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

Thus it is concluded that zirconium analyses are systematically higher with XRF, and that these
may in fact be more representative of the Zr content of the rock. On the other hand, the Nb and
Ta analyses by ICP methods (ALS MS81H and Acme 4A/4B) are all sufficiently close that it is
not necessary to conduct additional XRF analyses of these elements. Given the important of Zr
to the overall economics of the deposit, drill core should be routinely analysed by XRF methods
for Zr as otherwise the ZrO2 grade may be systematically understated in resource estimates.
Avalon monitors the results of the Company’s internal standards during routine analysis of drill
core. Due to the large number of elements involved, being fifteen rare earth elements and three
rare metals (Nb, Ta, Zr), it would be impractical to apply a normal logic table of failures where
an analysis batch is failed on the basis of issues with one element. In addition, all core is
analysed and so about two-thirds of the samples that have chemical data are not significant in
terms of the economics of the deposit. As a result, Avalon followed the following procedure for
assessing analytical data:
• Batches were not failed if the samples analysed were clearly far below any economic
levels (not mineralized), unless the standards results were very grossly out.
• The results of the standards were reviewed to see how many elements were out of
acceptable range as recommended in the standard certification, and if four elements
were out of range (greater than three standard deviations), but two high and two low,
and the remaining 14 elements were in range, the batch was accepted.
• If five elements or more elements were out of acceptable range (greater than three
standard deviations), and all in the same direction, either biased all high or all low, then
the batch was re-analysed.
There were a few cases of blanks being out of acceptable range. However, on close
examination of the results, these were almost invariably clearly associated with sample
switching, and it was clear that a mineralized sample and the blank had been switched.
There was a noticeable reduction in the number of cases of standards being out of range in the
case of ALS method MS81H compared to MS81.
The overall conclusions of the QAQC work completed are as follows:
• Standard deviations of duplicate analyses on standards indicate that the precision of the
laboratories is satisfactory, both for ALS Laboratory and Acme Laboratory.
• Duplicate analyses of standards and the duplicate reject analyses indicate that there is
little systematic bias between ALS Laboratory and Acme Laboratory.
• ALS Laboratory and Acme Laboratory indicate means for the four standards utilized by
Avalon within 5% of the accepted values for most rare earth elements, Nb and Ta. Zr
Technical Report 43-101 – March 13, 2011 Page 14-7
Prepared by Avalon Rare Metals Inc.