Astro Resources NL (ASX:ARO) has strengthened the iron oxide copper gold (IOCG) credentials of Georgina Project in the Northern Territory with assays from Banks and Leichhardt West prospects confirming copper-bearing minerals and anomalous pathfinder elements for IOCG mineralisation.
The assays from diamond drilling completed by previous owner Greenvale Energy Ltd in mid-2022 have revealed similarities to IOCG deposits in the Tennant Creek region.
A hole at Leichhardt West, KNXLW001RDD, intersected 0.22% copper from 536.05-536.3 metres and 0.15% copper from 600-600.8 metres at the end of the hole and both intersections were associated with elevated bismuth and silver.
Astro has also completed downhole magnetic and electromagnetic geophysical surveying while core from Leichhardt East is being prepared for assay and expected to be delivered to the laboratory later this month.
“Positive early results”
Astro’s chairman Tony Leibowitz said: “I am pleased with the positive early results that indicate drilling may have hit the outer edge of a mineralised IOCG system within the Central Tenement.
“We’re now awaiting final results of our EM surveys, as well as assays from Leichhardt East, with this data to feed into a detailed review of the Central Tenement area to help plan next steps and prioritise drill targets.”
Astro’s East Tennant tenement holding, showing neighbouring holders and key regional prospects.
Chalcopyrite signs
Visual results reported by Greenvale indicated that both holes intersected trace to minor chalcopyrite (copper) mineralisation in prospective altered host rocks.
Laboratory assay results have now confirmed these visual observations of copper, as well as revealing anomalous levels of other elements commonly associated with IOCG deposits, eg bismuth which is commonly associated with Tennant Creek-style IOCG deposits.
General increased anomalism in copper, bismuth and silver were observed in spatial association with modelled 3D gravity and magnetic anomalies.
The Banks hole KNXBA001RDD intersected elevated copper, bismuth and silver from 433-440 metres.
Significant results
Astro considers the results as being highly significant as they suggest the drilling may have intersected rocks peripheral to an IOCG system, indicate a hydrothermal component to the Banks and Leichhardt West prospects, and illustrate compelling similarity to Tennant Creek IOCG deposits.
Gap Geophysics, a highly-regarded contractor, was engaged to conduct a downhole survey campaign at Astro’s highly prospective Central Tenement, comprising a triaxial magnetic survey and EM.
Downhole surveys
All three holes in the Central Tenement area were surveyed, with the Banks hole surveyed to 445 metres depth, Leichhardt West hole to 600 metres and Leichhardt East hole to 365 metres.
The main objective of the survey was to characterise the magnetic characteristics of the holes, as magnetic surveying is one of the principal tools utilised in IOCG exploration.
To complement data collected from these surveys, a selection of drill samples displaying magnetic properties will be sent to CSIRO for magnetic remanence test work.
In addition to triaxial magnetic surveying, downhole EM was also conducted. Downhole EM is designed to test for off-hole conductors, which may be the result of sulphide mineralisation.
Downhole magnetic responses were observed in basement rocks of all three holes, with downhole EM data yet to be finalised and interpreted.
Next steps
Once the company has received final data from the surveys and magnetic remanence test work, Leichhardt East assays and petrography, a holistic review of the whole Central Tenement area will be conducted.
This will include a broader review of elevated magnetic and gravity responses interpreted to be prospective for IOCG-style mineralisation, supported by the rock types, alteration and geochemistry results received for drill holes completed to date.