Welcome
Antonio Pedro, Director General of SEAMIC.

Official opening by
The Hon. Dr. Abdalah O. Kigoda, Minister of Energy and Minerals of the United Republic of Tanzania.

Introduction
Barthold Schroot, Chief Geoscientist of the Geodesa project

A review of the nature and evolution of the Archaean granite-greenstone crust of Southern Africa Prof. Carl Anhaeusser, Director Economic Geology Research Unit, Wits University, RSA.

Tectonic controls on gold mineralisation in the Zimbabwe craton: the use of large databases for gold exploration
Prof. Paul Dirks, Structural geologist, University of Zimbabwe.

Archaean Granite-greenstone metallogeny in Southern Africa with particular emphasis on gold mineralization Prof. Carl Anhaeusser, Director Economic Geology Research Unit, Wits University, RSA

Geological and chronological setting of the greenstone belts of NE Congo J. Lavreau, Royal Museum for Central Africa, Belgium

Historical review of the Swaziland gold mining and exploration in the greenstone belt of the Barberton mountain land
A.M. Vilakati, Director Deological Survey & Mines Dept., Swaziland Mineral deposits in the Zimbabwe craton Forbes Mugumbate, Acting Director Geological Survey Dept., Zimbabwe

Special session: Precambrian tectonic evolution
Proterozoic evolution of Africa Steven F. Olson, Sanu Resources, Tanzania.

A geophysical view of the Precambrian terranes of the 'Geodesa' region and its surroundings Colin Reeves, ITC, Netherlands.

Late-Archean growth and stabilisation of the Zimbabwe craton Prof. Paul Dirks and H.A. Jelsma, University of Zimbabwe.

Southern Africa's Mineral Treasures - A Brief Overview of the Nature and Occurrence of Early Proterozoic to Recent Ore Deposit Types
Prof. Carl Anhaeusser, Director Economic Geology Research Unit, Wits University, RSA.

Geotectonic evolution of the Ubendian belt of Central and Eastern Africa with special reference to magmatism.Prof. Henry Kampunzu, Univ. of Botswana.

Geology of the lower Proterozoic Syama gold mine, Mali, West Africa
Steven F. Olson, Sanu Resources, Tanzania

Shear zone hosted gold mineralisation of Kaabong, NE Uganda Baguma Zachary, Geological Survey and Mines Department, Uganda.

Diamond exploration in Botswana Terence Siamisang, Ministry of Minerals, Energy and Water Affairs, Botswana.

Dykes of the Geodesa countries Prof. Colin Reeves, ITC, Netherlands.

Reprocessing and back-calibration of airborne radiometric data (on the boundary between Archaean and Proterozoic), Tanzania Gosbert Kagaruki, Geodesa, Tanzania.

Regional surveys in identification of major geological terranes, Zambian example Mesfin Wubeshet, Geodesa, Tanzania.

VMS exploration in the Areachap terrane of South Africa: discovery implication for Mesoproterozoic of southern Africa Tony Cain, Iscor Ltd, South Africa.

Running rings around the NE Kibaran belt Sally Barritt, Applied Geophysics Dept. ITC, the Netherlands.

The prospectivity of the Kundelungu foreland for metallic ineralisation revised (Lufilian Arc, D.R. Congo) G. Franceschi, GF Consult, Belgium.

An overview of metallic mineral resources potential of Ethiopia Masresha G. Selassie, Ethiopian Institute of Geological Surveys.

Uranium-Gold distribution in drainage sediments of Kasama area, Zambia Mwape Fred Njamu, Geological Survey Department, Zambia.

Structures of gold mineralisation in western Tigray, Northern Ethiopia Getachew Tesfaye, Ethiopian Institute of Geological Surveys.

Geoscience data correlation and mineral assessment in the recambrian basement complex and Phanerozoic cover in the Kirk Range - Angonia Region of the Mozambican Belt Dominigos Pilale, National Directorate of Geology, Mozambique.

