Round 18 GDC Program Oonagalabi Diamond Drilling Final Report

Abstract

In June 2025, Litchfield Minerals Ltd (Litchfield) were successfully awarded co-funding in Round 18 of the Geophysics and Drilling Collaboration (GDC) Program administered by the Northern Territory Government. The co-funding was provided for two diamond drill holes testing magnetic anomalies within Litchfield's Oonagalabi Project in tenement EL 32279 in central Australia. The Oonagalabi prospect in the Harts Range hosts a sizeable Cu-Zn-Au-Ag mineralised zone within a 3 km trend of metasedimentary rocks, including calc-silicate rocks and marble. Previous drilling by Litchfield Minerals in March 2025 (hole OGRC002) indicated potential overprinting of copper and zinc by a Bi-Co +/- precious metal mineralisation associated with magnetite alteration, potentially related to a large magnetic anomaly. The co-funded drilling tested this anomalism at the Bomb Diggity target with an 800 m deep diamond drill hole (OGRD001) through a pipe-like magnetic feature generated through 3D inversions of 2024 drone magnetic data. The hole aimed to investigate if a magnetic intrusion could explain the magnetic anomalism in the Oonagalabi Main Zone and whether it was a potential source or trap for mineralisation. A second co-funded 300m diamond drill hole (OGDD002) aimed to test another magnetic anomaly, inferred to be a structural extension of the magnetic feature at Bomb Diggity into the western IP chargeability zone of the main Oonagalabi prospect. Hole OGRD001 at the Bomb Diggity Target drilled to 800 m depth including an 81.5 m RC pre-collar. The hole contained intercalated felsic gneiss and mafic amphibolite, with boudinage and sigma clasts in gneiss indicating high levels of shear. Magnetic susceptibility did not indicate a homogenous magnetic unit, as interpreted by geophysics after prior magnetic surveys. The geology observed may suggest that layers of amphibolite are responsible for the unexplained magnetic anomaly; however, the modelled anomaly does not follow expected local structural trends in stratigraphy. Quartz and calcite veins were minimal, as was presence of sulphides, except for a single 10 cm thick quartz-calcite vein containing apparent hydrothermal nickel, iron sulphide and molybdenite mineralisation. Hole OGDD002 drilled to 300.1 m depth and intersected typical Oonagalabi copper-zinc mineralisation within two limbs of meta-carbonate and calc-silicate rocks of the Oonagalabi Formation. Mineralised intervals within this hole contained pyrite, chalcopyrite, sphalerite, pyrrhotite, and galena, with minor magnetite, and very rare molybdenite. These sulphides range in coarseness and appear disseminated through the matrix of the rock (particularly in anthophyllite and calc-silicate zones). Some sulphides were observed within quartz and calcite veins and rarely appeared to show a sheared texture. There was no indication of a separate Bi-Co mineralising event, and magnetite appeared disseminated within the core, and in quartz and calcite veins.