Copper explorer Coda Minerals has credited January ambient noise tomography survey activity with giving it a better understanding of structural controls on mineralisation at its flagship project in South Australia and potentially opening an “exciting new avenue to pursue a tier-one IOCG discovery”.
Coda said the ANT programme – three surveys covering the broader “Emmie System” – resulted in a “material improvement in the company’s understanding” of the overall system and links between the Emmie Bluff sediment-hosted copper-cobalt deposit and the deeper Emmie iron oxide copper-gold (IOCG) mineralisation that underpinned its March 2023 scoping study.
The Emmie area covered included the basement-hosted IOCG targets, shale-hosted Emmie Bluff and Coda’s Elaine prospect. It has a whopping 701 square kilometres of ground about 100km south of BHP’s giant Olympic Dam copper-uranium-gold operation.
Coda said identification of a potentially significant north-east/south-west trending basement structure associated with IOCG mineralisation had highlighted new targets to test for copper-gold mineralisation at Emmie IOCG.
The company recently started a prefeasibility study focused on potential underground development at Emmie Bluff, and the satellite MG14 and Windabout near-surface copper-cobalt-silver deposits.
Deeper Emmie IOCG copper-gold mineralisation is immediately south-west of Emmie Bluff.
Coda is using an ANT survey system developed locally by Adelaide-based Fleet Space Technologies.
ANT is a geophysical method that uses faint ground vibrations produced by surface Rayleigh waves, recorded by seismic stations to image the subsurface. About 50 surface geophones were deployed in the survey areas to generate ambient seismic noise between stations. Fleet Space is also doing processing and velocity modelling of the data, which is reviewed by external consultants.
Coda said the previously unknown large-scale, north-south trending structure that appeared to control both main types of mineralisation so far drilled at Elizabeth Creek was potentially significant.
“The large palaeosurface valley resulting from these structures has provided the space for the deposition of shale-hosted copper-cobalt,” the company said.
“ANT data indicates that this valley extends well beyond the existing Emmie Bluff copper-cobalt resource, opening up numerous new resource expansion and exploration opportunities.”
Coda CEO Chris Stevens said: “Geophysical surveys are like a box of chocolates – you never know what you’re going to get, but in this case the high-quality ANT data has exceeded expectations.
“Through the ANT data, we have materially improved our understanding of the mineralising system controlling the copper-cobalt at our flagship Emmie Bluff deposit. This new information helps us to explain the relationship between Emmie Bluff and the deeper IOCG copper-gold mineralisation beneath it.
“We now have new targets, backed by strong geophysical evidence, to test for extensions of the shallower copper-cobalt mineralisation.
“At Emmie IOCG, the survey has helped our understanding of why we have so far only intersected high-grade, but small-scale conduits. The data appears to define a new structure to target where larger-scale mineralisation may have dropped out into a full-scale IOCG.”
Coda recently wrapped up a close-spaced gravity survey over the Emmie Bluff and Emmie IOCG prospects and says it will soon start a geologically constrained 3D inversion of the results in combination with the ANT data.
“The resultant model will precisely delineate major geological units and will allow for exceptionally detailed IOCG drill targeting,” it said.
“Hole planning for the next round of drilling at Emmie IOCG will commence following the receipt of that model – anticipated in Q2 2023.”