It has been noted by several gold prospectors that the soil survey response to the different types of golf mineralization is much expected than results from stream surveys and the interpretation is more delicate. Basically, an extensive dispersion pattern over disseminated mineralization and narrow, restrict dispersion over vein type mineralization. Whereas the anomaly over disseminate mineralization is usually high, that over vein mineralization is in some places very low, although the contrast is as good as or better that over the disseminated type.
The local threshold varies with rock type, in soils it may be 20 g/t of gold, over large parts of the surveyed area, a 10 g/t contour shows a rough coincidence with the contact mineralization. Based on the known mineralization a significant threshold value may be adopted to delimit areas of possible comparable mineralization where more detailed prospecting must be concentrated. On this basis, detailed soil sampling in specific areas will reveal several probable mineralized zones. Soil sampling outlines areas of possible economical mineralization. The general distribution pattern in soils may be similar, but the local variation may be minimal as function of rock type. Moreover, if the background level is much lower such as 0.5 g/t, and the threshold is significant such as 15 g/t, it is possible to define known gold mineralization greater than 5 g/t of gold.
It has been noted that the general distribution pattern of gold in the soils at one zone may be clearly recognizable as being typical of disseminated gold deposits even with the wide sample interval of 40 m. in this case, the gold exploration is not obliged to study in detail the point where it is possible to calculate a significant threshold defining mineralization. A local threshold may be estimated and by analogy with other results, a value may be adopted as significant threshold.
The profile over vein type mineralization may be significant different from that over disseminated deposits. The soil anomalies may be higher than local anomalies and relatively narrow. In this way, the anomalies may be less than even the local threshold values of disseminated gold occurrence. In some cases, massive sulphide mineralization occurs at depth in some veins and the content of gold decrease towards the surface and the vein horsetail upwards. These features contribute to the low anomaly and the multiple peaks associated with veins. For example, a vein is 20 cm wide, and the tenor of mineralization is uncertain at the location of the traverse, gold is present from trace amounts up to erratically distributed values of 60 g/t giving average of 2 g/t over 10 m strike length. In this case the soil sampling technique is of use in tracing the sub-outcrop of the veins.