Alluvial Dimonds
Geophysical methods can be used effectively to map the extent of alluvial channels and runs and to obtain a cost-effective solution together with drilling. The geophysical survey is often initially conducted to provide targets for drilling and to have a quick initial overview of the extent and positions of the gravel channels. A technique such as gravity works very well where the underlying bedrock is dolomite and a pothole type alluvial deposit is present.

Structural Geology
Mineralization is often controlled by geological structures and zones of weakness such as geological contacts, faults, fractures zones and dykes. Mapping and understanding of the structural geology is critical for development of a mineralization model and to effectively plan an exploration programme. Geophysical surveys such as magnetics and gravity are often used to map dykes and faults to assist in the mapping of the structural geology with magnetic being a relatively low-cost geophysical exercise and relatively large areas can be covered at reasonable costs.

Massive And Disseminated Sulphides
Geophysical surveys offer a very attractive exploration tool for the mapping of massive and disseminated sulphides. These targets are characterized by the presence of high chargeabilities (disseminated sulphides) and high conductivity (massive sulphides) which can be mapped using a combination of Induced Polarization (IP) and Electromagnetic Techniques.  Global Geophysical uses the IRIS system (ELREC Pro and VIP4000 transmitter) for IP surveys and the MaxMin system for frequency domain EM investigations.

Undeground Mining: Roof Integrity Investigations
Ground Penetrating Radar (GPR) offers a very efficient method of investigating shallow roof conditions in the underground mining industry for rock engineering and safety concerns.  Features such as dome planes, disseminated layers, chrome triplets, and other zones/planes of weakness can be imaged rapidly and efficiently with minimal data processing. About 8 systems are currently being used by various Chrome and Platinum mines in South Africa with data being collected and processed by the Rock Engineering personnel on the mines. Open Ground Resources provide training and technical support and sales of these systems in collaboration with Red Dog Scientific Services which is the GSSI system representative in Africa.

Shear Wave Velocity Measurements
The measurement of shear wave velocities is important for the design of large structures where the calculation of the site stiffness (elastic moduli) needs to be calculated. Global Geophysical utilizes the MASW (Multi-channel Analysis of Surface Waves) technique to determine site shear wave velocities.

Bedrock Topography And Weathering
The foundation design for large structures and dam sites require accurate knowledge of bedrock depth and the quality of the bedrock. The Seismic Refraction technique provides an accurate measurement of compressional (p-wave) seismic velocity and bedrock topography.  Global Geophysical utilizes a Geometrics 24 channel system with a hammer and plate source for imaging up to depths of 50 metres below surface on average (note that penetration is a function of the ambient noise and site conditions). SeisOpt2D software is used to determine the actual seismic velocities of the subsurface based on measured arrival times, this method does not require any pre-selection of different layers, and works well in areas of large lateral velocity changes, and gradual depth of weathering.

Dolimite Gravimetric Surveys
Potential instabilities associated with the karst topography of dolomite and potential voids require a proactive approach in terms of development of housing and other structures. Gravity is an extremely effective technique for mapping of the dolomite bedrock, and the presence of possible voids which are invisible from surface. Global Geophysical uses a CG-5 gravimeter with a Trimble RTK GNSS R8 system to provide very accurate gravimetric measurements which are typically performed on a grid of between 5 and 30 metres. Smaller grids are required to image smaller targets, while larger grids can be used to map larger variations of the target. Typical surveys include gravity surveys for housing developments, golf estates, tailings dam geotechnical investigations, mapping of voids associated with undermining, etc.

