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GEOLOGIC DATA BASE.

Tanzania is fortunate in possessing a geologic and mineral database, which is virtually complete for work done since the mid 1930s. Such a comprehensive collection is a major asset in the evaluation of the country mineral resources.

The Geological Survey of Tanzania at Dodoma, within the Ministry of Energy and Minerals, manages this database. The Government and the United Nations started to establish a fully computerized geological database and documentation centre in Dodoma in 1991, which is being developed and updated.

Another valuable data source in Dar es salaam is the Southern and Eastern African Mineral Centre (SEAMIC), a regional geoscientific agency, which has published a number of reports on mineral resources. It also possesses a modern rock mechanics laboratory. Additional geological data are available at the State Mining Corporation, various other Government agencies and the Geology Department, University of Dar es salaam. The database available at the Geological Survey in Dodoma include the following:

•  Topographic Maps.

Topographic maps of various scales, covering most of the country, are on file in Dodoma. Maps at the scale of 1:50,000 are available for most of the country. The maps may be purchased at the surveys and mapping division, Ministry of lands and human settlement.

• Aerial Photography.

The whole country has been covered by aerial photography at varying scales. A library of aerial photographs is available for review in Dodoma. Aerial photographs can purchased at the Survey and Mapping division in Dar es salaam.

• Landsat.

A remote sending Unit has been established under the Tanzania Geological Survey in Dodoma. The Unit carries out satellite image processing.

The resulting data are combined with relevant geological, geophysical and geochemical data to enhance maps using GIS methods. Image scenes are purchased directly from international agencies such as NASA (USA), RCSSMRS (Nairobi,Kenya) and SPOT (Toulouse, France).

•  Geologic Maps.

Geologic maps at various scales cover over 80% of the country. Of the 322 Quarter Degree Sheets (QDS) covering the whole country, 161 have been mapped and published at a scale of 1:125,000, two have been mapped but not published. A total of 59 QDS have not yet been mapped. In addition four Degree Sheets (DS 17, 18, 29 and 52 have been published at a scale of 1: 250,000 with explanation of the geology.

• Geophysical Surveys.

Countrywide airborne coverage by magnetic, electromagnetic (VLF - EM), and radiometric surveys is available. It was flown from 1977 - 1980 by Geosurvey International GmbH and totaled over one million line kilometers with a terrain clearance of 120m. Fligh lines were mainly E -W at a spacing of 1km with tie lines at a spacing. The final product covers 322 Quarterdegree sheets at 1: 100,000 scale. Nine different maps were produced for each sheet making a total of 2,898 maps. Results of the airborne geophysical surveys are archived with the Geological Survey at Dodoma.

In addition to the Geosurvey work, a number of other surveys have been made over specific targets, the majority of them in the Archaean greenstones. Detailed surveys, flown at line spacing of 250 m and altitude of 90m above ground level (a.g.l) were also undertaken over five selected areas, namely Mwadui, in search of kimberlite pipes and Kabanga investigating for nickel associated ultramafic bodies; also uranium, in the Chaya, Manyoni and kwa Mtoro areas in Central Tanzania. Inventories of airborne geophysical surveys in Tanzania have been published ( Parker, 1991; Parker and Marobhe, 1991). These reports summarize airborne geophysical surveys from as long ago as 1951.

Other detailed surveys have been conducted by the following:

• BGR (1988), Helicopter borne geophysical surveys over the SigaMabale Hills greenstone belt;
• BHP (1995), Helicopter magnetic surveys over the Kagera concession area;
• RTZ Mining Exploration (1995), Airborne magnetic and radiometric surveys over Tabora East; and
• TANZAM 2000 (1999), Detailed fixed wing geophysical surveys (Triaxial Gradiometer, 256 channel Radiometrics and Geoterrex Geoterm EM) covering an area of 3587.32 sq km over their concession west of Bulyanhulu towards Biharamulo.

Recently, the Government in collaboration with Nordic Development Fund conducted high resolution airborne magnetic, radiometric and electromagnetic surveys in selected areas including parts of kahama, Biharamulo, Mpanda and Mara.

High resolution Airborne Magnetic Map from Mpanda Area

Geochemical Surveys. Reconnaissance geochemical surveys have been conducted more than 70% of the land area of Tanzania. The surveys were particularly on base metals such as copper, silver and zinc. Other elements were also included in some surveys depending on the purpose of the survey, as presented in the tables 1 and 2.

Most of these data were acquired by companies including Williamson Diamonds Ltd between 1959 and 1974 (520 000 Km2) and Western Rift Exploration Ltd in 1956 -1960 (87 000 km2). Two areas have been covered by the UNDP, west of Lake Victoria in 1975 -77 (19020 km2) and the northern part of the eastern branch of the East African Rift Valley (16 000 km2) in 1980 - 81. In addition there have been several smaller surveys by companies and the Geological Survey in collaboration with the German and Tanzanian Gold Project.

The sampling media and analyzed elements in all of the surveys vary considerably (Table 1).

Large Scale Geochemical Reconnaissance Surveys.

Library.

The Geological Library in Dodoma contains approximately 2,500 published documents dealing with a wide variety of Geological and geotechnical topics, including many international journals.

Core and Rock Library.

Four warehouses are maintained in Dodoma with core and chip samples from drilling programmes carried out during the preceding decades of exploration work. The rock library is at the Tanzania Geological Survey in Dodoma, while the core warehouses are located at the Kizota industrial area in Dodoma Municipality. The core warehouses that store thousands of metres of core, from nearly 1,000 geological and exploration projects, are being rehabilitated. An inventory is on file in the archive.