Archive for category Airborne

GEOMODEL – online time-domain EM data inversion

Posted by on Tuesday, 19 May, 2015
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Significant improvements have been made since the last presentation of the webapp on ExplorationGeophysics.Info pages. Now the shareware TDEM data inversion web application (ww.geomodel.info) has easy and comfy Eng-Rus interface, the input supports six different file formats (airborne and ground systems), sounding stations position can be represented on the scalable Google Map, data is showed in a sheet, TEM off-time decay chart and calculated apparent resistivity with time or depth.

AppResChart

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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The software can be used with data from WalkTEM, TerraTEM, ProTEM, Geotech airborne VTEM, TEM-FAST 48HPC, Tsikl and other TEM systems. A user can suggest any new data format and provide GEOMODEL developers with corresponded information.

The inversion process is interactive (forward modeling with thickness and/or resistivity changing) or iterative (automatic iterations to get correspondence between calculated and measured decay curve).

The inversion is based on 1D algorithm with support of CSIRO Division of Exploration and Mining and Australian Mineral Institute Research Association (AMIRA), P223F project.

Inversions

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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The next procedures can be done with TDEM Geomodel webapp:

-Import-export TEM data and inversions from a large number of industrial formats, including USF;

-Viewing and analysis of transient field decay curves;

-Editing individual decays or tens of decays together in a fast and easy way;

-Runing 1D inversion and compiling resistivity sections;

-Saving results in ASCII format for further processing and presentation in third-party software (Surfer, Autocad, Geosoft Oasis Montaj, etc.).

-Saving inversion results as resistivity sections and maps in different image file formats.

The next example shows  Geotech airborne VTEM  data inversion (Alberta, Canada):

 

The development team welcomes user’s comments and suggestions.


The next UAV magnetic system

Posted by on Wednesday, 29 April, 2015

Abitibi Geophysics together with GEM Systems announced about creation of  the partnership AeroVision™ for using UAV magnetic system which explores two potassium sensors. The system is going to be available since June, 1.  Sampling interval is promised 2 meters and resolution of .0001 nT, absolute accuracy  +- 0.05 nT. Laser-altimeter, GPS and auto-pilot are included.

The UAV mag surveys cost is going to be over 50% of the present ground geophysics pricing.


IP or not IP? (notes about IP in transient EM)

Posted by on Tuesday, 28 April, 2015

by Alexander Prikhodko

During the last few years the topic about IP effect (induced polarization) in the EM (electromagnetic) transient method (mostly in airborne time-domain) has been actively raised by many authors through geophysical magazines, conferences and meetings.

Here we will look into the topic without formulas and deep theory for a better understanding of the IP effect by general users of electro-prospecting  methods.

The nature of the IP phenomenon is universal regardless of an electric field source inducing (causing) the phenomenon or a measurement way of the appearance. First of all, the IP theory is out of Maxwell equations solutions because the process is accompanied by mass transfer and connected with EM field transformations. In contrast to IP theory Maxwell’s equations deal with electromagnetic induction which the time-domain (transient) method is built from.

In the case of IP the term “induced” means “caused” and does not relate to the concept of EM induction.

The concept of Induced Polarization (a substance ability to separate opposite charges) incorporates different phenomenons but related processes that occur:

1) in heterogeneous fluids or in pores filled with fluids;

2) due to electrochemical processes.

These two phenomenons – electrokinetic (1) and electrochemical (2), is a key to understanding how IP is used in applied geophysics.

Electrokinetic processes occur on contacts between ionic conductive fluids and a solid phase.

Electrochemical processes occur on contacts, or surfaces, between phases with electronic (metallic) and ionic (non-metallic) conduction. This is fundamental when IP method used when exploring for sulfide mineralization, especially if the sulfides are disseminated as the IP effect will be stronger than for massive sulfides of the same volume because its surface area is less.

Historically electrochemical nature of IP phenomenon first investigated and used in geophysics by Conrad Schlumberger (published in 1920). Later, during further electronic industry development and equipment sensitivity and bandwidth increasing, IP effect began to be observed all over the geologic environment due to the possibility of measurement of rapid and comparatively weak IP signal of the electrokinetic nature.

Generally, the IP effect of both natures potentially may affect data obtained with any electro-prospecting method including inductive time-domain method, regardless that the strongest IP effect occurs in the geologic environment at galvanic (grounded) way of the current inducing and the voltage measuring.

So, the IP component in transient or time-domain data is a parasitic effect which is not under Maxwell’s EM theory. (By the way, in the widely employed original DC-IP method, the inductive component is considered as a source of noise.) There are some technical requirements to sensitivity, bandwidth and geometry of a time-domain system to get better the parasitic signal superimposed on the inductive, native to the method, component.

