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Woodlawn Exploration

Near Mine Exploration

Figure 1: Woodlawn near-mine exploration prospects with underlying geology.

Heron’s near mine exploration strategy is to discover and delineate additional resources within easy trucking distance of the Woodlawn plant and thus extending the mine life and overall value of the operation. In the mid 1990s approximately 0.5 million tonnes of high-grade ore (of similar grades to Woodlawn, 20% ZnEq) was mined and trucked from the Currawang deposit, 10km north-west of Woodlawn. The Currawang area is therefore a focus for exploration with several other areas also being highly prospective. Land access in the area is generally good with standard land access agreements in place with the relevant farm owners.

The near mine exploration is targeting prospects extending up to 15km from the Woodlawn mine that have been identified from historic work and confirmed by the various geophysical surveys undertaken since 2014, including detailed aeromagnetic and gravity surveys. Areas of focus include extensions of the Woodlawn Volcanics north and northwest of the mine namely Currawang, Montrose, Kalua and the Murphy-Cowley Hills Trend, see Figure 1.

Currawang Prospect

The Currawang Mine is located 10km NW of the Woodlawn Mine (EL 7257) and historically produced approximately 0.5 million tonnes of high-grade polymetallic ore from underground in the early 1990s. Heron undertook a technical review at Currawang and in 2017 a diamond-drilling program (part funded by NSW New Frontiers Cooperative Drilling) targeted extensions to the known Currawang lenses.

Figure 2: Currawang Mine workings with recent drilling

Hole CWDD0002 intersected 5.3m of semi-massive, stringer-style zinc and copper sulphide mineralisation from 486m down-hole and below the main lens. This is interpreted to represent a new zone of significant mineralisation, see Figure 2. Down-hole geophysics was undertaken, which revealed an anomaly below the main workings.

The red-brown mineral is sphalerite (zinc sulphide) and shows hydrothermal, replacement style of formation with clots of dark green chlorite being original basalt fragments entrained within the sphalerite. The white mineral is quartz and indicates the vein-style of formation of this zone.

Montrose Prospect

Figure 3: MNRC004 showing sulphide zone intersected. The pyrrhotite present within the Montrose drill holes (MNRC001 – MNRC004) is sufficient to explain the various modelled EM plates which are shown.

The Montrose prospect is located 6.5km NW of Woodlawn, straddling the contact between the Woodlawn Volcanics and the Currawang Basalts. Previous drilling at Montrose focused on a 100m long section, with drilling giving a best result of 5.3m @ 4.9% ZnEq from 145m, and little attention was given elsewhere. Re-modelling of surface Moving Loop EM (MLEM) and Down-Hole EM (DHEM) at Montrose identified several conductors within a 700m zone. The geophysical responses are complex but point to a possible deep sulphide body that had not been drill tested.

Figure 4: RC drilling at Montrose

A modern high-powered MLEM was completed at Montrose and followed by an RC drilling program (4 holes for 981m, MNRC001 – MNRC004). All holes intersected weak to moderate disseminated pyrite / pyrrhotite mineralisation within either the Currawang Basalt or the underlying Woodlawn Volcanics with the pyrrhotite being sufficient to explain the EM anomalies. At the south end of the Montrose trend, hole MNRC004 contained a 20m zone (from 246m) of strong disseminated pyrite / pyrrhotite and chalcopyrite mineralisation with a basalt unit, see Figure 3. Such zones of sulphide mineralisation are often proximal to massive sulphide lenses and more work will be undertaken here.