By Grain Wyson Phillip MalungaFIMMM Minerals, Geology, Environment & Corporate Affairs Consultant
Gold mining in Malawi is associated with placer gold in the Lisungwe Valley, north of Blantyre to the west of Zalewa – Balaka road. Recent gold rush has been seen in Makanjira area within Unga River catchement and in Nathenje river catchment around Mazengera and Chimutu.
All these areas were already known through previous geochemical exploration of stream sediments as well as recent geophysical surveys. These targets are usually underlain either by schists and granulites or marbles and calc-silicate granulites. The main source of gold in these areas seems to be quartz veins and sulphide bands associated with hydrothermal activities.
1. GEOLOGY OF GOLD EPOSITS
Gold occurs in as primary deposit or secondary deposit. Primary deposits form where gold precipitates from reaction with hot fluids (hydrothermal solutions) and metal bearing rocks in the earth’s crust.
Secondary deposits (placer deposits) form through chemical and mechanical processes of weathering and erosion, and later get deposited in traps within sediments of water courses.
Primary gold deposits are classified as either epigenetic or syngenitic. Epigenetic deposits formed after the formation of the surrounding rocks whilesyngenitic deposits formed the same time as surrounding rocks. These deposits occur in association with other minerals such as iron, copper, lead and zinc. Recent visit by Chimwemwe Chikusa in T.A. Mazengera, Chimutu, Tsabango and Chadza revealed that gold mineralization occurs in brecciated and limestone zones showing signs of epigenetic formation. These zones have been eroded and deposited the gold in alluvial environments.
Secondary gold occurrences (placer deposits) are formed by the deposition and reconcentration of gold-bearing sediments from primary gold occurrences. In Malawi they are popularly known as alluvial gold due to their occurrence in river and stream valleys as is the case in Lisungwe and Unga Rivers in Neno and Mangochi respectively. The source for these places deposits are the primary sources upstream.
Malawi consists of Precambrian metamorphic and granitic rocks overlain in some areas by a thin cover of sedimentary rocks occupying broad shallow basins. These are separated by mobile belts mainly related with rift systems associated with the Eat African Rift system.
Gold bearing zones have been observed in paragneisses, schists and calc-silicate granulites. The main sources of gold are auriferous silicified zones and quartz stringers of hydrothermal origin.
2. NOTABLE EXPLORATION TARGETS
Primary sources of gold observed so far are quartz stringers in Lisungwe River valley, Unga River valley (Makanjila), Myovwe Hill (Chapananga), Kadyalumba Hill (Dwangwa) and the Misuku belt in Karonga-Chitipa area.
Ngala Hill near Maperera (Chikwawa) has gold hosted in hydrothermal sulphides associated with tectonism of the Thyolo escarpment fault. Auriferous quartz bands associated with Arsenic – sulphide bands have been observed in the Nathenje area. Gold-pyrite-graphite association has been observed in the Malingunde area (Lilongwe).
Alluvial or placer gold has been reported in Unga, Lisungwe and Dwangwa river catchments.
3. ARTISANAL GOLD MINING
The above gold occurrences were observed in various exploration activities. Among them Garson M.S. (1961), Kemp J. (1968), Oversees Geological Surveys (1961), Kirkpatrick I. M. (1962), British South Africa Company (1968) and Harrison D.R. (1969). Support for large scale production was discouraged due to the size of gold occurrences.
Alluvial gold panning started in Lisungwe Valley and later spread to Unga River catchment area and Nathenje area where both elluvial and alluvial gold panning were practiced.
The main driver of these activities are poverty and lack of alternative sources of income generating activities.
Government has moved in to flush these artisanal gold miners out. This is not a smart way of solving problems. Artisanal miners of this nature help discover primary sources of gold. Countries such as Tanzania have benefited from artisanal gold mining because if properly monitored and assisted they attract large scale mining. Tanzania is among the top five largest gold producers in Africa.
What government should have done was to move in quickly study the organisational structure of gold mining and the marketing aspects including environmental issues. This would have followed up with formalisation efforts using cooperative organisation and then creating formal markets which would have created revenue stream for government in terms of royalties. Other income would have come from market fees for local councils as various businesses would have sprang up.
Advantages of the above approach would have borne the following:
• non-polluting artisanal gold production.
• Encouraging artisanal miners to start their own gold mining projects resulting in the creation of employment.
• Utilising the results of the artisanal mining for the encouragement of large scale exploration and mining through symbiotic relationship.
• Large companies would have created more jobs through exploration and mineral development activities
• Markets would have been created for additional materials and specialised technical services
All these would have led to a base for growth of local and regional economy.