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Gyro Electromagnetic

An aeromagnetic survey is a common type of geophysical survey carried out using a magnetometer aboard or towed behind an aircraft. The principle is similar to a magnetic survey carried out with a hand-held magnetometer, but allows much larger areas of the Earth's surface to be covered quickly for regional reconnaissance. The aircraft typically flies in a grid-like pattern with height and line spacing determining the resolution of the data (and cost of the survey per unit area).

As the aircraft flies, the magnetometer records tiny variations in the intensity of the ambient magnetic field due to the temporal effects of the constantly varying solar wind and spatial variations in the Earth's magnetic field, the latter being due both to the regional magnetic field, and the local effect of magnetic minerals in the Earth's crust. By subtracting the solar and regional effects, the resulting aeromagnetic map shows the spatial distribution and relative abundance of magnetic minerals (most commonly the iron oxide mineral magnetite) in the upper levels of the crust.

Because different rock types differ in their content of magnetic minerals, the magnetic map allows a visualization of the geological structure of the upper crust in the subsurface, particularly the spatial geometry of bodies of rock and the presence of faults and folds.

Geology and Geophysics

Partnering with the top minds in the industry, Geo Science has over a 100 years of experience in Geology and Geophysics. Our experienced team has worked across Africa and gained a world of knowledge regarding the geology of the different parts of Africa.


With extensive work across Africa we have gained access to persons of interest to assist us with fast and accurate data acquisition, minimizing costs and time wasted on acquiring the right information.


This is particularly useful where bedrock is obscured by surface sand, soil or water. Aeromagnetic data was once presented as contour plots, but now is more commonly expressed as colored and shaded computer generated pseudo-topography images. The apparent hills, ridges and valleys are referred to as aeromagnetic anomalies.

A geophysicist can use mathematical modeling to infer the shape, depth and properties of the rock bodies responsible for the anomalies.

Aeromagnetic surveys are widely used to aid in the production of geological maps and are also commonly used during mineral exploration. Some mineral deposits are associated with an increase in the abundance of magnetic minerals, and occasionally the sought after commodity may itself be magnetic (e.g. iron ore deposits), but often the elucidation of the subsurface structure of the upper crust is the most valuable contribution of the aeromagnetic data.

Aeromagnetic surveys are now used to perform reconnaissance mapping of unexploded ordnance (UXO). The aircraft is typically a helicopter, as the sensors must be close to the ground (relative to mineral exploration) to be effective. Electromagnetic methods are also used for this purpose.

Portable Electromagnetic

The portable electromagnetic device is small and operated by a single operator. This instrument is used when higher resolution data sampling is needed of target areas identified by the Gyro or Remote Sensing techniques. This instrument is used only in small areas as it is done on foot.

Resistivity

Electrical resistivity tomography (ERT) or electrical resistivity imaging (ERI) is a geophysical technique for imaging sub-surface structures from electrical resistivity measurements made at the surface, or by electrodes in one or more boreholes. If the electrodes are suspended in the boreholes, deeper sections can be investigated. It is closely related to the medical imaging technique electrical impedance tomography (EIT), and mathematically is the same inverse problem. In contrast to medical EIT however ERT is essentially a direct current method.

A related geophysical method, induced polarization, measures the transient response. The technique evolved from techniques of electrical prospecting that predate digital computers, where layers or anomalies were sought rather than images. Early work on the mathematical problem in the 1930s assumed a layered medium (see for example Langer, Slichter). Tikhonov who is best known for his work on regularization of inverse problems also worked on this problem. He explains in detail how to solve the ERT problem in a simple case of 2-layered medium. During the 1940s he collaborated with geophysicists and without the aid of computers they discovered large deposits of copper.



As a result they were awarded a State Prize of Soviet Union. When adequate computers became widely available the inverse problem of ERT could be solved numerically, and the work of Loke and Barker at Birmingham University was among the first such solution, and their approach is still widely used.

With the advancement in the field of Electrical Resistivity Tomography (ERT) from 1D to 2D and now-a-days 3D, ERT has explored many fields. The applications of ERT include fault investigation, ground water table investigation, soil moisture content determination and many others. In industrial process imaging ERT can be used in a similar fashion to medical EIT, to image the distribution of conductivity in mixing vessels and pipes. In this context it is usually called Electrical Resistance Tomography, emphasizing the quantity that is measured rather than imaged.

Geo Science currently use either a Syscal or an ABEM unit. The units allow for +- 120m depth penetration.

Below a 2D image of a construction site, identifying rock formations.

(Dark red as hard rock)

Resistivity

Making use of the 2D data and advanced 3D software we were able to map and model the rock body.

Resistivity-3D

Seismic

Seismic refraction is a geophysical principle (see refraction) governed by Snell's Law. Used in the fields of engineering geology, geotechnical engineering and exploration geophysics, seismic refraction traverses (seismic lines) are performed using a seismograph(s) and/or geophone(s), in an array and an energy source. The seismic refraction method utilizes the refraction of seismic waves on geologic layers and rock/soil units in order to characterize the subsurface geologic conditions and geologic structure.


