Newly released paper discusses MT applications and implications in the Red Lake Greenstone belt following Metal Earth initiative using SPARTAN MT .

Crustal conductivity footprint of the orogenic gold district in the
Red Lake greenstone belt, western Superior craton, Canada
Ademola Q. Adetunji1, Gaetan Launay1, Ian J. Ferguson2, Jack M. Simmons1, Chong Ma1, John Ayer1 and Bruno Lafrance1
1Mineral Exploration Research Centre (MERC), Harquail School of Earth Sciences, Laurentian University, Sudbury, ON P3E2C6, Canada
2Department of Earth Sciences, University of Manitoba, Winnipeg, MB R3T2N2, Canada

ABSTRACT
A magnetotelluric (MT) study across the Red Lake greenstone belt of the western Superior craton, Canada, images a 50-km-long north-dipping conductor (<20 Ω·m) at 20–25 km
depth and subvertical conductors spatially correlated with crustal-scale shear zones and
large orogenic gold deposits. The conductors are interpreted to be the conductivity signature
of the deep crustal source of the auriferous fluids and pathways of the orogenic gold system. The geophysical results, supported by existing geochemical and fluid inclusion studies,
suggest that the Au- and CO2-rich fluids responsible for gold mineralization were released
by devolatilization of supracrustal rocks underthrust to mid- to lower-crustal levels during
subduction. This MT study links shallow gold mineralization to a deep crustal source region,
demonstrating the connection between a crustal suture zone and the formation of orogenic
gold deposits in an Archean greenstone belt.

Geophysical imaging of the Healy property was achieved with deep-seeing Titan™ IP and MT surveys (induced polarization and magnetotellurics), transecting five kilometers across the three target areas where drilling was conducted. The surveys were carried out towards the end of the field season due to contractor availability. The IP and MT surveys, which imaged up to 800 meters and 4 kilometers depth respectively, support the presence of shallowly dipping, east-verging architecture with mineralisation occurring along low angle thrust faults and steeper cross-cutting fault corridors. Broad zones of disseminated sulfide and strong alteration are well-defined in the chargeability and resistivity data with zones of combined high chargeability and low resistivity (high conductivity) correlating well with mineralised intercepts from the 2021 drill program. The imaging of additional strongly conductive and chargeable zones, between drilled prospects, highlight significant exploration targets which warrant follow-up drill testing.

Our Phase Two exploration program will test a porphyry target at our San Pablo Gold Project that was identified in our recently completed Titan Geophysical survey. We have budgeted 15,000 meters for this purpose.” Mr. Griffiths went on to say, “I am encouraged by the scope of opportunity that exists for Andean to grow organically in Bolivia. Exploration is a key element of this growth, complementing our San Bartolomé mine life Expansion Study and the continued extension of our government contracts.”

Twelve diamond drill holes were completed at San Pablo in 2021 for a total of 3,580 m, as reported in the press release of November 30, 2021. The highlight was an intersection of 53.8 m grading 1.17 g/t Au from 211 m depth in hole SP21-01. All twelve holes encountered anomalous gold throughout their lengths.

Quantec Geoscience subsequently carried out a 9-line, 20.3 line-kilometers, Titan 24 deep induced polarisation survey (“DCIP”) and magnetotelluric survey (“MT”) at San Pablo that was completed in December. On many lines the DCIP shows a thick, very conductive layer close to the surface that limits the depth of penetration. The magnetotelluric survey, which is a passive method that uses the earth’s natural electromagnetic field as the source field to image subsurface resistivity structure, achieved depths of investigation of about 1,200 m. The survey detected very low resistivity anomalies at depth that are interpreted to be altered porphyry intrusions. These will be tested in the forthcoming Phase Two drill program. The holes are being targeted on the basis of low resistivity, high chargeability which may be due to sulphides with associated gold, and geology.

TORONTO, June 11, 2021 /CNW/ – Orefinders Resources Inc. (“Orefinders” or the “Company”) (TSXV: ORX) is pleased to announce the completion of a DCIP-MT ORION SWATH ground-based Geophysical Survey (“Survey”) on its McGarry Gold Project (“McGarry”). McGarry is adjacent to the Kerr Addison Mine that produced approximately 11 million ounces of gold before closing in 1996.

The initial 2-D modeling of the Survey data has shown significant IP (Induced Polarization) and MT (Magnetotelluric) anomalies associated with the Larder-Cadillac Fault Zone between the McGarry headframe and the Barber-Larder open-pit and also at other less explored target areas at McGarry (Figure 1).

“This sort of survey, combining quasi 3-D IP and deep-penetrating MT technologies has never been conducted on McGarry. This approach is aimed at delineating new exploration drill targets that could lead to new gold discoveries on a highly prospective project along the Larder-Cadillac Fault Zone,” said Keith Benn, Orefinders Vice President of Exploration.

The Survey was designed to gather high-resolution data at depth that will be key to identifying ‘under cover’ exploration targets, i.e., potential ore bodies that do not reach the surface. Subsequent 3-D modeling of this geophysical data set along with machine learning applied to all available data for McGarry will allow the Company to prioritize exploration targets for a drilling program later in 2021.