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Earth Explorer is an online source of news, expertise and applied knowledge for resource explorers and earth scientists. Sponsored by Geosoft.
November 30, 2016
After a series of upgrades, the twin detectors of LIGO, the Laser Interferometer Gravitational-wave Observatory, have turned back on and resumed their search for ripples in the fabric of space and time known as gravitational waves. LIGO transitioned from their engineering test runs to full science observations at 8 a.m. Pacific Standard Time on November 30...
November 9, 2016
For the first time, the United States will host the international Volcano Observatory Best Practices workshop, previously held only in Italy. The workshop will take place this month in Vancouver, Washington. It is designed specifically for volcano observatories around the world and their staff to exchange ideas and best practices with each other...
October 4, 2016
USGS has completed a comprehensive assessment and inventory of potential mineral resources covering approximately 10 million acres of Federal and adjacent lands in Idaho, Montana, Nevada, Oregon, Utah and Wyoming...
October 3, 2016
Uganda is well endowed with mineral resources and, like many naturally-gifted African countries, is becoming keen on ensuring that these resources play a transformative role in its long-term structural transformation dream - the Vision 2040...
September 9, 2016
Conservation organization Rare announces the Meloy Fund for Small-Scale Fisheries at Our Ocean Conference. The Global Environment Facility, one of the largest funders of conservation worldwide, will be investing $6 million into the fund...
September 1, 2016
Scientists operating research aircraft over West Africa have detected organic materials in the atmosphere over a number of urban areas, contributing to concerns of the rise in pollution across the region...
August 17, 2016
International Geoscience Services have released a series of base metal prospectivity maps for the Ngamiland District of northwestern Botswana using free geodata available on the recently-launched Botswana Geoscience Portal, hosted by Geosoft. The maps identify favorable areas for copper, zinc and lead mineralization using geological, geochemical and geophysical datasets downloaded directly from the portal.
August 11, 2016
NexGen Energy reported the discovery of a new high grade zone of mineralization 4.7 km northeast of the Arrow Deposit as part of an on-going summer drilling program on its 100% owned, Rook I property, Athabasca Basin, Saskatchewan...
August 10, 2016
E.ON has confirmed that the two unexploded devices, detected along the Rampion offshore cable route will be safely disposed this week following the consultation with the Marine Management Organisation...
August 9, 2016
The oil industry’s history demonstrates clearly that new plays and prospects have long been found in mature basins that were thought to be well on the way to being squeezed dry. Through the acquisition of new data, developing new concepts and coming up with fresh interpretations, long-producing basins around the world from the North Sea to Malaysia have continued to reveal new riches...
August 8, 2016
Northern Shield Resources announced the results of the interpretation and modelling of the VTEM survey from the Séquoi Property in the Labrador Trough of Quebec . Séquoi is owned 100% by Northern Shield and is being explored for Noril'sk style Ni-Cu-PGE massive sulphides. After geophysical modelling and interpretation of the VTEM data from Séquoi, six VTEM anomalies of significant interest have been identified...
August 3, 2016
Rio Tinto will put the weight of an exploration big data push and its newly-formed Growth and Innovation group behind its desire to identify a "tier 1" copper asset. Speaking at the annual Diggers & Dealers conference in Kalgoorlie, Growth and Innovation group executive Stephen McIntosh said Australia was "overdue for a tier 1" mineral discovery of any type...
August 1, 2016
Tetra Tech announced that it has been awarded a $200 million, single-award contract by Naval Facilities Engineering Command (NAVFAC) Atlantic. Through the Comprehensive Long-term Environmental Action Navy (CLEAN) contract, Tetra Tech will provide environmental engineering support services to installations within the NAVFAC Atlantic Area of Responsibility...
May 3, 2016
This international project cooperates closely with CHEMSEA (Search and Assessment of Chemical Weapons) Project for and sharing and knowledge transfer...
April 12, 2016
Renewed optimism about the outlook for gold saw investors pile back into gold stocks, pushing many stock to 52-week highs in heavy volumes...
April 11, 2016
Medgold Resources is pleased to announce new assay results from contiguous rock-chip sampling from the Limarinho South zone at its Boticas gold project in Portugal, which include a highlight of 6.0m @ 5.7 g/t Au...
April 8, 2016
Nuclear energy currently provides around 11 percent of the world's electricity. China, the European Union, the United States, India, Russia, South Korea, and other nationsâ€™ have major existing fleets...
April 1, 2016
Gascoyne Resources Limited announced that it has received the final assay results from the 10,000 metre aircore exploration drilling programme...
March 26, 2016
After a significant reduction in investments over the past two years, oil companies can no longer overcome the production declines from legacy wells...
March 15, 2016
Subsea IMR provider, N-Sea, has signed a letter of intent with CERES Recherches & Expertise Sous-Marine and TechSub Industrie Environement, to provide subsea survey, installation and remediation services to the French offshore wind industry...
March 9, 2016
Optimism and opportunity abounded at the PDAC 2016 Convention of The Prospectors & Developers Association of Canada in spite of recent industry challenges...
