Geology And Geophysics

Will Gold Glitter in Nigeria



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Will gold glitter in Nigeria?
Introduction
Records of gold occurrences are numerous in literature. Woakes (1988) noted over thirty occurrences (earlier described by other authors) in alluvial terrain, quartz veins, sheared silicifed conglomerate.
Chukwu (1988) discussed the distribution of gold mineralization in the Basement Complex of Nigeria in relation to orogenic cycle and structural setting. The cycles are:
Archaean rocks
Rocks associated with the Eburnean orogenic cycle
Rocks as associated with the Kibaran orogenic cycle
Pan Africa Belt
Unfortunately, these reports of occurrences have made no useful contributions on genetic model and exploration models. The dim nature of the gold industry is also reflected in the production/export statistics available.
Table 1: Gold Production, Export and Revenue 1946 -1974 [Culled from Chukwu-Ike 1993]
Year Production (Troy oz) Export (Troy) Revenue ($)
1946 5,547 1984 17,085,000
1949 2,858 176 1,884,000
1953 861 59 650,000
1960 972
1965 81.15
1970 120
1974 169

There are no records of export/revenue after 1953 and records of production are not available after 1974. Most production was from alluvial sources, which in general were not scientifically characterized.
On the other hand, gold has glittered for decades in Ghana. Archaean greenstone belts have provided gold to the world market especially from South Africa, Zimbabwe, India, Brazil and Canada. In these and a number of other countries, gold has continued to glitter, undimmed in its lustre and a firm global demand.
Will gold glitter in Nigeria?
Gold Mineral Industry Global Context
a) Geological features
World gold supply comes from a number of geological environments. The key ones being:
- Archaean greenstone belts
- Porphyry copper
- Placers and paleo-placers
- Association with other minerals in a number of variety of environments
Current information indicates very large reserves in South Africa, United States, Australia, Indonesia, Russia and Peru.
Some of these deposits were based on empirical models and traditional prospecting methods. The scientific genetic models were subsequently proposed. A good example is gold in the Archaean terrain. Two genetic models have a general acceptance.
Type1- Exogenous/epigenetic e.g. Eastern Goldfields Province, Western Australia
Type 2 Indegenous/syngenetic and epigenetic e.g. Stratabound gold ores of Zimbabwe. The two models emphasize host lithology and in a strict sense represent effort to explain what has been observed. Another indicating feature is the increasing importance of gold associated with porphyry copper. U.S. Geological Survey (2006) noted An assessment of U.S gold resources indicated 33,000 tons of gold identified (15,000) and undiscovered resources (18,000 tons). Nearly one quarter of gold in undiscovered resources was estimated to be contained in porphyry copper deposits. The gold resources in the United States, however, are only a small portion of global gold resources'.
Porphyry copper has been described variously. The term was introduced because some of the first large copper deposits that were mined in western United States occurred in porphyritic granodiorite and quartz monzonite.
Today, the term is widely accepted to imply large low-grade disseminated copper deposit, which may be also in schists, silicated limestone, and volcanic rocks, but quartz-bearing igneous rocks are always in close association. There are other examples of evolution of genetic models in the minerals industry, some prodigiously confusing.
Gold industry in Nigeria In retrospect
Table 1 may be interpreted in a number of ways including the following:
i) Gold production fluctuated between 1946 and 1974
ii) Records of production and export are not available after 1974 and 1953 respectively.
Some sources suggest that the date indicate ineffective official production. Decline in production may also be due to exhaustion of known alluvial sources. The alluvial sources have not been characterized scientifically - relationship to source rocks has not been determined. It must be emphasized that the bane of mineral exploration in Nigeria has been the import of genetic models and application of the same in the development of exploration models without due consideration of the features of the search area climate, structure, stratigraphy etc.
Gold exploration in the Precambrian terrain is a good example.
Nigeria stands astride the West Africa craton and east of the mobile belts. The Pan Africa event has modified the structure considerably and introduced problems in age determination. The classification of the orogenic cycle has generally been arbitrary with limited geochronological input. There is undoubtedly, uncertainty in what rocks are Archaean, Eburnean, Kibaran or of Pan Africa terrain. The Thermotectonic event may have had a number of episodes of deformation and metamorphism.
Nwabufo-Ene (1995) observed that there were indications that the terrain that may host substantial gold deposits have been deformed a number of times, complicating the structure and overprinting' the ages.
Gold Industry in Nigeria In Prospect
The dimmed lustre'and inability to glitter of gold in Nigeria may have resulted from a number of factors, the key ones being:
i) Poorly defined empirical and genetic models
ii) Empirical models and genetic models have not been appropriately integrated with relevant features of the search areas to develop exploration model
iii) Limited geochronological data, especially for the Precambrian
iv) The erstwhile major sources of gold (the alluvial sources, have not been scientifically characterized production has been based on luck and instinct'
v) Poor analytical facilities
vi) Economic incentives have not been clearly defined
Gold has a variety of uses jewellery and arts, electrical and electronics, dental etc.
The future?
The foregoing has indicated the factors that have adversely affected the gold industry in Nigeria. Gold may glitter if there is positivity in both the extractive and non- extractive sectors. Production will be enhanced by:
a) Development of effective exploration models. Empirical and genetic models must be integrated with local features. For example, gold exploration in Ghana (within the West Africa Craton) will be different in some aspects from gold exploration in Nigeria (astride of the craton). Alluvial sources need to be characterized.
b) Effective analytical facilities and techniques are of critical importance.

References
Nwabufo-Ene, K.E.1995-Reflection on the minerals industry in Nigeria.Proc.1st National Symposium and Field Workshop on the Minerals Industry in Nigeria. Enugu, Nigeria 21p
U.S Geological Survey (2006)-Mineral commodity summaries (gold) January 2006-2p

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