Today’s Technology: Mineral Exploration Trends and Developments in 1999
The Geological Survey of Canada (GSC) is Canada’s national agency for geoscientific information and research. It has supplied Canadian Mining Journal with unbiased reportage about the trends and developments in geophysics every year since 1965.
Part of Natural Resources Canada, the GSC supplies the fundamental geoscience knowledge required to support effective mineral and hydrocarbon exploration and development across Canada; to provide the geological basis necessary to understand and address health, safety and environmental issues; and to advocate the interests of Canadian geoscience at the international level.
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The last year of the 20th century will not go down in history as a ‘boom’ year in mineral exploration, especially in geophysical exploration activity. Significant new technological developments of hardware, software and methodology continued, but it was a year more notable for ‘restructuring’, mergers, acquisitions and just plain surviving.
Aero Surveys (Uxbridge, Ont.) has joined forces with EDCON Inc. of Denver creating EDCON AERO SURVEYS INC. (EASI). The company is incorporated in Colorado, and the official headquarters is at EDCON’s office in Denver.
Geosoft Inc. (Toronto) opened its core OASIS montaj platform for development by third party software developers with the ‘OASIS Public Programming Interface’ and an unsupported version of its ‘GX Developer’ software toolkit.
In October, High-Sense Geophysics Ltd. (Richmond Hill, Ont.) and Geodatos S.A.I.C. entered into an agreement to offer fixed wing geophysical surveys using the Geodatos Argentine-registered Piper Navajo aircraft equipped with High-Sense geophysical equipment.
During 1999, Sander Geophysics Ltd. (SGL) (Ottawa) performed the first test flights and the first commercial aerogravity survey using their new Airborne Inertially Referenced Gravimeter (AIRGrav).
Terraplus Inc. (Richmond Hill, Ont.) has become the exclusive distributor in Canada of borehole logging equipment manufactured by Mount Sopris Instrument Co. of Colorado.
World Geoscience Corp. Pty. Ltd. (WGC) (Perth, Australia) commenced commercial surveys with the new TEMPEST EM system, starting with a large survey in Temora, New South Wales.
In October, Fugro N.V. of the Netherlands, signed an agreement to acquire the business and assets of Geoterrex-Dighem from its French owners, Compagnie Generale de Geophysique. Geoterrex-Dighem, with headquarters in Ottawa, employs 155 people and operates throughout the world with permanent representation in Europe, Africa and Australia. Fugro also signed an agreement to acquire the business and assets of WGC from its owners, Aerodata Holdings Ltd. WGC operates throughout the world, with permanent representation in North and South America, Europe, Africa and the Middle East. The company employs 130 people of whom 18 are involved in R&D programs. In November High-Sense signed a letter of intent for the transfer of corporate ownership at year-end to Fugro. These acquisitions became effective on January 1, 2000.
AIRBORNE GEOPHYSICAL SURVEYING
In Airborne data acquisition and processing news, Geometrics (San Jose, Calif.) delivered a state-of-the-art airborne geophysical survey system to the National Geophysical Research Institute in Hyderabad, India. The system comprises a G-822A/823A Cesium Magnetometer, RMS AADCII airborne compensator, Exploranium GR-820 spectrometer with 1024/256 crystal pack and Trimble TrimFlight DGPS navigation.
Geoterrex-Dighem successfully applied its most recent technological development, the DIGHEMVRES resistivity mapping system, to industrial minerals and environmental surveys in the United States. The company reports that B-field data are now requested as a deliverable on a large portion of surveys, particularly in conditions where conductive cover is considered to be a problem. Geoterrex-Dighem also reports that use of conductivity-depth transforms is becoming increasingly popular among GEOTEM users.
Geosoft released a 256-channel tool for processing radiometric data and mapping geology, and a new GeoStrike trend enforcement tool for eliminating grid aliasing problems.
High-Sense was awarded a major World Bank mapping project for the Minerals Commission in Ghana in 1999. The combined magnetic-radiometric-VLF survey will cover over 105,000 line-km.
