SEMINOR ONGEOCHEMICAL METHODS IN MINERAL EXPLORATION.

CONTENTS INTRODUCTION GENERAL PRINCIPLES OPTIMIZATION OF EXPLORATION PLANNING OF EXPLORATION SELECTION OF PROFESSIONAL LEADERSHIP SELECTION OF AREAS THE EXPLORATION SEQUENCE CHOICE OF EXPLORATION METHODS TARGET SIZE PROPETRY CONTROL RELIABILITY OF METHOD COST VALUE OF EXPECTED ORE THE ROLE OF GEOCHEMISTRY ORGANISATION AND OPERATIONS Field operation Laboratory Supervision CONCLUSION REFERENCE

INTRODUCTIONoGeochemical prospecting for minerals includes any method of mineral exploration based upon systematic measurement of one or more chemical properties of a naturally occurring material. oThe chemical property measured is most commonly the trace content of some element or group of elements.o The naturally occurring material may be rock, soil, gossan,glacial debris, vegetation, stream sediment, or water. oThe purpose of the measurements is the discovery of a geochemical "anomaly" or area where the chemical pattern indicates the presence of ore in the vicinity.

GENERAL PRINCIPLES OF GEOCHEMISTRY

Mineral deposits represent anomalous concentrations of specific elements, usually within a relatively confined volume of the Earth's crust.

Most mineral deposits include a central zone, or core, in which the valuable elements or minerals are concentrated.

This zone surrounding the core deposit is known as a primary halo or anomaly.

OPTIMIZATION OF EXPLORATION Any exploration requires an immediate outlay

of money and time, with the hope that discovery and exploitation of an ore body in the future will more than repay the initial cost.

At the initiation of a typical exploration project , the probability of success on the project is very small.

The total costs must include not only those for the reconnaissance survey and any successful detailed surveys.

PLANNING OF EXPLORATION Exploration normally involves a sequence of steps ,

both in the planning stage and in the execution stage.

SELECTION OF PROFESSIONAL LEADERSHIP

• Many exploration surveys have fallen short of expectations through lack of experience and technical training.

• More often it is necessary to build up a team ,the member of which cooperate to provide the necessary virtues.

• The critical phases of orientation, planning and interpretations can be done by professional exploration geologists or geochemists.

SELECTION OF AREAS

The main purpose of this stage is to select areas or regions that have good mineral potential and that can be prospected effectively.

Initial selection of areas should be based on a most through review of the known geology and records of past mining and prospecting activity.

Based on recorded mineralization and on the geological environment.

THE EXPLORATION SEQUENCE

o A large exploration program is commonly organized as a logical sequence of operations.

o Each stage in this sequence involves the study of methods in most effective.

o At the end of the each stage ,the available information is evaluated and used to select smaller areas for detailed study ,or to terminate the program if the initial premises have been disproved.

CHOICE OF EXPLORATION METHODSo For greatest overall effectiveness, an optimum

balance must be struck between the various geological , geophysical , and geochemical methods that are known to be applicable.

o The choice must be based on relevant previous experience and case-history data.

o Selection of methods is also strongly influenced by the size of the target and by property control.

TARGET SIZE

Some features of ore environment, such as favorable host rocks ,geological structures , or geochemical provinces , are related to the genesis and localization.

Each geological , geophysical ,and geochemical features of the ore environment defines a target area of characteristic size , shape ,and relationship to the ore.

PROPETRY CONTROL

The acquisition of property rights ,in most countries ,is an extremely tedious and expensive phase of mineral exploration.

The general pattern of exploration may be modified or even dominated by property consideration.

RELIABILITY OF METHOD Reliability depends not only on how effective the

exploration method is in locating the target , but also extent to which an anomaly is specifically related to ore and the abundance of non-significance anomalies that may confuse interpretation and require fallow-up survey.

COST The cost of an exploration survey is the only one

of the critical factor that can be estimated with any degree of accuracy.

VALUE OF EXPECTED ORE

The expected value of the ore body being sought and the chances of success may have an appreciable bearing on the applicability of a given method.

Thus a high-cost survey is justified for large ore bodies are expected and there is relatively little chances of overlooking a deposit.

Conversely , a low cost-survey is justified in areas of small targets.

THE ROLE OF GEOCHEMISTRY IN AN EXPLORATION SYSTEM Geochemistry is an essential component in most

modern integrated mineral exploration programs, for the following reasons:-

(1) Economic mineral deposits are commonly characterized by their low grade and large tonnage. Discovery, assessment and development are highly dependent upon geochemical methods and analyses.

(2) Exploration activity is mostly carried out in tropical and subtropical environments where chemical weathering has predominated and where geochemical prospecting techniques have proven most effective.

Recent estimates suggest that between 10 and 25% of exploration budgets are allocated to geochemistry.

ORGANISATION AND OPERATIONS

Every geochemical survey organization , irrespective of it’s scale, is based on three main functional units :

Field operation

Laboratory

Supervision

FIELD OPERATION Most operation in a

systematic sampling program can be carried out by team of local workers under the supervision of trained field assistants.

LABORATORY In general ,most

efficient ,reliable ,and economical analytical work is done in an established laboratory.

In many laboratories , sample preparation and analysis is performed by locally recruited labor.

SUPERVISION

Geochemical surveys should always be the responsibility of one who is first experienced exploration geologist.

His responsibilities will include :(1) Orientation to establish both field and

laboratory techniques.(2) Maintenance of technical efficiency and

coordinate throughout the operation.

CONCLUSION Geochemical methods of exploration

constitutes an important tool in the investigation of the economic mineral deposits.

Any geochemical investigation to be effective, must take into consideration several aspects of the ore body, including genesis and cost at various stages of exploration.

REFERENCE H. E. Hawkes and J. S. Webb (1979)

Geochemistry in mineral exploration ,second edition ,Pp:535-548.

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