Malawi NI 43-101 - December 2011 - Gold Canyon Resources Inc.

35(such as apatite or the barium aluminum phosphate gorceixite ), or in REEfluorocarbonates of the bastnäsite group. Less is known of the leachability ofthese minerals but it likely is less than the ionic clay type.Weathered soil profiles in the REE deposits of south China are of lateriticcharacter and range from 5 to 30 m depth, are generally 8-10 m thick but maylocally reach as much as 60 m (Chi and Tian (2008) , Bao and Zhao (2008)).Typically there is a surface layer of organic soils (A soil layer), a stronglyweathered clayey, grey, yellow to red coloured layer (B soil layer) which usuallyhas the highest REE enrichment, and a lower pale-coloured layer with remnantsilicate minerals in clay (C soil layer) that may also retain primary igneoustextures (“saprolite”).About 60 to 90% of the total REE are adsorbed on clays such as kaoliniteand halloysite (Chi and Tian (2008)).The grade of raw ore is between 0.05 % and0.35% total RE oxides but there is considerable variability (2 to 6 times) in gradewithin a single deposit, commonly with better grades on ridges than gullies. Thedeposits are relatively small, generally 3,000 to 12,000 tonnes but the annualoutput from this type of deposit from China is about 10,000 tonnes REE oxideaccording to Bao and Zhao (2008). According to Chi and Tian (2008) “provenreserves of RE are approximately 1.48 million tons” in ion-adsorption deposits,inferior only to the resource at Bayan Obo.This type of deposit is important as providing a significant proportion of midand heavy REE in China. Figure 11 shows the REE distribution in two importantChinese ion-adsorption deposits (Longnan and Xunwu) compared with threecarbonatite-related REE deposits Mountain Pass REE Mine, the Bayan Obo REEMine and the Mt Weld REE deposit. Individual ion-adsorption deposits vary intheir distribution of the REE but Figure 11 shows some characteristic features.The carbonatite deposits have a high proportion of light REE, while the ionicdeposits have low light REE, higher mid and heavy REE. They also commonlyshow a distinctive deficiency in Ce and sometimes in Eu. The Ce deficiency hasbeen explained (eg Bao and Zhao , 2008) by the tendency of Ce to oxidize fromCe 3+ to Ce 4+ , the formation of cerianite or absorption of Ce on Fe and Aloxyhydroxides .