Summary:
The Daisy Mining Centre lies along the Bulong Anticline within the Gindalbie Terrane of the Norseman-Wiluna Greenstone Belt. The core of the Bulong Anticline (the Yindarlgooda Dome) contains mineralised granitic intrusive rocks in a sequence of felsic to intermediate conglomeratic sedimentary rock, structurally overlain by a mafic-ultramafic succession. Quartz-feldspar porphyry dykes and sills intrude the sequence.
A northwest striking (50°), south dipping shear (the Godard Shear) separates the ultramafic sequence to the south from the felsic volcaniclastic rocks to the north. The structural setting of the Daisy Complex is analogous to that of the Kanowna gold mining centre, with is located on shears spaying away for the regional Kanowna Shear.
The Daisy Mining Centre includes the Daisy Complex underground mine as well as surrounding projects such as Mirror/Magic and Lorna Doone.
The Daisy Complex comprises intermediate to felsic volcanic rocks. The mineral deposits are located east and beneath an overlying north-northwest trending ultramafic unit of approximately 250 m thickness, comprising mostly variably serpentinised peridotites with localised talc alteration.
The entire sequence is intruded by two quartz-feldspar porphyritic units. One group (the footwall cross-cutting porphyries) are oriented northwest and dip at 45°–60° west, while the other set (Main porphyries) are oriented north–south and are vertical to steeply east dipping. There are also numerous east–west trending Proterozoic mafic dolerite intrusive dykes, ranging from a few centimetres to several metres thick, distributed throughout the deposit area.
Mineralisation occurs along north–south trending, transpressional structures, commonly along or associate with the Main porphyry contacts and/or north–south shear structures. Haloes of sericitepyrite-fuchsite alteration around mineralised quartz carbonate veins typically highlight metal-rich fluid pathways. Galena and sphalerite are generally enriched in typical Daisy ore veins and compressional shear structures on vein margins are also excellent indicators of gold mineralisation.
Mineralised veins are typically subvertical, vary between 0.05 m and 1 m in width, generally trend north–south and exhibit significant wall rock alteration. Milky white (bucky), often wide (>2 m) nonmineralised veins trend east–west, have significant alteration halos and cross-cut ore mineralisation.
Mineralisation is not bound to one lithology or structural type at the Daisy Complex. Observations highlight that gold mineralisation has occurred along a north–south series of planes and that fluids have used favourably oriented structures during migration. Deposition appears to be structurally controlled; however, some chemical deposition may have occurred near the overlying ultramafic unit.
In the Daisy complex, the Daisy-Milano underground deposit is the main deposit.
Daisy Milano
The deposit type is classified as an orogenic gold deposit within the Norseman-Wiluna greenstone sequence. The accepted interpretation for gold mineralisation is related to (regional D2-D3) deformation of the stratigraphic sequence during an Archaean orogeny event.
Locally, the mineralisation is characterised as a deformed vein, hosted within intermediate volcanic and volcaniclastic units and closely associated with felsic intrusive rock types of the Gindalbie Terrane. The metamorphic grade is defined as lower green-schist facies.
Dimensions
The Daisy Milano resource extents are 3000m strike, 800m across strike and 3,000m down dip and open at depth. These extents host approximatel1y 91 known ore zones (ore domains).
Mirror Magic
Mirror Magic mineralisation is located at the southern end of the Kurnalpi Terrane (formerly the Gindalbie Terrane) on the western limb of the Bulong Anticline. The Mirror Magic area lies to the west of the Juglah Monzogranite – an oval intrusion emplaced into a domed sequence of felsic to intermediate volcaniclastic and volcanic rocks. The Majestic and Imperial mineralisation occur within a small quartz diorite/tonalite stock to the immediate west of the Juglah Monzogranite. Quartz diorite is the dominant lithology at Imperial and hosts the mineralisation. The gold mineralisation is associated with crystalline and disseminated sulfides, dominantly chalcopyrite and pyrite.
The Miror Magic resource has a strike length of 750 m. It is 340 m across strike, 400 m down dip and open at depth.
Lorna Doone
Spinifex-Lorna Doone mineralisation is located at the southern end of the Kurnalpi Terrane (formerly the Gindalbie Terrane) on the western limb of the Bulong Anticline. The core of the Bulong Anticline (the Yindarlgooda Dome) contains mineralised granitic intrusives in a sequence of felsic to intermediate conglomeratic sedimentary rock, which are structurally overlain by a mafic-ultramafic succession. Quartz feldspar porphyry dykes and sills intrude the sequence. The Bulong Domain is bound to the west and separated from the Kalgoorlie Terrane by the Mount Monger Fault. The terrane has undergone significant deformation which has been described as four major events D1–D4 inclusive. The host rocks at Spinifex-Lorna Doone comprise a sequence of volcaniclastic sandstone and polymictic conglomerates of intermediate composition. The volcaniclastic rocks are intercalated with the ultramafic rocks, which are typically altered to talc, chlorite, serpentine, calcite and magnetite and commonly contain calcite veins. Three thick feldspar quartz porphyry sills have been modelled at the deposit. Mineralisation cross-cuts these porphyries. All logged rock types dip moderately to the southwest parallel to the earliest deformation (D1) foliation of S1. Mineralisation zones display a strong enrichment in sulfides, including pyrite, pyrrhotite and arsenopyrite. The sulfides are typically dispersed through the host rock in contact with sheared quartz veins. Pervasive sericite alteration, moderate chlorite and silicification is also commonly observed in mineralisation zones.
The Spinifex-Lorna Doone resource has a strike length of 950 m. It is 450 m across strike, 560 m down dip and open at depth.