Geophysical Exploration in the Erzgebirge
- Helmholtz Institute Freiberg for Resource Technology (Coordinator)
- TU Bergakademie Freiberg
- German Federal Institute for Geosciences and Natural Resources
- Saxon State Agency for Environment, Agriculture and Geology (expert support)
Research area: Geyer-Ehrenfriedersdorf im mid Erzgebirge region, Saxony
What Are the Project Objectives?
Our goal is to test, evaluate and develop modern techniques for the delineation of mineral resources to depths reaching 500 meters. Using these methods, it is possible to detect natural resources with minimal environmental disturbance. Another aim of the project is to develop mathematical methods to create a realistic 3-D model of the geological subsoil from the geophysical data collected.
Why Did We Select the Geyer-Ehrenfriedersdorf Area?
The research area is located in the Erzgebirge in the district of Erzgebirgskreis. It covers an area of about 110 km² between the towns of Grünhain-Beierfeld and Elterlein to the south, Zwönitz to the West, Gelenau to the north and Ehrenfriedersdorf and Geyer to the east.
This region has a heritage of mining and exploration, which is why it is very well documented. Our scientists are able to use this data and compare it to new research findings. In addition, the area studied is largely unaffected by factors such as surface shape, human settlement, infrastructure, abandoned mines, or coverage by more recent rock layers.
Which Natural Resources Do We Study?
In the Geyer-Ehrenfriedersdorf area, we are aware of significant concentrations of the following elements: tin, zinc, tungsten, molybdenum, copper, iron, lead, silver and indium. In practice, these metals are used in many industries and applications: such as tin in microelectronics; zinc in the metal industry; high-tech metals such as indium in monitors and microelectronics.
The Measurements in the Research Area Have Been Completed. Which Methods Did We Use?
- Aero-Electromagnetic Measurements
Between 2014 and early 2016, the German Federal Institute for Geosciences and Natural Resources (BGR) conducted geophysical studies using a helicopter. In contrast to exploration drilling, these surveying flights cover the entire area and are non-invasive. The helicopter flew over the surveyed area at a height of approximately 100 meters at a speed of 100-120 km/h. During the first flights over the Geyer Forest in October 2013 and April 2014, BGR used a 10 meter aerial probe. During the last flight in early 2016, the flight sensor was only half as long. Both probes were suspended beneath the helicopter on a 45 and 30 meters cables, respectively. These probes induced electric fields in the subsoil of the earth, providing information about electrical conductivity, which can be used to assist the mapping of mineralization in the rock.
- Reflexion-Seismic Measurements
This kind of measurement was conducted at the surface of the earth in 2015 independently of the aero-electromagnetic measurements. Scientists drop weights onto the ground, causing almost imperceptible underground oscillations, the faint reflections (echoes) of which are recorder to measure acoustic impedance, another important indicator of subsoil structures.
- Transient-Electromagnetic Measurements
The method called Transient ElectroMagnetics (TEM), which was also employed in 2015, detects subsoil electrical conductivity down to depths of several hundred meters. A series of different induction processes allow researchers to measure a transient voltage that reflects the distribution of electric resistance in the subsoil. These measurements are also conducted at the earth’s surface.
How Are We Using the Measured Data Right Now?
Several students are working on their Ph.D. and Master’s theses, developing mathematical methods to use the data measured to create a 3-D model that will reveal the remaining resource potential present in the subsoil in the Geyer-Ehrenfriedersdorf area. The project partners have committed to publishing their results by 2017.
Status: April 16, 2016