Geophysical and geochemical integrated data - NE Kibaran V.B. Ntulanalwo. Y.F. Myumbilwa, B.J. Shubi, Tanzanian Geological Survey - (MADINI).

The geochemical landscape of Swaziland Frank van Ruitenbeek and Beauty Mazibuko, Geodesa, Tanzania.

Regional Geochemical and Geophysical Exploration Surveys – A GIS based inventory in eastern and southern Africa – Hans Erren and Frank van Ruitenbeek, Geodesa, Tanzania.

Visualisation of geochemical exploration data from the Rift Valley, Tanzania Abdul Ishegize and Mbasha, Geodesa, Tanzania.

Exploration for kimberlites using indicator minerals sampling method Anna-Karren Nguno, Geological Survey of Namibia.

Gold exploration in the Kirk Range - Lisungwe Valley Charles E. Kaphwiyo, Geological Survey of Malawi.

Integration of exploration data to assess mineralisation potential in eastern Zambia Emmanuel Mulenga, Geological Survey Department, Zambia.

Re-assessment of pre-1960 mining archives with present-day GIS technology: Case studies from the D.R. Congo Max Fernandez, Royal Museum for Central Africa, Belgium.

Digital thematic mapping of the NE Kibaran mobile belt Julius Nyakana, Geological Survey Dept. Uganda.

Busumbu phosphate resources, southeastern Uganda Katto Edwards, Geological Survey Dept. Uganda.

Antonio Pedro started the proceedings and welcomed all present. He made special mention of the evident healthy representation from the 'stakeholders' including the private exploration sector. He explained the origins of SEAMIC (formerly ESAMRDC) and stated briefly how the Geodesa project came into being. While the mineral sector worldwide might now be in relatively depressed state, things were keeping up quite well in parts of Africa and he suggested that, where it was necessary, best use should be made of any slack to 'take stock' of the geological potential of the region.

Hon Abdalah O. Kigoda (Minister of Energy and Minerals) stated that the theme of the workshop required technicians for its execution but also the creation of an enabling environment, peace and the right mindset; There was no sense in shouting about the resources of the region without the other necessary aspects of support. To achieve this, the national governments should work as a 'smart partnership' rather than adopt a 'beggar thy neighbour' approach. Further, profit motives should be tempered with social and cultural consciousness realisable through private sector-government cooperation. He thanked the Geodesa project, SEAMIC and the European Union before formally opening the workshop

For the benefit of those attending this workshop for the first year, Barthold Schroot stressed the role of Geodesa in three fields: (1) improving the accessibility of data (2) Training geoscientists and (3) creating a forum for the interaction of geoscientists. The workshop fell within the last category. The morning session then continued with two presentations, one on the South African Archean, and the other on that of Zimbabwe.

Professor Carl Annheuser gave an opening review of the state of knowledge of the evolution of the Archean granite-greenstone terrane in southern Africa. The stratigraphy of the Barberton greenstone belt was reviewed and he emphasized the transition from komatiitic igneous rocks at the base to more or less felsic ones at the top with cherts, stromatolitic remains and arenaceous continental sediments, fluvial structures, etc. Three separate cycles of granitic intrusion were evident at 3.5-3.4 Ga, 3.1 Ga and 2.8 Ga. The entire transition from a presumed oceanic environment to a stable continental block with a thickness of 35 km was achieved in 700 million years. He concluded by drawing some comparisons with the Pilbara block of Western Australia, the Zimbabwe craton and, finally with the Kaapvaal craton south of Mafeking.

Professor Paul Dirks addressed the occurrence of gold in the Zimbabwe craton and the search for geological controls on its distribution. He discussed a database his group had constructed with over one million entries referring to known gold showings and occurrences in Zimbabwe. He highlighted the frequency of shear zones in greenstones and the high coincidence of gold with both. He also pointed out the increase of grade with proximity to shear zones. In the discussion, the contribution of other methods to mapping shear zones was raised, including aeromagnetic and satellite imagery. Prof Dirks stressed that even drainage patterns could be used to map them quite clearly.

