GG306 Exploration Geology
School of Environment & Technology
Semester 1 Examinations January/February 2013
GG306
EXPLORATION GEOLOGY
Instructions to Candidates:
Time allowed: TWO hours
Answer THREE questions. Either compulsory question 1a OR 1b, and any TWO
other questions.
All questions carry equal marks
21st January–1st February 2013
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GG306 Exploration Geology
Question 1a
A ground investigation is being carried out at a former industrial site, which is due for
redevelopment. The site hosted a series of unmapped subsurface fuel storage
containers, and produced metallic waste which may now be capable of releasing
heavy metal contamination into the environment. The site is located on
approximately 1m of clay-rich soil, overlying an alluvial sand and gravel aquifer.
Describe the chemical sampling techniques you would use to investigate the source,
extent and nature of contamination, and how they could be complemented by
shallow geophysical techniques to investigate the overall extent of contamination.
(100%)
OR
Question 1b
A 3-D seismic survey is being carried out to investigate the potential for stratigraphic
traps in coastal shelf sediments. Explain the operation of the survey, how the results
of seismic surveying can be used to assess both vertical and lateral variations in the
subsurface geology, and how key relationships between reflecting horizons can be
used to assess the stratigraphic and sedimentological development of the area.
(100%)
Question 2
(a)
Explain the operation of a resistivity survey designed to generate a resistivity
pseudosection using a Wenner array.
(40%)
(b)
Explain the layout of resisitivity logging circuits used for normal and lateral
logging.
(30%)
(c)
Why is it important to know the properties of the lubricant (drilling mud) used
when interpreting a set of resistivity logs produced using tools with different
electrode arrangements?
(30%)
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GG306 Exploration Geology
Question 3
(a)
Explain the concepts of ‘threshold’ and ‘contrast’ in defining a geochemical
anomaly.
(40%)
(b)
A mineral exploration program is targetting copper deposits in an area
covered by approximately 8m of glacial till. Explain the sampling technique
you would use to look for a chemical anomaly related to mineralisation and
the issues you would have to take into account to interpret the dispersion
pattern of the anomalous elements.
(60%)
Question 4
(a)
Explain what is meant by induced polarisation in geophysical surveys, and
how it can be used in exploration for metallic minerals.
(30%)
(b)
Explain the operation of electromagnetic surveying techniques for
measurement of the apparent conductivity of the ground.
(30%)
(c)
A survey is being carried out over a disused landfill site to determine the
extent of landfill and any potential environmental impacts. Explain why
electrical and EM techniques are particularly suited to this application.
(40%)
Question 5
(a)
Explain the application of microgravity measurements for subsurface void
detection in engineering site investigations.
(50%)
(b)
What other techniques could be applied alongside gravity surveys to locate
subsurface voids resulting from historic mining? For each technique you
identify explain why it would be suitable.
(50%)
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