Fortunately the IP parasitic signal is opposite to the inductive secondary field component allowing to recognize it and separate out it in some cases from the measured total secondary field. The favorable condition to get IP component from time-domain data and investigate it is rapid decaying inductive secondary field, i.e. resistive environment in general is favorable, but there are cases  when a strong IP component is prominent in presence of long inductive decay.

Unfortunately the existing theories of the electrokinetic and electrochemical natures of the IP phenomenon are on a qualitative basis. It means there is no chance to get petrophysical or/and petrochemical parameters of the geologic environment and to classify the IP sources according to their nature. On practice, empirical approximations are used for the IP process description with limited controlled parameters (in particular, Cole-Cole formula and the corresponded parameters) despite the nature of the phenomenon. To our delight it enables creative and thoughtful geological interpretation of the IP data if we get it correctly.


Foreign investments in mineral exploration in Kazakhstan

Posted by on Monday, 27 April, 2015

Galym Nurjanov (a head of JSC “National exploration company “Kazgeology”) has held a press conference at RSU “Central Communications Service for the President of the Republic of Kazakhstan” and reported about success in investments attraction in the mineral exploration sector of Kazakhstan economy.

Over the past two years the four major foreign investors came to Kazakhstan – the Australian-British concern “Rio Tinto”, a South Korean corporation “KORES”, the Australian company “Iluka Resources” and the German investment fund “ULMUS FUND”. These companies are willing to invest into the mineral exploration sector over $ 5.5 billion tenge.  Airborne geophysical surveys are going to be started soon in connection with Rio Tinto and Iluka Resources projects. The advanced airborne geophysical technologies including VTEM and ZTEM which are used right now in Kazakhstan, have been brought by Canadian company Geotech Ltd.


Factors of Modern Discoveries

Posted by on Wednesday, 8 April, 2015

“INTEGRATING NEW TECHNOLOGY WITH HISTORICAL DATA, GEOLOGICAL INTUITION AND A LITTLE LUCK, COMPANIES ARE FINDING SUCCESS WHERE OTHERS HAVE NOT”

E&MJ News

Mineral Exploration Strategies

E&MJ News published an article by Steve Fiscor where some factors of new mineral deposits discoveries have been outlined – these factors include applying modern geophysical technologies. The author provides some examples – airborne EM (VTEM, ZTEM), airborne gravity gradiometer, and airborne radiometric surveys which played key role in discoveries of mineral deposits.

“All of the discoveries were in the zone of other major discoveries, but most of them had been overlooked for one reason or another. The motivation could only be attributed to a geologically motivated hunch. New technology in the form of deep-penetrating airborne surveys allowed ground-based geophysical surveys to target undiscovered anomalies. Combining the new information with what they knew historically, exploration geologists were able to improve the drilling programs to quickly determine a resource.”

The next discoveries made with airborne geophysical technologies:

Albany Ultra-pure Graphite – VTEM survey

The Balboa Discovery at Cobre Panama – ZTEM survey

Kennady North Kimberlite Discoveries – airborne gravity gradiometer survey

PLS High Grade, High Techand Contrarian – airborne radiometric survey

Details..

 


Novel technologies for greenfield exploration – GEOLOGICAL SURVEY OF FINLAND 2015

Posted by on Wednesday, 1 April, 2015

The Geological Survey of Finland (GTK) reports about new mineral exploration and mapping methods which were developed in the project ‘Novel technologies for greenfield exploration’ (NovTecEx) carried out in 2012–2014. The project was a part of the Green Mining Programme funded by Tekes. The research partners of the project were the Geological Survey of Finland and the University of Oulu. The main study areas were in the SavukoskiPelkosenniemi area and in the Lätäseno area in Finnish Lapland.

The methods include a tool for Audiomagnetotelluric (AMT) measurements, GUI developing for 2D MODELLING AND INVERSION SOFTWARE FOR AIRBORNE TIME-DOMAIN EM DATA, and description  THE EQUIVALENT SOURCE METHOD for CALCULATION OF THE DERIVED BOUGUER ANOMALY.

The report pdf


Current Issue of “Exploration Geophysics” – Airborne Electromagnetics AEM 2013

Posted by on Monday, 30 March, 2015

Exploration Geophysics
Volume 46 Number 1 2015
6th International Conference in Airborne Electromagnetics (AEM 2013)

This special issue of Exploration Geophysics comprises papers from the 6th International Conference in Airborne Electromagnetics (AEM 2013) held in South Africa, and showcases the latest ideas and advancements in the discipline of airborne electromagnetic geophysics.

