Mineral Deposits and Exploration Potential of Nigeria

By Moses A OLADE

Nigeria, the most populous nation and largest economy in Africa is endowed with abundant mineral resources, including energy fuels, industrial minerals, gemstones, and metallic minerals. As West Africa has become a major destination for mining investors and exploration companies, Nigeria's mineral

• Language: English
• Publisher: Prescott Resource Publishers
• Release date: Sep 30, 2020
• ISBN: 9781087862125

Moses A OLADE

Dr. Moses (M.A.) Olade is a retired Professor of Economic Geology who has lectured and published widely on the mineral deposits of Nigeria. He obtained a B.Sc. (Hons.) degree in Geology in 1969 from the premier University of Ibadan, Nigeria, and M.Sc. in Economic Geology from the University of Alberta, Edmonton, Canada in 1972 where he studied sandstone uranium deposits. He completed his Ph.D. at the University of British Columbia, Vancouver, Canada in 1974 where he worked on porphyry copper deposits. He was a post-doctoral research fellowship at the Geological Survey of Canada, Ottawa he investigated uranium occurrences in alkaline igneous complexes. He was Professor and Head of Department of Geology at the University of Ibadan Program Director of the first UNDP-sponsored Postgraduate M.Sc. training program in Mineral Exploration for Africa, and pioneer Dean of the College of Earth and Mineral Sciences at the Federal University of Technology (FUTA), Akure. Supervised several dozens of M.Sc. and Ph.D. theses; and is the author of over 100 journal articles and technical reports. After two decades in the United States working on mineral resources development and environmental protection and teaching as adjunct faculty at the University of Phoenix, he returned to Nigeria in 2012 as a Visiting Professor and Dean at the Achievers University, Owo where he lectured and provided leadership in developing academic programs at the new University, as well as collect data and conduct field visits for this book. Prof. Olade is a distinguished Fellow of the Nigerian Mining and Geosciences Society and former Editor-in-Chief of the Nigerian Journal of Mining and Geology.

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Mineral Deposits and Exploration Potential of Nigeria

Moses A. Olade, Ph.D., MBA

Prof. Moses A. Olade, Ph.D., MBA

Achievers University

Department of Geological Sciences

Owo, Nigeria

[e-mail]

ISBN 978-0-578-67943-3

Prescott Resource Publishers

www.prescottbooks.com

Copyright © by Prescott Resource Publishers, 2020

Geotectonics LLC

2620 Golden Creek Ln, Houston TX 77584

All rights reserved. Printed in the United States of America. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form, or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of the publisher.

Preface

Nigeria, the most populated and largest economy in Africa, is endowed with abundant mineral resources, particularly energy fuels (petroleum, coal, and bitumen), and extensive deposits of industrial minerals, gemstones, and metallic minerals. Prior to the discovery of petroleum in the Niger Delta in 1958, Nigeria was a prominent mining nation and one of the world’s leading producers of cassiterite (tin ore) and columbite (niobium ore). Over the years, mineral production declined substantially, almost to a trickle, due to neglect by the Federal Government and the increased focus of both private and public investments in the petroleum sector. The solid minerals industry has been very much underdeveloped, contributing only 0.3% to the Gross Domestic Product, although it is well known that Nigeria has considerable mineral resource potential. In recent years, with the declining revenue from crude oil sales, the Federal Government of Nigeria has embarked on a path of diversification of its economy through priority development of the solid minerals and mining sector. The implementation of a proposed roadmap involves policy initiatives that encourage private investment in exploration and mineral development projects. Recently, the streamlining of the procedure for acquiring mineral titles and other regulatory and financial incentives have attracted an influx of private investors and exploration and mining companies from several countries including Australia, Canada, the United Kingdom, Germany, Korea, and China, which has led to some discoveries of iron ore, gold, nickel, platinum, uranium, silver, manganese, and lead-zinc ores.

Since the publication of the book entitled Geology and Mineral Resources of Nigeria by N. Obaje in 2009, which contained some review and collation of information on known mineral occurrences in Nigeria, a significant body of information has since emerged through exploration and research work, which needs to be incorporated into our current knowledge on Nigeria’s mineral deposits. This book furnishes a more detailed description of Nigeria’s metallic, non-metallic and energy mineral deposits with emphasis on their location, geological setting, distribution, mode of occurrence, physical and chemical characteristics, origin and metallogeny. The book also provides a geoscientific analysis of mineral production, mineral resource potential, conceptual models and ideas for targeting that will assist exploration and mining companies interested in both greenfield and brownfield exploration in Nigeria.

