The Blatchford Lake Intrusive Complex is commonly known for intruding Archean Metasediments, and plutonic rocks of the Southern Slave Province in early proterozoic time period. The complex it self can also rather be divided into a western series of gabbrotic, granitic, and syenite rocks. These are also known to be cut by a large circular peralkaline granite and syenite to the east. In addition to this, the eastern series is commonly determined to host the Grace Lake Granite, and the Thor Lake Syenite at its center. Further mineralization and altered rocks are commonly known to occur within the northwest side of the Thor Lake Syenite, and gradually extends into the Grace Lake Granite. Gravity studies which became completed had indicated that this intrusion is a thin tubular body, which floored to a depth of 1.5 to 1 kilometer. For the most part, the Thor Lake Syenite can also be subdivided into six mineralized sections and texturally distinct units./Much of the vicinity of this mineral deposition is also considered to consist of massive, medium to coarse grained assemblage of subhedral to Euhederal K Feldspar that associated with amphibole (Riebeckite, Arfvedsonite), magnetite, and minor quartz. In many cases, olivine, and pyroxene are also associated with this deposit, and are either serpentinized or sericitized within the local geological area. The Thor Lake Syenite is also determined to be very much weathered, and is known to be brown and crumbly.
Much of the Grace Lake Granite is commonly known to be texturally similar, but its more determined to be pinker in color, and has a resistance to weathering, unlike the Thor Lake Syenite. Quartz are commonly known to be the main distinguish features between the granite and syenite formations. The mafic minerals which chiefly occupy this geological setting are known to composed of Riebeckite, Iron (Fe), and Titanium oxides and much lesser biotite. Other statements had also reported that much of the contact between the granite and syenite, is gradational than intrusive in appearance. It also determined that the outer margin of the Thor Lake Syenite is referred as the Rim Syenite, which weathers in relief, and displays a shallow inward boundary against the granite formation.
Diabase Dikes are also determined to cut all major lithologies of what is known as the Hearne Dyke, and is also altered and cut by later syenitic phases of the north Thor Lake. This type of information rather provides that the evidence of the five main zones of altercation, and mineralization that are associated with this deposit. Prior to this evidence, it also became determined that only two mineralized are considered to be of economical potential. These two zone are rather determined as the Lake and T zone areas. The remaining three zones within the area are considered to also be much smaller, and this geological section is also considered to carry a fluorite zone. It was at the time when the area was being further explored that had indicated a large Be ore reserve, and further studies were being place at developing this zone. Upon further examinations its revealed that the T Zone was 1 km long, and up to 275 meters wide, and had narrowed to 5 m at the south end and extends to a depth of 150 m. Much of the trending of this zone was also considered to have been north-northeast, and was further away from what is known as the Lake Zone. Reports on this zone had indicated that it was an irregular dyke like body with a much subcircular body at its north end. Unlike the Lake Zone, it was also stated that the T Zone was entirely within the Grace Granite, and the Lake Zone was formed in the Thor Lake Syenite. Other reports would also state that the south T-Zone is covered by abundant diabase dykes that are present in this geological area.
Much of the whole entire T Zone area is known to also be grouped into four zones of altercation, which are the Wall Zone, Lower intermediate Zone, the Upper Intermediate Zone, and the Quartz Zone. In some extend these zones are commonly considered to be gradual within each other. In terms, the polymetalic character of the T Zone is known to make it difficult to differentiate specific rare earth. However, beryllium enrichment is known to be found within the UIZ, and to a lesser degree in the LIZ. Yttrium is known to also occupy the UIZ and the LIZ, with rare earths near the Quartz/UIZ boundary, and in the LIZ. Other rate earths that are found consist of niobium in the LIZ and not least Gallium in the WZ. Mineralogy within the South T Zone is also very similar to that of the North T Zone, but the former zone had not been well explored.
One of the largest zones within the Thor Lake Rare Earth Prospect is the Thor Lake Deposit, and was the main focus of the Ta, Wb-U exploration prior to the discovery of the Be in the T-Zone. Although its considered that very little Be is observed within the Lake Zone section. However, the Lake Zone rather comprises of enrichment of Nb, Ta, Y, Zr, and REE deposits that makes it a economical. At the time, 29 diamond drill holes were put down on the Lake, in which outlined an indicated ore reserve of 64 million tonnes, grading 0.03% Ta, 0.40% Nb, 1.7% REE and 3.5% Zr. Much of the zone is rather triangular in plan with 2 km long sides About half of this zone is known to also underlie Thor Lake, and because of poor outcrops, the Lake Zone is mostly known from drill core and geophysical surveying. A 1983 gravity survey had rather suggested that the zone has quartz. and is filled with accessory minerals. These accessory mineral are commonly known to included zircon, fluoride, allanite, ferro-columbite, and bastnaesite group minerals. Breccia Texture are rather known to occupy the mafic rocks, which are similar to those in feldspathic zones, but altercation is more intense and the feldspar is commonly altered.
