The highest density veining and highest gold grades are developed in the hanging wall of the moderately NW dipping Generator Fault. The key timing relationship between formation of mineralisation and the Generator Fault and the age of the rocks below the Fault was previously unclear. A review of the East Hill FY22 drilling was conducted with the aim of understanding the potential for more and better ore at Yandan.

Work focused on defining the overall hydrothermal system including, host lithology, mineralisation style and controls on ore distribution. Mapping the distribution of the host lithologies defined volcanic facies contacts perpendicular to stratigraphy. Lava, tuff, and agglomerate juxtaposed against other volcanics suggests the presence of a NW striking graben or half graben that is coincident with the East Hill mineralisation.

Though the presence of the graben is yet to be confirmed, low sulphidation epithermal systems are hosted by similar structures worldwide. A conglomerate with clasts of sinter, epithermal vein and altered andesite, overlying well laminated sinter and strongly silicified and variably brecciated limestone was intersected by 21YEDD002. Herein termed the Epiphany Conglomerate, this unit was previously unrecognised and given the clast types is interpreted to represent reworked hydrothermal eruption breccia.

The Epiphany Conglomerate was also intersected below the Generator Fault in 21YEDD001 and 008. In the latter drill hole, a 1 metre interval containing clasts of epithermal quartz vein with well- developed bladed textures assayed 1 m @ 3.69 g/t Au from 599 m. Other stratigraphy below the Fault comprises siltstones interbedded with fossiliferous limestone /marl layers that display a moderate dip to the south consistent with mapped prospect-scale folding. Previous geological models interpreted the rocks underneath the Generator Fault to be Ukalunda Formation and part of the basement.

Given the presence of Epiphany Conglomerate and fossiliferous limestone the company now ascribe the units below the Generator Fault to the St Anns Formation that overlies the East Hill deposit. This was the significant breakthrough in geological understanding compared to previous work. Extensive brecciation is intimately linked with mineralisation at East Hill and was observed in many of the 2021 drill holes.

The extent and significance of the brecciation was not previously recognised and must be included in any system model. Vein styles and mineralisationtypes had been well documented by previous workers except for the relationship to brecciation. Veins vary with increasing depth from silica-pyrite to massive chalcedony and chalcedony with bladed replacement of carbonate, to banded crustiform colloform quartz-chalcedony-adularia carbonate veins with local bladed replacement, to veins with moss, needle and crystalline adularia and quartz overprinting chalcedony in the deeper central part of the system.

Vein textures and compositions suggest drilling has only tested the chalcedonic zone (i.e., upper part) of a low sulphidation epithermal system (Dong et al., 1995). Quartz textures typical of the deeper parts of an epithermal system were not observed. Veins with bladed textures and brecciated andesite with silica-illite alteration were also intersected underneath the Generator Fault.

Together with the reinterpreted geology model above, GBM now believes the Generator Fault crosscuts and offsets mineralisation. Similar to previous workers (Morrison and Beams, 1995) GBM interprets Yandan to be a hot spring style system that may have been localised in a graben. Sinter is underlain by hydrothermal breccia which is overprinted by chalcedonic and crustiform-colloform banded veins.

The veins are more prominent deeper in the system and have potential to continue at higher grade underneath the Generator Fault.