| dc.description.abstract | The Coldwell alkaline Complex is located on the north shore of Lake
Superior, and consists of three Centers representing three magmatic
episodes. Center I consists of gabbro, and layered and unlayered ferroaugite
syenite. Center II consists of alkalic biotite gabbro, miaskitic
nepheline syenite, amphibole nepheline syenite, perthitic nepheline
syenites and recrystallized nepheline syenites. Center III consists of
magnesio-hornblende syenite, ferro-edenite syenite, contaminated ferroedenite
syenite, and quartz syenite.
The textures and compositions of the feldspars and apatite from these
three Centers were examined using cathodoluminescence (CL) and the
scanning electron microscope (SEM). All of the colours described in the
text refer to cathodoluminescence colours. The feldspars in Center I
consist of light blue to light violet blue, optically homogeneous alkali
feldspar; braid microperthite and incipient perthi te; and irregular vein
or patch perthite. The irregular vein and patch perthite contain light
violet blue cryptoperthitic patches, light blue exsolved albite and dull
blue exsolved K-feldspar. During late-stage fluid-induced alteration,
these feldspars were replaced by violet secondary albite and purple
secondary K-feldspar; and were coarsened by a deuteric antiperthitic rim.
The Fe-rich antiperthitic rim consists of deep red secondary albite and
brown secondary K-feldpsar. The later dominates in the upper series of
the layered and unlayered syenites. The homogeneous alkali feldspar
crystallized at high temperatures :t!700°C, exsolved into microperthite at
650-550°C and formed irregular vein and patch perthite at 520-420°C. | en_US |
