INTRODUCTION

Ghana today remains the second largest gold producing country in Africa and even with that it

has contributed considerably to the world economic market; its own development in all aspects

and as well created good deal of employment for Ghanaians.

GEOLOGY AND ECONOMIC MINERAL DEPOSITS OF GHANA

GEOLOGY OF GHANA

About two-thirds of Ghana is dominated by Paleoproterozoic Birimian rocks consisting of five

evenly spaced volcanic belts trending northeast-southwest. The intervening basins between the

volcanic belts are filled by sediments. The remaining one-third is made up of post-Birimian

rocks. The supra-crustal rocks are highly deformed. However, the sedimentary rocks are

particularly characterized by extensive folding.

The Geological Map of Ghana

The lavas are mainly of basaltic composition, though andesitic, dacitic and rhyolitic rocks are

also present. Some pattern of facies distribution is shown by the Birimian sedimentary basins

from the margins towards the basin centres.

The transition zone between the volcanic belts and the sedimentary basins is marked by a

chemical facies, which has of late been found to be the site of much of gold mineralization in

Ghana.

Previously it was thought that the Birimian sedimentary rocks were older than the volcanic

rocks. However, recent studies indicate that the volcanic belts and sedimentary basins are lateral

facies equivalents.

Both the volcanic belts and sedimentary basins are intruded by three types of granitoids differing

in age, mineralogy and chemistry, namely:

Granitoids in the sedimentary basins - the Cape Coast type - are dominated by two-

mica granites

Granitoids associated with the volcanic belts - the Dixcove-type - are dominated by

hornblende-bearing granites

The late K-rich granitoids (post-Tarkwaian) comprising the Bongo, Tongo and Banso

granitoids

Each of the Birimian volcanic belts contains meta-sedimentary rocks - the Tarkwaian Group –

that lie unconformably over the Birimian. The Tarkwaian consists entirely of conglomerates,

sandstones, phyllites and slates derived from the Birimian country rocks.

The Birimian and Tarkwaian rocks occur mainly in the Eastern, Central and Western Regions,

including Ashanti, Brong Ahafo and the western part of the Northern and Upper Regions.

The Dahomeyan System occupies the southeastern corner of Ghana and occurs as four alternate

belts of acid and basic gneisses, trending south-southwest to north-northeast direction. A greater

part of the System forms a monotonous low-lying plain broken by isolated inselbergs and ridges

of mainly ultramafic intrusives and hills forming outliers of Togo rocks. The areas occupied by

the basic gneisses are flat (Accra Plains), while the areas occupied by the acid gneisses give rise

to gently undulating topography.

The Togo Series are made up of meta-sediments and Buem Formation dominated by meta-

sediments and metavolcanics, support a range of hills lying in the eastern corner of the country.

Undeformed, flat-lying Neoproterozoic clastic sedimentary rocks forming the Voltaian System

cover the eastern third of the country.

A strip of Paleo-Cretaceous to Tertiary sediments occurs along the coast. These consist of the

Accraian Series (in Accra area), the Sekondian Group (Elmina, Komenda and Sekondi areas),

Apollonian Formation (Tano and Keta areas), and the Amisian Formation (the Saltpond area).

THE GEOLOGICAL PROVINCES OF GHANA

On the basis of age, tectonics and lithologic characteristics of the supra-crustal rocks, Ghana can

be divided into five geological domains or provinces (Fig. 2) namely:

1. The Western Unit, which lies at the eastern margin of the Precambrian West African Shield

or Craton.

2. The South Eastern Unit, which is at the southeastern part of the country belonging to the

Precambrian mobile belt.

3. The flat lying Central Unit made up mainly of the sediments of the Voltaian System.

4. The Coastal Basins

5. Tertiary to Recent deposits.

ECONOMIC MINERAL DEPOSITS OF GHANA

Mineral deposits of economic value that occur in Ghana include gold, manganese, bauxite and

diamonds. Large deposits of iron ore of medium quality are also known.

The Birimian rocks are the most important in Ghana for minerals such as gold, diamond, bauxite,

manganese and iron. For example, the following gold belts and gold districts are associated with

the Birimian rocks.

