Astro Resources NL’s (ASX: ARO) latest exploration results have further upgraded the prospectivity of its 80%-owned Georgina IOCG Project in the Northern Territory.
The company had received promising assay results diamond drilling at the Banks and Leichhardt West prospects, and downhole geophysical surveying completed.
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,” Chairman, Tony Leibowitz, said.
“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.”
Assay Results
Assay results have been received for two diamond drill holes completed by previous owner, Greenvale Energy, at the Banks and Leichhardt West prospects in mid-2022. Visual results reported by GRV1,2 indicated that both holes intersected trace to minor chalcopyrite (copper mineral) 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 (e.g. bismuth which is commonly associated with Tennant Creek style IOCG deposits).
Results include:
• Leichhardt West hole KNXLW001RDD intersected 0.22% Cu from 536.05-536.3m associated with elevated bismuth and silver.
• Leichhardt West hole KNXLW001RDD intersected 0.15% Cu from 600-600.8m (end of hole) associated with elevated bismuth and silver.
• General increased anomalism in copper, bismuth and silver observed in spatial association with modelled 3D gravity and magnetic anomalies.
• Banks hole KNXBA001RDD intersected elevated copper, bismuth and silver from 433-440m.
The results are considered 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.
Downhole Geophysical Surveying
Highly-regarded contractor, Gap Geophysics, was engaged to conduct a downhole survey campaign at Astro’s highly prospective Central Tenement, comprising both a triaxial magnetic survey and EM. All three holes drilled in the Central Tenement area were surveyed as part of the campaign, with the Banks hole surveyed to 445m depth, Leichhardt West hole to 600m and Leichhardt East hole to 365m.
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. Magnetics are important for several reasons, including that remanent magnetism (a permanent magnetic field direction recorded in magnetic minerals) is observed in some IOCG deposits, such as at Tennant Creek. Furthermore, magnetic characteristics of overlying ‘cover’ rock types (such as the Helen Springs Volcanics, observed in all holes drilled to date at Georgina), may have a ‘masking’ or influencing effect on the response of underlying host rocks in surface geophysical data.
To complement data collected from the downhole surveys, a selection of drill samples displaying magnetic properties will be sent to CSIRO for magnetic remanence testwork. 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.
