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Location: 1 km S from Grassy, Tasmania, Australia
Level 7, 157 Ann StreetBrisbaneQueensland, Australia4000
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On 26 June 2023, Group 6 Metals Limited announced the inclusion of the Bold Head Mine to the reserve inventory and projected mine life of the Dolphin Tungsten Mine. The Bold Head Mine is a satellite deposit located 2km north of the Dolphin process plant and has similar geology and mineralogy to the larger Dolphin Tungsten Mine.Scheelite skarn mineralisation has formed within the metamorphic aureole of the Carboniferous Grassy Granite where it is in proximity to the calcareous sediments and carbonates of the Lower Grassy Group. The Dolphin and Bold Head deposits are hosted in a similar stratigraphic sequence.Dolphin Tungsten MineMineralisation is hosted within a 100-200m thick sequence of complex skarn mineralogy with two main horizons known as B and C Lens both of 10-30m thickness separated by a similar thickness of skarn altered volcanic sediments. Skarn formation and mineralisation have occurred where carbonates come into direct contact with the intrusion, or adjacent to brittle faults intersecting the intrusion. Mineralisation in the Dolphin deposit is best developed within C Lens which has several distinct mineralogical components including a garnet hornfels, a pyroxene-garnet hornfels and banded pyroxene garnet hornfels. B Lens is an upper dolomite horizon which has been variably hornfelsed and metasomatised with sporadic mineralised pyroxene-garnet skarn.The Dolphin deposit dips east to southeast at approximately 30° before steepening to 50° in proximity of the Decline Fault on the eastern margin of the deposit. The host stratigraphy is broadly folded by several southeast dipping open anticlines or vergence folds with wavelengths of a few tens of metres. Several major southeast and east trending normal faults associated with the folding cut the orebody into discreet fault blocks. The Northern Boundary Fault truncates the mine sequence to north juxtaposing the Lower Grassy Group against the Fraser Formation quartzite. The Mine Sequence is truncated to the south by the granite, the surface of which dips and plunges shallowly north and east.DimensionsSemi-continuous SE shallow plunging and dipping stratabound mineralisation extends 1150m in strike, by 750m width and dips from 80m above sea level in the west to 380m below sea level in the east.Bold Head MineThe Bold Head Mine is hosted in Proterozoic calcareous volcaniclastic sediments near the base of the Grassy Group and is a direct analogue of the Dolphin Orebody. Scheelite mineralisation is associated with calc-silicate skarn developed adjacent to the contact of the Lower Grassy Group and the Silurian Bold Head Granodiorite. Stratabound mineralisation is localized in and around two main carbonate horizons termed B lens and C lens as well as occurring in calcareous volcaniclastic rocks known as the Banded Footwall Beds. Mineralisation is best developed at the top and bottom of carbonate horizons directly in contact with faults, particularly the Boundary Fault and No 2 Fault and to a lesser extent the Western Fault.The host sequence is bound to the north, south and west by the Bold Head Granodiorite, and a major N-S trending reverse fault known as the Boundary Fault to the east. A major east-west trending ductile shear known as the Grahams Road Fault has attenuated and down warped the Grassy Group on its southern margin before truncation with the later granodiorite intrusion. These geological structures limit the potential for near mine resource extension drilling with the deposit constrained within a plunging basin of 650m strike length by 200m width. The deposit plunges south at approximately 20-30 degrees. The north-south striking No2 Fault offsets the mineralised lenses by 20m and was a major conduit for mineralisation. Skarn mineralisation varies between 1 and 15m in width within both B and C lens. Minor resource extensions are possible on the extreme southern margin and in the northwest of the basin.DimensionsSemi-continuous south shallow plunging and dipping stratabound mineralisation extends 550m in strike, by 200m width and dips from 110m above sea level in the north to 200m below sea level in the south.
