Rockfire Resources plc (LON: ROCK), the gold and base metal exploration company, is pleased to announce its unaudited interim results for the six months ended 30 June 2020 and provides an update in respect of the Company's exploration activities on its 100%-owned licences in Queensland, Australia.
Rockfire has maintained a focused and strategic campaign of continuous exploration on its portfolio of tenements. The Company's exploration activity has focused on the Plateau gold deposit ("Plateau"), which lies within the Lighthouse tenement and is situated 17km east of the operating Pajingo Gold Mine. The geological and mineralisation model for Plateau is based on the operating Mt Wright Gold Mine, which lies 47km to the north east of Plateau.
Exploration by the Company at Plateau has identified a gold mineralising system similar to that at Mt Wright. Similarities in geology, mineralogy, geophysics and geochemistry have been supported by the intersection of broad, low-grade gold intervals over several hundred metres, starting from surface. The majority of the gold ore at Mt Wright occurs at depths between 400 m and 850 m from surface, with underground mining reaching depth of 1,200m below surface. Nearly 1.5m ounces of gold have been mined at Mt Wright and Rockfire is exploring for a similar high-grade core to the gold already intersected at Plateau.
Recent, post-period exploration has intersected various types of sulphides, with the observation of pyrrhotite being made for the first time in drilling at Plateau. Pyrrhotite is an important component of the high-grade core at Mt Wright and Rockfire is keenly awaiting further drill results, including core from this pyrrhotite zone. The Company is encouraged by the observation of these sulphides, indicating multiple mineralising episodes which is often favourable for gold deposition and enrichment. Rockfire's Phase 2 diamond drilling programme is nearing completion, which is designed to drill 6 holes to approximately 500m from surface to test for a high-grade gold core to the mineralising system. Drilling results are pending.
· 1,155m of reverse circulation (RC) drilling in six holes was completed at Plateau in January. The results included:
§ 171 m @ 0.4 g/t Au in hole BPL027 (from 26 m)
§ 170 m @ 0.4 g/t Au in hole BPL030 (from 37 m)
§ 154 m @ 0.2 g/t Au in hole BPL026 (from 97 m)
· Silver assays include 187 m @ 6.3 g/t Ag (from 15 m) and 203 m @ 3.68 g/t Ag.
· Rock sampling at Cardigan Dam returned gold assays up to 23.4 g/t Au.
· 3D magnetic imagery confirmed a gold target down to and beyond a depth of 600 m at Plateau.
· RC drilling recommenced at Plateau in June, with approximately 1,000 m of drilling planned.
· A 6 hole diamond drilling programme commenced at Plateau in late July to test the gold system at depths of around 500m from surface.
RC drilling of 1,155 m in six drill holes was completed in January at Plateau. Drilling was designed to test to depths of around 250 m below surface and to follow-up hole BPL025, which intersected 177 m @ 0.5 g/t Au in December 2019.
These follow-up holes returned extensive intercepts of continuous gold mineralisation, comparable to hole BPL025. An important project milestone was reached with a + 2.0 g/t Au zone being encountered over 11 m from 145 m downhole. All drill holes encountered broad intervals of sulphides and each hole also returned significant silver assays.
All drill holes hit gold, expanding the Plateau footprint to +200 m long, +70 m wide and +200 m deep. Assay results included 171 m @ 0.4 g/t Au in hole BPL027, including 39 m @ 1.0 g/t Au and 11 m @ 2.3 g/t Au (from 145 m). Hole BPL030 intersected similar lengths and grades of 170 m @ 0.4 g/t Au, including 10 m @ 1.0 g/t Au (from 54 m) and 19 m @ 1.0 g/t Au (from 174 m). These holes extended mineralisation more than 100 m east of drill hole BPL025.
Long intervals of anomalous silver (Ag), zinc (Zn) and lead (Pb) were intersected, providing further evidence that Plateau is a significantly large mineralising system. Silver assays up to almost one and a half ounces per tonne (43.9 g/t Ag) over a 6 m section of drilling, including 1 m @ 113 g/t Ag represent some of the highest silver grades encountered so far at Plateau.
