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Global GeophysicalGlobal GeophysicalGlobal GeophysicalGlobal Geophysical

Geophysical Service Solutions

GLOBAL GEOPHYSICAL is a geophysical consultancy firm specializing in providing geophysical solutions to appropriate

mining, environmental and engineering problems. Site-appropriate geophysical techniques best suited to a specific

geological/geotechnical environment are combined to provide the following cost-effective service solutions:

ENVIRONMENTAL

Mapping of pollution plumes

Preferential groundwater flow path & aquifers

Landfill and waste dump investigations

Structural geology, faults, fractures and dykes

Locating buried objects

ENGINEERING

Mapping of bedrock topography and rippability

Structural geology, faults, fractures and dykes

Mapping of subsurface cavities and old mineworkings

Mapping of subsurface services, pipes and leaks

Road and pavement investigations

Shear wave velocity measurements

Concrete integrity& rebar

Gravimetric dolomite investigations

Road, water & sewer pipelines, contour and borehole surveying

Resistivity for cathodic protection

MINING & EXPLORATION

Underground Mining: Roof integrity investigations

Surface Mining: Mapping of subsurface cavities and old mineworkings

Structural geology and mineralization

Massive and disseminated sulphides

Alluvial and kimberlite exploration

Geophysical Techniques

Seismic Refraction, Spectral Analysis of Surface Waves (MASW), Ground Conductivity (EM-31 and EM-34), Ground Penetrating Radar, Magnetometry , Gravity and Microgravity, Resistivity, Resistivity Tomography, Induced Polarization,

Frequency Domain Fixed Loop EM

GLOBAL GEOPHYSICAL believes that the successful execution of any geophysical project is determined in the initial planning

of the geophysical survey in close conjunction with the Client. Clients are made fully aware of the limitations and deliverables

of geophysical projects before commencement of fieldwork.

GLOBAL GEOPHYSICAL has extensive experience in the successful execution of mining, environmental and engineering

geophysical projects ranging from imaging underground geological features to large-scale geotechnical investigations.

GLOBAL GEOPHYSICAL 2 Goerap Street, Erasmuskloof, Pretoria

PO Box 11353, Erasmuskloof, Pretoria, South Africa Tel: +27 (0) 12 347-0078, Fax: +27 (0) 86 687-4281, Cel: +27 (0) 82 450-5077

Email: [email protected] Internet: http://www.globalgeo.co.za


Company Profile & Background

GLOBAL GEOPHYSICAL is a geophysical consultancy firm specializing in providing geophysical solutions to appropriate

mining, environmental and engineering problems. It was established in 2001 and is currently based in Pretoria.

The company was formed by Alten du Plessis who holds a Masters degree in Physics obtained from the University of

Stellenbosch in 1992. After spending one year at the Atomic Energy Corporation as a Researcher, and two years in the

Department of Mineral and Energy Affairs, he joined ISS International Limited in Welkom, specializing in the application of the

RockRadar Ground Penetrating Radar system. In 2001 he formed his own consultancy company which currently employ a junior

geophysicist and 2 field technicians.

GLOBAL GEOPHYSICAL has extensive experience in the successful execution of mining, environmental and engineering

geophysical projects ranging from imaging underground geological features, large-scale geotechnical investigations and mineral

exploration. Projects have been successfully completed in countries such as South Africa, Zimbabwe, Botswana, Tanzania,

Malawi. Major CLIENTS include Escom, Anglo Platinum, Anglo Coal, Sasol, Jones & Wagener Consulting Civil Engineers,

Horizon Blue Resources, Sasol, Etruscan Diamonds.

EQUIPMENT & SOFTWARE

GSSI SIR-3000 Ground Penetrating Radar system with 40, 100, 400, 500 & 900 MHz antennas

24 channel Geometrics SmartSeis Seismograph with roll-along capability

IRIS Elrec Pro and VIP4000 Induced Polarization System

AGI Supersting R8 Resistivity and IP system

Scintrex CG-5 Gravimeter

G5 Proton Magnetometer

Trimble R8GNSS GPS System

Omnistar VBS Survey System

ENCOM Profile Analyst 8.0 Geophysical Interpretation Software

EarthImager 2D Resistivity and IP Inversion Software

Res2dinv Resistivity & IP Processing & Interpretation Software

WinSeis Turbo Seismic Reflection Processing Software

SurfSeis Surface Wave Processing Software

SeisOpt2D Seismic Refraction Processing Software

Radan 6 Ground Penetrating Radar Software

GPR Slice 3D Radar Processing & Imaging Software

TYPICAL PROJECTS COMPLETED: 2005 TO 2008

• Mapping of Massive and Disseminated Sulphide Mineralization, Insizwa Complex, Kokstad, Eastern Cape using

Induced Polarization (IP) and Resistivity Tomography

• Multichannel Analysis of Surface Waves (MASW) Investigation at proposed nuclear power station site, Eastern Cape

