Adapted from a talk by Dr. Gerry Carlson, President La Teko Resources Ltd.
Available topographic maps
Available air photos
Physical conditions - topography, outcrop pattern
2. Known Deposits/Target: Deposit type(s)
Alteration Host rocks
- both for model deposit and for actual deposit characteristics
- information sources geological maps, geologists, local knowledge,
local mines and prospects
Available geological maps and reports combined with
information concerning geological associations of known target/deposit
types help tomorrow down the area of search and highlight the prime
A. Ore Exposed at Surface
Although some may feel that all significant ore deposits exposed at
surface have already been discovered, they are wrong. New logging roads
are being cut, glaciers are receding and trees are falling over, all
exposing new outcrop. In addition, many ore deposits, especially gold, are
difficult to recognise at surface. One of the most important prospecting
methods therefore is simply breaking open as much outcrop and locally
derived boulders as you can. Examine fresh faces on each broken piece with
your handlens for evidence of mineralisation or associated alteration.
When in doubt, label and save the specimen for geochemical analysis or
assay or examination by a professional.
B. Ore Covered by Thin Overburden Layer
2.Recognize alteration in outcrop (see above).
3.Recognize ore minerals or alteration in locally derived boulders
collected from overburden or stream channel.
4.Sample altered bedrock for geochemical analysis, possibly
recognise slightly enhanced metal values.
5.Sample soil for geochemical analysis, outlining an area of enhanced
6.Sample stream sediment for geochemical analysis, outlining a portion of
the drainage basin with enhanced metal values.
(Broadly speaking, the five properties that geophysics seeks to
measure are: magnetic fields; electrical fields; gravity fields;
radiation; and rock density).
7.If the ore or associated rocks contain magnetic minerals, such as
magnetite or pyrrhotite, look at government airborne magnetic maps or
carry out a ground magnetic survey.
8.If the ore is massive and conductive, consider an electromagnetic survey
such as VLF or HLEM (horizontal loop).
9.If the ore is disseminated, consider an IP survey.
10.If the rocks associated with the deposit have differing geophysical
characteristics or if they are faulted, all of the above geophysical
techniques can provide information about the bedrock geology.
11.If the ore is massive and much denser than the surrounding rock, and if
the topography is subdued, a gravity survey could be considered.
C. Ore Covered by Thick Overburden or Bedrock
In this case, all of the above prospecting methods apply except for direct
observation, method 1. Geology is still a useful tool to outline the
appropriate regional environment for the occurrence of the target deposit
type, but direct ore associations and alteration are usually hidden. In
addition, because of the thicker overburden cover, the proportion of ore
related boulders, such as mineralisation or alteration, unmineralised
boulders is much smaller. Geochemical methods can be successfully applied
to narrow down the target search area, but they seldom provide an actual
drill target. As a result, prospecting in such areas tends to rely more
heavily on geophysical methods to outline drill targets and ultimately on
drilling to make the initial discovery. Costs are usually much higher and
out of the range of individual prospectors.
Prospecting involves the detailed examination of surficial materials
and underlying bedrock in search of an ore deposit, or evidence of the
nearby existence of an ore deposit, utilising geological, geochemical and