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
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Beside these ring-dykes and cone-sheets, numerous calcitic and dolomitic dykes, cogenetic to
the dolomitite and calcitite cone-sheets, have been cross-cut by Soquem drill holes (Fortin,
1977).
Regarding the dip of these different ring-dykes and cones-sheets constituting this carbonatite
complex, besides the shallow exploration drill holes data of Soquem interpreted with a 70°
dipping structures (Vallée and al., 1969), mine drill holes data (surface and underground),
show to a depth of 800m, a sub-vertical to 70° dipping to the north of the Mine carbonatite
structures (C5 and C3).
Considering the concentric structure of this carbonatite complex, a conical geometry with a
strong dip of the different units toward the center of the cones remains the more probable
scheme for this carbonatite complex.
A northwest-southeast schematic geological cross section has been established, to better
visualize and understand the spatial internal organization of the St-Honoré carbonatite
complex (Figure 6).
9.2.1.3 The Carbonatite complex Zoning
Following the petro-geochemical study of the carbonatite complex (Fortin, 1977), zoning
seems to manifest itself between the different facies units of the carbonatite regarding their
geochemical composition and their chronology:
• The carbonatite complex has a reniform shape consisting of a central portion of
carbonatic rocks enclosed in an alkaline syenite;
• The age of the different units of the syenite show a chronologic evolution in the
following magmatic suite from ”Ijolite-Urtite-Foidite (to) syenite-Feldspathoidic
syenite (to) Alkali syenite-Lamprophyre-Carbonatite”;
• The age of the different units of carbonates decreasing progressively inwards from
alkali syenite, calcitite through dolomitite to ferro-carbonatite;
• The carbonatite comprises concentric lens which evolved from calcitite through
dolomitite, to a brecciated core of ferrocarbonatite;
• The carbonatite shows an outward inward carbonate evolution expressed
mineralogically by the suite “calcite- dolomite- ankerite-siderite”,
In spite of the similarities with other carbonatite complexes, (1) such as the presence of a
carbonatite core bordered by a syenite in Oka, (2) zonality between calcitite and dolomitite as
in Firesand carbonatite (Superior province, Ontario), the St-Honoré carbonatite complex is
different by the absence of ultramafic rocks as in Oka (Fortin, 1977).
3400, chemin du Columbium, St-Honoré-de-Chicoutimi, QC G0V 1L0 Canada – tel. : 418 673-4694 Fax : 418 673-3179
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