• Multichannel Analysis of Surface Waves (MASW) Investigation to map rock fracturing and shear velocity at Kimberley

• Escom conductivity and resistivity measurement for Cathodic Protection at proposed Mmamabula, Dedisa, Victoria-West and

Bravo power stations using EM-34 and Resistivity

• Seismic Refraction Investigation at proposed Braamhoek & Lima Pump Storage Schemes for mapping bedrock topography

and structural geology

• Mapping of structural geology and depth of weathering at proposed Lwala Smelter, Burgersfort, Mmpumalanga,

• Micro-gravity survey for Meletse Golf Estate to map dolomite sinkholes and bedrock topography

• Resistivity Tomography Investigation at Algorax, Port Elizabeth, to characterize in-situ soilcrete

GLOBAL GEOPHYSICAL

2 Goerap Street, Erasmuskloof, Pretoria PO Box 11353, Erasmuskloof, Pretoria, South Africa

Tel: +27 (0) 12 347-00781, Fax: +27 (0) 86 687-4281, Cel: +27 (0) 82 450-5077 Email: [email protected] Internet: http://www.globalgeo.co.za


Environmental Geophysics

The use of geophysical methods in groundwater

contamination investigations requires an integrated

geophysical approach to provide useful solutions. GLOBAL

GEOPHYSICAL uses traditional and state-of-the-art

geophysical methods such as EM-31/EM-34, Magnetics,

Multichannel Analysis of Surface Waves (MASW) and

Seismic Refraction to map pollution plumes and preferential

groundwater flow paths between pollution source and

recipients.

GLOBAL GEOPHYSICAL also performs geophysical investigations for landfill and waste dump characterization. Geophysics

is the ideal non-destructive solution for investigating the subsurface and can provide cost-effective answers if used

appropriately and in suitable environments.

GLOBAL GEOPHYSICAL



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Rayleigh wave phase velocity

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Resistivity to map preferential groundwater flow along a dyke in quartzite bedrock.

Dyke

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Seismic velocity cross section

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Engineering and Geotechnical Geophysics In addition to seismic refraction and ground penetrating

radar to map bedrock topography, quantitative

geophysical solutions are used in geotechnical and

engineering investigations.

For example, GLOBAL GEOPHYSICAL uses

Multichannel Analysis of Surface Waves (MASW) as a

solution to map shear wave velocities, which are used to

calculate the shear modulus profile of a site.

In-field data quality control is

implemented to ensure that data of

sufficient quality and volume is

collected to ensure quality results.

• Mapping of subsurface cavities and old mineworkings

• Mapping of subsurface services, pipes and leaks

• Mapping of bedrock topography

• Shear wave velocity measurements for geotechnical investigations

• Hi-Resolution structural investigations

• Road and pavement investigations • Characterization of site geology

Geophysical data is integrated with area plans, allowing visual interpretation and analysis. GLOBAL GEOPHYSICAL strives to deliver quantitative and useful answers to engineering and geotechnical problems, in providing solutions tailored to the specific needs of the CLIENT.

GLOBAL GEOPHYSICAL



Shear modulus-depth profile

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Ground Penetrating Radar for Mapping of Services

Example of GPR scan to map the presence of shallow service

GLOBAL GEOPHYSICAL



Small Pipe at Depth of 35 cm Depth in metres

Horizontal Distance in metres

The example to the left shows the

hyperbola image created when

scanning over a subsurface service

such as an electrical cable or a pipe.

GPR offers an advantage in that it

can detect both metal and

PVC/concrete pipes.

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Figure 7.5 - Outside Area 1 - Depth 2.1 to 2.7 metres

WGS-84 LO-29

Manhole

Drain

Possible services

Service Global Geophysical utilizes advanced 3D software

processing & interpretation to create 3D model and

depth slices to assist in interpretation of services.

This approach requires that data be acquired on a grid

(typically 0.5 to 1.0 metres spacing between scans) to

allow for a high-density coverage of any target of

interest.

The advantage of this processing technique is that

features can be mapped and visualized which may not

be visible during a conventional survey where

interpretation only relies on the inspection of 2D data.

In the example shown in the figure on the left, one can

observe a weak reflector corresponding to a

subsurface service. This service was not at all visible

using a conventional 2D approach and would have

been missed if a conventional survey was performed.


Surface Waves for Shear Wave and Elastic Moduli Measurements

Multichannel Analysis of Surface Waves (MASW) is a relative new seismic approach to map shear wave velocity as a function of depth without the use of boreholes as required with borehole shear wave velocity measurements. The technique utilizes the dispersive nature of Surface Waves (also known as Rayleigh waves or Ground Roll), to determine shear wave velocity as a function of depth and distance. A shear wave velocity cross-section can be generated with shear wave velocities mapped for all layers of interest.

MASW offers the following advantages compared with Seismic Refraction and is often successful where Seismic Refraction has

failed:

• MASW utilizes high-energy surface waves and can be used in seismically noisy areas where Seismic Refraction body waves not have

sufficient signal to noise ratio for accurate first arrival picking.