Developing an efficient modelling and data presentation strategy for ATDEM system comparison and survey design
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Magdel Combrinck
pp. 3-11

A proposal to simplify the display of ATDEM responses through the concept of a three-dimensional signal:noise nomo-volume is presented. It contains the signal:noise values of all system time channels and components for various target depths and conductances integrated into a single interactive three-dimensional image.

3D-spectral CDIs: a fast alternative to 3D inversion?
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James Macnae
pp. 12-18

Spectral 3D approximations of the EM response can efficiently model vortex induction and current gathering for simple geological target geometries. This paper presents results of a spectral model fitting algorithm to automatically pick, locate and define a sulphide target from VTEM data at the Forrestania test range, Western Australia.

The analysis of ZTEM data across the Humble magnetic anomaly, Alaska
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Daniel Sattel and Ken Witherly
pp. 19-26

ZTEM data acquired across a magnetic anomaly of almost 30 000 nT were analysed for the presence of a magnetic gradient response and the effects from elevated magnetic susceptibilities. Modelling results indicate distortions in the conductivity structure recovered by 3D inversion when elevated magnetic susceptibility values are ignored during the inversion.

Regional TEMPEST survey in north-east Namibia
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Geoffrey Peters , Gregory Street , Ivor Kahimise and David Hutchins
pp. 27-35

A regional scale low-cost TEMPEST208 survey in north-east Namibia has provided a geo-electric map of the area, including an indication of Kalahari cover thickness. While there are limitations in terms of detail and depth penetration, the results will assist explorers in selecting areas of shallow cover to reduce costs.

Helicopter EM (ZTEM–VTEM) survey results over the Nuqrah copper–lead–zinc–gold SEDEX massive sulphide deposit in the Western Arabian Shield, Kingdom of Saudi Arabia
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Jean M. Legault , Carlos Izarra , Alexander Prikhodko , Shengkai Zhao and Emad M. Saadawi
pp. 36-48

Magnetic and electromagnetic (EM) results from both time-domain (VTEM and AFMAG (ZTEM) helicopter EM surveys are compared over the Nuqrah sedimentary exhalative (SEDEX) massive sulphide deposit in Saudi Arabia. The magnetic and EM data map major controlling structures but only the EM surveys are able to define the Nuqrah deposits.

MULTIPULSE – high resolution and high power in one TDEM system
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Tianyou Chen , Greg Hodges and Philip Miles
pp. 49-57

The MULTIPULSE technology airborne TEM system transmits a high power pulse and low power pulse(s) (trapezoid or square) within a half-cycle. The high power pulse ensures good depth of exploration and the low power pulse allows higher near-surface resolution and better sensitivity to weak conductors as confirmed by field results.

Geobandwidth: comparing time domain electromagnetic waveforms with a wire loop model
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Greg Hodges and Tianyou Chen
pp. 58-63

The effect of time domain EM waveform, power and receiver sampling times are effectively compared for a wide range of time constants using a wire loop conductor model. Peak time constant and equivalent frequency can be determined analytically or numerically. Arbitrary waveforms can be modelled as a sum of simple short ramps.

Not extinct yet: innovations in frequency domain HEM triggered by sea ice studies
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Andreas A. Pfaffhuber and Stefan Hendricks
pp. 64-73

Operational use of frequency domain HEM for sea ice thickness mapping was the driving force for developing new purpose-designed systems. We present improvements in decreasing noise levels by one to two orders of magnitude, and implemented control signals to eliminate system drift. Ground tests and airborne field data confirmed the achievement of these goals.

Airborne electromagnetic modelling options and their consequences in target definition
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Alan Yusen Ley-Cooper , Andrea Viezzoli , Julien Guillemoteau , Giulio Vignoli , James Macnae , Leif Cox and Tim Munday
pp. 74-84

Given the range of geological conditions under which airborne EM surveys are conducted, there is an expectation that 2D and 3D methods used to extract models of geological significance would be favoured over 1D inversion and transforms. We analyse data from the Musgrave province, South Australia, used for mineral and for hydro-geological prospecting.

Modelling an arbitrarily oriented magnetic dipole over a homogeneous half-space for a rapid topographic correction of airborne EM data
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Julien Guillemoteau , Pascal Sailhac and Mickael Behaegel
pp. 85-96

In mountainous areas, the airborne electromagnetic system can be at an angle with regard to the ground. We analyse how the data and the eddy current are affected in such a context. We also suggest a simple correction for the data and for the sensitivity function that reduces topography effects.

