The occurrence of gold deposits is variable and some vein-type deposits may be associated spatially and probably genetically with large masses of rock. The description within or near the masses gives information about the economic mineralization and its concentration in zones of structural complexity developed along one or more of the major faults, especially those with a especial trend. The gold content of the veins tends to increase in some orientation or direction. The geochemical program must be oriented to evaluate stream and soil responses over a vein system.
An area could probably have only been found through a stream sampling interval adjusted to the relatively short drainage train associated with the gold vein mineralization. The geochemical study demonstrates that careful sampling of the system within the mineralized area indicates the general location of mineralization through anomalies. Follow up soil sampling will detect the presence of veins. In these systems is possible detect copper minerals, but there is not necessarily a relationship or dependence between gold and copper.
It is important to make a geochemical study in tracing the gold bearing vein structures. Severe contamination may preclude any assessment being made of the possibilities of finding the area by reconnaissance sampling. In some cases, vein-type deposits may have been deliberately sought or suspected and the sampling program was dictated considering a dispersion train from such mineralization is not likely to be more than several kilometers in length. Reconnaissance soil sampling at 20 m intervals along major ridges and spurs tend to reveal all the known major vein structures. Detailed geological control and follow up work must be done to assess the meaning of the many anomalies found that are not related to known mineralized structures.
Some gold zones may be assessed as a base metal prospect. Surface indications consist of alteration zones and minor gold mineralization along faults. Geochemical sampling and geological mapping may be performed to evaluate the gold prospect. Detailed sampling and geological study helps to indicate the economical significance of the deposit. In some gold deposits, the rocks belong to a sedimentary-volcanic sequence and the gold bearing minerals may be preferentially emplaced in the coarser members of the sedimentary rocks. Other gold mineralization occurs in vein form along major trending faults. In this case, the work is oriented to obtain data on the geochemical response of gold in the several mineralized structures and also to investigate the dispersion of gold as a possible indicator of gold ore bearing zones.
Mineralization is indicated by gold assays in points located at a distance of about two km in veins oriented to opposite directions. When the complexity of geology is significant, the presence of mineralization and its general type may be determined geochemical studies.