Geological and Geotechnical Assessment of some Derelicit Barite Fields in the Abakaliki Basin, Southeastern Nigeria

Filed in Geology by on October 27, 2020

Geological and Geotechnical Assessment of some Derelicit Barite Fields in the Abakaliki Basin, Southeastern Nigeria.

ABSTRACT

The proliferation of abandoned surface excavations in the Benue Rift not only contributes to land degradation and landscape disruption but also results in loss of economic deposits, dearth of mining data and generation of unprotected spoils with known potential to contaminate ground and surface water sources.

This study employed field description and measurements, laboratory testing and numerical simulation techniques to evaluate some derelict barite fields in the rift with the aim of factoring geological and geotechnical issues that will enable the reclaiming of untapped reserves and forestall the creation of abandoned excavations.

Field  studies indicate a consistent rock sequence in which exposures of arkosic sandstone are overlain by profusely fractured shale and both rock types play host to barite ore deposits, brine ponds and intrusives. The  area displays some major lineaments which exhibit, in order of decreasing magnitude, N-S ,NE-SW, NW-SE, and E-W structural styles.

Ore deposits occur in varied modes as disseminated nodules, strata-bound  deposits  as well as in two dominant NW-SE and N-S trending vein sets with steep dips. The modes  of  occurrence, structural styles and lithofacies associations predispose the ore deposits to manual extraction and vertical stripping using surface excavations.

The complex and varied geologic setting of ore incidences predicate significant errors in interpretation of their geophysical signatures and obtaining reliable ore quantity estimates. Ore grades vary widely due to the varying geologic framework and appear to  depend  on such  factors  as  mining depth, presence of gangue minerals and location within the barite fields.

INTRODUCTION

Globally, an estimate of over a hundred million people including men, women and children are engaged directly or indirectly in artisanal abstraction of minerals and construction materials in over fifty developing countries (Darby and Lempa, 2006).

Despite the economic contribution and social significance of artisanal mining, it commonly attracts critical scrutiny from government agencies, major mining companies and environmental activists. Such repulsive view follows from environmental and health problems that emanate from the processes of ore extraction at small and artisanal scale.

At such scale, extraction protocols are not systematic, which invariably predict difficulty in implementation of regulatory framework (Darby and Lempa, 2006) such as labor, environment and safety standards. The main challenge to the regulators is the unorganized nature of artisanal mining which often leads to oversights.

The consequences of the unfortunate situation are not only child labor and fatal accidents but also loss of deeper seated ore reserves and dearth of mining data. These issues will become more aggravated at increasing depth and size of surface excavations that artisans often adopt as the major extraction technique.

For instance, there is a high safety, economic and material stability risks often associated with deepening artisanal surface excavations. Further, artisanal mining encourages the proliferation of derelict surface excavations and indiscriminate dumping of spoil heaps both which may not only result in land degradation and devaluation but also constitute a potential contamination threat to surface and groundwater sources.

REFERENCES

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Akande, S.O. and Abimbola, A.E., 1987. Aspect of the genesis of lead-zinc-fluorite-barite mineralization in the Nigeria Benue Trough. Current research in African Earth Sciences. G.Matheis and H. Schamelimier( eds) Bulkena press.pp.365-369

Akande, S. O. Zentilli, M. and Reynolds, P. H. 1989. fluid inclusions and stable isotope studies of Pb – Zn – florite – barite Mineralization in the Lower and Middle Benue Trough, Nigeria; Mineralium deposits, vol. 24, p. 183 – 191.

Akande, S.O. and Mucke, A.,1989. Mineralogy, Textural and paragenetic studies of the lead- zinc-copper mineralization, lower Benue Trough and their genetic implications. Journal of African Earth Sciences, vol.9,pp.23-29.

Akande, S. O., 1999. Fluid flow Histories in the Cretaceous Sediments of the Benue rift Basins, Nigeria: Fluid inclusions, Isotopes and Alteration Mineralogy Constraints. NAPE Bull. Vol. 14, p. 112 – 129.

CSN Team.

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