Donald Mineral Sands Project

Victoria, Australia

Geology

The Donald and Jackson deposits are fine grained WIM style heavy mineral sands accumulations. The Donald Mineral Sands project represents the first commercial development of such a deposit, and is amenable to staged, long life mining operation.

Diagramatic representation of WIM – style deposit. Source MCA

The Donald and Jackson deposits are fine grained WIM style mineral sands accumulations. Donald will represent the first commercial development of such a deposit, and is amenable to a staged, long life mining operation.

The deposits were discovered by CRA Exploration in the 1980’s as part of their multi-commodity regional survey. The deposits represent part of the wider mineral sands occurrences in the Murray Basin, although most other deposits are strandline deposits.

Once CRA established the full extent of the magnitude of the fine-grained deposits, the company initiated grid drilling on the first of the large deposits at the end of 1982. In 1999, following the merger of CRA and Rio Tinto, who owned mineral sands operations, QIT (Canada) and Richards Bay Minerals (South Africa), the combined company’s focus shifted, and the Victorian tenements were relinquished.

Heavy mineral (HM) deposits in the Murray Basin are of two principal types: coarse grained, strandline deposits, and finer grained WIM style accumulations. Strandline deposits are characterised by relatively narrow linear ore bodies with HM from 2 metres to 12 metres in thickness.

WIM style deposits are larger scale, and are characterised by their tabular or sheet like geometry, with finer grained sand characteristics (<100 μm grain size). These shallow marine sands containing HM accumulations were deposited in the Loxton-Parilla sands of the Murray Basin in the late Miocene to Pliocene age between 7.2 and 4.5 million year ago. WIM deposits are thought to represent accumulations formed below the active wave base in a near shore environment, possibly representing the submarine equivalent of the strand style deposits.

Strandline deposits tend to be relatively rich, with heavy mineral grades in the range of 5% to 20%, but are relatively low tonnage, and from a mining perspective, can be short-lived. In the Murray Darling Basin, this has meant mining infrastructure has required relocation, often as frequently as every three or four years.

While WIM style deposits tend to have lower HM grades ranging between 2% to 5%, their tonnages are of a magnitude much greater than that of strandline deposits*. 

Given WIM style deposits usually contain greater tonnage, and are generally more consistent in HM grade characteristics than coarse grained strand line deposits, equipment selection and design criteria are expected to allow for greater operational grade and recovery management during operations, increasing economy of scale for initial capital investment.

In the Donald deposit, fine grained HM mineralisation tends to form internal higher grade zones, which trend North to South and are the focus for the initial stages of the mining operation. To the West, the mineralisation deepens, increasing overburden. On the Southerly margins, the fine-grained silty sand ore disperses in an East to West direction, following silty clay units, which are interpreted as washout zones that tend to contain no heavy minerals.

* Refer: Department of Primary Industries: Heavy Mineral Sands in the Murray Basin of Victoria, GeoScience Victoria, Geological Survey of Victoria Technical Record, 2012/1.

 
Donald WIM style deposit and typical Murray Basin strand line deposits. Source MCA
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