Australian diversified exploration company Astro Resources (ASX:ARO) has confirmed the presence of copper-bearing minerals with new exploration results at the Georgina Iron Oxide Copper-Gold (IOCG) Project in the Northern Territory.
The company says new assays have been returned from 2 diamond drillholes completed at the Banks and Leichhardt West prospects in mid-2022 by previous owner, Greenvale Energy (ASX:GRV). Visual results reported by GRV indicated that both holes intersected trace to minor chalcopyrite (copper) mineralisation in ‘prospective’ altered host-rocks.
Astro reports laboratory assays have now confirmed these visual observations of copper (Cu), and also revealed anomalous levels of other elements associated with IOCG deposits, such as bismuth.
“[RESULTS] indicate drilling may have hit the outer edge of a mineralised IOCG system within the Central Tenement”
New results recorded include hole KNXLW001RDD (Leichhardt) with 0.22% Cu from 536.05m, and 0.15% Cu from 600m; and KNXBA001RDD which intersected elevated copper, bismuth, and silver from 433m.
The company says 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 a ‘compelling’ similarity to Tennant Creek IOCG deposits.
Commenting on the drill results, Astro Resources 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 (electromagnetic) survey, 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 also reports that contractor Gap Geophysics was engaged to conduct a downhole survey campaign at the Central Tenement, which comprises both triaxial magnetic survey and electromagnetic (EM).
All 3 holes drilled in the Central Tenement area were surveyed as part of this campaign, with the hole at Banks surveyed to a depth of 445m, the Leichhardt West hole to 600m, and the Leichhardt East hole to 365m.
The main objective of the survey was to characterise the magnetic characteristics of the holes, noting magnetic surveying is one of the principal tools utilised in IOCG exploration.
Astro says remnant magnetism, which is a permanent magnetic field direction recorded in magnetic minerals, is observed in some IOCG deposits, such as Tennant Creek.
Magnetic characteristics of overlying cover rock types such as the Helen Springs Volcanics, which has been observed in all drillholes completed 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, the company reports 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 aiming to test for off-hole conductors, which may be the result of sulphide mineralisation.
Downhole magnetic responses were observed in basement rocks of all 3 holes, with downhole EM data yet to be finalised, and interpreted.
Following the completion of Leichhardt East hole KNXLE001RDD in December 2022, Astro reports work has been prioritised on mark-up and processing of drill core. This hole intersected anomalous copper mineralisation including bornite and chalcopyrite, ironstones with sulphide veining, widespread chlorite, and hematite IOCG-style alteration.
Since completion, the company says the hole has undergone detailed geological logging with bulk density, and magnetic susceptibility measurements taken. The drill core will also be cut, sampled and despatched for assay this month.
Once Astro has received final data from the surveys and magnetic remanence testwork, Leichhardt East assays and petrography, and a holistic review of the entire 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 rock types, alteration, and geochemistry results received for drillholes completed to date.
Astro Resources is an Australian diversified exploration company focused on advancing its Georgina Basin IOCG Project in the Northern Territory, the Governor Broome Mineral Sands Project in Western Australia, and the Needles Gold Project in Nevada, US.
Images: Astro Resources N.L.