Emily Ann Mine Geology
The Emily Ann orebody is a folded and highly mylonitised shear-hosted nickel sulfide and ultramafic unit, in the form of an open overturned synclinal structure plunging shallowly north-east. This synclinal structure has a lower limb dipping 30 degrees east, and an upper limb dipping between 40 and 60 degrees east.
The Emily Ann sulfides are hosted within a discontinuously boudinaged ultramafic unit sandwiched within the felsic footwall units, a position considered to be the product of inclusion within a shear. The sulfides are concentrated within boudin necks between ultramafic boudins and lozenges.
The morphology and position of the Emily Ann sulfides and ultramafics are unique and somewhat controversial. At its simplest, magmatic nickel sulfides are not usually found displaced so far into the footwall as at Emily Ann, where the material has moved up to 600m off the basal contact of the ultramafic unit. Models used to explain the shape and form of the orebody include;
- Attenuation of thickness during ductile deformation and movement into the footwall along a shear
- Folding of the resultant shear-hosted nickel sulfide and boudinage of the ultramafic unit during shearing
Read more about this topic: Emily Ann And Maggie Hays Nickel Mines
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