27 February 2025

Tertiary Minerals plc ("Tertiary" or the "Company")

Brunton Pass Copper-Gold Project - Drilling Results

Further to its announcement dated 16 December 2024, the Company is pleased to announce the results of drilling from the Phase 1 Drill Programme at its 100% owned Brunton Pass Copper-Gold Project in Nevada, USA.

Highlights:

·    Four reverse circulation percussion drill holes completed for a total of 890m in first pass drill programme.

·    All four holes intersected thick intervals containing anomalous copper values associated with fresh and oxidised pyrite and trace chalcopyrite.

·    Cumulative drill thicknesses up to 210m grading 170ppm copper (Hole 24TBPRC002) with values up to 0.19% copper over 1.53m.

·    Anomalous copper values extend to at least 212m vertical depth, 630m east-west and 560m north-south.

·    Surface mercury and arsenic indicator anomalies persist at depth.

·    Deeper diamond drilling is justified to test the core of the target Induced Polarisation ("IP") geophysical anomaly.

·    Petrographic and additional geochemical analysis planned to assist future drill targeting.

A map and two cross sections can be found at the end of this release illustrating the exploration results to date.

Commenting today, Patrick Cheetham, Executive Chairman of Tertiary Minerals plc said:

"This short drill programme, our first at Brunton Pass, has confirmed that the main IP geophysical anomaly is due to sulphide mineralisation and thick intervals of anomalous copper, mercury and arsenic have been found in association with this anomaly and over a wide area. However, only the peripheral parts of the IP anomaly have been intersected at depth so far and the stronger parts of the anomaly remain untested. Our working thesis is that we may have drilled within the halo of a porphyry copper deposit and that deeper drilling is justified."

Further Information:

Market Abuse Regulation

The information contained within this announcement is deemed by the Company to constitute inside information as stipulated under the Market Abuse Regulations (EU) No. 596/2014 as it forms part of UK domestic law by virtue of the European Union (Withdrawal) Act 2018 ('MAR'). Upon the publication of this announcement via Regulatory Information Service ('RIS'), this inside information is now considered to be in the public domain.

Detailed Information

The Brunton Pass Project (the "Project") is located in central Nevada, USA, 25km northeast of the high-sulphidation epithermal Paradise Peak gold deposit that produced over 1.6 million ounces of gold, over 44 million ounces of silver and at least 457 tons of mercury. The Project was acquired in 2021 after sampling of prospector small-scale surface workings revealed high copper values.

Mineralisation at Brunton Pass occurs within a series of limestones, siltstones and sandstones of the Triassic-age Luning Formation that have been widely converted by thermal metamorphism and metasomatism to hornfels and calc-silicate skarn units. These altered rocks form a 1.8km x 0.75km, uplifted "window" (horst block) in fault contact within younger Tertiary-age volcanic rocks. Evidence for an underlying body intrusive is found in surface outcrops of granite/granodiorite and at least two phases of diorite intrusion.

Soil sampling has delineated several copper-in-soil anomalies with individual grades of up to 953ppm copper. The largest of these anomalies in the southwest quadrant of the property has dimensions of 340m x 310m and they are mainly coincident with areas where rock grab samples contain percent-level copper values in small prospecting pits.

In 2022, the Company excavated two trenches in the area, T7 and T8, which encountered low-level copper mineralisation at surface including 27.4m grading 0.1% copper. Further details can be found in the news release dated 16 December 2024.

Drill holes 24TBPRC001 and 24TBPRC002 were drilled to test for mineralisation below the main copper soil anomaly and trenches T7 and T8.

Hole 24TBPRC001 intersected three intervals of anomalous copper with a cumulative downhole thickness of 123.45m and a weighted average grade of 149ppm copper as shown in the table below.

Mineralisation is mainly oxidised, but in the lower part of the hole the iron-sulphide mineral pyrite occurs with trace chalcopyrite. Sporadic quartz, gypsum and quartz-calcite veins were also intersected.

The main host to mineralisation in hole 24TBPRC001 is a biotite-rich rock which at surface has been mapped as a diorite intrusive but which may also be a metamorphosed sedimentary rock. Further mineralogical work is required to make a definitive determination.

Hole 24TBPRC002 was drilled approximately 265m east of, and directed towards, hole 24TBPRC001. It intersected a sequence of sandstones and limestones, mainly altered to hornfels and calc-silicate rock. It intersected two main zones with anomalous copper values having a cumulative downhole thickness of 210m and a weighted average grade of 170ppm copper. A 1.53m interval grading 0.19% copper was intersected from 59.71m downhole and the hole ended in mineralisation at 252.98m depth.

