technical report on the nechalacho deposit, thor lake project ...

8. DEPOSIT TYPES
The mineral deposits at Thor Lake site bear many of the attributes of an apogranite (Beus, et
al., 1962) originating as an apical or domal facies of the parental syenite and granite. The
deposits are extensively metasomatized with pronounced magmatic layering and cyclic ore
mineral deposition. The Nechalacho deposit essentially forms part of a layered, igneous,
peralkaline intrusion.
According to Richardson and Birkett (1996) other comparable rare metal deposits associated
with peralkaline rocks include:
• Strange Lake, Canada (zircon, yttrium, beryllium, niobium, REE)
• Mann, Canada (beryllium, niobium)
• Illimausaq, Greenland (zircon, yttrium, REE, niobium, uranium, beryllium)
• Motzfeldt, Greenland (niobium, tantalum, zircon)
• Lovozero, Russia (niobium, zircon, tantalum, REE)
• Brockman, Australia (zircon, yttrium, niobium, tantalum)
Richardson and Birkett further comment that some of the characteristics of this type of deposit
are:
• Mineralizing processes are associated with peralkaline intrusions and the latter are
generally specific phases of multiple-intrusion complexes.
• Elements of economic interest include tantalum, zircon, niobium, beryllium, uranium,
thorium, REE, and yttrium, commonly with more than one of these elements in a deposit.
Volatiles such as fluorine and carbon dioxide (CO 2 ) are typically elevated.
• End members may be magmatic or metasomatic although deposits may show the
influence of both processes. Alteration in magmatic types is often deuteric and local
while alteration in metasomatic types is generally more extensive.
• This type of deposit is typically large but low grade. Grades for niobium, tantalum,
beryllium, yttrium and REE are generally less than 1%, while the grade for zircon is
typically between 1% and 5%.
• These deposits display a variety of rare metal minerals including oxides, silicates,
calcium phosphates and calcium fluoro-carbonates. Niobium and tantalum
mineralization is typically carried in pyrochlore and less commonly in columbite.
The main chemical features of the Nechalacho deposit that contrast to those overall features
are that uranium is not particularly high with anomalous but modest levels of thorium and the
lack of beryllium mineralization. Beryllium is present in the North T deposit, a separate smaller
deposit to the north with dissimilar geology.
Technical Report 43-101 – March 13, 2011 Page 8-1
Prepared by Avalon Rare Metals Inc.