World’s first borehole muon tomography field trial successfully imaging alteration surrounding compact uranium ore pods.
This trial of borehole muon tomography demonstrated the effectiveness of the technique to image low-grade mineralization and alteration surrounding high-grade compact uranium deposits. Outcomes matched the existing geological model, delineating structural trends and mapping broad alterations surrounding uranium mineralization. Minor variations in density (in the range of 0.1 – 0.2 g/cc) within the alteration zone correlated spatially with the known mineralization halo.
McClean Lake is located within the eastern part of the Athabasca Basin in northern Saskatchewan, 850 kilometres north of Saskatoon. Orano’s McClean Lake operations include the world’s most technologically advanced uranium mill for the processing of undiluted, high-grade uranium ore. The Sue deposits, one of which was the site of this trial, are situated along the western margin of the Archean Collins Bay granitic dome within a graphitic pelitic gneiss corridor known as the Sue Trend. The uranium mineralization in this area is mainly composed of uraninite as nodules, shear vein fillings, and veinlets.
This project followed on an earlier successful fi eld trial conducted at McArthur River, SK using Ideon’s large-format muon detectors positioned in underground drifts at 600m depth. When development on the borehole-format detectors was completed in spring 2021, the fi rst prototype units were deployed at McClean Lake. Six borehole detectors were positioned in a chain at multiple points down a single drillhole 300m deep. Two of the six sensors were positioned above the known deposit to map (and eliminate) near-surface geological complexity. Ideon staff traveled to the site to deploy the detectors. Data were gathered over a period of about 7 months (with some inefficiencies due to power outages), with data collection completed in January 2023. Data intake and analysis were conducted remotely throughout this period to verify quality and calibration.
Imaging results closely matched the known data signature for the target area. Subtle variations in density within the alteration zone correlated spatially with the known mineralization halo. Tomographic reconstruction yielded a 3D map of density that conformed well to the existing geological model. Simulated and field-data-generated radiographic images for the six detector locations show the expected and measured muon flux in each direction from all detectors. High muon flux corresponds to low average density along the direction from the detector to the surface. The muon data maps quite well to the expectation.
Orano McClean Lake – SK, CANADA
“It is virtually impossible for us to detect high-grade deposits using traditional geophysical exploration techniques. Muon tomography gives us the ability to accurately locate subsurface anomalies while reducing the need for drilling. We expect it to transform the nature of how we explore.”
Research & Development and Innovation Director
Deposit: Unconformity-related uranium
Location: Athabasca Basin, Saskatchewan, Canada
This 3D density model slice shows the reconstructed density model from muon data, overlain with the borehole muon detectors (blue dots) as shown positioned down the single drillhole. For comparison, the model of the alteration, overlain on the reconstructed density model, is derived from Orano-provided data.
The muon data corresponds well to the existing geological model, delineating structural trends and mapping broad alterations surrounding uranium mineralization.
The geological context is complex around the mineralization. The low-grade halo is shown in pale red, and very small high-grade pods are shown within that halo. The high-grade pods themselves were too small to be imaged; however, the bulk mineralization structure could be reconstructed. An open pit to the North of the drill hole was also within the fields of view of all detectors except the shallowest.