1. Prestea Belt

2. Akropong Belt

3. Obuasi Belt

4. Obuom and Konongo Belts

5. Asankragwa-Manso Nkwanta Belts

6. Tokoase and Bibiani Belts

7. Sefwi and Sunyani district Belts

8. Sekondi, Axim and Tarkwa district Belts

9. Cape Coast, Saltpond and Winneba district Belts

10. Western Akim and Birim district Belts

And those above could be categorized into six main gold belts including;

1. Kibi-Winneba gold belt

2. Ashanti gold belt

3. Sefwi gold belt

4. Bui gold belt

5. Bole- Nangbodi gold belt

6. Lawra gold belt.

Some gold belts and gold districts associated with the Birimian System

GOLD MINERALIZATION OF GHANA

Occurrence

There is a wide spread occurrence of gold in the Birimian and Tarkwaian rocks of Ghana. The

three main types of auriferous deposits are:

i) The reef, vein or lode-type gold deposits.

ii) Auriferous quartz-pebble conglomerates.

iii) Recent alluvial and eluvial deposits all associated with rocks of the Birimian Supergroup and

Tarkwaian Group.

(i) The Reef, vein or lode-type gold deposits

This type of gold is associated with quartz veins or any gold bearing lode or dyke. This type of

gold deposit is associated with rocks of the Birimian Supergroup. It occurs in five distinct forms

as namely:

Auriferous quartz veins which cut the Birimian Supergroup

Veins and stockworks in granite porphyries which intrude the Birimian

Sulphide ores which have arisen through mineralization of the country rocks in

the Birimian Supergroup

Oxidized ores which have been concentrated by chemical and mechanical

weathering of gold-bearing veins

Pegmatite dykes associated with the granitic rocks in the Birimian

(a) Auriferous quartz veins or reefs which cut the Birimian System

This type is the most important source of gold in Ghana and occurs as intrusive veins in phyllites

and greenstones in the Birimian. The veins occur at two main places.

near or/at the contact of the Metasedimentary and Metavolcanic Birimian rocks.

as reefs within the Birimian (Prestea-Obuasi-Konongo belt)

The lodes or reefs range from a fraction of a metre to 30 metres or more in width and a few

metres to several metres in length. The lodes consist essentially of quartz with little ankerite

{CaCO3(Mg,Fe,Mn)CO3}, pyrite, arsenopyrite, sericite, graphite, galena, pyrrhotite, sphalerite

and gold. The sulphides and the gold often occur in fractures in sheared and shattered quartz. The

bulk of the gold is carried in smoky grey sheared and laminated quartz. Two other types of vein

quartz that exist are the hard, milky-white quartz which carries some gold but generally of low

grade and the barren, glassy quartz which occurs in small veins filling tension cracks in the

aforementioned types.

The host rocks are usually dull black phyllites which were originally carbon bearing muds. The

reefs are lenses generally rich in gold where they are long and wide. They are poor in gold where

they are short and narrow. The lenses are often a few 100m apart longitudinally and are up to

1000m or more in depth. There is rarely any payable ore in the channels between the lenses.

In most of the most payable reefs the gold occurs in fractures, in sheared and shattered quartz

which readily disintegrate on weathering and rarely forms outcrops. The barren quartz often

makes prominent outcrops.

Examples of these reef type of gold deposits are found in Obuasi and Prestea.

b) Veins and stockworks in granite porphyries which intrude the Birimian

Auriferous quartz veins in Dixcove granite and porphyry and in granodiorite and diorites occur

in many parts of the country. The values are generally low. Examples can be found the former

Atta Gold Mines near Dunkwa and Mpasatia Mine near Kumasi.

c) Sulphide ores in mineralized rocks in the Birimian

Mineralised country rocks of the Birimian consisting of tuffaceous phyllites within the green

stones series have been found to be an important source of sulphide ores. The tuffs can be up to

30m or more in width and range from a few 1000m to many 1000's of metres in strike length and

carry disseminated and thin stringers of pyrite and arsenopyrite with small amounts of gold e.g.

in Prestea and Obuasi. Recent studies have shown that the mineralized Birimian tuffs occur in a

specific stratigraphic horizon.

d) Oxidised ores

These have been concentrated by chemical and mechanical weathering of gold-bearing veins.

