NI 43-101 Technical report, Surface diamond drilling ... - Iamgold

R a r e E a r t h E l e m e n t E x p l o r a t i o n P r o g r a m M a r c h - 2 0 1 3
W i n t e r - S u m m e r 2 0 1 2 P a g e | 29
The REE are largely hosted by rock-forming minerals where they substitute for major ions.
Higher concentrations of REE are required to form their own minerals (Miller, 1986).
Around 200 minerals are known to contain REE, although a relatively small number are or
may become commercially significant.
The REE in carbonatites are almost entirely LREE which occur in minerals such as
bastnaesite, allanite, apatite and monazite (Gupta and Krishnamurthy, 2005). REE do not
occur naturally as metallic elements, they occur in a wide range of mineral types including
halides, carbonates, oxides and phosphates.
The vast majority of resources are associated with just three minerals, bastnaesite, monazite
and xenotime. In some REE minerals, the LREE are particularly enriched relative to the
HREE, which in others the opposite is the case. Bastnaesite and monazite are the primary
source of the LREE, mainly Ce, La and Nd. Monazite has a different balance as it contains
less La and more Nd and HREE. It is also significant to note that monazite contains the
thorium, a radioactive element.
Figure 7: Schematic section and plan view of a carbonatite complex (SIDEX.ca)
Schematic section and plan view (mid-level) of a carbonatite complex, showing cylindrical
shape of intrusion that evolves upwards into a diatreme breccia and layered tuffs. Late dikes
(bold lines) display a radial or concentric pattern. The intrusion consists of three phases:
sövite (calcite-rich carbonatite), iron-rich magnesian carbonatite, and ijolite (nephelinepyroxene
rock). The host rocks are fenitized (alkaline metasomatism) and desilicified.
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