II: Execution of new surveys (two stages: fieldwork and training)

  • regional soil sampling survey, and detailed soil-sampling

Phase III: Final Products (GDB with existing survey data)

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