Geochemistry is defined as the branch of Earth Sciences that employs chemical principles to explain the mechanisms influencing the Earth’s processes, including the formation of the Earth, its crust, oceans, and atmosphere. It can be applied to the exploration of mineral deposits, for which it is necessary to understand the fundamentals of geochemical prospecting, the geochemical dispersion of elements based on their chemical properties.
Geochemical prospecting is a branch of earth science that applies geochemical principles to locate mineral deposits. It involves studying the primary and secondary dispersion of elements through methods such as lithogeochemical analysis, stream sediment sampling, surface water testing, soil surveys, and other related techniques.
A mineral deposit is a mineralized area of the Earth’s crust, containing ores of sufficient size and grade (concentration) that, under favourable conditions, can be economically extracted and have adequate reserves for potential exploitation [1].
The metal concentration in mineral deposits can vary greatly—from just a few parts per million (1–100 g/t or ppm) for noble metals such as platinum (Pt), palladium (Pd), gold (Au), and silver (Ag), to low percentages (1–10 wt.%) for metals like copper (Cu), zinc (Zn), and lead (Pb), and to much higher grades (40–60 wt.%) for aluminum (Al), chromium (Cr), iron (Fe), and construction aggregates [2].
In geochemical prospecting, “pathfinder,” “indicator,” or “tracer” elements (Table 1) are key parameters. These elements are relatively mobile, influenced by the physicochemical conditions of the solutions in which they occur [3].
Table 1: Examples of pathfinders in some types of mineral deposits.
|
Mineral deposit |
Metals/elements of economic interest |
Pathfinders |
|
Chromium Orthomagmatic (stratiform) |
Cr |
Cr, PGE, High Mg |
|
PGE Orthomagmatic (stratiform mafic-ultramafic) |
PGE (Pt, Pd, Ru, Re, Os) |
PGE, Cu, Ni, Cr, Ti, High Mg |
|
REE in Carbonatite |
REE, Nb |
Th, U, Ti, Zn, Nb, Y, Ce, Mo, Cu, V, P, Mn, S, La, Pb, Zr, Ba |
|
Porphyry Copper |
Cu, Mo, Au |
Cu, Mo, Au, Ag, W, B, Sr, High S |
|
VMS |
Cu, Zn, Pb |
Cu, Zn, Co, Ag, Ni, Cr |
|
Epithermal Gold |
Au, Ag, Cu |
Au, As, Sb, Hg, Ag, Pb, Zn |
|
SEDEX Zn-Pb |
Zn, Pb |
Cu, Pb, Zn, Ba |
|
Sandstones Uranium |
U |
U, V, Mo, Se |
|
Phosphates |
P, REE (by-product) |
P, N, F, C, U |
|
Lateritic Nickel |
Ni, Sc or Co (by-product) |
Ni, Co, Cr |
References
[1] W. L. Pohl, “Economic Geology Principles and Practice: Metals, Minerals, Coal and Hydrocarbons – Introduction to Formation and Sustainable Exploitation of Mineral Deposits,” Wiley, Apr. 2011. doi: 10.1002/9781444394870.
[2] J. L. M. Carreño, “Geochemistry Applied to the Exploration of Mineral Deposits,” in Geochemistry and Mineral Resources, IntechOpen, 2022. doi: 10.5772/intechopen.103941.
[3] “Principles of geochemical prospecting,” 1957. doi: 10.3133/b1000F.
