The Penfold Nickel Project tenements cover part of the extensive Late Archaean granite-greenstone terrane of the southern Eastern Goldfields Province (EGP). The greenstone successions of the EGP form elongate NNW-trending arcuate belts separated by granite-gneiss terranes and an anastomosing series of NNW-trending, regional-scale faults. The Penfolds Nickel Project tenements are located within the Kalgoorlie Terrane. The Kalgoorlie Terrane is a tectono-stratigraphic terrane within the southern EGP that is defined by juxtaposed greenstone belts that share a distinctive stratigraphy and deformation history. The stratigraphy is characterised by relatively abundant komatiitic volcanism and rare banded iron formations (BIF) in contrast to adjacent greenstone terranes (Swager et al., 1995). Swager et al., (1995) divide the Kalgoorlie Terrane into six, fault-bounded, geological domains displaying a consistent regional stratigraphy defined by a lower basalt unit, komatiite ultramafic rocks and komatiitic basalt, and overlying felsic volcanic, sedimentary and coarse clastic rocks.
The four major domains are the Kambalda, Ora Banda, Coolgardie and Boorara domains; the two minor domains are the Bullabulling and Parker domains located on the margins of the Kalgoorlie Terrane. The Kambalda and Ora Banda domains contain the complete stratigraphic succession whereas in the Coolgardie domain the upper basalt unit is absent or thin and discontinuous. Repetition of the stratigraphy, as recorded in the Kambalda, Boorara and Coolgardie domains, is attributed to early D1 thrusting rather than repeated cycles of magmatism, eruption and sedimentation.
Four deformation events are recognised within the Kalgoorlie Terrane (Swager et. al., 1995). D1, which resulted in recumbent folding and thrust stacking, is best preserved in the Kambalda domain. Early thrust stacking within the Coolgardie domain is inferred from duplication and intense deformation of the mafic-ultramafic greenstone sequence. The D2 event gave rise to regional NNW-trending upright folds with gently plunging to horizontal fold axes and imparted the dominant structural features. Continued ENE-WSW compression (D3) resulted in NNW-trending transcurrent faulting and en echelon folding within fault-bound domains. N-NNE striking dextral faults (D4) displace the greenstone sequences in all domains.
The Penfolds Nickel Project tenements include ultramafic sequences assigned to the Coolgardie, Ora Banda and Kambalda geological domains. The ultramafic sequences can be broadly divided into three geographic groups. From west to east, these are
- The Yillara or Horseshoe Ultramafics
- The Saddle Hills or Yilmia Ultramafics and
- The Abattoir or Moorebar East Ultramafics
|Geological domains and nickel deposits of the project area|