There are twenty chapters in the book, divided into five parts. Part I is an introduction to mineral resources and discussion of the geological and tectonic setting and classification of Nigeria's mineral deposits. Part 2 provides detailed descriptions of known deposits of eighteen metals (Fe, Au, Pb, Zn, Cu, Ag, Sn, Nb, Ta, Mo, W, Ti, Bi, Cr, Ni, Pt, Mn, Al) with emphasis on their geological environment, mode of occurrence, mineralogy, origin, ore reserves mining history, and exploration. Part 3 describes the distribution, geological setting and reserves of solid energy minerals (uranium, coal, and bitumen), while Part 4 focuses on the geological occurrence, mineralogical and physical properties, mineral reserves and uses of non-metallic minerals comprised of thirty industrial minerals/rocks and several gemstone minerals. Part 5 reviews the status of the solid minerals industry, new mining regulations, mineral production statistics, mining practices, metallogenic provinces and assessment of resource potential and exploration targets in Nigeria. A Glossary of Common Terms in Economic and Mining Geology is included at the end of the book.

This book will not only serve as an excellent source of information for all geology and mining students at various universities and polytechnics but also for practicing geoscientists and other professionals and administrators in government and private companies who are interested or involved in economic geology, mineral exploration, mining, mineral economics and mineral resource development in Nigeria. The book is an offshoot from several years of research on mineral deposits, from providing consultancy services and from teaching economic and mining geology at several universities in Nigeria and abroad. It has also benefited from information and the research work of many of my colleagues and students in Nigeria, as well as information from innumerable sources. This book has involved several years of collecting data, conducting field visits and writing several drafts while teaching as a Visiting Professor of Geology.at Achievers University, Owo

Lastly, I want to extend my heartfelt appreciation to my wife, Mrs. Esther Seymour-Olade for her support, patience, and understanding; and to my adult children; particularly to Dr. Roger Babatunde, Mr. Lincoln Olalekan, Mr. Randall Ademola, Dr. (Mrs.) Tolu Olubori and Ms. Sheena Jardine for all their support and encouragement while writing this book.

April, 2020

Moses A. Olade

Houston, Texas

Table of Contents

Introduction

Part I: Mineral Deposits and Geological Setting

Chapter 1: Introduction to Mineral Deposits

Definition of Terms

Types of Mineral Resources

Nature of Mineral Deposits

Life Cycle of Mineral Deposits

Types and Distribution of Mineral Deposits

Mode of Occurrence and Size

Formation of Mineral Deposits

Nature of Ore-Forming Fluids

Magmatic Liquids

Hydrothermal Solutions

Metamorphic Fluids

Chapter 2: Geological Setting of Nigeria’s Mineral Deposits

Introduction

Major Rock Groups

Basement Complex

Migmatite-Gneiss-Quartzite Complex

Schist Belts

Pan-African Granitoids (Older Granites)

Minor Felsic and Mafic Intrusive Rocks

Mesozoic Intrusive and Volcanic Rocks

Sedimentary Basins

Benue Trough

Anambra Basin

Bida Basin

Sokoto Basin

Bornu/Chad Basin

East Dahomey Basin

Niger Delta Basin

Cenozoic Volcanic Rocks

Tectonic and Structural Framework

Precambrian Tectonics and Crustal Evolution

Tectonic Events

Structural Deformation

Geotectonic Evolution and Models

Jurassic Uplift and Alkaline Magmatism

Cretaceous - Recent Tectonics and Magmatism

Chapter 3: Distribution and Classification of Nigeria’s Mineral Deposits

Introduction

Distribution of Mineral Deposits

Classification of Metallic Mineral Deposits

Metallic Content Classification

Geological Classification

Genetic Classification

Classification of Non-Metallic Minerals

Igneous Minerals (and Rocks)

Sedimentary Minerals (and Rocks)

Metamorphic Minerals (and Rocks)

Hydrothermal Minerals

Residual Minerals

Part II: Metallic Minerals

Chapter 4: Iron Ore Deposits

Introduction

Iron Ore as Raw Materials

History of Iron Ore Exploration

Geological Occurrence and Types of Iron Ore

Ferruginous Quartzites

Itakpe Iron Deposit

Ajabonoko Iron Deposit

Ajashe (Ogbomoso) Iron Deposit

Banded Ferruginous Schists (Iron Formation)

Maru Iron Deposit

Birnin Gwari Iron Deposit

Muro Iron Deposit

Iron in Amphibolites

Kakun Deposit

Jaruwa Deposit

Gujeni Iron Deposit

Sedimentary Iron Ore

Agbaja Ironstone

Kogi Iron Mine

Konto-Karfe Ironstone

Enugu Ironstone

Lateritic Ironstone

Historical Overview of Nigeria’s Iron and Steel Industry

Nigeria’s Iron Ore as Raw Material

Types of Iron Ore

Quality of Iron Ore

Iron Content

Deleterious Constituents

Mineralogical and Textural Characteristics

Quantity of Iron Ore

Raw Material Challenges for Nigeria’s Iron and Steel Industry

Chapter 5: Gold Deposits

Introduction

Geological Occurrence

Types of Gold Deposits

Primary Gold Deposits

Distribution

Mineralogy

Origin

Major Goldfields

Anka Goldfield

Maru

Malele

Tsofon Birnin Gwari

Kwaga

Bin Yauri

Gurmana

Okolom-Dogon-Daji

Iperindo (Segilola)