New developments in AEM discrete conductor modelling and inversion
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Marc A. Vallée
pp. 97-111

In the last 20 years, sphere and plate models have been integrated in parametric inversion programs which are used today for interactive interpretation of airborne electromagnetic surveys on powerful workstations. Different problems encountered in the implementation and application of these models are discussed and a case history from Abitibi, Canada, is presented.

Rapid approximate inversion of airborne TEM
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Peter K. Fullagar , Glenn A. Pears , James E. Reid and Ralf Schaa
pp. 112-117

Two algorithms have been developed to perform rapid approximate 3D inversion of airborne TEM. VPem1D performs 1D inversion at each data location above a 3D model. Interpretation of cover thickness is a natural application. VPem3D performs 3D inversion of resistive limit data. Conversion to resistive limits delivers a massive increase in speed. Both programs can operate on geological models to foster integrated interpretation.

Modelling the superparamagnetic response of AEM data
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Daniel Sattel and Paul Mutton
pp. 118-129

VTEM data flown at different system elevations across a known sulphide body and surface cover with elevated superparamagnetic (SPM) properties were analysed. The results indicate that SPM responses can be distinguished from deep conductor responses if the vertical AEM gradient is measured, with EM sensors being offset vertically by 2–40 m.

Using the in-line component for fixed-wing EM 1D inversion
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Adam Smiarowski
pp. 130-135

In conductive areas, the in-line component of an offset transmitter–receiver EM system can be more sensitive to the near-surface than the vertical component. Using estimated noise levels, this paper calculates the expected uncertainty on the inverted parameters of a bathymetry model and compares this to inversion results from field data.

Extending the range of time constants recorded by the SPECTREM AEM system
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Peter B. Leggatt
pp. 136-139

The Spectrem AEM transmitter has no off-time; secondary signals are recorded at the same time as the transmitter primary. By assuming the secondaries have decayed away by the last window, the signal value is used as an estimate of the primary. The result is underestimation of the secondary amplitudes if the target is highly conductive. This paper describes a method to compute a better estimate of the primary amplitude.


EM surveys over Green Giant graphite property in Madagascar

Posted by on Tuesday, 24 February, 2015

by Alexander Prikhodko, 24 Feb., 2015

Graphite mineralization has a high electrical conductivity, which makes it an excellent target for electromagnetic (EM) methods.

Energizer Resources Inc. and it’s predecessors have conducted several airborne and ground electromagnetic  surveys over different areas of Green Giant graphite property in Madagascar (province of Toliara). Different EM technologies have been used in accordance with their progress.

Geological position and characteristics of the property:

Regional position – Ampanihy Shear Zone, NS foliation of rocks;

-Vertical to sub-vertical nature;

-The area is underlain by supracrustal and plutonic rocks deformed with N-NE trending structures;

-Graphitic zones consist of multi-folded graphitic strata;

-Graphitic schist and gneiss with vanadium mineralization.

 Geologic map (magnetic field interpretation)

Green_Giant_quick_Mag

 

AEM

 

 

 

 

 

 

 

 

 

 

 

 

 

 

AEM surveys covering with different technologies is in the picture above.

The basic AEM surveys results which demonstrate a potential of the territory and effectiveness of the applied methods are below.

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DIGHEM survey

Inverted (EMflow, Encom) DIGHEM data. Conductivity 3D voxel, sections and a map.

(conductors in red, resistors blue colors)

DIGHEMConVoxel

 

 

 

 

 

 

 

 

 

 

 

 

 

sections

 

condmap

 

 

 

 

 

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VTEM survey

Time-domain EM TAU parameter calculated with sliding window algorithm picks up the most conductive part of the geoelectrical section on each station-sounding.

TAU

 

 

 

 

 

 

 

 

 

 

 

 

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The resistivity-depth imaging (RDI) of EM time-domain data is a base of depth positioning of conductors potential for graphite mineralization and the first approximation of their geometry and dimensions.

rdisections

 

 

 

 

 

 

 

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3D apparent resistivity distribution with <1 Ohm-m clipping areas:

RDIvoxel

 


2014 issued patents by Assignee Geotech Airborne Limited

Posted by on Tuesday, 27 January, 2015
Patent number: 8878538
Abstract: An airborne geophysical surveying system comprising a receiver coil assembly for towing by an aircraft, the receiver assembly including a receiver coil for sensing changes in a magnetic field component of a magnetic field, and a receiver coil orientation sensing system for sensing orientation changes of the receiver coil. A controller receives signals representing the sensed changes in the magnetic field component from the receiver coil and the sensed orientation changes from the receiver coil orientation sensing system and corrects the sensed changes in the magnetic field component to provide a signal that is corrected for noise caused by changing orientation of the receiver coil in a static geomagnetic field.
Filed: November 26, 2010
Issued: November 4, 2014