These oxidised ores are very close to the surface in the residual above the water-table within an

average depth of about 30-80m. They are highly lateritic full of iron oxide, clays, weathered

mica and quartz pebbles. The gold is free milling and very fine, eg. Pepe (Tarkwa), Blackies &

Tom Collins (Obuasi) & Obenemasi quarry.

e) Pegmatite dykes associated with the granitic rocks in the Birimian

Lode gold can be found in pegmatite dykes a few metres or less in thickness. The gold occurs in

the free state or is mixed with pyrites eg Mankwadze - Winneba district.

Distribution of veins & lode type deposits

This type of deposits are found commonly

i) in the vicinity of the boundary between the metavolcanic and metasedimentary Birimian rocks

ii) where metavolcanic Birimian greenstones are intruded by Dixcove granite or porphyry

iii) where metavolcanic Birimian greenstones are in close proximity to manganese deposits

iv) where the metasedimentary Birimian is intruded by Dixcove granites.

Generally the older granite (Cape Coast) and the more highly metamorphosed Birimian rocks do

not contain gold deposits.

Areas of smoky and bluish grey mineralised quartz, containing partings, streaks & fragments of

the altered wall rocks are more favourable for gold mineralization than areas where white and

glassy quartz are found. Arsenopyrite needles and galena are good indicators of gold but in some

ores, the gold is associated with pyrite or tourmaline also. Gold frequently occurs in fractures in

sheared and shattered quartz reefs, commonly as elongated flat bodies of irregular shape and

thickness that lie along and within shear zones.

Genesis of vein and lode-type gold deposits

The mineralised reefs are associated with deep-seated overthrust fault channels and shear zones

along the margins of synclines and particularly along the contact between meta-volcanic

Birimian greenstones and metasedimentary Birimian phyllites. The quartz reefs contained in this

zone were unquestionably formed after the initial period of shearing, but shearing continued after

the reefs were formed. The gold mineralization came from external sources for, in all the

mineralized reefs, there is a very close association of gold and pyrite or arsenopyrite. It is shown

that the gold is present as minute specks within the sulphides - the gold and sulphides were

formed during the period of mineralized solutions permeating upwards through the shear zone

from a deep seated & probably magmatic source were responsible for mineralization of the

shattered zones. Thus the degree of mineralization depends not only on physicochemical factors

such as alkalinity and strength of the solution, temperature and lithology of the wall rocks, but

also on the rate of flow of the solvent through the zone it was mineralizing. In the relatively open

fracture and crushed zones, the rate of flow would have been greater than through zones of

sheared, less competent rocks such as phyllites and greenstones

ii) Auriferous quartz-conglomerates

The auriferous quartz-pebble conglomerates occur within the Tarkwaian Group. The Banket

formation is economically the most important member of the Tarkwaian Group as it contains the

auriferous conglomerates. The gold is mostly concentrated in the basal 20 cm of the lowermost

horizon and the highest contents are associated with well-sorted and well-packed hematite-rich

conglomerates which occur in the thinner horizons. These where enriched with hematite, contain

the most gold. The gold is very fine grained and free. The pay streaks are in the form lenses

better-developed and better-sorted conglomerate up to 150 m wide and 100 m in depth. The gold

content and the number of conglomerate bands are lower in the middle horizon than the

lowermost rudites and are even lower in the uppermost horizon.

These reefs have a similarity to those of the great Witwatersrand and the banket reefs of the

Transvaal, South Africa.

Origin of gold in the conglomerates

The gold in the Tarkwaian System is generally believed to be of placer origin. It is not uniformly

distributed through the Banket and very often, has its highest values along the contact. This is in

accordance with the placer origin hypothesis, since the gold would become concentrated in the

bottom parts of the pebble and shingle beds over which the river flowed. Other factors such as

the river flow rate in different parts of its course, uneven distribution at bands and sudden floods

due to torrential rain will have played their part in the patchy and uneven occurrences of the

values which are quite characteristic of the Banket deposit. The Banket reefs are essentially low

grade and mining has to be carried out in a very large scale, at a high level of efficiency if an

economically viable operation is to be achieved.