Placer Gold Deposits

New Exploration Activities

Ogun State

Cross River State

Kwara State

Chapter 6: Lead and Zinc Deposits

Introduction

Geologic Occurrence

Types of Lead-Zinc Deposits

Lead-Zinc in Cretaceous Sediments

Lead-Zinc Mineral Districts

Abakaliki-Ishiagu Mineral District (Lower Benue)

Enyigba Lode

Ameri Lode

Ameka Lode

Isiagu Lode

Akpatakpa Lode

Wanikande-Wanakom Mineralization

Akwana-Arufu Mineral District (Middle Benue)

Zurak-Wase Mineral District (Upper Benue)

Lead-Zinc in Precambrian Basement Complex

Lead-Zinc in the Younger Granites

Chapter 7: Copper Deposits

Introduction

Types of Copper Deposits

Copper in Sedimentary Rocks

Copper Associated with the Younger Granites

Copper in Precambrian Metasediments

Chapter 8: Tin-Niobium-Tantalum Deposits

Introduction

History of Tin-Niobium Mining

Primary Mineralization in the Younger Granites

Disseminated Mineralization

Biotite Granites

Peralkaline Granites

Vein Deposits

Ririwai Lode

Tibchi Lodes

Primary Mineralization in Pegmatites

Distribution

Mode of Occurrence

Mineralogy

Origin of Pegmatite Mineralization

Older (Pegmatite) Tin Fields

Nasarawa/Keffi Tin Field

Wamba Tin Field

Ijero-Ekiti Tin Field

Placer Tin and Niobium-Tantalum Deposits

Chapter 9: Tungsten-Molybdenum-Silver

Introduction

Tungsten

Tungsten Associated with the Younger Granites

Molybdenum

Silver

Chapter 10: Manganese Deposits

Introduction

Geologic Occurrence

Mode of Occurrence and Distribution

Kebbi State

Zamfara State

Kaduna State

Niger State

Edo State

Cross River State

Origin of Manganese Deposits

Future Prospects

Chapter 11: Nickel Deposit

Introduction

Geologic Setting

Mode of Occurrence

Origin

Future Prospects

Chapter 12: Chromium

Introduction

Geological Setting

Mode of Occurrence

Origin

Chapter 13: Titanium, Platinum and Bismuth

Titanium

Platinum

Bismuth

Part III: Solid Energy Minerals

Chapter 14: Uranium Deposits

Introduction

History of Uranium Exploration

Geologic Occurrence

Nature of Uranium Mineralization

Uranium in Peralkaline Granites

Vein-type Uranium Mineralization in Granites and Rhyolites

Mika Prospect

Ghumchi Prospect

Kanawa Occurrence

Gubrunde Occurrence

Uranium in Sandstones

Zona Prospect

Mayo Lope Prospect

Idomi-Ugep Uranium Discovery

Phosphorite Uranium

Ore Genesis

Chapter 15: Solid Energy Minerals (Coal and Bitumen)

Introduction

Coal Deposits

Introduction

Distribution

Geologic Occurrence

Coal Districts

Kogi Coal District

Benue Coal District

Enugu Coal District

Lignite

Quality of Nigerian Coals

Current Status and Future Prospects

Bitumen Deposits

Introduction

Distribution

Geologic Setting

Mode of Occurrence

Exploration and Exploitation

Part IV: Non-Metallic Minerals

Chapter 16: Industrial Minerals

Introduction

Industrial Minerals Production

Barite

Introduction

Distribution

Mode of Occurrence

Lower Benue Trough

Middle Benue Trough

Upper Benue Trough

Zamfara State

Quality of Nigerian Barite

Origin of Barite Mineralization

Bentonite

Clays and Kaolin

Kaolin and Kaolinitic Clays

Ball Clays

Fire Clays

Feldspar

Gypsum

Halite (Salt)

Limestone

Introduction

Geological Occurrence

Use of Limestone in Cement Production

Cement Factories

Marble

Phosphate

Silica Sand

Talc

Trona

Zircon

Other Industrial Minerals

Bauxite

Beryl

Diatomite

Fluorite (Fluorspar)

Graphite

Lepidolite

Metamorphic Minerals

Mica

Chapter 17: Gemstones

Introduction

Geological Occurrence

Older Granite Pegmatite Gemstones

Younger Granite Gemstones

Alkali Basalt Gemstones

Metamorphic Gemstones

Distribution of Gemstones

Gemstone Minerals

Tourmaline

Sapphire

Emerald

Aquamarine

Garnets

Topaz

Amethyst

Zircon

Other Gemstones

Origin of Gemstones

Gemstone Mining

Part V: Metallogeny, Mining and Exploration

Chapter 18: Metallogenic Epochs and Metallogenic Belts

Introduction

Geologic and Tectonic Setting

Metallogenic Epochs

Archean Epoch

Late Proterozoic Epoch

Early Paleozoic Epoch

Jurassic Epoch

Cretaceous Epoch

Metallogenic Provinces and Belts

Pb-Zn Belt (Benue Trough)

