Page 100 - Introduction to Mineral Exploration

5: FROM PROSPECT TO PREFEASIBILITY 83

FIG. 5.8 Typical exploration
trench, in this case on the South
African Highveld.

S N
Banded mica marble
Barren pink 29°N with 3 cm band moderately Str. 090 mag. Str. 040 mag.
mineralized with malachite dip 21°N dip 18°NW
marble
1410
75
25
470
345 40 1950 Marble with 750
Finely banded qtz - mica Barren pink Marble, weakly 2510 traces malachite Marble with local
marble
schist, thin qtz horizons, mineralized with traces of malachite
possible isoclinal malachite
folding, flat dip
750 Sample with ppm Cu

0 5 10 15 20 25
Distance (m)

FIG. 5.9 Sketch of a trench testing a copper anomaly in central Zambia. (From Reedman 1979.)

An alternative to disturbing the environ- surveys. Not all the information obtained will
ment by trenching is to use a hand-held drill be useful, indeed some may be misleading, and
for shallow drilling. This type of drill is light- distinction should be clearly made between
weight and can be transported by two people. measured and interpreted data. Geophysical
It produces a small core, usually around 25– and geochemical surveys can indicate the sur-
30 mm in diameter. Penetration is usually lim- face or subsurface geology of the potential host
ited, but varies from around 5 m to as much as rocks or more directly the presence of mineral-
45 m depending on the rig, rock type, and skill isation as discussed in Chapters 7 and 8. Tradi-
of the operators! tionally the results of these surveys have been
combined by overlaying colored transparent
copies of the data on a topographical or geolog-
5.1.8 Merging the data
ical paper base. It is then possible to determine
The key skill in generating a drilling target is the interrelation between the various data
integrating the information from the various sets. More recent developments have allowed