During February to May and whilst the wet season was active in North Queensland, Rockfire completed further technical interpretation on Plateau. Technical data analysis and comparison studies between Plateau and the nearby Mt Wright Gold Mine remained a priority for the Company.
Mr Gregg Morrison of Klondike Exploration Services, the pre-eminent expert in North Queensland geology, analysed the results of the Company's work and continues to assist Rockfire's geology team. Mr Morrison developed the multi-element geochemistry classification and zonation model which was used to characterise the Mt Wright Gold Mine. Gregg has observed many similarities between Plateau and the early observations at Mt Wright.
At the beginning of June 2020, the Company announced that modern, three-dimensional ("3D") reprocessing of aeromagnetic data flown in 2011 by Ramelius Resources at Plateau was helping to clarify drill targets at depth. A gold target down to and beyond a depth of 600 m was evident and appeared to support a steep easterly plunge of the low-magnetic mineralised rhyolite host. The geophysics also revealed a rolling, north-south change in dip direction of the southern margin of the host rhyolite.
Rockfire resumed RC drilling at Plateau on 11 June 2020, with six drill holes and approximately 1,000 m of drilling planned. This drilling ("Phase One"), includes the drilling of a water bore to provide sufficient water for planned diamond drilling. This first phase of RC drilling was designed to define additional gold close to surface at an area called the "Central Breccia" and especially within the top 100 m. A second aim of this phase of drilling was to test mineralisation down to 200 m in areas where drilling is sparse, to increase confidence in gold grades to these depths.
Rockfire Project Portfolio
During the period, Rockfire sought quotations from geophysical companies to fly aeromagnetic surveys over the Company's two porphyry copper projects, also in Queensland, Australia. Both projects are listed in the "Global Mineral Resource Assessment", published in 2010 by the US Geological Survey.
The Copperhead Project is an under-explored porphyry copper/molybdenum deposit. Exploration success from the early 1970's shows indications for bulk-tonnage, low-medium grade potential. Based on 5 diamond drill holes drilled by Carpentaria Exploration in 1972, Copperhead has a non-JORC historical estimate of mineral content of 35,000,000 t grading 0.35 % Cu Eq., with significantly more growth potential.
Copper Dome is a porphyry copper/gold deposit which lies approximately 50 km to the southwest of Copperhead. In 1972, three percussion drill holes and six diamond drill holes, totalling 1297m were drilled. Each drill hole intersected geological/alteration features which are indicative of a large-scale porphyry deposit. Best results from this drilling include 12m @ 0.61 % Cu (including 3m @ 1.24 % Cu), 15m @ 0.88 % Cu (including 5m @ 2.28 % Cu), 24m @ 0.27 % Cu, 12m @ 0.17 % Cu and 38m @ 0.13 % Cu. Only sporadic gold analysis was done, with gold values peaking at 1.86 g/t Au. This indicates the potential for the porphyry system to contain a significant gold component.
Rock sampling by previous explorers focussed on faults in close proximity to historical copper workings. The best rock sampling results included 5.4 % Cu (0.41 g/t Au), 1.8 % Cu (13 g/t Au), 0.19 % Cu (2.45 g/t Au), 1.5 % Cu (0.2g/t Au) and 1.8 % Cu. Subsequent rock sampling by Rockfire in March 2019 returned peak values of 23.4 % Cu, 3.2 g/t Au and 952 g/t Ag.
Both projects will be flown by a helicopter-supported magnetic survey, which is expected to be completed prior to the end of the 2020 calendar year. The helicopter survey will provide optimum terrain contouring in both areas, which are highly undulating.
Rockfire also holds the Marengo, Kookaburra and Monarch gold licences in Queensland. Exploration activity is currently focussed on the Plateau Gold Deposit within the Lighthouse tenement and our potentially large-scale copper projects. During the reporting period, the small New Leyshon exploration licence was relinquished after a thorough review of past exploration demonstrated low prospectivity. The tenement was originally acquired for its proximity to the Mt Leyshon Gold Mine however, with low exploration potential, the licence was subsequently relinquished.