In April the South Australian government awarded Kevron Geophysics Pty. Ltd. (Perth, Australia) a 104,000-line-km magnetic and radiometric survey as part of its TEISA (Targeted Exploration Initiative South Australia) project. Kevron flew a 43,000-line-km magnetic and radiometric survey for the Northern Territory Department of Mines and Energy, and commenced flying a large 400,000-line-km magnetic and radiometric survey in July, for the Queensland Department of Mines and Energy.
SGL introduced a complete compilation suite for airborne gravity surveying, with enhanced GPS processing and gravity processing, including eotvos and terrain corrections.
SIAL Geosciences Inc. (Montreal) added a Cessna 421 to its fleet of survey aircraft, which were used in a survey over the Cordillera of Ecuador. The company also completed an extension of its survey program in Argentina.
To support the introduction of TEMPEST, WGC has developed new processing software known as “C-in-3D”, which can display conductivity data as animated views of iso-surfaces from different perspectives, or a series of conductivity slices taken at increasing depths.
In Aeromagnetic surveying, Geoterrex-Dighem conducted HRAM (High Resolution AeroMagnetic) surveys offshore Eastern Canada, offshore Gulf of Mexico and, in association with Geomag, offshore Brazil. A 160,000-line-km combined magnetic/radiometric survey was also flown for the Geological Survey of Namibia.
In fixed-wing surveys, High-Sense conducted a 130,000-line-km aeromagnetic survey in North Africa, 85,000 line-km in southern Ontario-upstate New York, and 80,000 line-km in Wisconsin. The company also conducted a 30,000 line-km vertical/horizontal gradiometer survey in Mauritania. In helicopter-borne surveys, High-Sense was awarded part of the large Ontario Geological Survey (OGS) Operation Treasure Hunt HEM/Magnetic project in northern Ontario.
As a substitute for conventional ground magnetics, Kevron reports flying a comparatively large 70,000-line-km magnetic/radiometric survey at a line spacing of 25 m and a terrain clearance of 25 m, covering an area of over 2,500 km2.
SGL flew over 200,000 line km of aeromagnetic surveys including a 140,000-line-km regional aeromagnetic survey over Greenland for GEUS (Geological Survey of Denmark and Greenland) and several aeromagnetic surveys for the United States Geological Survey (USGS) in California and Nevada.
Spectra Exploration Geoscience Corp. (Calgary) completed a high resolution aeromagnetic survey in the Clear Hills area in northwest Alberta and commenced a 29,000-line-km survey in the Wapiti-Tumbler Ridge area.
WGC reports that major aeromagnetic contracts were secured in Namibia, Botswana, Angola, Brazil, Canada, Australia and Iran.
Airborne electromagnetic advances saw Geoterrex-Dighem develop the DIGHEMCOMPACT system, utilizing a shorter, lighter bird containing four coplanar coil pairs and frequencies from 600 Hz to 75 kHz for surveys at lower cost than the full length DIGHEM birds, where the decrease in data quality is acceptable. The Mississauga, Ont., office successfully completed over 80,000 line-km of EM, magnetics and radiometrics with two DIGHEMV systems in the Anti-Atlas and High Atlas Mountains for the Ministry of Energy & Mines of Morocco. The company completed helicopter-borne EM/Magnetic/Radiometric surveys in northern New Brunswick and in Alaska and acquired almost 50,000 line-km of DIGHEMV EM data in the NWT in Canada. Of the 104,000 line-km of AEM surveying commissioned by the OGS under Operation Treasure Hunt, nearly 80% was awarded to Geoterrex-Dighem, split roughly 50/50 between DIGHEM and GEOTEM. Surveying with the MEGATEM deep-penetrating electromagnetic system continued in Chile and Peru in 1999.
WGC reports that Questem surveys were flown in Canada, Mexico, Brazil, Turkey, Indonesia and Australia.