Opening the afternoon session, Carl Anheusser reviewed the metallogeny of the Archean in southern Africa, stressing the large percentage of presumed Archean terrane that was hidden by more recent cover. He gave a well-illustrated tour of many active mines in the region, emphasizing, of course , the world-class stature of South Africa's gold production from the Witwatersrand gold field. For exploration he stressed the need for combining the geological (map) knowledge with a theoretical approach to understanding the basis of ore deposit formation.

Jean Lavreau gave an intriguing review of the NE Congo gold district - a large area of little-explored and even more poorly exposed granite-greenstone that has been explored only superficially in more than 100 years, extending from Uganda to the Central African Republic. It follows a NW-trending mega-feature in the drainage of central Africa, one of many references made during the workshop to the unknown but prominent role of NW-SE and NE-SW trending 'lineaments' across the whole of Africa and even further afield. Gold output to date has exceeded 400 tonnes and reserves stand presently at more than 100 tonnes. The formations there include tonalites dated at 2.7 to 2.9 Ga and granites dated at 2.4-2.6 Ga. Again, much of the gold production can be attributed to discoveries located in shear zones.

A.M.Vilakati reviewed the history of gold mining in Swaziland and its association largely with 3.5 Ga reef formations. He pointed out that the greenstone are of Swaziland is now a nature reserve, deemed outside of exploration.

Forbes Mugumbate returned to the theme of the mineral resources of the Zimbabwe craton. This is known for its gold, but also some success has been achieved with kimberlite exploration. The platinum reserves of the Great Dyke were described, but it is the gold that is produced at about 20 t per year since 1900 (???). Most deposits are very small, many based on ancient workings rather than modern technology. The time is ripe, he claimed, to revisit some of the 600 or more occurrences. The legislation is right, the licenses are cheap and exploration has taken off.

In the ensuing discussion, Paul Dirks re-iterated the poorly understood tectonics of greenstones. He advocated accretionary plate tectonics with repeated overthrusting. On the other hand, Carl Annheusser indicated that no Cyprus type ophiolite had ever been found in any Archean greenstone. Similarly, no komatiite is ever found in present day oceans, despite their abundance in Archean times. Henri Kampunzu stressed the change in thermal regime at about 2.6-2.8 Ga. Guy Franceschi drew attention to the relative lack of mineralisation in the Birrimian (West Africa), despite geological features that are very greenstone-like, except for the occurrence of Mn rather than Fe. Henry Kampunzu pondered the lack of porphyry coppers in the Archean, despite their appearance in the Proterozoic. Jean Lavreau mentioned the possible role of the mantle and meteorite impacts. Paul Dirks remarked about the difficulty in finding an evident contact of the true Archean of Zimbabwe with the Proterozoic to its east where a 1000 Ma overprint is clear. The 'Archean' evidently goes a lot further than expected, now emerging as a reworked alias in much of northern Madagascar as well.

The second day started with a fresh look at the geological architecture of Africa (and its burdensome nomenclature) by Steve Olson. This served to underline the complexity of the continent as a whole and the many unknowns that surround most aspects of its evolution over time. Repeated accretion and polyphase metamorphism produced a large stable continental plate by the end of the Precambrian that included not only Africa but all the other 'southern' continents as well (Gondwana). Adopting a geophysical mapping approach, Colin Reeves then attempted to look at the same supercontinent by working backwards from the present day to the Precambrian. The reassembly of Gondwana by the start of the Jurassic was demonstrated using a computer animation. The relation of the Precambrian of Madagascar, India and Antarctica to the formerly adjacent areas of Africa (many Geodesa countries) was emphasized, together with the importance of intra-plate tectonics in reshaping Africa and, perhaps, creating - or at least exploiting - the NW-SE and NE-SW lineations. Paul Dirks then used the Zimbabwe craton as the best-exposed Archean craton in the world as a site to explore Archean crustal evolution, from 3.6 Ga to 2.58 Ga when the Great dyke was emplaced, testifying to the stability of the total craton. His ideas stressed the repeated stacking of stratigraphic sections by overthrusting, leading to non-consecutive age-dates and a multiplicity of very thin shear zones. From about 2.5 Ga, more 'conventional' plate tectonics took over.