Sn-Nb Province (Younger Granites)

Sn-Ta Pegmatite Belt

Ni-Cr Serpentinite Belt

Gold Province

Iron Province

Significance of Metallogenic Provinces and Belts

Chapter 19: Solid Minerals Production and Mining Practices

Introduction

Nigerian Economy and Solid Minerals Sector

Strategic Minerals

Solid Minerals Production

Solid Minerals Export

Solid Minerals Revenue

Roadmap for Revitalization of the Solid Minerals Sector

Mining in Nigeria

Historical Perspective

Current Mining Practices

Artisanal and Small-Scale Mining (ASM)

Corporate Mining

Quarrying

Environmental Impact of Mining

Physical Disturbance of the Landscape

Public Safety Hazard

Contaminated Soils

Lead and Mercury Poisoning

Surface Water and Groundwater Pollution

Vegetation Loss and Ecosystem Damage

Air Pollution

Chapter 20: Mineral Resource Potential and Exploration Prospects

Introduction

History of Mineral Exploration

Legal Framework for Mineral Exploration and Development

Reconnaissance Permit

Exploration License

Strategic Minerals for Development

Roadmap for Boosting Mineral Exploration

Recent Developments

Nigeria’s Mineral Resource Potential

Mineral Potential Indices

Geologic and Tectono-Metallogenic Analysis

Litho-Metallogenic Units

Archean Migmatite-Gneiss-Quartzite Complex

Proterozoic Schist Belts

Proterozoic Serpentinites and Amphibolites

Early Paleozoic Granites and Pegmatites

Jurassic Younger Granites

Deformed Cretaceous Sedimentary Rocks

Undeformed Cretaceous-Tertiary Sedimentary Rocks

Cenozoic Alkali Basalts

Metallogenic Provinces and Mineral Exploration

Search for Minerals (Mineral Exploration)

Mineral Exploration in Practice

Approaches to Mineral Exploration

Mineral Exploration Cycle

Desk Study and Program Design

Prospecting and Reconnaissance Exploration

Geophysical Exploration

Geochemical Exploration

Advanced Exploration (Drilling)

Ore Reserve Estimates

Status of Mineral Exploration and Mining Projects

Target Selection for Mineral Exploration in Nigeria

Gold

Conceptual Framework

Potential Targets

Maru (Zamfara State)

Anka (Zamfara State)

Malele (Zamfara State)

Tsofon Birnin Gwari & Kwaga (Kaduna State)

Bin Yauri (Kebbi State)

Gurmana (Niger State)

Okolom-Dogon-Daji (Kogi State)

Iperindo (Segilola) (Osun State)

Uranium

Conceptual Framework for Exploration

Target Areas for Uranium Exploration

Lead-Zinc

Conceptual Framework

Potential Targets

Chromium-Nickel-Platinum

Conceptual Framework

Potential Targets

Manganese

Conceptual Framework

Potential Targets

Iron Ore

Conceptual Framework

Potential Targets

Aluminium (Bauxite)

Conceptual Framework

Potential Targets

About The Author

Bibliography

Glossary of Common Terms in Economic and Mining Geology

Introduction

Nigeria is Africa’s most populous country with over 200 million people, and credited with the largest economy in Africa, and the 20th largest in the world. For these reasons, Nigeria is often described as the Giant of Africa (Figure 1) with an economy worth more than 400 billion dollars in nominal Gross Domestic Product (GDP), and $1 trillion in terms of purchasing power parity. Nigeria is situated in the southeastern edge of the West African sub-region and lies between longitudes 3 and 14 degrees east, and latitudes 4 to 14 degrees north. It covers a landmass of 923,768 square kilometers and is bounded to the north by the Republics of Niger and Chad, to the west by the Republic of Benin, and the east by the Republic of Cameroon (Figure 2). Nigeria is a maritime nation, bordered in the south by the Gulf of Guinea along the Atlantic Ocean, and possesses 800 kilometers of coastline that facilitates international trade and provides a transportation corridor for landlocked countries further north, including Chad and Niger Republics.

The modern state of Nigeria originated as a political entity established by British colonial rule in the early part of the 19th century. It took its current boundaries in 1914 after the amalgamation of both the Southern Nigeria Protectorate and Northern Nigeria Protectorate. Nigeria became independent of British rule in 1960 and has since been administered as a Federation, now comprised of 36 states and a Federal Capital Territory at Abuja (Figure 3). The Nigerian States are subdivided into 774 Local Government Areas (LGAs). In a geopolitical arrangement, these States are aggregated into six regions or zones, namely: North-West, North-East, North-Central, South-East, South-South, and South-West (Figure 4).

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Figure 1: Map of Africa showing the location of Nigeria

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Figure 2: Map of Nigeria showing major cities and adjoining countries

A clickable map of Nigeria exhibiting its 36 states and the federal capital territory.

