Geochemistry

    A good description of a mineral deposit is an area where specific substances – minerals or metals - exist in concentrations that are a lot higher than normal. To put it in other words, the deposits themselves are what we could call anomalies. The aim of geochemical exploration is to find anomalous concentrations of elements.

    Exploration geochemists have distinguished traditionally between primary and secondary distribution of chemical elements. The processes of primary distribution are the ones which in the first place form the ore deposits, they are the ones that disperse metals and other chemical elements through the surrounding bedrock.weathering, glaciation, and the movement of ground and surface water move the elements around more – into soils, lake and stream sediments and waters, out to sea, and even into the atmosphere and plants are the secondary processes.

    The knowledge of details of the geological processes which cause the dispersion is required to trace the metals back to their source. This is geochemistry’s realm. In most typical geochemical surveys, the prospector takes samples of a particular material, maybe water, soil, bedrock or something else entirely. The samples are afterwards chemically analyzed for the elements of interest, and the results are plotted on a map.

    In the simplest case, the prospector will follow up on samples that have the highest concentrations of the metals which he looks for. More often, the geochemist has to interpret the distribution patterns to reconstruct the path which the elements have followed. For instance, glacia action can “smear” soils along the direction that the glacier travels through, and the geochemical pattern will be moved away from the mineral deposit in which it was created.

    in most explotation programs Geochemistry is used routinely. In temperate areas that have residual soil, it is the exploration technique which is frequently the most important. The use of geochemistry is often more complex in areas that have been glaciated, depending on the exact nature of the area’s glacial history, in the tropics, the deep weathering of soils can make geochemical patterns to be very obscure. 

    There Is Not One Best Method
    There is no one best geophysical or geochemical method. One or more methods may be very useful depending on the kind of deposit a prospector is looking for, some of them are apt to provide helpful additional information, and others may have no use whatsoever. In most cases, a well-designed explotation program uses several different methods, chosen to fit the geological environment which the prospector is exploring. Most of the time, the best methods can be found by trail-and-error surveys over known mineralization in the area, a technique which is known as orientation surveying.

    Lightweight toolswhich are for geophysical prospecting are making the prospector´s job less difficult and more precise. But there is still no substitute for geological insight, and no easy road to a discovery of minerals.