Tectonostratigraphic architecture and uplift history of the Eastern ...

Sunrise DamSunrise Dam is a multi-million ounce deposit located in the southern Laverton district. The depositis complex and there is debate over the structural history. The traditional understanding is that theearly recumbent folds and thrusts are related to D1 thrusting (N-S), and these are overprinted byupright F2 folds, which are parasitic to the larger Spartan Anticline to the east (Newton et al.,2001). Interpretation of the sense of shear has been described as both sinistral and dextral. Littlemention is made of the extensional history.Figure 16 is a PT-dihedra analysis of the mapping of a wall in the pit by Davis (2003). Davis notedextensional geometries including S-C fabrics (Fig. 17). Davis also noted that the main gold-bearingshears had top to the NW sense of shear, which on NW-dipping shear planes is extensional. Theresolved PT-dihedra from Davis’s work also indicate that the main fabric is extensional with downto the NNW shearing on shallowly dipping shear planes and layering (Fig. 18).Figure 16: Summary structural stratigraphy of Sunrise DamEvent Regionsnumber ofσ 1Simplifiedview ofσ 1Characteristicstructuresof deformation2 FA NO126AuDown to the NNWshearing alongshallowly NNW to NEdipping shear andbedding planes.2 SHFO2 SHFO2 SHFO2 SHFO2 SHFO2 SHFO2 SHFO2 SHFOAll structuresare synchronous2 SHFO2 SHFO2 SHFO2 SHFO2 BED BeddingStructural information from Brett Davis talk to GSA WA division 1 July 20030227