Summary:
Paulsens is located on the northern limb of the Wyloo Dome. The geology is characterised by rocks comprising the Hardey Formation of the lower Fortescue Group sequence. The Hardey Formation has been informally subdivided into five members termed the Horsewell Sandstones, Melrose Argillite, Madang Clastics, Tin Hut Basalt and the Beaghy Sandstones. These members are defined as a predominately sedimentary succession of siliclastics with minor mafic flows which have been intruded by doleritic to gabbroic dyke swarms and sills of varying ages.
The prominent structural grain is defined by the trend of the regional dome, where local stratigraphy plunges 30° towards the northwest. A penetrative south-dipping axial planar fabric is typically present and is locally overprinted by a steeper, sub-parallel fabric which develops discrete and narrow shear zones with undefined origins. Towards the east of the project area, a regional brittle fault termed the “Hardey Fault” offsets stratigraphy.
Locally, the mine area is dominated by the Paulsens Mine Gabbro (40-60m in width) that has intruded the sediments prior to mineralising events. This Gabbro has been offset by normal faulting, causing a plunging ‘tear’ in the unit at ~30° towards the NW. This tear has been filled with a massive and barren quartz vein that was host to the historically mined mineralisation. Late-stage diorite dykes cross-cut the geology and mineralisation.
Mineralisation is generally concentrated on, or close to, the margins of the massive, quartz vein that fills the tear within the offset Mine Gabbro. Mineralisation is also found within the Mine Gabbro itself, forming narrower, high-nugget quartz/sulphide veins. The various mineralised veins plunge from outcropping at surface towards WNW at around -30° and are mostly constrained to either within the quartz or Gabbro.
Belvedere is situated within a sequence of mafic volcanic and sedimentary rocks collectively known as the Mount Roe Basalts. The units are folded along a moderate to steeply-dipping axial southwest plane with an overall shallow NW plunge. Post-folding and shearing, the volcano-sedimentary rocks appear to have been dissected by a series of NE trending normal faults with NW side down displacement. The Belvedere Fault appears to localise the mineralisation.
The rocks are intruded by a suite of steeply dipping, northerly striking (350°) dolerite dykes. A large dyke has exploited the weakness provided by the Belvedere Fault. Mineralisation is hosted in and adjacent to laminated quartz veins containing Fe-carbonate and arsenopyrite (+/- galena), formed within or at the margin of the re-oriented dolerite dyke. These veins appear to be associated with a set of steeply north dipping, roughly EW oriented mineralisation faults that probably comprise a damage zone formed contemporaneous with the mineralisation. These faults have associated minor quartz veining and sericite (+/- carbonate alteration) and locally deform the intrusive dolerite; partitioning of strain between these faults probably controls the horizontal extent of the larger mineralised quartz veins.
The main host at Belvedere is a mineralised quartz vein (defined by drilling) between 2m to 12m thick dipping from near surface at 52->280° for 180m to a depth of around 100m RL. The geometry of this vein appears to be analogous to the historically mined vein on the hill above it, but it is most probably a SW en-echelon step across from this vein rather than a direct (co-planar) extension of it.
The various mineralised veins plunge from outcropping at surface towards WNW at around -30° and are mostly constrained to either within the quartz or Gabbro.
Dimensions:
Upper Paulsens: Strike length = 1,100m down plunge at 30-35 deg to the west;
Width = ~80m (though high-grade component ~ 5m wide);
Depth = from ~130m below surface to ~550m below surface.
Voyager: Strike length = 1,850m down plunge, 25-30 deg to grid west;
Width = ~190m;
Depth = from ~550m below surface to ~1,100m below surface.
Titan: Strike length = 350m down plunge, 25 degrees to grid west;
Width = 50m;
Depth = from 750 to 925m below surface.
Galileo: Strike length = 360m down plunge,10 degrees to grid west;
Width = 50m;
Depth = from 380 to 520m below surface.
Gabbro Veins Strike length = 800m down plunge at 20-30° down Gabbro intrusion
Width= 220m of corridor (individual veins 0.2 – 0.8m).