March 3, 2016
6 Alpha Associates, a specialist risk consultancy practice, with expertise in the assessment and management of unexploded ordnance, has launched a dedicated explosive ordnance disposal division...
New data generated from the largest airborne geophysical survey ever undertaken in Nigeria is helping to position the country as an exciting destination for explorers.
By Graham Chandler
Accessing detailed geological and geophysical information for any part of Nigeria is about to become a whole lot easier. With the country’s new National Geophysical Data Management System, an interested explorer will be able to simply go online, zoom in on an area of interest, place an order, make the payment and download the data. “The availability of these geophysical data sets will help investors both local and international to take less risky and quick decisions on investment in the country,” says Olaniyan Oladele a geologist with the Nigerian Geological Survey Agency (NGSA). “This will in turn boost mining activity in the country and in Africa in general.”
What has made it possible began with a massive country-wide airborne geophysical survey started in 2003 which has amassed several thousand flying hours. Several thousand more person-hours have gone into the processing and presentation of the data. As it nears completion, there are still more hours to come—ground truthing, and some more intense aerial coverage of oil and gas prone areas.
The new undertaking is sorely needed. Aeromagnetic surveys in Nigeria flown in the 1970s have played a key role in understanding the country’s regional geology, but due to their low resolution had become of limited use. Although they covered most areas of the country, the survey data was acquired at 2 km flight line spacing and exists in analogue paper format in the archives. Government initiatives to diversify the country’s national income away from dependence on crude oil resulted in the new project—proposed to carry out airborne and radiometric surveys for all parts of the country and further electromagnetic and gravity surveys in specific mineralized areas, says Oladele.
The survey was initiated by Professor Siyan Malomo, Director General of the NGSA, and it was conducted in two phases. Phase 1 was financed entirely by the Government of Nigeria. All of the airborne geophysical work – data acquisition, processing and interpretation, was carried out by Fugro Airborne Surveys. Phase 1 was completed in September 2007 and included 826,000 line-km of magnetic and radiometric surveys flown at 500 m line spacing and 80 m terrain clearance; and 24,000 line-km of time-domain electromagnetics surveys flown at 500 m line spacing and 80 m terrain clearance using Fugro’s GENESIS EM system. Fugro was also tasked with interpretation of these data.
Phase 2, completed August 2009, surveyed blocks not covered in Phase 1. It included 1,104,000 line-km of magnetic and radiometric surveys flown at 500 m line spacing and 80 m terrain clearance. These levels of survey are intensive: often a total of seven aircraft of three different types were active at one time.
Phase 2 was supported by the World Bank as part of a major project known as the Sustainable Management for Mineral Resources Project. Fugro Airborne Surveys carried out the data acquisition and data compilation. Another firm, Paterson, Grant & Watson Limited (PGW) is carrying out the data processing and interpretation. PGW is also preparing the nationwide grids and synoptic interpretation, incorporating all Phase 1 products and the results of an earlier pilot project from Ogun State in the southwest part of the country. A consortium of independent consultants, Geoexploration Nigeria, GeoWitch and Earthworks, were contracted by the World Bank to provide advice, logistics, training and quality control (QC).
Additional airborne EM was added in specific areas of interest. Past history, known geological information and geophysical signatures of metallic minerals such as lead-zinc and other sulphides were used to determine areas for further airborne EM surveying.
And there’s still more flying scheduled for 2010, when it is expected to wrap up. The entire Niger Delta block will be flown with aeromagnetics at 1 km line spacing, with a further one quarter of the Delta with airborne gravity.
As large as the acquisition task was, overall it was just one part of the workload. The task then came to pull together all the dozens of gigabytes of data, interpret and present them. It wasn’t just the new data, either. The older analogue data still contained useful indications so had to be integrated with the newly acquired. “Most of the old data have also been digitized and stored in a Geosoft database format,” says Oladele. “It’s been very interesting comparing the old data with the new dataset. Both show similar anomalies but at different resolutions.”
Interpretation has had its share of challenges. “The Nigerian Geological Survey Agency is currently transitioning from the analog to the digital world, particularly with its geological maps,” says Stephen Reford, vice president at PGW. “Getting our hands on some of the geological material took time, and certain new digital products were not properly geo-referenced.” But he says these issues have been rectified. Reford says that despite the country’s reputation for security and corruption, he found that didn’t match reality. “Our dealings with government agencies have been completely transparent and professional,” he says. “We have lived in and moved around the central part of the country without any sense of danger.” It bodes well: they have a month-long ground truthing program in many parts of Nigeria coming up this year, “which will be an interesting challenge to coordinate,” he says.
With such a massive and important project, it was imperative that a high degree of quality control was maintained throughout all phases. It was in fact a requirement by the World Bank; largely to ensure that data from different lots would be error-free, compatible and comparable, and could be compiled into a consistent countrywide dataset.
