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Project Topic
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The proposed collaborative research project ‘HITEM’ addresses the first topic area of the third ERA-MIN joint call (2015) towards the non-energy raw material value chain: the development of a new tool for the electromagnetic (EM) exploration of primary resources. Amongst the variety of EM methods in geophysics, the time-domain method TEM is used to generate a 3D illustration of the sub-surface electrical conductance especially for geological structures which provide a continuous conducting layer. The task in this project is to develop a new extremely high sensitive receiver based on high transition temperature superconducting quantum interference devices (HTS SQUID). New sensor fabrication and packaging technologies, innovative readout electronics and control systems have to be developed by the partners for the demonstrator in order to assess the performance in different field tests. Within the tests in Finland, South Africa and Germany a database for the development of a suitable remote reference method for TEM will be gathered. All these tasks will provide ultimate sensitivity for low frequency signals and thus enable detection of conducting resources well below 500 m. Based on the data recorded in the tests at sites with known deep deposits, which especially contain an economic grade of platinum-group-elements material often found in sulfidic deposits, new or adapted inversion and interpretation algorithms for SQUID based receiver data have to be developed and their results compared with prior knowledge of the according structures. Thus, the utmost important goal of this industrial driven proposal with partners from Finland, South Africa and Germany is to contribute to the exploration of natural resources of critical raw materials with the focus to provide European companies in the field of exploration with internationally competitive geophysical instruments and methods.
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Project Results
(after finalisation)
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The
potential for exploring resource deposits deeper than 500 m
from the surface is limited by geophysical techniques One method
successfully applied to date is so called transient, time domain or
pulse electro magnetics ( For volcanogenic massive sulphide
deposits (VMS as a subspecies of volcanic exhalative deposits),
conventional measurement techniques have already been able to
achieve exploration depths of up to a few hundred metres In
addition to non ferrous metals, these VMS deposits usually also
contain significant amounts of platinum and platinum group
elements, including platinum, palladium, ruthenium, iridium,
rhodium and osmium All of them contain valuable high tech
metals, which are necessary for future technologies
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Project HITEM
Highly sensitive receiver for measuring transient electromagnetic responses in Exploration for
deep buried mineral occurrences
Electromagnetic
exploration methods, such as TEM, are excellently suited for this type of deposit, as the metals
have an increased electrical conductivity Due to the previous limitation of the exploration depth, however, very
little is known about the depth extension of the deposits This applies in particular to Germany, where after
centuries of intensive mining, superficial resources are considered to be exhausted as far as possible In
thisproject the researchers have advanced this technology in order to enable extended penetration depths and
to explore VMS deposits for the acquisition of high tech metals In the HiTEM project, a higher penetration
depth of the method was not achieved byincreasing the transmitter pulse moment, but by increasing the
sensitivity of the sensors and the entire TEM receiver, particularly in the low frequency range This enabled to
make use of later times in the TEM signal decay after the transmitter pulse hasbeen switched off This task was
solved by means of new Superconducting Quantum Interference Detectors ( based on high temperature
superconducting ( materials The development of robust, low noise HTS SQUID sensors was part of the work
of Leibniz IPHT and was successfully realised The new sensors are faster to be fabricated, can be assembled and
encapsulated in fewer processing steps as well as they are more robust in operation which makes them more
cost effective For this purpose, new fabrication tools and technologies were implemented in the fabrication line
The performance of the sensors wascharacterized by the advanced and adapted receiver electronics For the first
time, control electronics based onhigh frequency AC Bias were developed and implemented for all three sensors
In the interaction of sensors and electronics, the system noise could be reduced, especially in the low frequency
frequency range, thus achieving a high signal quality and a greater depth of investigation The control
electronicsand all indicators arenow fully digitaland transferred to a browser based solution, so that now no
complex installation of additional software for setting the systems and system parameters is necessary The field
tests in Finland and possibly other countries on representative targets of this deposit type are to be completed in
this year Initial results on the improved system parameters have already been determined and validated Within
the scope of further field measurements, these results will be verified in the field ( and the developed
innovativemethods for the reduction of electromagnetic noise in the corresponding frequency range for TEM will
be analysed, validated and optimized In addition, new inversion and interpretation methods could be further
developed and implemented Due to different aspects the project had been prolonged by 6 monthsand ended in
October 2019 The project results prove that the expectations of the partners involved were fulfilled Against this
background, SUPRACONbelieves that a new, robust technology has been developed that will enable exploration
service providers and mining companies to make more accurate statements about potential deposits This might
be accompanied by a potential reduction in the number of drill holes required, as the expected deposits can be
determined more accurately
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