The methods depend on the fact that seismic waves have differing velocities in different types of soil (or rock): in addition, the waves are refracted when they cross the boundary between different types (or conditions) of soil or rock. The methods enable the general soil types and the approximate depth to strata boundaries, or to bedrock, to be determined.

Gravity

Gravimetry is the measurement of the strength of a gravitational field. Gravimetry may be used when either the magnitude of gravitational field or the properties of matter responsible for its creation are of interest. The term gravimetry or gravimetric is also used in chemistry to define a class of analytical procedures, called gravimetric analysis relying upon weighing a sample of material.


The instrument is portable and operated by a single operator. The technique is used to get more information on target zones identified by Gyro or Remote Sensing.


Low Frequency Electromagnetic

The main idea of magnetotelluric method (MT) is using the natural source of EM energy to study the frequency characteristics of the Earth’s crust to obtain the information about conductivity of geological objects.

MT sounding provides the largest depth of investigations (up to 100 km) among all geophysical methods.


Basic applications

• Deep and regional studies

• Oil and gas exploration

• Solid minerals exploration

• Geothermal exploration

• Engineering and groundwater studies

• Permafrost studies

Due to cost of the equipment, skilled operators are very limited. Geo Science has 1 of only 2 operators in South Africa in-house. With +- 450 sounding (Individual Station Readings ) under the belt and experience in hydrocarbon exploration we are well placed for oil and gas projects.

Remote Sensing

There are two main types of remote sensing: passive remote sensing and active remote sensing.[3] Passive sensors detect natural radiation that is emitted or reflected by the object or surrounding areas. Reflected sunlight is the most common source of radiation measured by passive sensors. Examples of passive remote sensors include film photography, infrared, charge-coupled devices, and radiometers. Active collection, on the other hand, emits energy in order to scan objects and areas whereupon a sensor then detects and measures the radiation that is reflected or back scattered from the target. RADAR and LiDAR are examples of active remote sensing where the time delay between emission and return is measured, establishing the location, speed and direction of an object.



Remote sensing makes it possible to collect data on dangerous or inaccessible areas.

Remote sensing also replaces costly and slow data collection on the ground, ensuring in the process that areas or objects are not disturbed.

Utilizing Remote Sensing allows Geo Science to identify target areas in a license area. This limits the cost of on the ground investigations.

Combining the Remote Sensing with the Gyro results allows for a more accurate target identification.

Remote Sensing

Remote Sensing results super imposed onto Google Earth. Bright green indicating target zones for the occurrence of kimberlite.

Project Management

To accurately control and mange, time, resources and costs each license area is registered as a project onto our system. This allows us to allocate and track resources and costs more effectively.

Your system allows for a Web based interface that allows clients to also track the project progress



The project manager will be in contact with the client on a weekly keeping the client in the loop at all time.

With large scale projects monthly progress meetings will also be help with all roll players, the meetings are there to discuss any problems or expected problems on the road forward and progress reports.

Data Acquisition

Data acquisition entails collecting as much data regarding the given area of interest. A trip to the given country, allowing for access to local libraries and geology departments.



Contacting people of interest in the area and collecting on the ground intelligence have turned out to be of great use in past projects.

Remote Sensing

Making use of Satellite images, spectral libraries and image cleaning techniques developed over the last 5 years. Making use of known resource locations in the giving country, we attempt to identity target areas within the license area.


Satellite image processing is a time consuming process and can take up to 7 days to process 1 license area.

At Geo Science we have a structured phase approach to exploration. We also insist that each phase is completed, if not we cannot guarantee success.

Phase 1

Phase 2

Phase 3

Phase 4

Phase 5

Exploration Process

Geo Science Exploration

Geology Work

Making use for all the information acquired the geologist will draw up a model of the license area and the surrounding area.

Interpretation Report Phase 1

Taking into account all the information : Data Acquisition , Remote Sensing, Geology, a report will be compiled identifying possible target zones for the Geophysical ground work.

Geophysical Ground Work

The techniques for the ground work will be determined by the Phase 1 interpretation report.

Only target zones of high interest will be investigated.

Sampling

Due to our phase approach and Geophysical work on target zones of interest we are able to reduce the excessive cost of sampling. With high resolution data results from the Geophysical ground work we can identify the most promising targets to sample from.

Finale Interpretation Report ( Phase 4 )

Reports

Geo Science Exploration

Optional Reports ( Phase 5 )

Please note Phase 4 report is a prerequisite for this option.

  1. SAMREC ( South African Mineral Codes )
  2. www.samcode.co.za
  3. National Instrument 43-101 ( Standards of Disclosure for Mineral Projects )
  4. http://en.wikipedia.org/wiki/National_Instrument_43-101
  5. JORC
  6. Reporting of Exploration Results, Mineral Resources and Ore Reserves )
  7. http://www.jorc.org/

With our well placed partners we are able to issue a competent persons report that adheres to any of the above mentioned standards, depending on the clients requirements. The report will be singed of by one of our accredited partners.


Geo Science Exploration

Sir Roderick Impey Muchison

“Physical geography and geology are inseparable scientific twins.”

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