Rare Earth Elements (REEs)
The Colosseum Project is also prospective for rare earths, with the Company’s experts confirming that rock units surrounding the breccia pipes at Colosseum are genetically related to the nearby Mountain Pass Rare Earth Mine, the highest-grade rare earth mine globally.
Rare earth elements (REEs) are a group of 17 chemically similar elements found in the Earth’s crust. They have unique electronic, magnetic, and optical properties that make them crucial in a wide range of modern technologies.
They are essential components in various applications such as electronics, renewable energy technologies, defence systems, telecommunications, catalysis etc.
Example applications include: producing permanent magnets for electric motors and generators, catalysts in petroleum refining, phosphors in energy-efficient lighting, screens of electronic devices, and rechargeable batteries.
China has been a dominant producer of rare earth elements, accounting for a significant portion of global supply. However, other countries and companies are actively exploring and developing rare earth element resources to reduce dependence on a single source.
The Mountain Pass Rare Earth Mine
The Mountain Pass Rare Earth Mine and Processing Facility is the only scaled site of its kind in North America.
Production at Mountain Pass started in 1952. With one of the world’s highest-quality deposits and more than 7% rare earth content, Mountain Pass became the primary global source from the 1960s to the 1990s.
In 2020, MP Materials produced more than 38,500mt of rare earths in concentrate, representing more than 15% of global consumption.
Colosseum Rare Earths Exploration
In June 2021, Dateline reviewed work undertaken by the USGS to identify radio metric signatures for the Colosseum – Mountain Pass corridor.
The radiometric signatures showed coincident Potassium, Uranium and Thorium signatures trending NNW that end inside the Colosseum claim boundary.
The Mountain Pass Rare Earth Mine is in the same geological setting and less than 6.5 miles from Colosseum.
USGS – Airborne Thorium Radio Metric signature from Mountain Pass to Colosseum
Mountain Pass mine is located at approximately 5,000ft above sea level and has been disturbed since the 1960s. The Rare Earth baring structure was discovered at surface
Colosseum is located at 6,000 ft above sea level, which indicates that the structure that contains the Thorium is probably 1,000ft below the surface when compared to Mountain Pass
Radiometric readings only extend approximately 2 inches below the surface
Extra ground disturbance at Mountain Pass means greater exposure of thorium which in turn provides for a stronger signal
The presence of a thorium signature that runs parallel to a known fault line and on-trend from the Mountain Pass ore body is encouraging information when looking for rare earths
Colosseum Production and Exploration History
The Colosseum Mine has been mined intermittently since before 1910.
Over 40 million tonnes of material have been removed and over 7 million tonnes processed using the CIP method.
The majority of the industrial-scale mining took place between 1986 and 1993.
The waste dumps and the Tailings area cover much of the natural geology.
Extensive surface mapping was undertaken on the site to identify the location of a Rare Earth baring carbonatite like the one at Mountain Pass.
An extensive surface mapping program was completed by Tony Mariano, a geologist that specializes in Rare Earths Minerals
Mr Mariano was accompanied by a structural geologist in an effort to identify the orientation of the rare earth-baring outcrops and mantle-derived rocks
Rock Chip samples were collected to determine the similarities between Mountain Pass and the Colosseum.
Map Legend
- Red lines are the location of Rare Earth baring Fenite
- Green lines are the location of mantle-derived Trachytes
- Light Grey is rock that has been previously mined and the tailings
- Rectangle is private property owned by the company
- Squares are the two gold pits
Comparison of Colosseum and Mountain Pass Fenite
Fenites can vary in mineralogy and texture depending on several factors, such as the type of host rock that was invaded by the fenitizing fluids.
One particular fenite sample collected from the Colosseum property (images on in first row) shows a striking petrographic similarity to a fenite sample collected approximately 6,000 feet to the south of the Mountain Pass pit (images in second row).
Macrographs of these two rocks are shown in the figures below. Horizontal dimensions of the samples are 46mm.
Macrographs of fenite rock samples from Colosseum (Top) and Mountain Pass (bottom) showing similar mineralogy and texture.
The same rock samples were analysed using shortwave ultraviolet light, illustrating the similarity of texture and mineralogy.
The same rock samples were analysed using shortwave ultraviolet light, illustrating the similarity of texture and mineralogy.
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A ground-based gravity survey was undertaken to identify drill targets that may be close to the rare earth-baring fenites.
The gravity data confirms there are several areas of interest, and there exists the potential for more than one carbonatite dyke within the claim boundary.
Figure 1 – Structural Geology Mapping
Map Legend
- Red lines are the location of Rare Earth baring Fenite
- Green lines are the location of mantle-derived Trachytes
- Light Grey is rock that has been previously mined and the tailings
- Rectangle is private property owned by the company
- Squares are the two gold pits
Figure 2 – is the gravity data at 100 metres below the surface
Note the gravity high to the north of the gold pits that are coincident with the fenite and the other gravity highs on the property
Figure 3 – figures 1 and 2 overlain onto a Google Earth image
Note the coincident mapping of Rare Earth baring fenites with the known regional fault and the location of the gravity high that was identified using geophysics tools