ICE  RIVER  COMPLEX  NEPHELINE  SYENITE

 

British Columbia’s Ice River Complex has quite a few unusual & scarce igneous rock types (see also ferrocarbonatite [scroll down about 2/3 of the way on that page]  & sodalite-aegirine-albite pegmatite from there).  Here’s a nepheline syenite from the Ice River Complex.  This general lithology is commonly observed in & associated with alkaline igneous complexes and carbonatite bodies.  Nepheline syenites are alkaline, intermediate intrusive igneous rocks.  They lack quartz and K-feldspar and plagioclase feldspar.  They are relatively deficient in silica (SiO2) and rich in alkaline elements such as Na and K.  The two rock-forming minerals in the sample shown below are nepheline (greenish-gray - (Na,K)AlSiO4) and amphibole (black).  Notice there are quite a few scattered yellowish crystals - that’s sphene (a.k.a. titanite - CaTiO(SiO4)).

 

Nepheline syenite from the Late Devonian/Early Mississippian-aged Ice River Complex in southeastern British Columbia, Canada.  Greenish-gray = nepheline; black = amphibole; yellowish = titanite/sphene.  Field of view: 5.2 cm across.

 


 

Home page