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

south of Hearne Channel demonstrates that the two structures represent extensional fractures
bordering a basin that was subsequently filled with sedimentary and volcanic rocks.
Later phases of tectonic movement were principally compressional and relate to closure of the
rift, over-thrusting, nappe emplacement and recumbent folding in the East Arm, and collision of
the Great Bear Magmatic terrain. Younger (Proterozoic) metasedimentary and metavolcanic
rocks south of Thor Lake were deposited in the failed arm of the triple junction rift, and their
position now represents the location of this feature.
DIABASE DYKES
Two ages of diabase dyke swarms are present known as the Mackenzie and the Hearne. The
Mackenzie dykes are dated at 1.27 billion years, have a north-northeast strike orientation and
are part of the largest dyke swarm on Earth. Although there are Mackenzie dykes in the general
vicinity of Thor Lake none are known to cut the Nechalacho deposit.
The Hearne dykes are dated at 1.902by and trend ENE. Diabase dykes locally cut the
Nechalacho deposit and these are interpreted as Hearne-age dykes. At present, the dykes are
not well constrained as drill intercepts are infrequent, due to the near vertical nature of the
dykes and the mainly vertical drilling. However, in a few cases, vertical drilling has gone down
the interior of dykes, and also where there are multiple intercepts, the steep nature of the dykes
is clear. At present, there is no evidence that the Hearne dykes are implaced in fault structures
that have experienced significant displacement. However, this possibility should not be ignored
during the exploration program.
STRUCTURE AND TECTONICS
It is interpreted that the Nechalacho deposit is a virtually undeformed deposit where most of the
features observed were generated by the magmatic and hydrothermal processes. In the least
altered portions of the deposit, delicate primary textures are well preserved and no penetrative
tectonic or metamorphic fabric is observed.
The distribution of most of the rock units and the mineralization generally follows a subhorizontal
pattern that can be traced for several hundreds of metres. However, the subhorizontal
pattern is interpreted to be locally disturbed by changes in elevation of up to 40 m.
These changes in elevation may occur erratically or along linear trends. As noted above, the
deposit is also cut by late diabase dykes, which are part of the ENE trending Hearne dyke
swarm.
Technical Report 43-101 – March 13, 2011 Page 7-5
Prepared by Avalon Rare Metals Inc.