In Airborne radiometric news, Exploranium (Mississauga, Ont.) released the GR-830, a new generation of airborne gamma-ray spectrometer intended to replace the GR-820. Major new features include an individual ADC for each crystal and a new Energy Linearization ADC system that converts incoming non-linear data from the detector to a fully linear spectrum. Some novel new features are: ‘remote access’ (via telephone modem), which permits Exploranium engineers to fully analyze systems and check system performance remotely in any field location; and ‘remote calibration’, which can now be done at the field site via telephone from Exploranium.
SGL flew radiometric surveys over the Darlington and Pickering nuclear power stations in Ontario. Projects in Scotland and France over nuclear power stations and military bases were also completed.
In Airborne gravity developments, March 1999 saw Australian Geophysical Surveys Pty. Ltd. (Jandakot, Australia) successfully test, over a known gravity anomaly, a prototype gravity meter installed on a helicopter, replicating the gravity change recorded by a Scintrex CG-3 gravity meter to within a milligal. Phase 2 was planned to be test flown early in 2000; it has a target of a gravity reading interval less than 200 m when flying in a Cessna Caravan 208B at 120 knots.
EASI developed an ‘Integrated Survey Program’, which involves flying a survey area twice, once with gravity/mag at ‘high’ constant barometric altitude, and then at ‘low’ drape altitude with either high resolution magnetics (called ‘ISMAP’ for Intrasedimentary Magnetic Mapping) or high resolution magnetics with gamma-ray spectrometry (ISMAP/ GammaSense) followed by interpretation. The company has undertaken ‘Integrated’ projects for clients in Peru and in Bolivia.
The first test flights, and the first commercial aerogravity surveys were performed by SGL in 1999 using its new airborne gravity system. The Airborne Inertially Referenced Gravimeter (AIRGrav) system is based on an entirely new gravimeter, designed and built by SGL over the last five years and is the only purpose-built airborne gravimeter currently flying commercial surveys. Airborne tests calibrated with ground gravity data demonstrated an accuracy of better than one mgal with a resolution of approximately 2.5 km. The first system is installed in one of the company’s Cessna Grand Caravans, with additional systems being prepared for use in 2000.
GROUND SURVEY TECHNIQUES
There were several new developments in the area of Data processing and positioning. New step response transformation software was introduced by Crone Geophysics for surface and borehole Pulse EM surveys near highly conductive targets. The transformation can now be performed with any of Crone’s three precisely-controlled linear current ramps of 0.5, 1.0, and 1.5 milliseconds, and with any channel configuration.
Geonics Ltd. (Mississauga, Ont.) in co-operation with Interpex (Golden, Colo.), performed substantial theoretical and experimental work, resulting in Interpex introducing a new version of the TEMIX layered earth inversion program that accounts for the effect of the bandwidth of PROTEM coils and receiver. Geonics has also completed its work on the software development of 30 gates for the BH43-3D three-component borehole probe.
Geosoft delivered two new Windows-based ground geophysical software systems: the Interactiv IP application for rapid verification of both time and frequency-domain data, and the Xcelleration Gravity tool for reduction and processing of data from ground gravity surveys.
Geoterrex-Dighem introduced safety-monitoring software for field crews globally. The software constantly monitors daily data transmissions and crew communications via Satphone to the company’s Bulletin Board System (BBS), and is able to detect indications of a Health/ Safety/Environment problem.
As part of their strategic alliance with JVX Ltd. (Richmond Hill, Ont.) for developing new geophysical technologies, ClearView Geophysics Inc. (Brampton, Ont.) is conducting tests to determine if Spectral IP can be used effectively to characterize contamination in environmental investigations.
Northwood Geoscience (Nepean, Ont.) announced its Vertical Mapper Version 2.5, which provides users with more ways to create, analyze and display grid-based information. Some of the new features include kriging, grid reclassification and grid info autotracking.
GOCAD advanced earth modeling system released in 1999 is now available to the mining industry exclusively from Mira Geoscience Ltd. (Montreal), a new division of Quantec Geoscience Ltd. GOCAD is the result of a 10-year combined effort by over 30 companies and 30 universities in developing new tools and methods for 3-D modeling of any spatial 3-D data.
