AMC at Complex Orebodies Conference 2018

AusIMM has partnered with the Sustainable Minerals Institute to host a conference aiming to cover the spectrum of challenges faced by Complex Orebodies. The Complex Orebodies Conference will take place in Brisbane,  19-21 November 2018. AMC Consultants is pleased to sponsor the lanyards and name badges for this conference and and  looks forward to presenting two papers, Martabe Gold Mine, Indonesia: a positive solution for positive reconciliation and A comparison of opportunity and risk in deep sea and terrestrial metalliferous mining projects.

Martabe Gold Mine, Indonesia: a positive solution for positive reconciliation

Session 4: 3:10 PM – 4:45 PM Monday, November 19, 2018

Maree Angus

The prospect of a positive mill reconciliation at a mine is a double-edged-sword. Much back slapping happens. The bank and the board can’t get enough until the downside becomes apparent. Over a prolonged period, there becomes an issue with market perception and the potential for shareholders to be misinformed regarding the potential value of the project. In addition, there are impacts on mine scheduling, waste allocation (or lack thereof), government expectations and the potential for misguided external assumptions regarding the ‘unexpected’ results.

The Martabe Gold Mine has shown a significant undercall, in the order of 25% total gold metal, between the Mineral Resource Estimates (MRE) and Grade Control Estimates since production commenced in 2012. Recently the undercall has been reduced by incorporating the use of grade control drilling in the Resource estimates. Despite the recent improvement in reconciliation, drilling in 2017 at both Purnama and Barani showed that infill RC holes were producing significantly higher grades than the block model.

During 2017 PTAR commissioned a variety of studies aimed at qualifying the causes of, and quantifying the undercall. Two key factors were identified as the cause: 1. Underestimation of contained gold due to an ‘information effect’ whereby many higher grade, small scale structures cannot be accurately defined in wide spaced resource definition drilling; 2. Volume variance effect between diamond drilling and reverse circulation drilling sampling. The outcome of the studies enabled development of a set of options that can be used at the resource estimation stage to mitigate the undercall going forward. Adjustments have been applied to the inputs to the 2017 MRE at Martabe and reconciliation will be monitored and the adjustments reassessed prior to future MRE updates. The studies that have been competed ensure that the material information related to the adjustments can be reported in a transparent manner in accordance with the JORC Code principles.

A comparison of opportunity and risk in deep sea and terrestrial metalliferous mining projects

Session 12: Wednesday, November 21, 2018 3:25 PM – 4:40 PM

Ian Lipton

The existence of metalliferous mineral deposits on the deep-sea floor has been known since manganese nodules were discovered in the Arctic Kara Sea in 1868. Modern exploration with the aim of defining commercially viable base and precious metal deposits began in the 1970s and gained further momentum in the last decade. High grade deposits have been delineated but investors remain cautious, perhaps considering deep sea mining projects to be riskier than terrestrial projects.

This paper compares opportunities and risks presented by terrestrial base metal mines and those presented by three deep sea mineral deposits; the Solwara 1 volcanic-hosted massive Cu-Au-Ag sulphide deposit, the Atlantis II Deeps sedimentary base metal sulphide deposit and the Mn-Ni-Cu-Co nodule deposits of the north-eastern Pacific Ocean. These are advanced deep-sea projects with published mineral resource estimates, on the cusp of development. They provide a basis for comparing exploration and geological uncertainty, the technical risks of proposed mining systems and the potential environmental and social impacts.

In many respects the risks of development of seafloor resources are lower than for terrestrial resources and the post-closure management of deep-sea mining projects may be much less problematic than for competing land-based projects. The limited precedents for seafloor mining may currently challenge investors and regulators but with several groups on the verge of committing to trial mining or full-scale mine development this impediment may soon disappear.