The people, science and technology behind discovery

Subscribe to the Magazine

Get new articles sent directly to
your mailbox.

Join the network

Twitter Updates Group Forum

Earth Explorer is an online source of news, expertise and applied knowledge for resource explorers and earth scientists. Sponsored by Geosoft.

News & Views

News Archive

December 7, 2016

Geosoft introduces IP and resistivity inversion in VOXI Earth Modelling

Geosoft has added induced polarization and resistivity data inversion to its VOXI Earth Modelling 3D inversion software service. Geoscientists are now able to create detailed 3D models of conductivity and chargeability from IP and resistivity survey data with VOXI. The resulting models can assist in interpreting and targeting regions for mineral and environmental applications...

December 5, 2016

Mexico's Deepwater Round Exceeds Expectations

Some of the world's biggest oil companies showed up Dec. 5 and agreed to invest on the Mexican side of the Gulf of Mexico, proving that deepwater exploration still has a pulse despite challenging market conditions...

November 30, 2016

Magnetic inversion results for Ngamiland available for download

A regional-scale geophysical inversion of magnetic field data in the Ngamiland region of northwestern Botswana is now available for download from the Botswana Geoscience Portal, a partnership initiative of the Botswana Geoscience Institute, industry sponsors and Geosoft...

November 30, 2016

LIGO Resumes Search for Gravitational Waves

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

International Volcano Scientists Unite

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 Assesses Mineral Potential for Sagebrush Habitats in Six Western States

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 Targets Up to U.S.$100 Million for Mineral Exploration

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

Small-Scale Fishers Get A Big Boost With First-Of-Its Kind Impact Investment Fund

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 take to the skies to track West African pollution

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

New IGS Xplore prospectivity maps for Botswana

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 Makes New High Grade Discovery

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

Rampion UXO Disposal to Take Place This Week

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

Diamonds In The Rough: E&Ps Find New Reserves In Mature Basins

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 Identifies High Quality VTEM Targets at Séquoi

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 tailors big data drive to copper

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 Awarded $200 Million Navy CLEAN Contract

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

NATO Science for Peace and Security (SPS), MODUM Partners announce "Young Scientist Summer School on Sea Dumped Chemical Weapons"

This international project cooperates closely with CHEMSEA (Search and Assessment of Chemical Weapons) Project for and sharing and knowledge transfer...

April 12, 2016

Monday mad rush for gold stocks

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: Continues to Expand the Boticas Gold Project, Portugal; Proposes $200,000 Private Placement

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

De-carbonizing our energy sector

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 nations’ have major existing fleets...

April 1, 2016

Follow-Up Drilling Results Indicate Wide Gold Zones at Hendricks Gold Discovery

Gascoyne Resources Limited announced that it has received the final assay results from the 10,000 metre aircore exploration drilling programme...

March 26, 2016

The Oil Market Is Finally Hitting Its Breaking Point

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

N-Sea Expands into the French Offshore Wind Industry

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

PDAC 2016 Convention Exceeds 22,000 Attendees

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 Launches EOD Contracting Division

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...

Best targets yet to be drilled at Promesa’s Alumbre project in Peru

by Virginia Heffernan on July 31, 2014 applied

[Click to enlarge]

Figure 1:  The image on the left shows the historical ground based magnetic data (i.e. Total Maganetic Intensity) and the image on the right illustrates 3D MVI inversion in grey underneath with historical ground based magnetics in the background and drillhole traces Stage 1 program.

[Click to enlarge]

Figure 2: Plan view of the magnetic susceptibility 3D MVI inversion with Stage 1 drillhole traces (Magnetics (pink) – Isosurfaces of susceptibility, +10 x 10-3 SI* in pink and dark pink 30 x 10-3 SI isosurface).

[Click to enlarge]

Figure 3:  Cross Section View at 9,065,750 N of drillholes 3, 4 and 5 with andesitic volcanics (green colour) overlying porphyritic tonalites and diorite intrusives (beige colour) at Alumbre.

[Click to enlarge]

Figure 4:  Plan view - Magnetic susceptibility 3D MVI inversion with copper field sample (Magnetics (pink) – Isosurfaces of susceptibility, +10 x 10-3 SI* in pink and dark pink 30 x 10-3 SI isosurface).

With drilling costs averaging more than $200 per metre, explorers are looking for ways to improve confidence in the drill targets they choose.  Australian junior Promesa Ltd (ASX Code: PRA) believes it may have found an answer in geophysical inversion or, more specifically, Magnetization Vector Inversion (MVI).

“Detailed surface and subsurface geology, geochemistry, geophysics and the recent 3D modelling using the MVI process has increased confidence in our exploration model,” says Ananda Kathiravelu, executive director of Promesa, which is exploring the Alumbre copper-molybdenum-gold porphyry system in northern Peru. “There is now a substantial body of information in support of the district-scale potential of the project.”

Magnetization Vector Inversion takes into account geological processes and geophysical effects that alter magnetization direction such as deformation, anisotropy, remanent magnetization and high susceptibilities – all obstacles for traditional susceptibility modelling. MVI is particularly effective at low latitudes, where the low inclination of the Earth’s magnetic field can make magnetic interpretation challenging.

The MVI technique is part of Geosoft VOXI Earth Modelling, a cloud-based geophysical inversion software that generates 3D voxel models from airborne or ground gravity and magnetic data.  By harnessing the processing power of the cloud, VOXI has made large, multi-parameter inversion modelling faster, more responsive and effective as a tool for target delineation.

At Alumbre, Geophysicist Barry Bourne, ‎Principal Consultant at Terra Resources PTY Ltd, reinterpreted historical ground magnetic data (Fig 1) using the MVI methodology to estimate magnetic susceptibility. The resulting model suggests a significant link between surface Cu-Mo-Au mineralization and a large subsurface area with a strong magnetic signature (Fig 2). There is potential for multiple porphyry intrusive centres.

Recent drilling has provided further validation of the model, intercepting seven metres grading 0.72% copper coincident with increased magnetite (Fig 3). The combination of magnetic susceptibility, MVI and downhole and surface geochemistry indicates mineralization associated with strongly potassic felsic to intermediate intrusives, hydrothermal breccias and andesitic tuffs may continue at depth, west and north of the discovery hole.

By incorporating the drilling data, Promesa will further refine the MVI model and use it to target boreholes for a second phase of drilling in August. Ground magnetic anomalies extend throughout the project area and the established association between copper and magnetite (Fig 4) increases their prospectivity.

Alumbre has never been systematically explored for porphyry style deposits, but magnetic modelling using methods such as MVI is catching on as an effective means of generating targets within similar porphyry systems, particularly at low latitudes.

“Magnetic inversion has developed into an important tool for targeting potential porphyry systems at Alumbre,” Promesa noted in a recent release. “This evaluation has resulted in a significant new interpretation of the magnetic susceptibility model of the project area.”

Source: Promesa Ltd

Related Articles

Magnetization Vector Inversion lends confidence to 3D modelling of mineral projects in South America

View all articles »