The exploration of faulted gold deposits is an interesting activity that geologists and gold prospectors have to practice in field. Where a gold deposit has been cut off by a fault the discovery of its continuation beyond the fault is a problem of the greatest importance. Numerous rules have been formulated to aid in a search for the continuation of a faulted body, but it is safe to say that the great variety and complexity of the results of faulting render such rules valueless in most cases. Where faulting dislocates a non-tabular ore-body that is contained in a homogeneous rock, the problem is insoluble, unless the fault carries a drag or trail of ore mixed with the fault filling. The direction of the striations on the walls of a fault, in simple cases, indicates the direction of movement, the deeper ends of the gold veins being pointed in the opposite direction to the movement of the opposite walls.
Occasionally a gold deposit may be deformed where faulted, the deformation pointing in the direction of displacement and passing into a drag or trail through the fault filling. Where a tabular orebody or gold vein is faulted, the problem is likely to be simpler, as the recovery of any portion of the vein beyond the fault will lead to the discovery of the continuation of the ore shoot. Where the enclosing rock is composed of a series of strata a knowledge of the succession of the strata is of the greatest assistance in the calculation. The cases are rare where complete data for the calculation of the total displacement are available, as, for instance, where a fault cuts a dike that itself cuts a series of known strata, or an older fault, or any combination of intersections that permits the recognition of a point rather than of a plane on both sides of the fault.
In an attempt to locate the continuation of a faulted gold deposit the striations or slickensides should be studied, and also the fault filling for possible fragments of ore, or of country rock other than that of the immediate walls of the fault; a survey, map, and sections should be made showing the dip and strike of both the fault and of the ore body, if of tabular form, and of every known stratum of the containing rock, igneous contact or dike, older fault or vein, or any distinguishing mark that may be recognized on both sides of the fault. The application of descriptive geometry, or trigonometry, to this data will result in all the information regarding the displacement that the situation renders possible; complicated formulae, like rules of thumb, are of no assistance in the solution of such problems. It is seldom that the direction and amount of total displacement may be measured directly, more frequently it is susceptible of calculation from related functions, and frequently it is not determinable until further exploration discloses the necessary data.
A comparison with known faults in the same district is frequently of great help in the consideration of an unknown displacement, and an apparently complicated fault system once worked out may become a relatively simple problem when again met with underground.