A mineralogical, geochemical and geochronological study of postorogenic carbonatites in the Eden Lake complex, northern Manitoba.
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Date
2009-08-24T22:26:26Z
Authors
Elliott, Barrett
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Abstract
The first documented carbonatites in Manitoba occur as dykes and pods up to 15 meters in length and several meters in width at Eden Lake hosted in a post-orogenic syenitic complex within the Trans-Hudson Orogen. The carbonatites consist dominantly of calcite with lesser clinopyroxene, feldspar, apatite and titanite. Primary and xenocrystic clinopyroxene have distinct compositions, whereas xenocrystic feldspar has well-developed plagioclase and alanite rims. The whole-rock major- and trace-element composition of the carbonatite is consistent with global averages for calcio-carbonatites. Stable-isotope compositions of calcite indicate an igneous origin; the low δ13C ratios may reflect the influence of subducted sedimentary carbonate. A zircon age of 1815±8 Ma corresponds with the time of emplacement, whereas younger titanite ages reflect local thermal history.
Although field relations suggest a genetic link to the host syenites, whole-rock geochemical data is incompatible with immiscibility or crystal fractionation models, suggesting a discrete mantle source for the carbonatite.
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Keywords
Carbonatite, Manitoba geology, Trans-Hudson Orogen, Eden Lake, Alkaline rocks