• MASW does not suffer from velocity inversions and can be used in areas where a shallow high velocity layer underlain by softer

material makes Seismic Refraction unusable. For example, in areas of shallow calcrete underlain by softer sand before the deeper

bedrock layers, MASW will be able to map all the layers of interest.

• MASW can be used on tar/concrete surfaces without any problems where high velocity waves traveling through the upper surface may

interfere in normal Seismic Refraction studies.

• MASW offers improved lateral resolution compared with Seismic Refraction and may be used to map narrow faults and fracture zones.

Global Geophysical uses SurfSeis software developed by the Kansas Geological Survey which utilizes advanced processing tools

such as overtone analysis for proper selection of the fundamental Rayleigh mode. The use of a multi-channel approach allows for

a more quantitative analysis of surface waves.

TYPICAL APPLICATIONS

Mapping of Shear Wave Velocity

Bedrock Topography

Liquefaction Potential Studies

Mapping of Shear Modulus and other Elastic Moduli

Improved Site Characterization combining Shear with Compressional Wave Velocities

GLOBAL GEOPHYSICAL



Multichannel Seimic Record

Advanced Overtone Analysis to distinguish between fundamental and

higher order Rayleigh modes and effective selection of only the

fundamental mode.

Inversion of Dispersion Curve to invert to shear

wave velocity from phase velocity.


Diamond Exploration

Global Geophysical employs a wide range of geophysical techniques for the location and delineation of Kimberlites and Alluvial

Diamond Deposits.

ALLUVIAL DIAMOND EXPLORATION

Other Geophysical Techniques Applicable to

Alluvial Diamond Exploration:

Resistivity, (Mapping of clay, gravel and bedrock

interfaces). Ground Penetrating Radar, (GPR), (Mapping depth to

bedrock in moderate conductive environments up to a

maximum depth of ± 30m).

Induced Polarisation, (Mapping of clay, gravel and bedrock

stratigraphy)

KIMBERLITE EXPLORATION

Other Geophysical techniques Applicable to

Kimberlite Exploration:

Micro Gravity Surveying, (Mapping depth of cover and

combined modeling of Magnetic and Gravity datasets).

Magnetotellurics (MT), (Mapping the orientation of the

kimberlite pipe and the delineation of it at great depths).

Seismic Refraction, (Mapping the depth of weathering with high

accuracy).

Electromagnetics, (EM), (Mapping of conductive overburden

and clays caused by weathering). Resistivity, (Mapping of resistive as well as conductive zones

associated with kimberlites). Induced Polarisation, (IP), (Measurement of the dispersive

effects caused by minerals such as clays or sulphides)

GLOBAL GEOPHYSICAL



Using Micro-Gravity

surveying to delineate old

paleo-channels within

dolomite bedrock.

High resolution Ground

Magnetic Surveying to

locate and model

Kimberlite Pipe.

Target areas visible

as blue end of the

anomaly spectrum.

Kimberlite Center

Modeling capabilities

of magnetic datasets

and derivations of

key variables, such

as, depth to top of

kimberlite, width of

kimberlite and the

general shape of the

pipe.


Gold Exploration

Native gold has highly unusual physical properties, e.g., it has the

highest specific gravity of any natural material and is an excellent

conductor of electricity, it is present at best in amounts of a few

parts per million by volume and therefore cannot be directly

detected in-situ by any known geophysical methods.

Thus, those geophysical methods which offer the possibility of

being used in the exploration for gold deposits fall back on less

direct approaches, for example, the structural relationship of gold

deposits (using magnetics and gravity) and the detection of

associated or pathfinder minerals which may be present in much

larger amount than the gold itself.

Other Geophysical Techniques Applicable to Gold Exploration:

• Gravity

• Seismic Refraction - (Mapping buried river channels for placer gold deposits).

• Resistivity - (Mapping of conductive sulfides and mapping of resistive near surface zones of silification associated

with gold mineralisation.

• Induced Polarisation - (Mapping of metallic sulfides and quartz veins).

• Electromagnetics (EM) - Used where massive sulfides, conductive faults or fracture zones, or more resistive

silicified rocks may be associated with gold mineralisation.

GLOBAL GEOPHYSICAL



Ground Magnetic Surveying is a

rapid and cost effective tool for

mapping local geology and

intrusions.

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Conductive Zone coinciding with a

mapped magnetic lineament

Conductive Zone coinciding with

localized quartzite outcrop

Conductive Zone,(Associated with sulfide

mineralisation)Possible fault

location

Known DykePosition

Magnetotellurics (MT) is a state-of-the-art

geophysical technique used to image the

subsurface at great depths. The figure (left)

depicts the change in resistivity with depth. The

blue end of the color scale represents conductive

zones and the red/purple end of the color sale

represents resistive zones.

Linear Magnetic anomalies are

usually caused by dykes, in this

case these dykes may be

associated with gold mineralisation,

the pole reversal, (red and blue),

indicates an age difference.

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