GG306 Exploration Geology
School of Environment & Technology
Semester 1 Examinations January/February 2014
GG306
Exploration Geology
Instructions to Candidates:
Time allowed: TWO hours
Answer either question 1A or 1B, and any 2 other questions.
All questions carry equal marks
27th January–7th February 2014
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GG306 Exploration Geology
Question 1a
An economic mineral exploration program is looking for Cu sulphide mineralisation
hosted in Precambrian metamorphic rocks including biotite schists, marbles and
metavolcanic rocks (dominantly amphibolites and meta-andesites). The area of
search is covered by up to 8m of glacial till. Mineral deposit models for the area
suggest Cu should be associated with the formation of magnetite and hematite,
alongside alteration of the host rocks to albite, K-feldspar and biotite. Explain the
physical and chemical exploration techniques that could be used for such an
exploration program, from regional mapping and area selection, down to target
definition for drilling and resource definition.
(100%)
or
Question 1b
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 gas storage
containers, and produced metallic waste, which may now be capable of releasing
heavy metal contamination into the environment. The site is located on Palaeogene
residual clay deposits, overlying a Cretaceous sandstone aquifer. Explain the
geophysical techniques you would use to determine the thickness and continuity of
the clay layer, and the chemical sampling and geophysical techniques you would use
to investigate the source, extent and nature of contamination.
(100%)
Question 2
(a) Explain the application of electrical resistivity in geophysical well logging,
including what account must be taken of the nature of the drilling lubricant.
(40%)
(b) Explain the operation of natural gamma and neutron density well logging
tools.
(20%)
(c) With reference to examples, explain how geophysical well logs can be used in
the correlation of stratigraphic boundaries for the characterisation of
hydrocarbon reservoirs.
(40%)
Question 3
(a) Explain the ray paths of the direct, refracted, head (critically refracted) and
reflected waves in a simple seismic experiment.
(30%)
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GG306 Exploration Geology
(b) Deconvolution and migration are two key stages in the processing of seismic
survey data. Explain the main effects these are designed to remove from
seismic data.
(30%)
(c) Explain how mapping of the amplitude of seismic wave reflections from
individual boundaries can assist in determining lateral variations in geology
and fluid content during a seismic reflection survey.
(40%)
Question 4
(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%)
Question 5
(a) Explain the purpose of orientation surveys within a geochemical exploration
programme involving stream sediment and shallow soil grid sampling.
(50%)
(b) Metals have different solubilities in the weathering environment. Explain the
significance of this to geochemical exploration.
(50%)
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