Dover Castle Project

“Put simply, the new economy starts and ends with critical minerals.”
(Queensland Critical Minerals Strategy, 2023)

 

Overview

The historic Dover Castle tin mine and operations in its periphery were exploited for their rich tin, silver, lead and zinc deposits beginning in the late 1800s, and made a significant contribution to the economic development of the local community and region.

Given the potential scale of the company’s flagship project, Dover Castle, the discovery of significant quantities of critical minerals, and the global focus on transitioning to a low-carbon economy, Dover Castle Metals has the potential to not only reignite the local community and region, but also Queensland and Australia’s economies.

The geological setting of the Dover Castle Project is intricate, and characterised by a diverse range of rock types, including volcanic welded ignimbrites, rhyolitic lavas, pyroclastics, and intrusive rhyolitic volcanics. The geological structures and alteration minerals in the area include intense silicification, sericitisation, and phyllic alteration.

Mineralisation

Dover Castle is an unusual type of deposit known as “Porphyry Tin” of which only a couple are known in Australia, and are mainly found in South America especially Bolivia. Porphyry Tin deposits are small magmatic intrusive bodies, generally less than 500 metres diameter that have tin enrichment in their upper apex regions and silica rich surrounding haloes. They are also renowned for being endowed with zinc and lead sulphides, silver and indium as narrow vein deposits extending upwards from the hidden intrusive bodies when the latter may not be visible at surface. The exploration challenge is to find the buried tin rich section.

The Project exhibits a variety of mineralisation styles, each with its unique characteristics. These include massive, disseminated, vein, breccia, interstitial, and overprinting polymetallic ores. The Project is particularly notable for its polymetallic mesothermal lode type deposits, which are associated with linear, steeply dipping fault systems containing metals such as zinc, lead, silver, tin, indium, copper and others in a variety of mineral species and concentrations. The alteration enveloping the veins, characterised by intense silicification and sericitisation.

The mineralised veins and faults typically exhibit a steep eastward dip, aligning with the prevailing structural trends of the region, characterised by north-south or north-northeast orientations—a critical feature for geological interpretation and exploration in the Dover Castle area.

The alteration and metal associations are zoned on a metre to ore-field scale. Around individual or clustered ore lodes, proximal alteration is dominated by sulfidation and intense phyllic and/or argillic alteration at scales ranging from 0.1 to 10m. The ores exhibit zoning from Sb-As-Ag-rich in the north to Zn-Pb-Sn rich in the middle, and Cu-Zn rich in the south, indicating a progressive increase in ore precipitation temperatures to the south — a zonation also observed vertically. Exceptional enrichments include >3000 ppm Ag, >10% Sn, >5000 ppm In, >20% Pb and > 20% Zn in individual 1m drill samples. All associated with rocks dominated by massive galena, sphalerite, and local arsenopyrite. The current mineralisation envelope is displayed below.

 

Exploration and value capture

The Dover Castle Project 2024 Mineral Resource Estimate (MRE), prepared by Measured Group, an international, industry leading, technical resource consultancy firm, was based on previous MREs and yielded outstanding results. Rigorous data management, geostatistical analysis, and block modelling have been employed to estimate Mineral Resources. The classification has increased from 100% Inferred in 2023 to 33% Indicated and 67% Inferred in 2024.

The MRE consolidated assays from a total of 199 boreholes, including 175 reverse circulation (RC) holes and 24 diamond drill holes (DDH). The combined length of these boreholes, shown on the figure below, was ~33,155m with an average of 167m per hole. The majority of the drilling has been completed by the Company, primarily since August 2022.

The 2024 JORC Mineral Resource Estimate is shown in the table below.

A sectional view of the block model displaying the Sn resource is displayed below.

The shallow surface deposit indicates that it is amenable to open pit mining, and preliminary pit optimisation and economic studies are highly encouraging.

The deposit remains open in all directions and at depth; there is significant potential to increase the total MRE through additional targeted drilling, which commenced in December 2023.

The exploration program was underpinned around Measured Group’s data driven resource model, with real-time feedback proving invaluable throughout the process.

Dover Castle Metals is excited to expand and upgrade the project based on our current program of works, while also evolving our metallurgical and economic studies, which will boost confidence in the Dover Castle Project.

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