Drill Holes 24TBPRC003 and 24TBPRC004 were drilled some 630m apart and were designed to test a north-south striking IP geophysical (chargeability)  anomaly that stretches over several hundred metres and which is coincident with a broad zone of mercury and arsenic anomalies in soils and trenches.

Hole 24TBPRC003 was anomalous in mercury throughout its 137m length averaging 9.25ppm, which is approximately 450 times background levels of 0.02ppm mercury. The rocks were variably altered with hematite and manganese oxides within a mixed sequence of hornfels, calc-silicate rock and limestone. The hole was also targeting altered rocks adjacent to a granodiorite dyke which contained high gold values but the hole stopped short of target.

Hole 24TBPRC004, drilled some 560m south of hole 24TBPRC003, also intersected anomalous mercury, with anomalous arsenic and copper and a cumulative downhole intersection of 132.69m grading 130ppm copper including 103.64m grading 142ppm copper, 488ppm arsenic and 3.5ppm mercury. Disseminated pyrite was present through most of the drill hole.

Drilling has confirmed that the copper anomalies seen in surface soil samples and trench samples persist at depth to at least the lowest level tested in the current drilling (212m below surface in hole 24TBPRC002) and in an area 560m east-west and 560m north-south. This is a large body of rock containing anomalous copper values and, on the eastern side, anomalous indicator metals, mercury and arsenic.

The Company's working thesis is that this large area may represent the halo to a buried porphyry copper deposit and that deeper drilling is justified.

GLOSSARY

Chalcopyrite.  A copper-iron-sulphide mineral and the most abundant primary copper ore mineral. It has the chemical formula CuFeS₂.

Chargeability.  A measure of how strongly a rock mass polarizes when exposed to an electric field. It is higher in rocks containing, for example, disseminated sulphide minerals.

Calc-silicate Rock. A rock comprised primarily of calcium silicate minerals produced by metasomatic alteration of impure limestone or dolomite strata adjacent to an intruding igneous rock.

Epithermal Deposit. A type of mineral deposit that forms in the shallow subsurface and which is related in time and space to more deeply formed porphyry copper deposits.

Granodiorite. A coarse-grained igneous rock similar to granite.

High-Sulphidation. A type of epithermal mineral deposit characterised by high levels of sulphide minerals and which commonly contain high levels of arsenic and mercury.

Hornfels.  A group name for a set of contact metamorphic rocks that have been baked and hardened by the heat of intrusive igneous masses.

Induced Polarisation ("IP"). A geophysical exploration method where a rock mass below surface is exposed to an electric field to measure, in this case, chargeability.

Metasomatism. A process whereby a preexisting igneous, sedimentary, or metamorphic rock undergoes compositional and mineralogical transformations by chemical reaction with hydrothermal or other fluids.

Porphyry Copper Deposit. A hydrothermal deposit of copper formed within or in close proximity to porphyritic intrusive rocks. Usually large and low grade, they are the source of the majority of copper mined in the world today with several known examples in Nevada.

Pyrite.  An iron-sulphide mineral commonly found in association with other metal sulphides. It is commonly found in the outer zone of alteration associated with porphyry copper deposits It has the chemical formula and FeS₂. 

Skarn. A group name for rocks formed by metasomatism of limestones or carbonate rocks. Common adjacent to porphyry copper and other intrusives. Can included calc-silicate rock.

Notes:

1. The information in this release has been compiled and reviewed by Mr. Patrick Cheetham (MIMMM, MAusIMM) who is a qualified person for the purposes of the AIM Note for Mining and Oil & Gas Companies. Mr. Cheetham is a Member of the Institute of Materials, Minerals & Mining and also a member of the Australasian Institute of Mining & Metallurgy.

2. The news release may contain certain statements and expressions of belief, expectation or opinion which are forward looking statements, and which relate, inter alia, to the Company's proposed strategy, plans and objectives or to the expectations or intentions of the Company's directors. Such forward-looking statements involve known and unknown risks, uncertainties, and other important factors beyond the control of the Company that could cause the actual performance or achievements of the Company to be materially different from such forward-looking statements. Accordingly, you should not rely on any forward-looking statements and save as required by the AIM Rules for Companies or by law, the Company does not accept any obligation to disseminate any updates or revisions to such forward-looking statements.