Evidence favours the source of the gold as having been derived from the Birimian schist which

forms the basement of the Tarkwaian System. No clear origin has been defined for the abundant

hematite that is intimately associated with the gold. Uplift of folds to the east of the Tarkwaian

belt created a westerly paleo-slope toward depressed tracts developed over synclines. Erosional

debris from the positive areas accumulated in the synclinal basins and at one particular interval

of time, the process of sedimentation led to the reworking and winnowing of sand-supported

gravels to produce significant concentration of gold in the matrices of the graves.

iii) Recent placer gold deposits.

Both alluvial and eluvial gold deposits occur in Ghana. The alluvial deposits however are the

most common and occur in gravels of streams, river flats, old valleys and on terraces and in

beach sands and gravels. They are derived mainly from the primary vein and lode-type deposits

associated with the Birimian. Important alluvial gold deposits can be found in most of the rivers

draining the Birimian rocks.

GOLD MINING IN GHANA

Ghana has made tremendous strides in the development of its mining sector since the inception

of the Economic Recovery Program (ERP) in 1984. Under this program several macro-economic

policies were initiated which have resulted in an upsurge of investment attractions to the country.

For example, prominent mining companies like Anglogold, Goldfields, Golden Star Resources,

and Newmont are investing significant amounts in the country. Other multinational companies

such as BHP-Bliliton, Alcan and Alcoa have also expressed interest in the bauxite industry in

Ghana.

Currently, proceeds from mining activities provide the largest foreign exchange earnings for the

nation with gold accounting for approximately 90% of these earnings. Gold production has

increased from 282,229 ounces in 1984 to over 2.3 million ounces currently. In addition to gold,

the country is endowed with other mineral deposits such as Manganese, Bauxite and diamonds.

There are also unexploited economic deposits of iron ore, limestone, kaolin, feldspar and silica

sands.

In addition to the 7 large scale operating gold mines in the country, over 200 gold reconnaissance

and prospecting licenses have been issued by the Government to both Ghanaian and foreign

entrepreneurs.

Ghana’s largest mine is in Tarkwa, owned by Gold Fields Ghana Ltd. The Tarkwa Gold Mine is

located in south-western Ghana, about 300 kilometers west of Accra. The project consists of six

open pits, two heap leach facilities, and a CIL plant. Tarkwa has a Mineral Resource of 15.3

million gold ounces and a Mineral Reserve of 9.9 million ounces. In 2010, the Tarkwa mine

produced 720,700 ounces of gold.

Newmont Ghana Gold Limited, Ahafo mine in Kenyase produced 531,470 ounces of gold in

2009, up from 524,000 a year earlier.

Gold Fields Ghana Ltd also owns the Damang mine, located in south-western Ghana, about 300

kilometers west of Accra. The Damang Gold Mine has a Mineral Resource of 4.7 million gold

ounces and a Mineral Reserve of 2.1 million ounces.

AngloGold Ashanti’s Obuasi operation, now dormant, used to produce 400,000 ounces a year.

AngloGold also owns the Iduapriem mine, which produces an average 190,000 ounces of gold

per year.

Bibiani gold mine, also now dormant, owned by Noble Mineral Resources, is located in western

Ghana, 250 kilometres north-west of Accra. The open-pit mine, which was commissioned in

1998, is in the Sefwi-Bibiani belt, and contains more than 17 million ounces of gold. The Sefwi-

Bibiani belt is the second-most significant gold- bearing belt in Ghana after the Ashanti Belt to

the east. Noble Resources planned a $9m drilling programme over a three-year period.

Golden Star Resources, which has two operating mines in Ghana, poured its two-millionth ounce

of gold from its Bogoso/Pretea and Wassa mines in 2009.