Pipes, Services, Void And Buried Objects
The mapping of pipes and services are routine conducted in investigations requiring accurate layout of existing services. The actual position of old services are usually not known due to lost information and contractors carry a high risk of cutting or trenching into water and sewer mains, electrical cables, fibre-optic cabling and other services. GPR is a high-resolution technique capable of mapping these features and Open Ground Resources uses the GSSI SIR-3000 cart system with a 400 MHz antenna to map services. Real-time site information can be marked on site, or can be surveyed using sub-cm accurate GPS system in complex areas, and the actual positions of services can be put on a site plan in electronic format. Subsurface voids can be mapped using various techniques such as resistivity, gravity and GPR, with GPR being a very quick and effective method for mapping of voids in build-up areas and roads. Buried objects such as fuel tanks, drums, and metal debris can be mapped using a combination of GPR, Magnetics and/or EM-31.

Resistivity For Cathodic Protection
Resistivity surveys are commonly performed at new steel pipeline locations for cathodic protection for which the subsurface resistivity must be known. Resistivity of the subsurface determines the rate of corrosion of an object and a proper cathodic system needs to be designed to minimise corrosion. Design of power station and substation earthing systems also require that the soil resistivity must be accurately determined. Global Geophysical uses the AGI Supersting system to map soil resistivity with EarthImager2D being used to calculate truth soil resistivity by inversion of the apparent soil resistivity data.

Roads, Pavement And Concrete Investigations
Maintenance and Remediation on roads and pavements require an assessment and understanding of the nature and extent of the problem before designing a comprehensive and effective maintenance programme. GPR is a rapid and accurate technique for mapping of the shallow road surface and to identify problems with the road layers, presence and extent of voids, and zones of water-saturated areas. The proactive identification of these areas can focus a remediation programme which is designed for the problematic areas only. GPR can be used to map the thickness of concrete slabs as well as voids below these slabs.

Preferential Groundwater Flow And Aquifers
Groundwater flow paths are important criteria in terms of the design of landfill sites, waste dumps, chemical factories and other sources of potential groundwater pollution. These structures need to be located in optimum areas in terms of minimizing potential groundwater contamination and it is therefore important to understand the various groundwater aquifers and groundwater flow patterns. Geophysical methods such as EM-34 and resistivity can effectively be used to map and characterize groundwater flow and to allow for the optimum positioning of groundwater exploration and monitoring boreholes. Geological structures such as dykes are important in terms of groundwater flow and can be mapped using a combination of magnetic, electromagnetic and resistivity surveys.

Landfill And Waste Dump Investigations
Geophysical methods are routine used to map the extent of old landfill sites and quarries which were used as landfill sites. The thickness of the waste material and the composition of the waste material can be mapped using resistivity and/or seismic refraction while the extent of the landfill site can be mapped using a technique such as gravity.

Pollution Plumes
Inorganic contamination of groundwater lower the electrical resistivity of the groundwater and surrounding soils and can be mapped using electromagnetic and/or resistivity methods. The movement of pollution plumes from the source can be traced by a series of parallel traverses downstream of the source positions, and the optimum position for groundwater monitoring boreholes can be determined.  The depth and possible lateral extent of contamination can also be sometimes extracted from the geophysical results.

Kimberlite exploration
The nature of kimberlites and its strong geophysical signature makes it a very attractive target for mapping with a range of geophysical techniques. Potential targets are usually identified from airborne geophysical surveys or site investigations, and ground geophysical methods can then be employed to characterize the pipe and to confirm its presence. Kimberlites usually have a strong magnetic signature and it thus suitable for mapping with magnetics, although the magnetic signature can be reduced by weathering, making the target magnetically invisible. Gravity is also a very good method for mapping kimberlite pipes due to the low density caused by the preferentially weathered kimberlite. A combination of the gravity and magnetic techniques is recommended for general exploration and characterization of kimberlite pipes.

Roads, Sewer And Water Pipeline, Manhole, Contour And Borehole Surveys
Open Ground Resources uses a Trimble RTK GNSS R8 system and Total Station to accurate map features such as roads and pavements, existing pipelines and manholes, fences, surface structures and buildings, general contour measurements, boreholes (existing and new positions), etc. Benchmarks can also be created according to the needs of the CLIENT which are referenced and tied to national trig beacons.