Bucking coil and B-field measurement system and apparatus for time domain electromagnetic measurements

Patent number: 8786286
Abstract: According to one example embodiment is a time domain electromagnetic (TDEM) geophysical survey system for producing a B-field measurement, comprising: a transmitter coil; a bucking coil positioned in a substantially concentric and coplanar orientation relative to the transmitter coil; a receiver coil positioned in a substantially concentric and coplanar orientation relative to the bucking coil; an electrical current source connected to the transmitter coil and bucking coil for applying a periodic current thereto; and a data collection system configured to receive a magnetic field time-derivative signal dB/dt from the receiver coil and integrate the magnetic field time-derivative signal dB/dt to generate, a magnetic B-field measurement, the transmitter coil, bucking coil and receiver coil being positioned relative to each other such that, at the location of the receiver coil, a magnetic field generated by the bucking coil has a cancelling effect on a primary magnetic field generated by the transmitter coil.
Filed: August 28, 2009
Issued: July 22, 2014

Airborne time domain electromagnetic transmitter coil system and appratus

Patent number: 8766640
Abstract: A tow assembly for an airborne electromagnetic surveying system, including: a transmitter coil frame supporting a transmitter coil, the transmitter coil frame being formed from a plurality of serially connected frame sections forming a loop, the transmitter coil frame having rotating joints at a plurality of locations about a circumference thereof enabling the transmitter coil frame to at least partially bend at the rotating joints; and a suspension assembly for towing the transmitter coil frame behind an aircraft, the suspension assembly being attached to the circumference of the transmitter coil frame at spaced apart locations.
Filed: May 23, 2011
Issued: July 1, 2014

Airborne electromagnetic transmitter coil system

Patent number: 8674701
Abstract: A tow assembly for an airborne electromagnetic surveying system including a semi-rigid transmitter coil frame supporting a transmitter coil, the transmitter coil frame being formed from a plurality of serially connected frame sections forming a loop, the transmitter coil frame having articulating joints at a plurality of locations about a circumference thereof enabling the transmitter coil frame to at least partially bend at the articulating joints; and a suspension assembly for towing the transmitter coil frame behind an aircraft, the suspension assembly comprising a plurality of ropes and attached to the circumference of the transmitter coil frame at spaced apart locations.
Filed: February 25, 2009
Issued: March 18, 2014

In the news – Geotech technologies in Kazakhstan and Russia

Posted by on Tuesday, 2 December, 2014

In the National TV News (Kazakhstan)

 

In the local (Yakutia) Russian TV news:


Geology For Investors about an airborne EM technology for exploration

Posted by on Monday, 1 December, 2014

Hunting for Giants: An Introduction to ZTEM Surveys in Mineral Exploration
By: Kylie Williams in Exploration Methods

ZTEM

 

 

 

 

 

 

 

 

Overview

It may just look like an enormous, flying spider web towed behind a helicopter, but the ZTEM airborne geophysical survey system has the potential to identify giant porphyry copper deposits and features of other large ore deposits up to 2000 meters below the surface.
Z‐Tipper Axis Electromagnetic (ZTEM) is an airborne electromagnetic survey system which detects anomalies in the earth’s natural magnetic field. These disruptions are caused by zones of rock that conduct or resist electrical current more than the surrounding rock, like ore deposits. The proprietary technology belongs to Canadian company, Geotech, who have flown over 250,000 line-kilometres with ZTEM in under 4 years.

History

Geotech Ltd. is a Canadian airborne geophysical survey company that began operations in 1982. The company developed the now well-known VTEM (the versatile time-domain electromagnetic) system in 2002.
The helicopter version of the airborne Z‐Tipper Axis Electromagnetic (ZTEM) system was introduced into commercial service by Geotech in 2006-2007, and the less-expensive fixed-wing (FW ZTEM) system was introduced in 2010-11.

