The document discusses geochemical concepts relevant to mineral exploration, including the geochemical environment, cycle, dispersion, and mobility of elements. It describes the deep-seated and surfacial environments and how materials move between them in the geochemical cycle. Mobility depends on factors like viscosity and particle size. Hypogene mobility occurs under high pressure-temperature conditions, while supergene mobility is influenced by siliceous or sulfide environments at the surface. Indicator and pathfinder elements are discussed for detecting targeted ore deposits.

2. CONTENTS
 INTRODUCTION
 GEOCHEMICAL ENVIRONMENT
 GEOCHEMICAL CYCLE
 GEOCHEMICAL DISPERSION
 GEOCHEMICAL MOBILITY
 HYPOGENE MOBILITY
 SUPERGENE MOBILITY
 ASSOCIATION OF ELEMENTS
 CONCLUSION
 REFERENCE

3. INTRODUCTION
 Geochemistry refers to the determination of
the absolute abundant of elements in the earth.
 Geochemistry as applied in mineral
exploration is mainly concerned with the
preparation and interpretation of geochemical
maps rater than the investigation of basic
principles
Geochemical prospecting can be realized only
through a understanding of the principles that
govern the distribution of element in the earth

4. Cntd
Geochemically and geologically the earth is a
is dynamic system in which materials move
from one place to another and change in
composition by a variety of geological
process like melting , crystallization, erosion,
dissolution, precipitation etc….

5. GEOCHEMICALENVIRONMENT
 Based on the differential pressure temperature
and chemistry the geochemical environment of
the earth can be broadly classified into deep
seated environment and surfacial environment .
 The deep seated environment extends
downwards from the lower levels of circulating
meteoric water to the deepest level at which
normal rocks can be formed.
 It is an environment of high temperature and
pressure, restricted circulation of fluids, and
relatively low free oxygen content

6. Continued
 The surfacial environment is characterized
by the process of weathering, erosion, and
sedimentation at the surface of the earth.
 It is characterized by low temperatures,
nearly constant low pressure, free movement
of solutions, and abundant free oxygen,
water, and CO2.

7. Geochemicalcycle
 The movement of earth materials from one
environment to another can be conveniently
visualized in terms of a closed cycle
referred to as the geo chemical cycle

8. Geochemical cycle

9. continued
 In the geochemical cycle starting on the right hand side of the
diagram and moving clockwise direction
 Sedimentary rocks are progressively metamorphosed as they are
subjected to increasing temperature, pressure, and increments of
new materials from out side the system.
 The may eventually attain a state of fluidity such that on
recrystallization they can differentiate into various kinds of igneous
rocks and hydrothermal extracts.
 When erosion brings the resulting suite of rocks into the surficial
environment again, the component elements are relative solubility
in water. redistributed by weathering agencies primarily in
accordance with their
 A new series of sedimentary rocks is then deposited ,and the cycle is
closed
 The geochemical cycle therefore includes both deep seated process
of metamorphism and igneous differentiation and the surficial
process of weathering, erosion, transportation and sedimentation

10. GEOCHEMICAL DISPERSION
 Any material on the earth is constantly
subjected to transformation as process through
different environment in the geochemical cycle.
 This process in which atoms and particals move
to new locations and geochemical environment
is referred to as geochemical dispersion.
 Geochemical dispersion may occur by
mechanical process or even chemical and
biological factors .

11. continued
The response of an elements to dispersion depends on
its mobility that is how easily it can be dispersed
relative to other associated material.

12. continued
 The distribution of elements of the constituents
rocks and minerals in response to various
geological process are referred to as
geochemical mobility.

13. GEOCHEMICAL MOBILITY
 Fundamentally, the response of an element to dispersion
process is governed by its mobility, that is the ease with
which it may be move in any given environment
 Mobility depends an the mechanical properties of the
mobile phase, and factors such as the viscosity of magmas
and solutions and the size shape , and density of clastic
grains in following scheme water.
 The relation between mobility and chemical
differentiation, an other hand is rather more involved .
 Here the prime factors are the changes in relative stability
of the various coexiting fluid (mobile) and crystalline
(immobile) phases that result from changes in the
environmental condition.

14. MOBILITY UNDER HIGH P-T CONDITIONS
(HYPOGEN MOBILITY)
 In crystallization of magmas ,the constituents that can not
be accommodated in the lattice structures of stable rock
forming minerals are concentrated in mobile residual
fluide.
 Water, which cannot be entirly accommodated in the
minerals of igneous rock , is progressively enriched in the
residual fluids .
 Hydrothermal vein deposits may be precipitated at this
stage in the primary geochemical cycle .
 At high P-T the hydrous minerals of sedimentary rocks
becomes unstable and water is released to become
principal constituent of the mobile phase.

15. Continued
The occurrence of an element as a
characteristic constituents of deposits
formed from fluids of various kinds,either
vapors,supercritical solutions,or normal
aqueous solutions,may also be an
indication of their hypogene mobility.
In this group are the elements of complex
pegmatites,hydrothermal vein
deposits,juvenile water, and gaseous
emanation.

16. Supergene mobility of elements
siliceous sulfide-free environment
Relative mobility
Very mobile
Moderately mobile
Moderately
immobile
Very immobile
Major elements
S,cl
Ca,na,mg ,k
Si,mn
Fe,Al,Ti
Minor elements
Br,l,mo,b,se
Zn,ba,u
Ni,co,cu,as,pb
Cr,Rare earths

17. ASSOCIATION OF ELEMENTS
In a geochemical survey an elements measured
to detect and ore body is referred to as an
“INDICATOR ELEMENTS”.
In many situation the indicator elements is the
same element as the ore deposits.
Example-Element gold for gold deposits.
 If the ore element is difficult to analyze then
another element associated with the ore will be
useful which is referred to as a “PATHFINDER
ELEMENT”
 Example- Arsenic for gold ,

18. PATHFINDERSTABLE
Pathfinder Material Ore type
elements sampled .
As Wall rock , residual soil vein type Au ore
Hg Wall rock & soil Complex Pb-Zn-
Ag ores
Se Gossan , residual soil Epigenetic
sulfides
Ag Residual soil Ag-bearing Au
ore
So4 Water sulfide deposits

19. CONCLUSION
The movement of earth material from one
environment to another can be explained by
this geochemical cycle.
Geochemical exploration is mainly governed
by mobililty of elements and the geochemical
cycle and geochemical environments help
understand the mobility of elements.

20. REFERENCE
 Geochemistry in mineral exploration H . E . HAWKES
and J . S . WEBB, HARPER and ROW,PUBLISHERS.
 ( 1979). Pp. 10 - 23
 WEB SITE -WWW.GOOGLE.COM
 http://en.wikipedia.org
 http://geochemical cycle.org

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