How to do Exploration Prospecting

It is common to perform the exploration in totally virgin territory. There generally is a minimal geological map outline where it highlights the trace of interesting minerals. This first phase, normally developed by national geological services, can be called “EXPLORATION phase”, and is normally done at a 1:500.000 or 1:200.000 scale.

The prospecting n a region is then decided based on the results obtained after the exploration.

Two cases scenarios can be found:

• Case 1: during the exploration phase no traces have been found, but by analogy with neighboring regions, geological & structural conditions are favorable of interesting mineralization presence. In this first scenario the general prospecting objective is to find traces with the importance being considered according to the discovery. The scale generally use is from 1:100.000 to 1:50.000.
• Case 2: mineral traces have been found during the exploration phase. The general prospecting program has been based in reference to the evidence in relation to geological and tectonic formations of the region. The object of this prospecting is to verify the value of the evidence and based on obtained data, find others. In this case the scale used would be from 1:25.000 to 1:10.000.

First case: in search of traces

The object of this search is to select the areas that will be studied more intensely in the next phase, or to make the decision of abandoning the search of each prospected area. It is developed in the following way:

C) Topographic removal of itineraries

In the best of cases the itinerary can be reported directly on the topographic map, on an aerial photograph or on a hydrographic reticule map designed from aerial photos.  

In tropical jungle, a hydrographic reticule map is indispensable since the prospecting must be done along riverbanks where it is more likely to find outcrop.

When these documents aren’t available and aerial photos aren’t useful due to dense vegetation, the topographic removal of itineraries will be done with a compass, measuring tape & altimeter (or with vertical azimuth reading of the compass or inclinometer). In this case it would be good to label the terrain of the itinerary with stakes, paint, cards or strips of plastic ties to trees every 100m, specifying the number on the itinerary & the traveled distance (the important part is to find the itinerary after sometime).

These itineraries can be placed directly on the map, or in bad environment or climatic conditions in the field book.

In the case of dense forest exploration the equipment should include:

1 team leader (using a compass)

1 “TOPOFIL” man or 2 using measuring tape

2 men using machetes to clear a path

Then the geologist passes for geological removal.

D) Use of gamma detector & ultraviolet light
(see also the Geophysical Prospecting chapter)

When searching for uranium it is recommended to take a gamma detector or a Geiger counter with sound signal. The gamma detector can also be used in the search of phosphate (detecting U phosphate) and sand with zirconia (including Th & U).

In the possible case of searching for florescent minerals, like scheelite (CaWO4) in skarn, or uranium minerals, you can use an ultraviolet lamp on samples or, at night, on outcrop, soil & alluvial. See in chart 1 the main florescent minerals to ultraviolet rays.