How ZTEM works

ZTEM specifications 300×225 Hunting for Giants: An Introduction to ZTEM Surveys in Mineral Exploration exploration methods ZTEM vtem uranium kimberlite exploration Geotech electromagnetism copper porphyry airborne geophysics
Flying spider web: the airborne loop of the ZTEM system (Geotech)
ZTEM is a type of electromagnetic (EM) survey to measure variations in the electrical properties of rocks.
EM surveys try to identify bodies of rock that conduct electricity well, like massive sulfide bodies of copper or nickel ore, or rocks that resist carrying current more than their surrounds, like the silicic alteration found in the core of porphyry deposits.
ZTEM surveys are different to other commercial EM systems because they measure variations in naturally-occurring EM fields rather than introducing an EM field into the ground and measuring the responding field, like VTEM.
Instead, ZTEM measures variations in the naturally-occurring or passive magnetic fields produced by thunderstorms around the world. This magnetic field is planar – constant in all directions – but areas of highly conductive or very resistive rock will cause measurable disruptions.
ZTEM surveys are designed to map resistivity contrasts to great depths, exceeding 1-2km, making ZTEM well-suited to finding porphyry-hosted and structurally-controlled exploration targets at depth.

What does a ZTEM survey look like?

The ZTEM system is transportable, able to be packed into small units which can be shipped around the world. There are two key pieces of equipment to the system, an airborne loop and ground receivers.
The airborne loops can be towed behind a helicopter or a fixed wing aircraft. The loop itself is a little over 7m across and looks a little like a giant, red-rimmed spider web. It is towed behind the aircraft at a height of around 100m above the ground to measure the vertical component of the magnetic field.
A 75-90m cable attaches the loop to the aircraft. The cable separates the loop from the vibrations of the aircraft and transmits the collected information back to the receivers in the plane or helicopter.
On the ground, base stations are set up in the survey area to measure variations in the horizontal magnetic fields.
GPS receivers are used on the coil in the air and also on the ground to keep track of the orientation of each of the parts, with respect to each other and the earth’s magnetic field.

A few Geotech case studies

Copper-porphyry, Alaska, USA
ZTEM was tested over a section of the world-class Pebble calc-alkalic copper-gold molybdenum porphyry deposit located in the Bristol Bay region of southwest Alaska in 2010. Some of the richest parts of the Pebble deposit are buried under up to 600 m of volcanic and sedimentary cover.
With careful processing, ZTEM was able to identify several of the distinctive alteration haloes found around the porphyry deposits, with more detail at depth than other systems.
ztem pebble Hunting for Giants: An Introduction to ZTEM Surveys in Mineral Exploration exploration methods ZTEM vtem uranium kimberlite exploration Geotech electromagnetism copper porphyry airborne geophysics
2D Resistivity cross-section over Pebble porphyry deposit in Alaska (Geotech)
Uranium deposits, Athabasca Basin, Canada
ZTEM tests were flown over unconformity-type uranium deposits in northern Saskatchewan, Canada, in 2008. The results correlated with known geological features to below 500m depth, penetrating through the thick cover materials to identify defining features in the basement rocks.
Kimberlites, Northwest Territories, Canada
A ZTEM survey flown over the Drybones Kimberlite near Yellowknife in NWT, Canada, was able to differentiate between diatreme (consolidated kimberlite) and the host rock buried under 100m of conductive cover sediments.

Further reading

The best place for information about ZTEM is the Geotech website, especially the ZTEM case study page

Several ZTEM case studies have also been published in peer-reviewed journals, for example:


Unlocking Australia’s hidden mineral potential with geophysics

Posted by on Friday, 1 August, 2014

Dr Richard Blewett:

“It is becoming increasingly difficult to discover near-surface mineral resources in Australia. New and innovative products and techniques are being developed as part of the UNCOVER Initiative to help attract mineral exploration investment that has the potential to lead to the discovery of new resources.”

One of the focus regions for the UNCOVER Initiative is the Thomson Orogen: “The Thomson Orogen is a large area that lies to the north and west of the Lachlan Orogen in New South Wales, South Australia, the Northern Territory and Queensland. Much of it is under the cover of younger sedimentary basins, with some up to several kilometres thick, and it is therefore a poorly understood element of Australia’s geology.

The southern Thomson Orogen is true ‘greenfields’ country. Although the mineral potential of the region is largely unknown, the northeastern Thomson Orogen (for example Thalanga, Charters Towers) and the similar-aged Lachlan Orogen to the south are well mineralised (for example Cadia, Northparkes, Lake Cowall Cobar). In order to attract exploration investment into the southern Thomson Orogen, and also to improve the geological understanding of the area, Geoscience Australia, the Geological Survey of Queensland and the Geological Survey of New South Wales have commenced a collaborative project to collect new (and synthesise existing) pre-competitive data.

