The tenements (Thunderbox Operations) are all held by Northern Star (Thunderbox) Pty Ltd, Northern Star (SR Mining) Pty Ltd and Northern Star (Talisman) Pty Ltd which are all wholly owned subsidiaries of Northern Star Resources Ltd.
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Summary:
Thunderbox is a mesothermal lode gold deposit located at the southern end of the Yandal greenstone belt in an area where several major shear zones converge and join with the Perseverance Fault.
The shear zone dips at 30° to 60° WSW, with the exception in the vicinity of the mineralisation, where the shear is vertical to steeply dipping. Mineralisation is hosted by strongly deformed, silicified and carbonate altered albite-quartz porphyry in the hangingwall of the shear zone. The shear juxtaposes foliated basalts and intrusive porphyries in the hangingwall against sedimentary rocks in the footwall. The zone of shearing is over 200m wide. An ultramafic unit occurs within the shear, in the footwall of the deposit and is attenuated along the shear. At the known extremities of the mineralisation, interpreted as a pepperitic apron, the porphyry host is less continuous and interchanges with mafic volcaniclastics.
The main gold related hydrothermal alteration assemblage comprises quartz-ankerite-arsenopyrite- pyrrhotite-galena and gold. Synmineralisation veins have a continuum of vein textures ranging from laminated to pseudo-breccias.
Throughout the Thunderbox Deposit, elevated grades occur within southerly plunging ore shoots that are more evident in the lateral extents of the orebody. Whilst the shoots persist centrally, the gold distribution is for more uniform and ubiquitous than in other areas.
Dimensions
Thunderbox mineralisation extends from 6879000mN to 6881000mN, 304000mE to 304400mE and 500 meters below surface
The Thunderbox shear generally strike NNW and dips 60° towards the WSW. In the vicinity of the strongest gold mineralisation the shear is vertical to steeply west dipping.
Rainbow
Locally the deposit is contained with a sheared unit with sediments in the footwall and mafics in the hanging wall. The shear dips to the west at approximately 450 and strikes 340 degrees.
Gold mineralisation at Rainbow occurs in shallow west dipping quartz +/-sulphide lodes within sheared basalts/sediments. Mineralisation occurs as one main lode, however other smaller lodes are apparent as is some supergene enrichment.
Dimensions
Rainbow mineralisation extends from 6888600mN to 6889200mN, 304750mE to 305000mE and 170 meters below surface. The shear system controlling mineralisation at Rainbow generally strikes North-South.
Otto Bore
Locally Otto Bore is situated within a NNW trending shear zone that dips moderately (50-60degrees) to the west. The mineralised zone largely hugs the rheological contact between the high-mg basalts and basalts. To the north mineralisation is also associated with a series of dolerites. Cross cutting NW trending faults are interpreted to disrupt the strike continuity of the main mineralisation and the southern extent of the Otto Bore deposit is terminated by a regional NNE trending shear. At depth higher grade mineralisation is typically associated with pervasive quartz veining and form short range southerly plunging shoots.
Dimensions
Otto Bore mineralisation extends from 6888600mN to 6889200mN, 304750mE to 305000mE and 170 meters below surface. The shear system controlling mineralisation at Otto Bore generally strikes North-South.
Kailis
Gold mineralisation at Kailis - Trump is hosted in quartz-sericite schist within a broad east-west trending, shallow to moderately dipping (40-50 degrees SSE) shear zone with a strike length in excess of 1800m. Mineralised intervals are often narrow (1-3m) but thicken to 8-20m in places. The shear zone encapsulates a high nugget mineralisation style with common occurrences of visual gold. The best gold grades tend to occur in the oxide and transitional zones with lower grades in the fresh rock. Mineralisation is open at depth but closed along strike.
Dimensions
The Kailis-Trump resource is contained within a + 40m wide shear zone which extends over a strike length of approximately 1,800m from 174,400mE to 176,200mE (MGA), and dips 30° to the south and flattens as move east toward Trump. Mineralisation is open at depth and to the west. It sits primarily within the oxide profile with economic mineralisation occurring at 30m below surface to 120m depth.
Bannockburn
The Central fault which hosts the Central orebody has a shallow northerly plunge and is the orebody on which the majority of the underground workings is focused There are a series of steeply east dipping lodes in the hangingwall of the central lode; these are interpreted as either tensional veins of reverse faults with shearing present along the veins. Black graphic shale units present within the stratigraphy have acted as a localised control on the mineralisation. The black shale units have taken up some of the deformation with stratigraphy parallel shearing and mafic sequences between the shales have extended to form steep east dipping extension veins.
Dimensions
Bannockburn mineralisation extends from 6849500mN to 6852500mN, 292500mE to 294500mE and 150 meters below surface. The Bannockburn gold deposit has a strike of 340° (NNW) and has a shallow plunge 5-10° to the NNW. The Bannockburn Shear dips steeply to the east, whilst the Central thrust varies from 30°dip to the west and east but is predominantly flat.
North Well
The mineralisation at North Well is confined to the Bannockburn Shear Zone (“BSZ”). The BSZ is a concave structure that has a strike length of approximately 30km, strikes roughly north south, and dips to the east. The BSZ is an approximately one kilometre wide zone of deformation that separates the basement granite/gneiss terrane to the west from greenstone terrane to the east. At North Well, the gold mineralisation is located approximately 400m from the main granite greenstone contact. Gold mineralisation is in east dipping basalts within a sequence of siltstones and acid volcaniclastics and occurs over a strike length of approximately 2600m and to a depth of 170m. Gold mineralisation is predominantly associated with quartz +/- sulphide filled shear structures. A strong S2/S3 lineation controls the mineralisation into a series of shallow (~25°) south plunging ore shoots that form en echelon zones along strike and down the dip of the shear zone. A series of east west late stage faults (some with dolerite intrusions) cross cut the mineralisation.
Dimensions
North Well mineralisation extends from 6853875mN to 6856525mN, 291700mE to 292500mE and 250 meters below surface. The Bannockburn shear generally strikes north-south along the North Well deposit.
Orelia
Orelia mineralisation consist mainly in a stockwork of quartz-carbonate-sulphide veins along the contacts of the Orelia dolerite and interflow sediment units that form a cigar/pipe like ore shoots. Cumberland has two styles of mineralization: the narrow high-grade often presenting boudinage and inch and swell withe quartz veins with minor sulphides and low grade stockworks of quartz and quartz-carbonate veins related to the main veins.
Dimensions
The Orelia Mineral Resource has an overall north-south strike, the mineralised corridor length is approximately 2,000m. The overall mineralised width of Orelia ranges between 100m and 400m, the majority is approximately 200m wide.
Mineralized zones are variable with true width ranging from 0.5m to 20m. They are extensive along strike and down dip, raging 100m up to 1000m along strike in case of the Cumberland mineralisation. The down dip extends range form 50m to 300m. Some of the lode present cigar like shapes.
Depth from surface is form 100m up to 500m approximately as the mineralisation plunges 30 degrees towards the south.