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NQ Minerals to explore Hellyer Mine potential

Published by , Editor
Global Mining Review,

NQ Minerals Plc has announced that it plans to break a 10-year hiatus in exploration work at its highly prospective Hellyer Project, located in the Mt Read Volcanic Belt; a geological terrain in NW Tasmanian renowned for large scale and high-grade polymetallic (copper-lead-zinc-silver-gold) deposits.

The Hellyer deposit was a large scale, very high-grade lead-zinc mine. Past production under Aberfoyle (1986 – 2000) totalled 16.5 million t at 13.9% zinc, 7.2% lead, 0.4% copper, 167 g/t silver and 2.5 g/t gold and under Bass Metals (2010 – 2012) totalled 0.5 million t at 7.8% zinc, 4.2% lead, 0.3% copper, 101 g/t silver and 1.7 g/t gold from the Fossey Mine. There has been no exploration work undertaken on the Hellyer Mine Lease since underground mining operations ceased in mid-2012.

NQ is currently producing lead and zinc concentrates (with significant gold and silver credits) by reclaiming the Hellyer Mine tailings generated from the former mining operations and processing through the Hellyer concentrator plant at the rate of over 1.2 million tpy.

Since acquiring the exclusive rights to the underground resources at Hellyer from Bass Metals Ltd on 7 January 2020, NQ has commenced interrogating a high-quality data set acquired from Bass. It is clear that work essentially ceased ‘mid-stream’ in early 2012 and left several significant ‘open’ targets’ at a time when Bass was at the cusp of gaining a greater understanding of the key ore-deposit indicators. This follows their discovery of the Fossey deposit only 150 m south of the large-scale Hellyer deposit, but in the footwall zone, below the classic ‘Hellyer ore position’, where the majority of exploration was targeted for the previous 30 years.

10 years later, with the benefit of significantly more advanced exploration tools, specifically more powerful geophysical techniques, NQ has commenced a systematic review of these targets, focused initially on ‘prioirty-1’ areas, namely in close proximity to the known deposits and existing mine infrastructure.

NQ Minerals’ Executive Chairman, David Lenigas, said; “There is now significant potential to define new and extensive high-grade mineralisation at Hellyer, one of the world’s great polymetallic high-grade mines. We are operating in one of the mostly highly mineralised geological terrains in the world and we have a golden opportunity to continue Bass’s work from 2012 to build-up the existing significant underground resource inventory and extend the Hellyer mine life to underpin this operation for a very long time. The tailings reprocessing Phase 1, now running at over 1.2 million tpy, has another 8 years to run with its current lead/zinc strategy and will generate significant cash flow for the company, but it’s a finite resource. Stage 2 of the current operations will focus on recovering the significant gold and silver inventory in the tailings, but metallurgical test work continues with respect to this next phase of tailings reprocessing. To move Hellyer back into underground mining is a logical and natural progression, especially considering we have the Hellyer plant fully operational.”

Mineralisation on the Hellyer Mine Lease comprises massive base metal sulphide lenses within the core of a broadly folded volcanic-sedimentary sequence which plunges to the north-northeast. As the mineralisation generally does not outcrop, geophysics has played a vital part in mineral discoveries in the Hellyer region and down-hole electromagnetics (DHEM) is a core technique. NQ has now completed a first pass review of historical DHEM data for 8 surveyed drill holes in the priority-1 area. Remodelling work of the DHEM undertaken by Southern Geoscience, with input from former Hellyer geologists, has highlighted the significant enhancement in modelling software, and has identified four high priority targets/zones, which warrant follow-up exploration work, represent significant potential for further base metals discoveries.

Next Steps

NQ is planning a major programme to assess these preliminary modelled targets which is planned to include:

  • Assessing the condition of each of the DHEM surveyed drill holes and possibly neighbouring holes to be able to re-enter and case with PVC to the required depth. The PVC casing is necessary to protect the DHEM probe which is lowered into the drill hole and costs ~US$100 000 to replace if the hole collapses and it cannot be recovered.
  • As required, clear the drill hole utilising a small drill rig and case with PVC pipe.
  • Resurvey and clear lines at surface to enable wire loop arrays (several kilometres in length) to be laid out on the ground as part of the new DHEM survey – for each target zone.
  • Mobilise geophysical contractor to Hellyer to undertake the DHEM surveys.

There have been significant enhancements to DHEM equipment since the last DHEM surveys were run at Hellyer approximately 10 years ago. This creates a new opportunity for NQ to leverage off major technical advances to better resolve spatially any potential targets and execute better targeted follow-up drilling if warranted. This includes:

  • Utilising much higher electrical power/current inputs to penetrate far deeper into the ground to detect any conductive bodies at greater distances from exploration drill holes.
  • Optimised Electro-Magnetic (EM) loop arrays to get better 3D resolution of any conductive units identified – through varied coupling scenarios.
  • Access to significantly enhanced modelling software to also resolve the position and dimensions of any modelled plates.
  • Working in the context of an updated geological target model which extends deeper below the traditional ‘ore-horizon’ such as hosts the new Fossey and McKay discoveries.

NQ plans to undertake this work program on site in the Australian Spring, possibly commencing October-November 2020, depending on rig and crew availability.

These technological advantages coupled with the important geological advances achieved by Bass, pre 2012, makes for a compelling exploration opportunity. There are further targets to follow-up, but those targets discussed were selected due to their proximity to existing mining and processing infrastructure leading to rapid development should they be proved up. Insights gained from these first four targets will be applied to other currently lower priority targets.

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