Geochemical methods in mineral exploration

1. SEMINOR ON
GEOCHEMICAL METHODS IN MINERAL EXPLORATION.

2. 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

3. INTRODUCTION
oGeochemical 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.

4. 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.

5. 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.

6. PLANNING OF EXPLORATION
Exploration normally involves a sequence of steps , both in
the planning stage and in the execution stage.

7. 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.

8. 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.

9. 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.

10. CHOICE OF EXPLORATION METHODS
o 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.

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

16. ORGANISATION AND OPERATIONS
 Every geochemical survey organization ,
irrespective of it’s scale, is based on three main
functional units :
 Field operation
 Laboratory
 Supervision

17. 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.

18. 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.

19. 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.

20. 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.

21. REFERENCE
 H. E. Hawkes and J. S. Webb (1979) Geochemistry
in mineral exploration ,second edition ,Pp:535-548.
 www.wekipedia.com

22. THANK YOU …