The Bogoso/Pretea project, in which Golden Star has a 90% interest (Ghana government owns

the remaining 10%), consists of approximately 85km mining and exploration concessions along

the Ashanti trend in south-west Ghana. They also produced 200,000 ounces in 2010. The Wassa

gold mine (also 90% owned by Golden Star), is located in the southwestern region of Ghana

approximately 35 km east of Bogoso/Prestea. In 2009, mining operations at Hwini-Butre

commenced and provided even higher grade ore to the Wassa mill.

Keegan Resources has two premier gold assets in Ghana. Keegan's flagship property is the

Esaase gold deposit. Updated resource calculations indicate a 2.025 million ounce and a 1.451

million ounce inferred resource averaging 1.5 g/t and 1.6 g/t Au respectively. Developments are

currently underway that would enable the project to be brought quickly to production stage.

Keegan is also exploring a second project, the Asumura gold property, is located along one of

Ghana's largest and most productive gold structures (Sefwi-Bibiani gold belt).

Moreover, there are a lot of registered small scale gold mining enterprises in this country who

are also making quite significant stream of success in this venture and contributing immensely to

the industry.

SMALL SCALE GOLD MINING IN GHANA

In Ghana, small-scale gold mining has been carried out for hundreds of years. It is currently and

widely operated in the country by both licensed operators and illegal miners popularly known as

galamsey operators. The Ministry of Lands, Forestry and Mines (2008) explains that the number

of small scale miners has increased rapidly by 941.72% from 1984 to 2004 after its legalization

by the Small-Scale Gold Mining Law, PNDC Law 218 of 1989.

This sector of gold mining has been identified to give relatively low gold revenue to the

government due to the lack of education and the potent methods of gold extraction. The Ghana

Minerals Commission estimated that in 2002, the small gold mining sub-sector contributed only

7% of the $694,970,543 gold revenue (Ghana Minerals Commission, 2002). However, according

to Campbell and Pittsfield (1994), the small-scale gold mining sector in Zimbabwe contributed

about 58% of gold revenue to the Zimbabwean government in 1994 while 68% of the

Philippine’s gold production in 1994 came from small-scale mining sector. It is therefore

believed that the method of gold extraction in those countries is potent enough yielding an

eventual considerable quantity of gold.

The predominant method of gold extraction in the small-scale mining sector in Ghana is by

simple gravity method and amalgamation by the use of Mercury since the mining laws of this

country forbids them to use the most effective Cyanidation as a process of gold extraction due to

its high level of toxicity because the government believes that the small scale miners lack the

technical know-how pertaining to handling the chemical (Cyanide) involved in the conventional

way to prevent it from poisoning the environment.

Pictures as displayed above show how small scale mining is carried out in Ghana

A gold ore is a rock material that contains gold yet to be mined and extracted. Generally, when

an ore is mined it is subsequently crushed into a powdered form making it easier for gold

extraction to take place. Interestingly, there are two types of ores; oxidized ores and refractory or

carbonaceous ores. Oxidized ores which are normally being referred to as free milling require

less or no pretreatment before gold leaching process is effected but for the refractory or

carbonaceous ores, the gold mineral is occluded in a mineral like copper, carbon-rich constituent

but the common one is pyrite which exist in various forms and it is required to execute a process

to break the bonds between them and the gold mineral before effective extraction could be

carried out.

These facts about gold ores, the way as they appear, are unknown to the small scale mining

operators since they lack formal professionalism in that regard, hence, they treat all materials in

the same way.

GENERAL OPERATIONAL OBJECTIVES

The acquisition of gold is the end product of a series of processes which includes; geological

mineral exploration, development of the targeted deposit, mine planning, mining, and

metallurgical extraction. This project seeks to narrow down the process of gold production into

two main stages, thus; mineral exploration (for the tailings) and the metallurgical extraction,

saving the cost and labour of following the other stages.

As stated earlier, almost all of these small scale miners, after having milled the ore material, use

mercury, through a process known as amalgamation, for gold extraction and mercury known for

its extremely low gold extraction potency, they are able to take only a meagre amount of the gold

mineral thereby leaving a stupendous quantity of the precious metal in the tailings (waste).

