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Updated mineral resource estimate for Colonna Zorzone deposit

Published by
Global Mining Review,

Alta Zinc Ltd (formerly Energia Minerals) has received an updated mineral resource estimate for the Colonna Zorzone deposit at its 100% owned Gorno Zinc project in Northern Italy from its consultants, Jorvik Resources Pty Ltd.

Alta Zinc commissioned a mineral resource estimation revision to include all drilling results obtained to date. The revision was primarily focussed on using the resource estimation to inform metallurgical and mining parameters for studies being completed on the project, and to increase the level of geological knowledge and confidence in the mineral resource. The updated information underpins:

  • The revised project configuration study that will be evaluated by potential financiers and off-takers.
  • The 2018 resource growth strategy focusing primarily on the North (Piazzole) and East (Pian Bracca) extensions.

The only material difference in data used in the new estimate compared to the previous May 2017 mineral resource estimate was the inclusion of eight diamond drill hole results received subsequent to the information cut-off date for the prior estimation. After consultation with Alta Zinc’s mining and metallurgical consultants, during this revised estimate significant attention was given to the encapsulation of geological, metallurgical, and mining parameters within the geological wireframes, and estimation block model. Particular attention was given to faulting, oxide/sulfide mineralisation distribution controls and locations, and the grade and dispersion of pyrite in the mineralisation.

The data generated has contributed extensively to the robustness of the mineralisation model, and the planning of future drilling, mining and processing techniques and other optimisation options.

As a result of the revised estimation the following material changes have occurred:

  • The global zinc grade has risen slightly (0.1%), increasing the contained zinc metal by 3000 t.
  •  Three mineralised zones within the resource have been modified to accommodate new drilling results.
  • Structural domaining of mineralised wireframes was completed to reflect more consistent local orientations of mineralisation.
  • The largest mineralised wireframe (Domain 10) has been modelled using ordinary kriging rather than co-kriging.
  • No material changes in the grade and contained metal of lead and silver or the estimation methodology has occurred.

Next Steps

Alta Zinc aims to increase the level of geological knowledge and confidence in the mineral resource and will continue to focus on implementing low-risk exploration strategies with the objective of expanding and improving the current mineral resource. Five mineralised areas have been identified adjacent to the existing mineral resource and plans are being developed to drill test these in 2018.

The commencement of these proposed drill programmes will be subject to obtaining sufficient funding. The company is currently investigating the most appropriate method to fund this exploration strategy.

Of these additional mineralised zones (North/Piazzole, East/Pian Bracca, Colonna Fontanone, Mt Arera and South/Riso Parina), the North (Piazzole) and East (Pian Bracca) extensions have been selected as the initial preferred options to expand the resource in 2018 given:

  • the historical geological information for these areas;
  • the results of recent underground mapping and sampling;
  • existing undergound access to be rehabilitated for drilling; and
  • the potential to improve the current mineral resource estimate in the most cost-effective way.

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