The afternoon session was opened by Prof. Carl Anheusser who gave a comprehensive overview of the world-leader gold production in the Witwatersrand where 40,000 tons of gold have been produced until now.

Prof. Henry Kampunzu then presented his paper on the geotectonic evolution of the Ubendian belt and emphasized the potential of seeing the magmatism as a tool for the geotectonic modelling. He concentrated on the Moba area west of Lake Tanganyika and decribed how the former ocean west of the Tanzanian craton was subducted below the congo craton, culminating in the collosion of the two continental blocks and the detachment of the down-going slab. He postulated the origin of a porpyry copper zone above this location, now eroded away. The copper of the Copperbelt owes its origin to this, he stated.

Steve Olson described the development of the Syama gold mine in Mali, near the border with ivory Coast. The mine lies within the greenstone-like belts of the Birrimian and was the site of ancient workings. even the tailings from these workings can be re-worked profitably and the gold-rich soil above provided the first year's input to the processing plant.

Bagumaa Zachary explained the history of the Branch Energy concession in NE Uganda near the Kenya border within the Mozambique belt. Despite extensive trenching and analysis and encouraging results, this occurrence has not yet proved profitably to develop.

The first Poster Session was held after the tea interval and lively discussions centred around the displays in the adjacent poster space.

After having discussed mineral deposits of Archean and Early Proterozoic age, some deposits hosted by Middle Proterozoic fold belts were discussed. Two presentations dealt with the Kibaran: Max Fernandez of the Royal Museum for Central Africa in Tervuren (Belgium) discussed the geology of the Kabungu-Musongati mafic/ultramafic belt in Burundi. The belt appears confined to a curved shear zone separating the internal from the external domain of the Kibaran belt in Burundi. Emplacement of the strongly sheared massifs appears to have taken place in two steps whereby ultramafic magmas were followed by mafic magmas. Geochronological dating indicates an age of 1275 ± 10 Ma for the (ultra)mafic massifs. In view of the fact that these bodies are post-kynematic the Kibaran Orogeny has to be attributed an older age than hitherto accepted.. It was concluded that the bodies have significant potential for Ni-laterite, Ni-sulphide and PGE deposits. Further exploration is needed, however. Sally Barritt of ITC in Delft (the Netherlands) drew attention to curvi-lineair dike swarms that stand out as striking features in air-borne magnetic imagery. They follow the grain of but are not restricted to the NE Kibaran belt. Parallel dikes are emplaced in the undeformed rocks of the Kibaran foreland and in older, pre-Kibaran rocks. The age of the mafic dikes is unknown but a correlation with the massifs of the Kabungu-Musongati mafic/ultramafic belt cannot be excluded. A lively discussion followed on the curved nature of the dike swarm. It was suggested by some in the audience that the dike swarm is part of a huge truncated collapse structure. Another discussion concerned the nature of lineaments. It was agreed that lineaments are linear features measuring nx100 km in length forming narrow corridors (1 – 15 km) of crustal yielding. Their positive relationship with mineral deposits may be explained by the fact that they constitute preferential sites of magma emplacement and fluid flow.

Tony Cain of IscorLtd. (RSA) reported on volcanogenic massive sulphide (VMS) exploration in the Middle Proterozoic Areachap terrane in the Northern Cape province of South Africa. The terrane is interpreted as a highly deformed and metamorphosed island arc and contains a number of VMS deposits and prospects, including the worked-out Prieska mine. The area has been actively explored by several companies without significant results. Grass roots exploration by Iscor started in 1995 and appears more rewarding. Extensive use is being made of modern metallogenic modelling, notably regional lithochemical alteration mapping to focus in to mineralisation. In the Areachap terrane footwall alteration may extend to over 10 km along strike and up to 100 m in thickness and constitutes an important area selection criterion. Parallels are drawn with similar gneissic terrains (or terranes) in Namibia and Mozambique that, so far, have remained virtually unexplored. Tony drew particular attention to peculiar rock types such as meta-cherts, Ca-silicate horizons and cordierite and/or garnet and/or anthophyllite-rich assemblages that may represent metamorphosed exhalites or alterites.