Thirteen companies reported developments in Borehole geophysics in 1999.
Allied Associates Geophysical Ltd. (Luton, UK) announced the availability of downhole sparker seismic sources and a downhole shearwave seismic source developed by the British Geological Survey (BGS). Minimum borehole diameter for a P-wave sparker source is 50 mm and for the shear wave source is 100 mm.
Crone Geophysics reports that the measurement of all three components of the TDEM field down the hole is now standard practice for all holes.
In 1999 Delta Epsilon Instruments Inc. (Delta, Colo.) in addition to North America, supplied borehole logging systems to exploration projects in Thailand, China, Indonesia, Mozambique, Chile, Brazil and Viet Nam. Collaboration on borehole transient EM systems continued with Zonge Engineering (Tucson, Ariz.). Delta Epsilon also expects to add a combination tool for water quality determination in groundwater investigations during 2000.
IRIS Instruments (Orleans, France) has completed the development of its frequency domain 3-D EM Slingram borehole system called SlimBORIS in which a transmitting and a receiving probe (42-mm diameter) are located in the same hole. An orientation module enables derotation of the data coming from the three sensors and computation of the location of anomalous bodies.
JVX now offers a deep drillhole Spectral IP service that incorporates four separate winches, each with 3,000 m depth capacity. JVX is also developing Crosshole IP logging that has the potential to look between holes 700 metres apart.
Lamontagne Geophysics Ltd. (LGL) (Kingston, Ont.) has developed a new, more accurate three-axis accelerometer orientation tool for use in the borehole and surface UTEM four sensors. The new sensors, digital encoding circuitry, and the new reduction and calibration software give measurements with lower temperature dependence, better repeatability, and greater shock tolerance than the previous accelerometer tool. With high quality hole trajectory (gyro) data, the new tools can orient the EM data with an azimuth error less than 2 for a hole dipping at 89. BHUTEM 4 also measures three-axis magnetic data to help orient data in holes that are vertical or in steep holes where hole trajectory azimuths are not known accurately enough to use accelerometer data.
In late 1999 Mal GeoScience (Mal, Sweden) performed successful field testing of its newly developed directional borehole radar system for application in very deep boreholes (depths to 3,000 m.). The self-contained system runs on a standard logging cable.
Mount Sopris Instrument Co. developed a new user-configurable multi-frequency monopole-dipole full waveform sonic sonde. Users can customize surveys with the sonde by changing the transmitted frequency and switching the transmitted wavelet with monopole or dipole acoustic energy. A new 40-mm diameter oriented optical imaging tool (OBI-40) and geophysical logging system has been co-developed with Advanced Logic Technology srl (Luxembourg).
Pajari Instruments Ltd. (Orillia, Ont.) released the esi 200, the first of its new line of borehole electronic survey instrumentation. This single shot magnetic azimuth and inclination instrument will take one survey per initiation but will store multiple surveys in its memory, which is downloadable to a computer. The other models in the esi series will each have features suitable for different applications.
Quantec Logging Services Inc., a division of Quantec Geoscience Ltd., has acquired a fully equipped multi-parameter logging truck with 2,150-m depth capacity. Besides physical property logging, the company now has optical log capability and full radioisotope licensing for density and porosity logging.
Reflex Instrument AB (Vallentuna, Sweden) introduced the 31.7-mm diameter electronic single shot, called “EZ-Shot”. The azimuth of a drillhole is measured with an accuracy of 0.5 by a three-axis fluxgate magnetometer, and the inclination with an accuracy of 0.2 by a three-axis accelerometer. The in-probe computer shows the parameters directly on the tool LCD display, where data remains in memory until the next survey when it is erased.
Robertson Geologging Ltd. (Deganwy, Conwy, UK) introduced the optical televiewer (OPTV), for use with its Videologger digital logging system in boreholes up to 1,500 m depth. The probe provides ‘unwrapped’ continuous colour images of the borehole wall oriented to magnetic North. A new ‘push-pull’ lightweight winch has been developed for logging in mines, that uses semi-rigid cable and a tractor drive to propel the probe in boreholes drilled in any orientation including directly upwards.