One of the first steps in this collaboration is to acquire airborne and ground geophysical data including airborne electromagnetics (AEM), gravity and magnetotelluric (MT) data. Regional AEM data has now been collected to map cover thickness and assess the geology and prospectivity of the Southern Thomson Orogen across the New South Wales-Queensland border around Hungerford and Eulo. These data will be interpreted using existing borehole stratigraphic data and a new solid geology compilation of the region developed between Geoscience Australia, the Geological Survey of Queensland and the Geological Survey of New South Wales.

 

The Geotech VTEM FullWaveForm
airborne electromagnetic acquisition
system used in the Southern Thomson
Orogen airborne electromagnetics survey.
Image credit: Geotech Airborne Limited.

 

 

 Geoscience Australia is a leading promoter of AEM surveying for regional mapping of cover thickness, under-cover basement geology and sedimentary basin architecture. Geoscience Australia flew three regional AEM surveys during the 2006-11 Onshore Energy Security Program (OESP): Paterson (Western Australia, 2007-08); Pine Creek-Kombolgie (Northern Territory, 2009); and Frome (South Australia, 2010) [1]. The surveys were primarily designed to provide reliable, fit-for-purpose pre-competitive AEM data for mapping critical features of uranium mineral systems.

Results from these surveys have now produced a new understanding of the architecture of critical mineral system elements and mineral prospectivity for a wide range of commodities of these regions and includes details on the thickness and character of the regolith, sedimentary basins and buried basement terrains. The data have since been found suitable not just for uranium, but for mapping a range of other mineral systems including gold, silver, copper, lead, zinc and potash, as well as for under-cover geological mapping and groundwater resource estimation.

The survey data are now processed using the National Computational Infrastructure (NCI) facility at the Australian National University to produce GIS-ready interpretation products and GOCADTM objects suitable for 3D modelling.

A number of 3D models are being developed to interpret the near-surface under-cover geology of cratons and mobile zones, the unconformity surfaces between these and the overlying sedimentary basins, and the architecture of those basins. These models are constructed primarily from AEM data using stratigraphic borehole control and show how AEM data can be used to map the cross-over area between surface geological mapping, stratigraphic drilling and seismic reflection mapping. These models can be used by minerals explorers to more confidently explore in areas of shallow to moderate sedimentary basin cover by providing more accurate cover thickness and depth to target information. A 3D model of basement-cover relationships and depth of cover will be developed for the southern Thomson Orogen.”


Advanced airborne geophysics technologies for new industry development and innovations in Kazakhstan

Posted by on Tuesday, 8 July, 2014

2 July 2014 – Astana, Kazakhstan

The President of Kazakhstan and the Government took part in the  meeting-report of the Ministry of Industry and New Technologies in the new high tech building “Nazarbayev Cener” (project of famous British architect Norman Foster) in Astana.

Astana- Nazarbayev Center

 

 

 

 

 

 

 

 

 

 

 

 

 

(“Nazarbayev Center”,  Astana)

Geotech Ltd., a world leader of airborne geophysics had been presented to the government, Prime Minister and the President. “Kazgeology” as a part of the Ministry is going to work together with Geotech Ltd. for geophysical surveying of Kazakhstan territory and providing the airborne geophysical service for exploration and mining companies in Kazakhstan and other countries of Central Asia.

Geotech-PresidentKazakhstan

(Keith Fisk, Managing Director of Geotech with the President Nursultan Nazarbayev)

GT-Minister

 

 

 

 

 

 

 

 

 

 

 

 

 

(with the Minister of Industry)

GT-clients

 

 

 

 

 

 

 

 

 

 

 

 

 

(future surveys discussions with Rio Tinto and Iluka Resources)

GT-interview

(Keith Fisk, Managing Director of Geotech  interview to central TV channel)

 

 

 


Geophysical Survey helicopter in promotional filming at Elko Regional Airport

Posted by on Tuesday, 24 June, 2014

ELKOGeotech takes to the air to figure out what’s underground with its geophysical surveys.

On Monday, a AW-119 “Koala” helicopter and an 85-foot geophysical survey apparatus were at Elko Regional Airport to film promotional footage for Geotech. The film crew works for Cineplex, a company based in Canada.

Geotech specializes in airborne geophysical survey systems, according to Field Operations Manager Darren Tuck. The company’s clients are usually mineral exploration businesses that are interested in starting up a mine, and use the survey to find promising mineral deposits, including coal, silver, iron and copper.

Tuck said an apparatus carried by a helicopter will produce an electromagnetic pulse into the ground it flies over. Those pulses reflect off magnetic readers, and Geotech makes a map of the area after the process.

“It provides our client with a map of what the underlying layers of a structure looks like,” Tuck said.

Geotech is a global company based in Canada. Tuck said the company has worked for local mines, although he wouldn’t name any of the company’s clients in order to protect their confidentiality.