The presentations on mineral deposits of Pan-African age focussed on the Copper Belt deposits of the Lufilian arc and the Kundulungu foreland and on the mineralisation within the Arabian-Nubian Shield of Ethiopia.

Francis Tembo from the University of Lusaka presented new insights into the tectonogenesis and metallogenesis of the Lufilian arc, a world class depository of copper and cobalt: 5000 Mt grading 3% Cu and 2000 Mt grading 0.2% Co. Polymetallic and precious metal mineralisation is hosted by the more than 10 km thick sequence constituting the Katanga Supergroup which was deposited in a Neoproterozoic rift structure (aulacogen?). The stratiform Cu-Co-Au-PGE mineralisation is related to the initial rifting phase characterised by bi-modal magmatism and deposition of clastic sediments. As the rift evaluated other types of mineralisation, including stratabound Pb-Zn-Cu deposits, were emplaced. Part of the mineralisation is remobilised during subsequent deformation along ductile shear zones (and as such can be used as a guide to deeper stratabound mineralisation). In the discussion following the presentation, one of the questions raised was whether the Lufilian rift had reached the stage of oceanisation. In other words whether the Katangan sediments are underlain by an oceanic floor. The presence of white schists and eclogites are indicative of HP-LT metamorphism and suggest subduction at one stage. This is being supported by the discovery of ophiolitic material as reported by Paul Dirks.

Guy Franceschi of GF Consult of Gent (Belgium) presented new data on the Kundulungu terrain, the foreland of the Lufilian arc. Hitherto this area, considered to be an pre-Karroo graben structure, was considered rather unprospective. Recent fieldwork suggests deformation including "décollement" and the formation of duplex structures. This may have transported deeply buried primary stratiform mineralisation to higher structural levels in dome-shaped structures. Although the type of duplex structures are not precisely known, the new structural model together with the presence of two modest but high-grade Cu(-Ag) mineralised bodies and numerous showings has drastically changed the prospectivity of the Kundulungo foreland.

Masresha Selassi and Getachew Tesfaye both of the Ethiopian Institute of Geological Surveys reported on exploration in those parts of Ethiopia belonging to the Arabian-Nubian Shield. Masresha started with an historical overview, highlighting the discovery of the Lega Dembi gold deposit (200 t) and the Kenticha tantalite deposit (25000 t). Search metals further include basemetals, PGE's, Mn and Fe. Getachew conentrated on recent exploration results in western Tigray, northern Ethiopia. Gold appears confined to dextral transpressional shearzones in or near altered serpentinites and quartz veins.

Fred Njamu of the Geological Survey Department, Lusaka, concluded session 4 by reporting on U and gold distribution in drainage sediments in the Kasama area in northern Zambia. Gold-uraninite bearing conglomerates at the base of the Mporokoso Group could prove to be an interesting exploration target.

This session only comprised a presentation by Anna-Karren Nguno of the Geological Survey of Namibia on the use of the chemistry and distribution of indicator mineral to distinguish between barren and diamondiferous kimberlites in the Gibeon area in southern Namibia. The geology of diamond is changing rapidly and it is questionable whether Clifford's Rule is still valid in view of recent diamond founds in Ireland?

The sub-title of the workshop is 'Their origin and how to find them'. In the past couple of days most presentations dealt with the origin, i.e., the genesis of metal deposits. A number of presentations were more concerned with the search process. The new model of granite-greenstone terrains presented by Paul Dirks will certainly have its impact on exploration. Tony Cain already stressed the importance of ore deposit models in the search for VMS deposits in a metamorphic and deformed environment. Guy Franceschi gave a good example as to how the new structural interpretation of the Kundulungu platform, the foreland of the Lufilian arc, can drastically change the prospectivity of the area. Anna-Karren Nguno demonstrated the value of the chemistry of indicator minerals in area selection for diamond exploration.

