The Mulga Tank Project (Impact Earning 100%)

Project Summary

The Mulga Tank Project covers 425 square kilometres in the emerging nickel province of southwest Western Australia. The region is host to Sirius Resources’ Nova nickel deposit; BHP Billiton Ltd – St George Mining’s Dragon disseminated nickel sulphide discovery; AngloGold Ashanti – Independence Group’s Tropicana gold mine; and the significant uranium deposit at Mulga Rocks (Figure 1).

The Project is highly prospective for:

  • bulk tonnage nickel deposits such as Mount Keith near Leinster, WA and the very large and significant Dumont deposit in Quebec that is progressing towards development (Royal Nickel Corporation (TSXRNX):  Reserve 1.1 Bt at 0.27% nickel, Measured, Indicated and Inferred Resources of 2.1 Bt at 0.26% nickel for a contained 8 Mt of nickel with significant credits for contained cobalt, PGE’s and magnetite);
  • high-grade nickel sulphide deposits similar to those at the nearby major WA mining centres of Kambalda and Forrestania;
  • gold deposits hosted in faults and shear zones within the greenstone belt stratigraphy similar to the many multi-million ounce deposits found throughout the Eastern Goldfields Province of the Yilgarn Craton; and
  • uranium deposits hosted by Cainozoic palaeochannels such as the nearby Mulga Rock deposit.

A review and synthesis of previous exploration data is ongoing at the Project.

Figure 1: Location of the Mulga Tank Project and significant nickel sulphide deposits (red dots). 

Project Snapshot

  • Highly prospective for both nickel and gold deposits, with significant potential for disseminated and massive nickel sulphides.
  • Located in the emerging nickel province of south west Western Australia – the Minigwal Greenstone Belt.
  • Recent analysis of previously unknown PGE and cobalt assay results include:

11 m at 0.37% nickel, 0.07 g/t PGE (Pt+Pd) and 116 ppm cobalt from 202 metres in MTD003 including 1 m at 1.12% nickel, 0.5 g/t PGE (Pt+Pd) and 271 ppm cobalt

  • Much of the nickel sulphide mineralisation is primary magmatic sulphide hosted in ultramafic rocks.
  • Two significant target areas, the North Feeder and South Feeder Prospects, have been identified with the potential to host high grade massive nickel sulphide deposits.
  • An award of $134,000 under the State Government’s Industry Drilling Programme will advance the identification of priority targets and significantly increase the scope of planned drill programmes scheduled to commence in late 2013.

Previous Exploration

Previous exploration at Mulga Tank focused on the dunite, a circular, strongly magnetic feature 3.5 km by 4 km in diameter that is interpreted to represent a flat-lying ultramafic sill (Figure 2).

Figure 2: Plan map of the Mulga Tank Dunite (airborne magnetic TMI image) showing the basal contact of the dunite, Pan Handle located in the northwest, > 800 ppb nickel-in-soil outline, historic diamond holes (black diamonds), RC holes (white circles), significant results, section lines, and target areas (A to D).

Although only four diamond holes have been drilled into the dunite, all of them returned wide intercepts of Mount Keith-style disseminated nickel mineralisation(Figures 2-4).

MTD001:     264 m at 0.2% Nickel from 68 m including 2 m at 0.93% Nickel (Figure 2 and 3);

MTD002:     214 m at 0.19% Nickel from 60 m including 1 m at 0.5 % Nickel (Figure 2 and 4);

MTD003:     Approximately 248 m at 0.2% Nickel1 from 60 m (Figure 3); and

DD1A:          Approximately 14 m at 0.3% Nickel1 from 195 m including 1 m at 0.6% Nickel and 12 m at 0.18% Nickel from 148 m (Figure 2).

A recent review of this diamond drill core has confirmed that much of the nickel sulphide mineralisation is primary magmatic sulphide hosted in ultramafic rocks. (Figures 5 & 6)

In places, the sulphide occurs as narrow massive layers up to several centimetres thick (Figure 5).

Thin section analysis of the disseminated nickel identified extractable nickel-cobalt minerals such as pentlandite, heazlewoodite and linnaeite.

Massive Nickel Sulphides and Potential for PGE and Chromite Mineralisation

A five-metre zone of ultramafic mesocumulate breccia (Hole MTD003) hosts narrow zones of massive nickel sulphide mineralisation. Although sampling of the breccia is incomplete, limited previous assays returned:

 MTD003: 1 m at 1.1% Nickel from 209 m and 1 m at 0.8% Nickel from 212 m (Figure 2 and 3).

The drill holes also showed that the dunite is flat lying, and therefore prospective for massive nickel sulphides at shallow depths, similar to the Perseverance nickel deposit north of Kalgoorlie that contains 45 Mt at 2.05% nickel. Only two of the diamond drill holes intersected the basal contact of the dunite.

Limited bedrock-cover interface percussion drilling completed by previous explorers focused on the southern contact of the dunite and returned a best intercept of:

 MRC09: 6 m at 0.9 % Nickel from 64 m including 2 m at 2% Nickel (Figure 2).

A zone of anomalous gold up to 0.2 g/t and chromium up to 0.14% occurs below the nickel breccia zone in MTD003 indicating the potential for significant zones of precious metals such as Platinum Group Elements (PGEs).

Given the limited exploration completed to date, and the significant size of the Mulga Tank dunite, Impact considers these significant previous drilling results to be very encouraging for the discovery of both high grade disseminated and massive nickel sulphide deposits.

Figure 3: Section line 518850 mE showing the interpreted ultramafic rocks, nickel-in-soil values, previous drilling and results, and conceptual disseminated and massive nickel sulphide lenses associated with the northern feeder vent.

Figure 4: Section line 519900 mE showing the interpreted ultramafic rocks, nickel-in-soil values, previous drilling and results, and conceptual disseminated and massive nickel sulphide lenses associated with the southern feeder vent.

Figure 5: Layer of massive pyrrhotite-pentlandite in diamond drill core from 210 m in Hole MTD003. The core is about 10cm wide.

Figure 6. Disseminated pyrrhotite-pentlandite in MTD001 at 154 m that indicate a magmatic sulphide origin.

Exploration Model, Volcanic Feeder Vent

Impact has now identified two possible feeder-vent structures –the North Feeder Prospect and the South Feeder Prospect (Figure 2).

High grade massive nickel-sulphide deposits hosted within ultramafic intrusions such as at Perseverance commonly occur near feeder-vent systems close to the base of the intrusions. Previous diamond drilling has shown that the Mulga Tank dunite is shallow dipping and therefore has significant potential to host high grade massive sulphides at shallow depths (Figures 3 and 4).

Coincident strong airborne magnetic and IP anomalies were interpreted to indicate the presence of highly magnetic and chargeable sulphide mineralisation adjacent to the interpreted feeder-vents (Figure 2). In addition, highly elevated nickel-in-soil partial leach assays confirmed the potential for significant deposits of massive nickel sulphide at depth near the interpreted feeder-vents (Figures 3 and 4).

Next Steps

Impact is awaiting the results of a ground EM survey that will support the identification of specific drill targets. In addition, a grant of $134,000 under the State Government’s Industry Drilling Programme, will allow Impact to significantly increase the size of its planned drill programmes scheduled to commence later in the year.