Sulfide and Deformation in a Gold Mine: Cosmo Howley, Northern Territory, Australia

Pyrite in Folded Shale Around Chert Nodules

Series of phototgraphs from drill core from the gold deposit of Cosmo Howley in the Northern Territory showing the interaction between competent silica nodules, folding in shale and deposition of pyrite. Scale bars are 1 cm long.

Figure 1

Deformation of sulfides around nodules in shale

Detail of above: Shear folding of shale, triggered by competent nodule. Notice pyrite in axial) plane of shear fold.

Detail of above: similar to previous photo, showing shear folds and a thrust, controlling deposition of pyrite.

Chert nodule controling folding in sulfides and shale

Figure 2. Flat chert nodule controlling folding in shale.

Figure 3. Pyrite strain shadowa around nodule.

Figure 4. Pyrite deposition around chert nodule. Pyritization took place along fracture in the shale and around the nodule. No pyrite was deposited along the fracture as it crossed the nodule.

Pyrite deposition in axial plane of fold

Figure 5. Pyrite deposition parallel to tightly folded bedding, and along axial planar fractures.

Flow and deformation in Cosmo Howley gold deposit, Pine Creek, Northern Territory, Australia

Roberto Weinberg, Monash University, Australia