'How to find ore bodies?' There is not a cooking book telling us how to find ore bodies. Finding economic deposits is still partly science, partly art whereby the best use is being made of tools and concepts. Phil Westerhof of ITC in Delft (the Netherlands) started the session by explaining that ore controls are active on different scales, from regional to local. He further stressed the differences in approach between academia and industry in ore deposit modelling, i.e. the use of theoretical versus empirical models. Most importantly, however, are the facts (the field observations and the geochemical and geophysical data).

Charles Kaphwiyo of the Geological Survey of Malawi continued with a presentation on gold exploration in the Kirk Range-Lisungwe Valley area. He started by outlining the history of gold exploration in Malawi, indicating a change to systematic exploation in 1994 making use of TM imagery and air-borne geophysics resulting in an re-interpretation of the geology. Gold mineralisation is believed to be related to dome structures that are supposedly underlain by granitic cupola. Field evidence to prove this, such as contact metamorphism (spotting), pegmatite or aplite dykes, is so far missing, partly due to scarce outcrops. More fieldwork will be carried out including an evaluation of the geology in the adjacent area in Mozambique.

After the coffee break Emmanuel Mulenga of the Zambian Geological Survey Department in Lusaka reported on the integration of exploration data (TM imagery, air-borne geophysics, stream sediment geochemistry and mineral occurrence data) for area selection in eastern Zambia. The proportion of the different lithologies in each catchment area were determined to take into account the background values of the different lithologies. Potential mineralisation appears confined to specific lithologies (metarhyolites?) and fault structures. Reduction of the geochemical data for manganese and iron will be carried out shortly and more fieldwork is planned.

Next, Max Fernandez took the floor with a presentation entitled ' Re-assessment of pre-1960 mining archives with present-day GIS technology: case studies from the D.R of Congo. Rightfully Max drew attention to the treasure of information on Africa's geology and mineral resources present in archives of the national geological surveys in Africa and Europe. Consulting old data (step 1 in the sequential exploration model) is most likely the cheapest part in exploration. The old data is extremely valuable – the older generation of geologists and mining engineers were good observers and meticulous bookkeepers – but clearly has to be re-interpreted and re-assessed using modern concepts. Modern GIS offers unprecedented possibilities for storage and retrievement. He also emphasised the need to inform the public what is available. In this respect an interesting initiative is taking place- under the aegis of Eurogeosurvey – to bring together in a single GIS all geo-science information on Africa stored in Europe. Apart from the geological surveys of France, the United Kingdom, Belgium and Portugal – the former colonial powers – also a number of specialised institutes with a long-standing commitment to Africa will participate. These include the BGR of Germany, the Royal Museum for Central Africa in Belgium and the ITC in the Netherlands. It was further stressed that geo-data archives, in whatever form, needs maintenance because technology is changing fast. To illustrate this the geochemistry of Rwanda may serve. The data set (approx. 40 000 samples) was digitised using hard- and software that has become obsolete and cannot be read any more. Also attention was drawn to the fact that many WB and EU sponsored projects pay very little attention to aftercare for data generated in their projects.

The next presentation was by Julius Nyakaana of the Geological Survey Department of Uganda on digital thematic mapping in the NE Kibaran belt. As remarked by the audience it would be tremendous step in the right direction when this desk study would be followed up by a multi-national (Tanzanian-Ugandan-Rwanda) team in the field. Last but not least, Katto Edwards, also of the Geological Survey of Uganda reported on the Busumbu phosphate resource, located in the Bukusu Coplex in eastern Uganda. The Busumbu project is an good example to demonstrate that national geological surveys need to up-grade prospects to a certain level in order to attract a (foreign) investor. Busumbu appears to have succeeded in doing so.

Just before closing the meeting, Steven McMullan expressed his desire to address the audience for five minutes on the topic of 'the value and accessibility of data' as a sequence to the talk of Max Fernandez. The importance of this issue follows from the fact that the discussion lasted for another hour. The contents can be found in Steven's contribution sent by e-mail on the very last moment.