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

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Figure 7-2<br />

Detailed Deposit Geology<br />

The various Thor Lake mineral <strong>deposit</strong>s occur within <strong>the</strong> Aphebian Blatchford Lake Complex<br />

(BLC), which includes Achaean Yellowknife Supergroup metasedimentary rocks of <strong>the</strong> sou<strong>the</strong>rn<br />

Slave geologic province. The BLC has an alkaline character and intrusive phases vary<br />

successively from early pyroxenite and gabbro through to leuco-ferrodiorite, quartz syenite and<br />

granite, to peralkaline granite and a late syenite (Davids<strong>on</strong>, 1982). There appears to be<br />

successive intrusive centres with an earlier western centre truncated by a larger centre that<br />

c<strong>on</strong>sists of <strong>the</strong> Grace Lake Granite and <strong>the</strong> Thor Lake Syenite. Nepheline syenite underlies <strong>the</strong><br />

Thor Lake Syenite <strong>on</strong> <strong>the</strong> Nechalacho <strong>deposit</strong>. This unit was recognized in drilling by Aval<strong>on</strong><br />

during 2007 to 2010. Outcrops of <strong>the</strong> nepheline syenite within <strong>the</strong> area of <strong>the</strong> Nechalacho<br />

<strong>deposit</strong> display str<strong>on</strong>g hydro<strong>the</strong>rmal alterati<strong>on</strong> and c<strong>on</strong>sequently <strong>the</strong> unit was not originally<br />

mapped as distinct from <strong>the</strong> Thor Lake syenite.<br />

Davids<strong>on</strong> (1978) subdivided <strong>the</strong> BLC into six texturally and compositi<strong>on</strong>ally distinct plut<strong>on</strong>ic units<br />

known as <strong>the</strong> Caribou Lake Gabbro, <strong>the</strong> Whiteman Lake Quartz Syenite, <strong>the</strong> Hearne Channel<br />

Granite, <strong>the</strong> Mad Lake Granite, <strong>the</strong> Grace Lake Granite and <strong>the</strong> Thor Lake Syenite. Based <strong>on</strong><br />

exposed cross-cutting relati<strong>on</strong>ships of dykes and <strong>the</strong> main c<strong>on</strong>tacts, Davids<strong>on</strong> recognized a<br />

sequence of five intrusive events. The rocks of <strong>the</strong> last intrusive event, being compositi<strong>on</strong>ally<br />

and spatially distinct, are sub-divided by Davids<strong>on</strong> into <strong>the</strong> Grace Lake Granite and <strong>the</strong> Thor<br />

Lake Syenite. Although <strong>the</strong>se two units are defined as separate entities <strong>the</strong>re are no known<br />

Technical Report 43-101 – March 13, 2011 Page 7-2<br />

Prepared by Aval<strong>on</strong> Rare Metals Inc.

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