Drill log reports from diamond drilling show a nephaline syenite that is 150 to 300 m below the present erosion surface. It also though that the altercation, and mineralization of the lake zone is developed in similar syenite or perhaps in the upper portion of the same syenite. The Fluoride Zone is rather situated on the southeast end of the Lake Zone where it terminates in a small faulted off appendage of metasomatically altered arfvedsonite syenite. Much of this zone is also approximately 150 m in length, and varies in width from one 15 m, and is composed of dark brown siliceous rock with local pods of fluoride. This also also associated with enrichment in Zr, Y, REE, Th, and U, that's variously in zircon, xenotime, allanite, and bastnaesite-group minerals.
The T Zone for the most part is subdivided by in 16 minerlogical well defined subzone lithologies that are grouped into the four border zones. The four border zones are commonly identified as the WZ, LIZ, UIZ, and the QZ geological sections For the most part, the North T Zone is also similarly particular to these zones that appear to be concentric "shells" although they are commonly intergradational. Whereas most lithologies are common to both the North and South T Zone, the following description apply specifically to the better studied North T Zone. On the other hand, the quartz zone is known to be essentially monomineralic quartz core of the North T Zone. Its also occupied by up to 35 m thick ceteral upper portion of the zone, and is gradational with the upper intermediate zone. Patchy zones of green fluoride and a separate zone with honey yellow aphalerite are also found near the footwall boundary. A bastnaesite is also an enriched zone within the UIZ and is known intermittently to cross into the footwall of the Quartz Zone.
Another zone known as the Upper Intermediate Zone is transitional with the quartz zone, and with the Lower Intermediate Zone, and the boundaries between these units are usually obsecure and vague. This zone is also occupied by Be enrichment that is mainly within the UIZ , and most importantly the Beryllium silicate phenakite. The zone also consist of significant Yttrium, and six subzones have therefor been recognized. For the most part, the Quartz-Mica, Quartz-Mica-Feldspar, and the Quartz Feldspar subzones contain massive lenses and anastomosing stringers of euhedral polyithionite in a quartz matrix. Other associations such as pink albite are known to become increasingly common downward, and green fluoride along with carbonates are common accessories. A quartz feldspar mica magnetite subzone is also highly altered and shows replacement by abundant phenakite interrelated with quartz. Large randomly oriented tubular crystals and biotite may also hae been originally riebeckite. The quartz Bastnaesite subzone is known to also consist of quartz with brick red bastaesite-group fluorocarbonate within a anastomosing skeins, blebs, and patches with accessory flouride.
Interestingly, a quartz-thorite feldspar subzone is within the lower half of the UIZ in which comprises of anastomosing stringers and blebs of fine grained mixtures of chocolate-brown Th minerals. These included thorite (Th-Y silicates) within a dark grey, very fractured quartz In addition to this, it commonly enriched in Y and B, and Berlyllium minerals that include phenakite, lesser amounts of bertrandite, and minor gadolinite. Dark purple fluoride is also common in the area.
For the most part, the Lower Intermediate Zone is known to exhibit gradational contacts with the UIZ, and with the Wall Zone Breccias. Granite, and syenite within the South T Zone is known to consist of xenoliths that exhibit varying degrees of altercation are abundant. Be, Y, and Nb enrichments are present in the LIZ, and the Six subzones are recognized. Quartz biotite and chloride feldspar are also associated with a subzone of dark grey and highly siliceous. Much of the upper boundary resembles the quartz feldspar subzone of the UIZ, but with biotite in place of polylithinite. Accessory minerals within this subzone included fluoride, and columbite with fine interstitial purple fluoride that is particularly common in the South T Zone.
This also includes a biotite, chloride feldspar carbonate quartz subzone that is ultimately found only in the south T Zone. Its rather similar to the Quartz-biotite-chloride-feldspar subzone, but contains up to 25% grey carbonate, that's mainly dolomite, as patchy masses and interstitial aggregates. Mineralization within the T Zone is known to display a crude zoning that's commonly overprinting lithologic boundaries. THe five enrichment Be Zone outlined in the North T Zone are known to show a trend in increasing Be-Enrichment upward and also an upward increase in the proportion of Be in phenakite, and concomitant decrease in the proportion of Be in bertrandite, and in the minor minerals gadolinite, and helvite. Yttrium that asssociated with the Xenotime and the Th-Y silicates, is known to occur centrally and to a lesser degree in the lower portions of the T Zone. Niobium thats associated with columbite tends to be the most abundant towards the lower portions of the T Zone, where rare earths occur in descrete upper zones of quartz bastnaesite, and to a lesser degree throughout the T Zone. Reserves that were determined on the basis of 135 diamond drill holes and by a 500 m decline are estimated at 1.6 million tonnes, grading0.86% BeO. It also concluded that the North T Zone reserves are 435,000 tonne grading1.4% BeO, and 0.26% Yttrium trioxide.