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National Plan of Geology

The country generates and publishes detailed geoscientific information, at different scales, to complement mining exploration. An example of this is the National Plan of Geology (PNG), which involves characterizing the Earth’s crust by defining its structure, composition and age, chemical element concentrations at the surface, and hydrogeological, geothermal, and mineral resources in the subsurface.  This information is of considerable importance and is a thorough requisite for mining explorers, enhancing mining exploration of new ore deposits and increasing competitiveness.

The geoscientific programs are:

Basic Geology Program

Consists of producing maps at a scale of 1:100,000 on the geological origin and evolution of the territory.  In these maps, amongst other data, are represented the rock age, genesis, structure, and so called stratigraphic relations, which indicate the order of disposition of the distinct rock units, hydrothermal alteration zones relating to metallic and non-metallic mineralization, and dynamics and chronology of the active and inactive geological faults (Figure 3). The initial stage of the program includes the area between Arica and La Serena and has achieved a progress of 77% with a surface coverage of 171.412 km2 from a total of 219.643 km2.

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Figure 3: Geological map 1:100,000 scale, of the Sierra Vaquillas Altas Sheet, located in the Domeyko Cordillera of the Antofagasta Region. This area forms part of the Eocene Metallogenic Belt, in which is located the super-sized Porphyry Cu-Mo ore deposits of Escondida and Chuquicamata, amongst others.

Geophysics Program

Produces maps at a scale of 1:100,000 on the magnetism and gamma radiation from airborne surveys.  These maps highlight anomalies of certain physical properties of the Earth, which can be interpreted as a radiograph of the surface and subsurface. The methodology consists of overflying the area with an airplane equipped with sensors that record the terrestrial magnetism and gamma radiation, the latter of which is generated by potassium, thorium, and uranium present in rocks and soils at the surface (Figure 4).  The coverage of these maps has reached 69% in the area north of La Serena and corresponds to a surface coverage of 109.342 km2 from a total of 158.698 km2.

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Figure 4: Airborne magnetic survey geophysical map of the Carrizalillo-El Tofo Area, Atacama and Coquimbo Regions. Note the contrast of intensity of the magnetic field between the coast and the interior where some of the IOGC type ore deposits are emplaced in the granitoids of the Early Cretaceous.

Geochemistry Program

Generates maps on a scale of 1:250,000 that identify the presence and concentration of 59 chemical elements contained in fluvial drainage sediment samples taken at the surface.  The anomalous presence (or absence) of specific elements and/or patterns of “tracer” elements in a given area is an essential tool in mining exploration.  Moreover, with these data, environmental baselines are established that indicate the concentrations of toxic elements such as the heavy metals of lead, mercury, cadmium, and other elements toxic to humans. (Figures 5 and 5a). The coverage of these maps has reached 33% in the area north of La Serena and corresponds to a surface coverage of 57.411 km2 from a total of 172.368 km2.

Proyecto Mapa Interactivo Hoja Pisagua_As

Figure 5: Geochemical map, 1:250,000 scale, generated in the Geochemistry Program. This particular map is the Pisagua Sheet, Arica-Parinacota and Tarapacá Regions. It shows the concentration of arsenic, interpolated by statistics from chemical analyses of approximately 600 fluvial sediment samples taken at the surface. With the database produced in the program, 58 similar interpolated concentration maps can be generated for different chemical elements for the same region.

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Figure 5a: The interpolated concentration map of copper from the compilation of three 1:250,000 scale geochemical sheets(Arica Sheet, Pisagua Sheet, and Iquique Sheet).

Through the Sernageomin website, users can access the catalog of products available, and they can select the maps for areas of interest at different scales (Figures 3, 4, 5).  Also, they can obtain detailed information of each map (text and GIS database) according to the region or zone of interest (Figures 4, 5, 6).

 

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Figure 6: Map of Chile indicating the available cartography of basic geology at different scales published by the Sernageomin together with projects in preparation for the northern zone of Chile.

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