During 1999 Scintrex Ltd. (Concord, Ont.) introduced its new slimmer SONIC tool. Completion of the Windows-based ALOG data acquisition system is set for early 2000.
Advances in Electromagnetic methods include a new version of the Crone Geophysics 4.8-kW Pulse EM transmitter, which now has a ‘delayed ramp’ feature, a 100-msec time base, and a ‘fast ramp’ option. Receiver modifications include a 42-channel configuration for the 150-msec time base, and a ‘full waveform’ configuration that reads the entire ramp and the off-time.
Geofyzika, a.s. (Brno, Czech Republic) has introduced the CM-138 conductivity meter for both conductivity and in-phase detailed measurements of the ground to a depth of 1.5 m. The new improved TM-93 and TM-D metal detectors are computerized versions of pulse time domain EM instruments made by Geofyzika.
The latest development from Geonics is the EM63, a high power, high sensitivity, full time-domain (20 to 30 time gates) metal detector.
LGL has been developing ‘Pebble’, a software package for surface element gridding of geologically useful shapes. The immediate use for Pebble is in designing 3-D model shapes for use in the MBEM 3-D EM modeling software. The steps in the gridding process are: the distribution of nodes on surfaces, the formation of a mesh, and finally the building of triangular elements. The software is automated, but it allows the user to observe graphically the grid building process and to interactively change gridding parameters.
In Induced polarization developments, Scintrex reports that the company is nearing completion of its new IP Transmitter, the VERSA. The first model in this new line of transmitters is the VERSA Tx-15. General specifications for this transmitter are 15 kVA maximum output, 5000 V, 30 A, and a full remote control capability.
For Ground magnetic surveying, IRIS Instruments announced NUMISPLUS, a modular one-person portable version of the NUMIS system based on the magnetic resonance method for groundwater investigations.
JVX has designed and used successfully the ‘JVX Rover’ system, which combines a cesium magnetometer with high resolution DGPS (Differential Global Positioning System) navigation mounted on a sled towed up to 25 metres behind a standard snowmobile. Navigation track-lines can be pre-programmed with 3-m interval readings. Survey speeds are 2 to 5 m per second over rough terrain; faster over lakes and flat areas.
Ground penetrating radar (GPR) again saw new developments from two companies in 1999. In September, Mal GeoScience introduced the RAMAC/GPR-MC4, a multi-channel radar unit with up to four channels available for measurements. New software called RAMAC GroundVision is capable of multichannel presentation and printing of RAMAC/GPR data. A new software interface for GPS receivers was developed, and now all RAMAC/GPR systems can be interfaced to any GPS system that has the industry standard NMEA output. Mal GeoScience also completed development of its new 100-MHz shielded antenna.
The Noggin Smart Cart was released in June by Sensors & Software (Mississauga, Ont.). The Cart has an integrated digital video logger for real-time display of subsurface images, and includes an interactive subsurface feature locator whereby users can immediately and accurately mark subsurface features. New software packages released by the company for use with the pulseEKKO GPR systems include EKKO_POINTER for automated target location in GPR data, EKKO_MAPPER for creating plan-view maps, and Win_EKKO, a Windows-based version of pulseEKKO software.
For Ground radiometric surveying, the new GR-130G available from Exploranium, is a hand-held instrument that can be used as a scintillometer (in the SURVEY mode) and as an ASSAY tool to give accurate automatic data assay in ppm eU, eTH and %K. This small, light weight unit uses a 0.07L BGO detector and features simple ‘joystick’ operation and long battery life. The GR-660 is a vehicle-mobile instrument integrating a gamma-ray spectrometer system, a GPS system, a computer and Windows-based software displays into a portable (easy-to-ship) gamma-ray mapping system. Real time displays show chart-recorder, spectra, location and special spectral analysis images.