Figure 3: Map showing the 36 States in Nigeria’s Federation

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Figure 4: The six geopolitical zones in Nigeria

Nigeria is made up of a varied physical landscape, ranging from lowlands along the coastal areas to high plateaus in the north-central region and mountains along the eastern border with Cameroon (Figure 5). The Jos Plateau is a prominent table landform about 1300 m above sea level and located near the center of Nigeria. It is renowned for its mild climate and mining history. Much of the country is well-drained by rivers and streams, particularly the River Niger that originates from the Guinea Highlands in southeastern Guinea, and the River Benue. Both rivers merge to discharge in a delta into the Gulf of Guinea. The climate in the southern part of the country is a tropical rainforest where annual rainfall ranges from 60 to 80 inches (1500 to 2000 mm) a year and decreases northwards into the central and northern regions. Temperatures across the country are relatively high, averaging about 25oC (77oF) with a minimal variation in seasonal and diurnal ranges (22-36oC). There are two primary seasons; a wet season, which lasts from April to October; and the dry season, which lasts from November till March. As a result of the rainfall pattern, there are two broad vegetation types: tropical forests in the south and savanna grassland in the north. Areas transitional between the two types are a mix of forest-savanna mosaic in which plains of tall grass are interspersed with short deciduous trees and shrubs.

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Figure 5: Relief map of Nigeria

Nigeria’s geology is characterized by the predominance of the Precambrian crystalline rocks and Cretaceous-Quaternary sedimentary rocks, each underlying about 50% of the landmass. In a geotectonic setting, Nigeria lies within the Pan African Mobile Belt, sandwiched between two ancient cratons of Archean to Lower Proterozoic age: the West African Craton to the west and the Trans-Saharan Meta-Craton to the east. The Pan African Mobile Belt extends northwards through the Hoggar massif into the Central Sahara (Figure 6). Nigeria is underlain by three major groups of rocks: the Precambrian Basement Complex, the Jurassic Younger Granites, and the Cretaceous-Quaternary sedimentary rocks. The Basement Complex is composed predominantly of Archean high-grade migmatite-gneiss-quartzite complex with intercalated amphibolite and schists, overlain by narrow belts of Proterozoic low-grade supracrustal metasediments, mainly schists, and phyllites, which are intruded by syntectonic to late-tectonic granites and pegmatites. The Jurassic Younger Granites of central Nigeria are high-level, anorogenic ring dike complexes emplaced within a zone of regional uplift. The Cretaceous-Quaternary sedimentary rocks of fluvial to marine origin accumulated in seven sedimentary basins, namely: Dahomey Basin, Benue Trough, Anambra Basin, Bida Basin, Bornu/Chad Basin, Sokoto Basin, and Niger Delta Basin. The youngest rocks are the Cenozoic basalts that are found in the plateau areas of central and northeastern Nigeria and along the Cameroon border.

Figure 6: Geological map of Nigeria

Nigeria is a country richly endowed with mineral resources particularly the liquid fuels (petroleum) and solid energy minerals such as bitumen and coal. With a daily production of 2.6 million barrels, Nigeria’s petroleum industry ranks as the largest in Africa and the 10th in the world, while its bitumen resources are the largest in Africa and 6th most abundant in the world. Petroleum plays a significant role in the Nigerian economy, contributing 40% of the nominal GDP and 75% of gross revenues, and over 90% of export earnings. Petroleum export is also the country’s primary earner of foreign exchange. Petroleum production is confined to the areas around the Niger Delta, where oil spills have negatively impacted the natural resources and ecosystem of the region. The oil-producing states in Nigeria are located in the southern part of the country (Figure 7). However, oil exploration in the Chad Basin in the northeast has discovered substantial resources in this area. Despite the country’s oil wealth, widespread poverty and lack of development in the oil-producing areas of the Niger Delta have led to agitation for better resource control and disruptions in oil production, which have prevented the country from exporting at full capacity.

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Figure 7: Petroleum producing States in Nigeria (2018)

As revenue from crude oil declined sharply in recent years, starting from 2015, Nigeria has struggled to find other revenue sources by trying to diversify its economy through energizing the minerals and mining sector. Over the past decade, the solid minerals sector had contributed less than 0.3% of the Gross Domestic Product. Nigeria is blessed with substantial resources of metallic and non-metallic minerals, if explored and developed that can be utilized both for export and domestic consumption. Large deposits of non-metallic (industrial) minerals and rocks are known, including but not limited to barite, gypsum, bentonite, halite (rock salt), limestone, shale, clays, silica sand, marble, talc, zircon that are harnessed as raw materials for industrial production, infrastructural development, and import substitution. Energy minerals, such as bitumen and coal are abundant within the country. Metallic ores of iron, lead-zinc, gold, tin-niobium-tantalum, nickel, chromium, and manganese are found in substantial quantities in some parts of the country.