“Comprising some two million line-km of three-sensor magnetic data and 256 channel gamma-ray spectrometry, this was not a job to be taken on by the faint-hearted, impatient or ill-equipped,” says Sally Barritt of GeoWitch. “Full coverage (almost) of the country was achieved using several aircraft over a series of blocks and sub-blocks, the flying of which needed to be coordinated to accommodate the quirks of the Harmattan and rainy seasons, while minimizing the effects of environmental variations on the quality of the data.”
Barritt says they accomplished the data acquisition part of the QC largely through a series of 10-14 day, on-site visits at approximately three to four month intervals. Each trip involved the routine QC of some 200,000 to 300,000 line km of data and a reassessment of the cumulative coverage. . “Any specific test/calibration data and or requests to check certain flights of data or other issues could be dealt with remotely during the intervening periods,” she says. “I would say that the biggest challenge was trying to ensure consistency between different aircraft systems and also, for gamma-ray spectrometry, consistency between data collected during different seasons.”
Similarly, QC of the final processing required several visits to the contractors’ offices and remote follow up; and consisted of preliminary/exploratory processing. “Not all potential problems, nor the geological value of the data, are immediately obvious in the raw field data,” she explains. In the end, she had to be sure of seamless, country-wide datasets. “With so many individual blocks and sub-blocks of pretty irregular shapes making up the countrywide coverage it was essential to ensure that these would all link together without the necessity for large shifts or warps.”
PGW’s massive task of processing is in the interpretation stage and still a work in progress, but Reford is pleased to be able to talk about some important conclusions that can already be drawn. He notes that depth-to-magnetic source mapping has proven very useful in assessing the inland basins, both to delineate the thicker accumulation of sediments where the oil & gas potential is higher, and to locate some quite large regions where the sedimentary cover is thin and the shallow basement has the potential to host minerals at economic depths. When it comes to gold deposits, these are hosted by schist belts in western Nigeria. “The magnetic and radiometric data have proven instrumental in extending the known schist belts,” says Reford, “characterizing their lithology and locating structures that are controls on the mineralization.”
There are more, he notes. Nigeria is known for its older and younger granites. “The airborne data show that the character of these granites varies considerably, and will allow assessment of which mineral deposit types may be associated with certain classes of granites,” says Reford. And, for diamond potential, the Kafur kimberlite pipe was already described in the literature as having been discovered in 1961 but the new data are revealing. “The aeromagnetic data display a discrete signature for this pipe and associated structures,” he says. “Similar magnetic anomalies in the area are targets for exploration.” Reford expects new findings in the oil-rich Niger Delta, too, once it is flown this year.
A wide range of software has been used to assist in all phases of QC, interpretation and presentation. Geosoft’s Oasis montaj mapping and processing software, and GXs (Geosoft Executables) developed by PGW were utilized for imaging, map preparation and interpretation; montaj Magmap was used for a range of processed magnetic images; variable reduction-to-the-equator to account for the wide range of magnetic inclinations and declinations across Nigeria; source edge detection to delineate magnetic contacts and anomaly peaks and source-parameter imaging for depth-to-magnetic source imaging.
“All final products are being delivered in ArcGIS, so the interaction between that software and Geosoft is quite important,” says Reford. “It has allowed us to combine the strengths of both products, for example using the ArcGIS ‘grid with barriers’ technique to combine interpreted structure with the depth-to-magnetic sources prepared with Geosoft.”
Reford says the interpretation is being prepared at the 1:250,000 scale on Nigeria’s standard map layout, with a nationwide synoptic interpretation at the 1:1 million scale. Each map sheet incorporates three interpretation products: litho-structural (basement, intra-sedimentary and sedimentary); geophysical (geophysical elements and character); and regolith (surficial material and geomorphology). Accompanying each map sheet will be a report, cross-section and series of images incorporating magnetic, radiometric, terrain and Landsat data. He adds that the interpretation and geophysical imagery will be delivered in a GIS format for digital archiving and interrogation.
Filling the requests for the new data sheets will be the role of the NGSA’s Customer Service. “The NGSA is mandated to archive all geological and geophysical datasets for the entire country,” says Oladele. “We provide the data to investors and researchers as demanded in both raw (.gdb or .grd) and image maps (PDF or JPEG) format.” He adds that the service will be more than simply providing data; they will help interested investors to further customize interpretation and further ground survey where necessary. As well, assistance such as providing extraction of smaller, regional or local grids from the much larger master grids is to be offered.
The NGSA has been working with Fugro Airborne Surveys who have sub-contracted Geosoft to deliver the National Geophysical Data Management System utilizing Geosoft DAP server technology. It’s all ultimately part of the World Bank supported Sustainable Management of Natural Resources Project in Nigeria.
“The new high-resolution airborne survey coverage in Nigeria provides a wealth of information that will illuminate geological thinking for decades to come,” writes PGW’s Reford in a summary for an upcoming international conference. “It forms a key component of the country’s strategy to encourage investment in the minerals sector and broaden oil & gas exploration beyond the Niger Delta.” He describes it as a “national treasure”.