Deposits Formed by Sedimentary and Surficial Processes - Metals and Society: An Introduction to Economic Geology - page 137

Table 5.6 Comparison of magmatic and lateritic Ni ores
Magmatic Lateritic

Origin Segregation of Ni sulfides

from mafic-ultramafic
magmas

Concentration of Ni in soil during
long weathering in hot humid
climates

Ore minerals Ni-Cu-Fe sulfides Ni-bearing phyllosilicates

Ore grade 0.5-5% 1-7%

Locations of major deposits Canada, Russia, Australia,

China

New Caledonia, Indonesian, Cuba,
Australia

Economic aspects
- Mining conditions Underground (rare open

cast)
mining of discontinuous
deposits in hard rock

Open cast mining of continuous
layers of shallow, poorly
consolidated soil

- Cost of refining Relatively low High (depends on oil price)

- Associated bonus metals Cu, PGE Co

- Toxic waste products Sulfur Acid or strong alkalis (from

refining)

from 0.2% to 0.3% in the peridotite to 1-3% in the ores. Cobalt is also concentrated
by this process and constitutes a valuable by-product. The rich garnierite ores of
New Caledonia develop in the lower part of the saprolith; the currently exploited
iron oxide ores are in the lower part of the pedolith.

Box 5.5 Exploration for Nickel Deposits
Imagine that you are a geologist in a major multinational mineral exploration
company and that your boss, the exploration manager, has asked you to plan
the future exploration program. The company economists have decided that
the price of all base metals will double in the next 10 years and the company
has decided to explore for nickel. Your tasks are as follows: (1) to decide what
type of deposit to target (magmatic or lateritic); (2) which part of the world to
conduct your exploration.
As part of your work you will have to decide whether to conduct
“greenfields” exploration (i.e. the search for deposits in parts of the world
where no deposits are known), or “brownfields” exploration (the search for
new deposits or extensions of deposits in regions known to be mineralized).
To decide on the region you will need to consider the geology of possible
target regions, their ages and tectonic makeup, the types of ultramafic rocks
they contain, and the climate over the past 100 million years. To decide on the
type of deposit you will need to consider the pros and cons of each type of
deposit, and, because the extraction of Ni from laterites requires so much
energy, the future oil price.
Summarize your arguments in a single page (the maximum the exploration
manager will want to read).