Samuel Metteer HBSc thesis abstract

Thesis Title: 
Mineralogy and Petrology of the Rabbit Foot Dyke, White River, ON

Diamond-bearing macrocrystic, and xenolithic rocks have been identified as occurring within the Rabbit Foot dyke within claim blocks held by Rio Tinto Diamonds Exploration Inc., 15km west of the town of White River, Northwestern Ontario.  Initial assessment of these rocks has led to their being classified “melnoite”, a term used to describe potentially diamondiferous ultramafic lamprophyres.

Olivine occurs in at least two distinct phases within the rocks of the Rabbit Foot dyke; macrocrystal olivine and groundmass olivine.  Macrocrystal olivine ranges in Mg/(Mg+Fe) from Fo₉₁ to Fo₉₃, while phenocrystal and groundmass olivine ranges from Fo₈₅ to Fo₈₇.  Phlogopite compositions range from Ba-phlogopite to tetraferriphlogopite. Spinel-group minerals commonly have chromite cores with titanomagnetite rims.  Spinel compositions follow the “Magmatic trend 2”, the titanomagnetite trend. Spinel-group minerals can be observed displaying atoll textures.  Spinel and perovskite are commonly spatially related, and can be observed surrounding larger macrocrysts such as olivine in a necklace texture.  Perovskite compositions are relatively pure CaTiO₃, lacking any REE concentrations.  In at least one outcrop of xenolithic rock, spherical magma clasts up to 10cm in diameter, which contain cores of olivine macrocrysts, can be observed.

The rocks of the Rabbit Foot dyke are in many ways analogous to kimberlite in texture and mineralogy, however, significant petrogenetic overlap with melnoites, or ultramafic lamprophyres, is evident.  The diamondiferous macrocrystic and xenolithic rocks of the Rabbit Foot Dyke can therefore be considered as kimberlite with melnoitic (ultramafic lamprophyre) affinity.