Gemstones such as sapphire, Paraiba tourmaline, emerald, and aquamarine of precious value are extracted in many parts of the country. However, Nigeria’s solid minerals and mining sector is very much underdeveloped owing to a lack of private investment and a shortage of financial and well-trained human resources that are needed for detailed exploration of the hundreds of known mineral occurrences. The current situations in which minerals that can be quickly produced and beneficiated in the country are being imported is not beneficial to the economy, and are currently being addressed by dedicated efforts to increase mineral production and local beneficiation.

Solid minerals have a significant role to play in the growth and diversification of the Nigerian economy. The establishment of an iron and steel industry that uses local raw materials can lead to rapid industrialization, infrastructural, and economic development. Efforts to transform the solid minerals and mining industry is in progress through the implementation of new policies targeted towards attracting private investment and providing the enabling environment for the development of industrial and energy minerals. In building a viable minerals and mining sector, the utmost priority is to increase production and domestic utilization of the country’s industrial minerals and rocks. The development of the moribund iron and steel industry using local raw materials along with the exploitation of coal and bitumen resources will accelerate the pace industrialization, infrastructural development and economic prosperity in the country.

A prominent and magnificent topographic feature of great tourist interest in Nigeria is the Zuma Rock (Figure 8), located on the highway as one approaches the Federal capital in Abuja. It is a large inselberg that is revered as a mysterious entity that holds legendary myths, similar to the ‘Rock of Gibraltar.’

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Figure 8: The Zuma Rock monolith on the highway to Abuja the capital city

Part I

Mineral Deposits and Geological Setting

Chapter 1

Introduction to Mineral Deposits

Definition of Terms

Mineral resources are useful earth materials of sufficient quantity and adequate quality to be extracted and used for human benefit. Since time immemorial, economic minerals have been exploited and used as raw materials for industrial production and to generate revenue for the national economy through export to other countries. Mineral resources can be subdivided into two broad groups, according to their form of occurrence: (1) Solid Minerals and (2) Liquid Fuels (petroleum). When solid minerals of economic value are concentrated in the earth’s crust in sufficient quantities to be of extractable, they are described as mineral deposits. Solid mineral deposits can be subdivided into three types: metallic, non-metallic, and energy minerals.

The total mineral endowment of a nation or region consists of two major parts: identified resources and undiscovered resources. Identified resources are those resources whose location, grade, quality, and quantity are known or can be estimated from specific geological information. In contrast, undiscovered resources are those whose existence is extrapolated based on broad geological knowledge. Mineral reserves refer to the portion of an identified mineral resource that can be mined at a profit. Private investment is a major driving force of mineral resource development in a capitalist system, and the desire to extract minerals at a profit becomes a paramount consideration in evaluating expected returns on investment.

Mineral resources are unique among other natural resources because they are not only of instant value but also are non-renewable. Consequently, there is a constant need to find new mineral deposits as the known reserves are depleted. Mineral resources play a significant role in the economic and industrial development of nations by generating revenues as well as providing raw materials for the construction of infrastructure and the manufacture of several products that affect human existence and quality of life. As the world’s population grows exponentially and living standards increase globally, the demand for mineral raw materials continues to escalate widely. New mineral deposits must be discovered regularly, which requires the trained expertise of economic geologists and related professionals to satisfy the world’s hunger for mineral raw materials. Knowing the quantity and quality of a country’s mineral resources and their sources are crucial to the sustenance of a nation’s economy and its national security

Types of Mineral Resources

Mineral resources can be classified into three types: metallic, non-metallic, and energy resources. A list of common examples is provided in Table 1.1.

Nature of Mineral Deposits

Economic geology is the study of mineral resources, and the ‘basic unit’ or ‘center point’ of such study is the mineral deposit. A mineral deposit is a substantial accumulation of useful minerals of economic value within a defined location. However, this definition does not, in any way, imply that a mineral deposit is economically viable, but just a substantial accumulation of minerals with economic potential. For example, the occurrence of chromite bands in a layered intrusive complex to a substantial extent and thickness to have potential economic value is called a mineral deposit. A mineral deposit that has been explored and tested, and found to be economically viable or mineable at a profit, is described as an ore deposit. Solid mineral deposits refer to accumulation of metallic, non-metallic and some energy minerals (coal and bitumen) that occur in nature in solid form (compared to oil and gas deposits).

Table 1.1: List of Common Economic Minerals

The following terms will be used to describe mineral deposits in terms of their economic potential:

Mineral Occurrence refers to any locality in which a useful mineral or earth material of unknown economic value is found. The fact that a mineral occurs in a location does not mean it is of adequate quantity and sufficient quality to be extracted at a profit. Consequently, based on this premise, mineral occurrences can be further categorized according to their potential economic value.

Mineral Showing is a mineral occurrence that is so small and only of geological or mineralogical interest but not necessarily of economic interest.

Mineral Prospect refers to any promising mineral occurrence that has been investigated by subsurface drilling or partially developed by underground or by above-ground techniques to determine the extent of mineralization.

Mineral Deposit is a substantial accumulation of economic minerals of sufficient size and concentration to have economic potential.

