Exploration has many phases for different departments but in geology most commonly for exploration of minerals

1. UNIT 1: ELECTRICAL PROPERTIES ASSOCIATED WITH ROCKS.
1.0 Introduction
In this unit, you will be introduced to the basic concept of Electric Current Methods.
Basic Electrical Properties Associated with Rocks is the first topic or Concept you are
required to study in this course. There are reasons among others why electrical
current
method should be first topic to study in this course
Several electrical properties of rocks and minerals are significant in electrical
prospecting. They are natural electrical potentials, electrical conductivity, or the
inverse electrical resistivity, and the dielectric constant. Of these, electrical
conductivity is the most important, while others are of minor importance. Certain
natural or spontaneous potential occurring in the subsurface are caused by
electrochemical or chemical activity. The controlling factor is underground water

2. Most rock-forming minerals are insulators, and electrical current is carried through a
rock mainly by the passage of ions in pore waters. Thus most rocks conduct electricity
by electrolytic rather than electronic processes.
2.Objectives
At the end of this unit, readers should be able to:
(i) Understand the basic concept of electric current methods
(ii) Identifying and understanding that Electrical prospecting uses three
phenomena and properties associated with Rocksin the

3. • 3.0 Main content
• 3.1 Electric Current Methods
• Many geophysical surveys rely on measurements of the voltages or
magnetic fields
• associated with electric currents flowing in the ground. Some of
these currents exist
• independently, being sustained by natural oxidation–reduction
reactions or variations
• in ionospheric or atmospheric magnetic fields, but most are
generated artificially.
• Current can be made to flow by direct injection, by capacitative
coupling or by
• electromagnetic induction (Figure 1.1

4. Surveys involving direct injection via electrodes at the ground surface are generally
referred to as direct current or DC surveys, even though in practice the direction of
current is reversed at regular intervals to cancel some forms of natural background
noise. Currents that are driven by electric fields acting either through electrodes or
capacitatively (rather than inductively, by varying magnetic fields) are sometimes
termed galvanic. Surveys in which currents are made to flow inductively are referred
to as electromagnetic or EM surveys.
Relevant general concepts are introduced in this note. Direct current methods are also
considered which also describes the relatively little-used capacitative-coupled
methods. Natural potential (self

5. • potential or SP) and induced polarization (IP)
methods are covered. Also discussed are EM surveys using local sources and with
VLF and CSAMT surveys, which use plane waves generated by distant transmitters.
3.2 Resistivity and Conductivity
Metals and most metallic sulphides conduct electricity efficiently by flow of electrons,
and electrical methods are therefore important in environmental investigations, where
metallic objects are often the targets, and in the search for sulphide ores. Graphite is
also a good ‘electronic’ conductor and, since it is not itself a useful mineral, is a source
of noise in mineral exploration. Most rock-forming minerals are very poor conductors,
and ground currents are therefore carried mainly by ions in the pore waters. Pure water
is ionized to only a very small extent and the electrical conductivity of pore waters