Exploration for minerals and oil

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Exploration for minerals
Drilling and downhole logging
Borehole drilling allows us to create a 3dimensional shape and size of orebody
We can find out the rock geochemistry through
chemical analysis ­ atomic absorption spectrometry (AA) /
xray fluorescence spectrometry (XRF) /
inductively coupled plasma mass spectography (ICPMS)
A borehole allows you to make a decision based on data of whether to mine or not
Downhole logging measures physical, chemical and structural properties of penetrated
geological formations using logging tools that are either lowered into the borehole on a
wireline cable or placed just behind the drill bit as part of the drill pipe itself.
The tools employ various acoustic, nuclear and electrical measurement techniques to
acquire downhole logs of properties such as
sonic velocity
density
electrical resistivity.
The wireline cable provides realtime communication between the tools and the surface
logging, while drilling tools typically record the logs in downhole memory devices,
which are subsequently downloaded when the tool returns to the ship.
Geochemical prospecting
Sampling stream, soil or vegetation to find particular trace element concentrations
which might indicate the presence of an economic resource, concentrations vary with
distance from the ore body, copper and lead
Advantages:
Sampling allows large catchment area to be investigated quickly
All elements have characteristic signatures which may show up in vegetation
response and are easily recognised in soil and water samples
Very dependable and cost effective
Disadvantages:
Contamination can be a problem (earlier mining, processing, windblown,
flooding)
Background rocks, variations in water pH and ore concentrations can give
misleading results

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Access may be difficult over wider areas
Geological mapping
Field work based ­ direct observation using trained geologists
Advantages:
High level of accuracy to pinpoint resources at the surface prior to exploitation
Can be very detailed ­ good to assess the problems of exploitation and viability
of resource
Samples can be collected for accurate analysis
Disadvantages:
Labour intensive and timeconsuming
Structural trends obscured on small scale
Accuracy depends upon sample points and interpretation
Possible problems of access in remote areas and lack of outcrops
Satellite…read more

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Geophysical surveying
Electrical Resistivity Survey
This method is used for gold exploration
Two electrodes are placed in the ground and an electrical current is passed between
them
If the rock is a good conductor it will have low resistance
Magnetic Survey
Using a magnetometer to measure magnetic readings.…read more

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