Ore Deposit is a mineral deposit that has been tested and found to be of sufficient size, grade, and accessibility to be mined at a profit.

A Glossary of Common Terms in Economic and Mining Geology is provided at the end of this book where terms used in the minerals and mining industry are defined for easy consultation by readers of this book.

Mineral deposits are concentrations of useful substances that could be exploited for various applications. The extraction and use of economic minerals are closely linked with the history of human civilization and industrial development. Metallic and non-metallic minerals (both known as solid minerals) are precious assets to both developing and developed countries where they can be utilized for industrial development or exported as a source of revenue for economic development. Currently, there is a mineral resource crisis in the world in which mineral consumption is growing even faster than the population. Most minerals are used in more developed countries (MDCs), while relatively small consumption occurs in less developed countries (LDCs). For example, MDCs account for 15% of the world population but consume 70% of world aluminum, copper, and nickel, 60% of world oil, 50% gas, and 40% coal. As the standard of living increases in LDCs, these nations will start to increase the consumption of their minerals. This pattern is already apparent in countries such as India and Brazil. If the global population increases as rapidly as consumption rates, the pressure to find and produce minerals will be enormous. There are limits to the discovery, extraction, and utilization of non-renewable mineral resources and the need for substitution by other natural or synthetic products is growing.

Africa is blessed with abundant mineral resources, and the continent ranks either first or second in quantity of known reserves of diamonds, bauxite, phosphate, platinum, cobalt, uranium, chromium, and gold (Table 1.2). The mineral industry of Africa is the largest mineral industries in the world. However, the consumption of mineral commodities in Africa is relatively low but keeps improving as the standard of living increases with time.

Revenues generated from mining activities often constitute a substantial component of the GDP in African countries. However, mineral production in developing countries like Nigeria is beset with several problems, including illegal mining, unregulated environmental impact, systemic corruption, insecurity, and lack of stewardship to the local communities affected by mining activities. Several African countries are highly dependent on the revenue from the export of minerals. For example, minerals constitute 80% of the revenue generated by Botswana. Minerals accounted for more than 50% of export earnings of Mali (gold), Mauritania (iron ore), Guinea (bauxite), and Sierra Leone (diamonds).

Nigeria is an example of a country whose 90% of its revenue derives from exporting petroleum. Before the advent of crude oil production in the 60s, mining of minerals was a mainstay of the economy and contributed up to 50% of the GDP. Still, the level of contribution fell dramatically to less than 0.35% in 2019 due to neglect over the years. As the price of oil dropped dramatically in recent years, Nigeria has been searching for ways to diversify its economy by developing its mineral deposits, including industrial minerals, metallic ores, such as iron ore and lead-zinc as well as energy minerals, such as bitumen and bituminous coal for power generation. Nigeria has identified seven minerals/or metals as strategic commodities for the country’s future development. They are iron ore, gold, lead/zinc, barite, limestone, coal, and bitumen.

Table 1.2: Share of World Production of Minerals from Africa

Source: Mineral Industries of Africa (2012)

Life Cycle of Mineral Deposits

Mineral deposits usually pass through a life cycle, in what is sometimes described as passing from cradle to grave; starting with the discovery, and ending with closure, after the ores are exhausted (Fig. 1.1). Below is a summary of the stages in the life cycle of a mineral deposit.

Figure 1.1: Life cycle of ore deposits

The overall life cycle of mineral deposits begins typically with the discovery of the mineral deposit through prospecting and/or reconnaissance exploration, except if it is an already known occurrence or prospect. This is followed by detailed exploration to define the extent and value of the ore body, which leads to estimation of ore reserves that helps determine the size and grade of the deposit. The reserve estimates obtained are used to conduct a pre-feasibility study to establish the potential economic viability of the ore deposit followed by a full feasibility study to evaluate the operational costs, financial viability, the technical and financial risks, and the robustness of the project. At this point, the exploration or mining company decides whether to develop the mineral deposit into a mine or to walk away from the project. Such detailed evaluation and decision to proceed with the mine project are usually followed by the mine design and planning for extracting the mineral resource. During this final phase, significant steps are taken to determine the economically recoverable portion of the deposit, the beneficiation process, and ore recoverability, marketability, and payability of the ore concentrate. These steps must be followed carefully to achieve success.

The engineering concerns, milling and infrastructure costs, finance, and equity requirements are usually evaluated, and an analysis of the proposed mine from the initial excavation through to reclamation is prepared. Once the feasibility analysis is complete, plans may move ahead to gain access to the mineral deposit through mining excavation

The total movement of ore and waste constitutes the mining process. Often, more waste than ore is mined during the life of a mine, depending on the nature and location of the ore body. Waste removal and placement is a high cost to the mining operation. The mine buildings and processing plants are built, and any necessary equipment is obtained. The operation of the mine to recover the ore begins and continues as long as the company operating the mine finds it economical to do so. Once all the ores that the mine can produce profitably are recovered, the mining operation ceases, and the mine is closed. This is often followed by reclamation which is the process of making the land previously used by the mine suitable for future alternative use. To ensure that the old mining areas are environmentally safe may require the final process of remediation and cleanups. The life cycle of a mine from discovery to closure usually lasts for an average period of 30 years.