Tuck said the Elko airport was selected as the location to film Geotech’s equipment, known as Versatile Time Domain Electromagnetic surveying. Tuck said Geotech has more than 30 VTEMs. The apparatus comes in a variety of sizes.

For information, visit www.geotech.ca.


Supervised Neural Network Targeting and Classification Analysis for Mineral Exploration

Posted by on Tuesday, 29 April, 2014

Karl Kwan (Geotech LTD) presented at Canadian Exploration Geophysical Society meeting (8 April 2014) methodology and examples of using Neural Network Targeting and Classification at mineral exploration.

“Geophysical survey contractors routinely offer multi-parameter data to clients. For example, a helicopter-borne survey may acquire Time-domain electromagnetic (TDEM), magnetic gradiometer and even gamma-ray spectrometer data (i.e., VTEMplus, Geotech LTD). Exploration geophysicists can certainly take advantage some of the readily available multi-disciplinary (geology, geophysics and remote sensing) and multi-parameter (potential field, EM, gamma-ray spectrometry, and others) datasets for mineral exploration. However, the integration and interpretation of these datasets can be time-consuming and even challenging, especially for large-scale datasets covering large areas with diverse geological conditions. The Supervised Neural Network (NN) Targeting and Classification technique for mineral exploration described and demonstrated by Reford, Lipton and Ugalde, 2004, “Predictive Ore Deposit Targeting Using Neural Network Analysis” (http://www.pgw.on.ca/downloads.html), can be a useful and promising tool for the analysis of multi-disciplinary and multi-parameter data.

In this presentation, the properties or responses of the two feed-forward multilayer Neural Networks, Levenberg-Marquardt (NN with LM training) and Fast Classification (FCNN), as implemented in the current version by PGW, are studied in detail. The supervised NN simulations are performed on specially constructed synthetic data. Intended as a tutorial and the NNs treated as black boxes, the objectives of the exercise are twofold, to demonstrate the targeting as well as classification capabilities of the Neural Networks, and at the same time to show one of the known limitations and to suggest a way to get around it. The utility of the NN tool is demonstrated again with real cases from the Republic of Niger.”

Geosoft is delighted to host the online portion of the Canadian Exploration Geophysical Society meeting with keynote speaker Karl Kwan, Geotech LTD.

YouTube:  


World class geophysics for Republic of Kazakhstan

Posted by on Sunday, 6 April, 2014

April 3, 2014, Astana. Vice Minister of Industry and New Technologies of the Republic of Kazakhstan Nurlan Sauranbayev and Chairman of the Board of JSC “Kazgeologiya” Galim Nurzhanov met with the Ambassador of Canada Stephan Millar and leading world class Canadian geophysical companies Phoenix Geophysics and Geotech Ltd.

“I want to thank you for the meeting. I see great potential for fruitful cooperation in the field of exploration, “- said Stephen Millar. Vice Minister of Industry and New Technologies Nurlan Suranbaev suggested for further cooperation JSC “Kazgeologiya”, which held preliminary talks with the companies.

 

 

 

 

 

 


Recent investigations of geophysics abilities in aquifer mapping and resource evaluation

Posted by on Thursday, 13 March, 2014

Buried beneath the glaciated terrain, valleys filled with coarse-grained permeable sediments  potentially are great sources of fresh ground water. During the last several years Geological Survey of Canada has been investigating geophysical methods potential, particularly airborne electromagntics, for mapping and resource evaluation of buried valleys.   Spiritwood valley aquifer in southern Manitoba has been chosen for the investigations. Heliborne AeroTEM, VTEM, fixed-wing TEMPEST and MULTIPULSE, ground electrical resistivity and time-domain methods, seismic reflection and borehole data have been involved into the complex analysis. Recently collected ground TEM data for Spiritwood and the report (G.A. Oldenborger and K. Brewer, 2014) has been released: http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=293700.

One of the successful heliborne TEM examples (Legault, J.M., Prikhodko, A., Dodds, D.J., MacNae, J.C., Oldenborger, G.A., 2012. Results of recent VTEM helicopter system development testing over the Spiritwood Valley aquifer, Manitoba. Symposium on the Application of Geophysics to Environmental and Engineering Problems. Environmental and Engineering Geophysical Society, 114–130.):

VTEM-ground

 

 

 

 

 

 

 

 

 

 

 

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Another recent example of the results of a combined seismic and airborne electromagnetic (AEM) interpretation of the shallow Quaternary sedimentsand  bedrock but in British Columbia (Horn River Basin) was presented on Geoconvetion-2013  .