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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.

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...

Los Filos: The Right Angle

by Virginia Heffernan on May 29, 2013 discovery

David Jones

David Jones reviews exploration plans for a Minaurum Gold project in the Guerrero Gold Belt (GGB).

Sometimes exploration success comes down to a decision as routine as choosing the angle of a borehole. That’s what David Jones learned when he drilled the discovery hole at Goldcorp’s Los Filos, now one of the largest gold mines in Mexico, with annual production of more than 300,000 oz.

Although the discovery was made almost two decades ago, it remains instructive for those exploring other projects along the Guerrero gold belt, currently one of the world’s hottest exploration plays -- but also one of the most frustrating because, although outcrop is plentiful, the gold rarely expresses itself at surface.

Jones, who continues to explore the belt in southern Mexico on behalf of juniors such as Minaurum Gold, Acapulco Gold and Citation Resources, says the first step to finding the elusive gold is to pinpoint the Tertiary granodiorite porphyries that characterize the 80-km-long belt and are most commonly associated with gold mineralization. While magnetics can sometimes detect them, detailed mapping of structure and alteration is Jones’s preferred method of tracking down these intrusive rocks and the ska rn alteration that surrounds them.

That advice comes after years of experience exploring the belt. In the 1990s, when Jones was mapping in the mountains just north of Acapulco, not far from the small Nukay gold mine that had operated on and off since 1947, there wasn’t a lot to see. Even though the host rocks outcropped, they were barren at surface. What did make Jones stop and think “I should drill this!” was some float with iron oxide veining in an area of endoskarn.

“It was puzzling because it was different from anything I’d seen before,” says Jones.

So he and his crew built a crude switchback into the area to serve as an access road for a drill rig. Rather than drill directly into the altered intrusive with a vertical hole, Jones decided to angle the hole to see if he could intersect the carbonate wall rocks where mineralization was more likely to have been deposited by cooling hydrothermal fluids.

It was the right decision. The hole hit 12 metres grading 11 grams gold per tonne, the first in a series of rich intersections at Los Filos for joint-venture partners Miranda Mining and Teck. When Jones revisited the site 600 holes later to see what would have happened had he chosen a vertical orientation, the corresponding intersections proved to be nearly barren.

Shown above is a mineralized intrusion sample from Goldcorp’s Los Filos mine.

The Los Filos find, combined with an earlier discovery nearby (Bermejal) and a rising gold price, accelerated exploration along the belt and resulted in the discovery of almost 21 million ounces of gold. Resources are being proved up at a rate of about 600,000 oz. per year, though this is bound to slow as juniors struggle to raise cash.

There are two main deposits at Los Filos, both of which are iron-gold skarns with minor amounts of copper and silver at the intrusive-limestone contact. The original Los Filos occurs in a diorite sill that acted like a “giant sponge,” soaking up the mineralization as it was dumped out of the fluids. Bermejal, brought into the Los Filos fold by Goldcorp in 1995,occurs both within the granodiorite stock and at the limestone contact. Together the two deposits contain remaining proven and probable reserves of about 7.4 million ounces, according to Goldcorp.

Bermejal, discovered in 1987 as a result of sampling jasperoid, is obvious at surface. Los Filos has no surface expression. Yet of the two ore bodies, Los Filos is the richer. For Jones, that discrepancy is one of the most important lessons for explorers along the Guerrero belt: the most subtle indicators often lead to the best deposits.

Since the continental crust under the belt is relatively thin, magmas tend to rise and and cool quickly. The resulting alteration halos – though intense and typically dominated byquartz, sericite, clays, hypogene iron oxide, and sulphides-- tend to be narrow and difficult to find without precise mapping practices.

Although many of the granodiorite stocks do not have magnetic signatures, geophysics has been successful in finding some deposits as well as detecting the Los Filos deposit retroactively. For instance, the main deposits at Torex Gold’s 4-million-ounce Morelos project--El Limon and Los Guajes-- have only a weak magnetic signature. But Torex is currently intersecting skarn that carries gold, silver and copper at the contact between the intrusive and sedimentary rocks by following up magnetic highs on the property.

Several companies exploring along the belt are using VTEM to detect the clay alteration that is often associated with the intrusives. At Minaurum’s promising Vuelcos del Destino project, for instance, helicopter-borne VTEM/magnetic surveys have outlined three targets which coincide with a 2-km-diameter granodiorite porphyry stock that has alteration and structural features similar to those of the Los Filos deposit. The geophysical targets are coincident with stream-sediment anomalies.

Meanwhile, Cayden Resources is using a 3-D magnetic inversion model to guide drilling at its Magnetita target. The property contains a magnetic stock that coincides with gold-in-soil and gold-in-rock anomalies. A 5,000-metre drill program is underway.

And at Citation’s Biricu project, a 1,400-line-km VTEM survey has identified 19 potential conductive and/or magnetic target zones. Six of these zones are aligned along a 5-km northeast-trending corridor. Mapping is underway to prioritize areas for drill testing.

If these juniors are able raise enough cash to follow through with their drilling plans, expect gold resources along the rich Guerrero belt to continue growing at a rapid clip this year.

The Eureka Drill Hole That Started It All: From the drill hole that hit right down in the center of Nukay (now Los Filos) to what is now an 80km trend of mineralized skarn gold discovery deposits. Watch the video posted by Minaurum Gold.

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