Types and Distribution of Mineral Deposits

Mineral deposits are of various types and can be grouped according to their geological environment or origin into the following: magmatic, hydrothermal, sedimentary, metamorphic, and residual mineral deposits. Magmatic deposits are those formed by igneous processes. They occur mainly as disseminations, layered bodies, or massive ores in igneous rocks and formed by processes of crystal settling, dissemination, liquid immiscibility, and crystallization fractionation in magmas. Hydrothermal deposits are formed by hot, ore-bearing fluids from various sources, including magmatic, connate, seawater and meteoric water. They are usually emplaced in pre-existing rocks as lodes, veins, and veinlets. Sedimentary deposits are formed within sedimentary basins as beds, layers, lenses, and cavity fillings produced by precipitation, evaporation, diagenesis, or volcanic exhalative processes. Metamorphic deposits are products of recrystallization of existing minerals or the formation of new minerals due to the effects of increased temperature and/or pressure. Residual deposits accumulate at or near the earth’s surface by chemical weathering, leaching, and concentration of useful materials through secondary enrichment.

The distribution of mineral deposits worldwide varies both in space and time due to the geological processes that formed them, and the timing of such events. Geologists have tried to unravel the reasons for the variation in the spatial and temporal distribution of mineral deposits. Research has shown that, as a result of geological and/or tectonic factors, mineral deposits of a specific metal or group of metals tend to be clustered in specific geographic areas or regions, known as metallogenic provinces of mineral belts. These spatial groupings occur because of shared geological processes involved in mineral deposition, such as the formation of sedimentary basins, emplacement of igneous bodies, and metamorphism in orogenic belts, tend to be controlled by larger processes of crustal evolution.

Mineral deposits have formed at various periods throughout geological time, ranging from Precambrian to Recent. The timing of ore-forming processes varies considerably and is known to spread throughout the geological time scale. Metallogenic epochs are units of geologic time during which conditions were particularly favorable for the formation of specific types of mineral deposits. There are geological records that show specific periods when the formation of a particular type of deposit was prevalent or common. For example, the Banded Iron Formations (BIFs), which are the dominant source of iron ore worldwide, were most widespread during the Archean to Early Proterozoic. This period was a metallogenic epoch for iron ores, which has been attributed to the absence of oxygen in the atmosphere during this period allowing iron to accumulate without oxidation.

The recognition and delineation of metallogenic provinces and epochs are of fundamental importance to Economic Geology because of their relevance to the search for new mineral deposits. It is most probable that future discoveries of new world-class metallic deposits will be made within these mineralized regions (metallogenic provinces) and within established geological time frames.

Mode of Occurrence and Size

Mineral deposits occur in various forms, shapes, and sizes, and are localized within a variety of host rocks of different composition. The mode of occurrence refers to the physical disposition of a mineral deposit, or simply, the way in which a mineral deposit occurs within the geological environment. It is a descriptive term that connotes the general appearance and relationship of the mineral deposit to host rocks and incorporates several characteristics of a mineral deposit that can be observed in the field, including shape and form. The mode of occurrence also reflects the total environment of the formation of a mineral deposit. In general, magmatic deposits are usually massive, layered, lenticular, or pod-like in form, while sedimentary ore deposits are roughly tabular or stratiform. Hydrothermal deposits may occur as lodes, reefs, veins, veinlets, stringers, stockworks, and replacement bodies, while most other deposits may appear in a variety of modes, including the blanket form for lateritic or residual deposits.

From the point of view of contact relationships and structural features, mineral deposits may be classified into two broad groups: epigenetic and syngenetic. Epigenetic orebody cuts across surrounding rocks and was emplaced after the host rock was formed, whereas syngenetic implies the mineral deposit is in conformity with surrounding rocks and formed contemporaneously with the host rocks. The relationship between mineral deposits and host rocks is significant in understanding the processes of ore formation and the origin of mineral deposits.

The size of a mineral deposit is an essential factor in its economic viability; it is a geometric reflection of the quantity and spatial disposition. Mineral deposits vary in size from very small to super-large, usually depending on the ore-forming process and geological environment. Size distribution has been studied extensively, and two distribution patterns have emerged: and are referred to as fractal and exceptional. A fractal distribution is associated with those deposits in which their sizes are dependent on the rate of accumulation within a defined space, such as a magma chamber or a fault zone. This is observed for both magmatic and hydrothermal deposits, reflecting a limitation in size but continuity and similarity in the processes that created both small and large deposits.

Exceptional size distribution is observed in deposits that appear to be genuinely exceptional in size and may reflect extreme or unique events in the Earth, such as meteoritic impacts that create massive space for ore accumulation, or mantle plume activities that create large igneous bodies