Considering, an extraction being carried out on an oxide ore, which requires no or less

pretreatment, Amalgamation could only yield 20% to 45% of gold recovery and on a sulphide or

carbonaceous ore, it could only do 0% to 7% gold recovery.

It is in view of this, that it has become a necessity to comb each and every corner of Ghana and

some parts of West Africa for places where prominent small scale mining operations with high

grade tailings are prevalent, erect a mobile gold extraction plant and feed on their waste products

(tailings). Our team of professionals have thoroughly researched and has been able to emerge

with methods of gold extraction other than Amalgamation but effective and efficient as

Cyanidation (able to give 95% of gold recovery) which is regarded as highly poisonous to the

environment and therefore small scale miners are prohibited from its usage but the law allows

large scale mines to apply. The newly identified methods can give gold recovery as high as 80%

to 98% but relatively quite expensive to execute and their toxicity level is very minimal. These

methods are listed as follows;

1. Ammonia Leaching

2. Thiocyanate Leaching

3. Ferric Chloride-Acid Brine Leaching

4. Hydrogen Peroxide Leaching

5. Nitrogen Catalysed Pressure Leaching

6. Platsol Leaching

7. Chlorine/ Chloride Leaching

8. Thiosulfate Leaching

9. Bisulfide Leaching

10. Sulfide Leaching

For any of the methods enumerated above, we intend to erect a mobile processing plant to treat

any type of gold ore encountered. We are using a mobile plant because we would be moving

from one place to another when we are done feeding on the tailings at each point in time. This

work proceeds unabated so long as small scale mining operations continue to stay active.

The kind and capacity of mineral processing plant we seek to build would be able to process

5,000 tonnes of gold ore with an average head grade of 4.5g/t and recovered grade of 4.05g/t in 8

hours giving an approximate yield of 25Kg Au.

Typical tailings dump produced from small scale mining operations

As a unit, it is our prime objective to extract gold from galamsey tailings and sell to our final

consumers and Ghana being the second largest gold producing country on the African continent,

posses a fairly unmatched credential in terms of gold quality and purity. As a cooperate unit we

are in search of genuine investors and buyers to partner with and support our ambition of

becoming a legal gold extraction and exporting company in Ghana. We would have ourselves

equipped with a unique obligation to give our customers quality services, prompt delivery of

products purchased and also work tirelessly to meet the international standard of the World Gold

Council requirement. Furthermore, we have plans of putting measures in place, as a company to

protect our potential buyers and investors against scam when buying from either us or other

purchasing points.

In addition, we have plans of establishing a security company with the main objectives of

handling precious minerals, coordinate and control other small scale miners which would operate

under the mother company, represent and look for potential buyers for their products gathered

for sales and export. The security body would be equipped with one of the most advanced

technological vaults in West Africa where all products collected from various extraction

sites would be kept safely for final export, and also as a company we would establish

professional relationships with tactically selected leading banks in Ghana where we would

acquire additional vaults for the safe keeping of our excess products. The company would also

coordinate the buying and selling of gold and silver within Africa for our buyers and as well,

represent those who intend to buy gold and silver but do not have representatives on the grounds

to ensure the security of their buying capital and interest to get the right products; see to the safe

shipment of their commodities into their very folds.

Moreover, in Ghana most of the large and small scale mining companies hire heavy duty mining

equipments and there is a great market for renting out such equipments. Hence, it would be

beneficial to indulge in this trade as well and as a company we have developed intimate contacts

with some of the mining companies where such equipments could be rented out for payment on

daily, weekly, or monthly basis.

CONCLUSION

There is so much gold in Ghana and West Africa; it is only left with the financial resources to

support the able professional and technical cause in producing the precious metal in large

quantities though on a small scale.

Tailings from small scale mining operations would be our sole source of feed to produce gold

and the plans and measures structured in place would ensure efficient work delivery. This will

save us the cost, time and labour of typical mineral exploration, mining planning, drilling and

blasting and mining.

It is a cost-effective adventure; with dedication and hard work of our workforce, high

productivity is guaranteed.

Compiled by;

Prince Okyere Boadu

BSc. Geological Engineering