Phosphate

Highland Plains, Northern Territory, Australia

Project overview

The Highland Plains Phosphate Project in the Northern Territory comprises of one granted exploration lease (EL25068 – 36.9 km²) which is 100% owned by Gibb River Diamonds Limited (ASX: ‘GIB’ or the ‘Company’). The project is located close to Australia’s northern coast and to Asian markets.

The project has a total JORC (2004) compliant Inferred Resource of 53 million tonnes at 16% P₂O₅ at a 10% P₂O₅ cut-off.
Positive metallurgical test work so far has established a method of beneficiation with excellent recoveries. The best flotation test to date gives a grade of 32.3% P₂O₅ (upgraded from 23.4% P₂O₅) at 76% recovery of phosphate.
Highland Plains Phosphate has low levels of the contaminants C (0.2%), S (0.06%), F (1.82%), Cl (112ppm), Cd (4ppm) and U (38ppm).

GIB is seeking a strategic investment partner to progress the project through feasibility studies and into production.

Figure 1: Highland Plains Phosphate Project and Logistics Distances

Geology and Mineralisation

The Highland Plains deposit is hosted by the Border Waterhole Formation in the Georgina Basin. Prior geological studies delineated two major tabular phosphatic intervals in the lower part of the formation. The lower of these (1.5–17m thick) is at the formation base. Some 7–17 m stratigraphically above this, the upper interval, which is 1.5–11 m thick, grades 16–30% P₂O₅.

To date, GIB has spent more than $10 million on exploration in the area, and together with historical drilling in the 1960s, the area has been subject to more than 80 air core/reverse circulation drill holes for more than 2,100m and 7 diamond drill holes for 136m.

The project has a total JORC (2004) Inferred Resource of 53 million tonnes at 16% P₂O₅ at a 10% P₂O₅ cut-off. The Western Mine Target Zone (WMTZ), a subset of the total resource, is shallower and has higher grade JORC Inferred Resource of 14 million tonnes at 20% P₂O₅ with a 15% P₂O₅ cut-off. Areas of the WMTZ outcrop and have been bulk sampled by the Company using a backhoe.

The Company has also identified a number of future exploration targets on EL25068, with potential to expand the known resource.

Infrastructure

Highland Plains is located on the Northern Territory’s border with Queensland, and offers multiple potential transport and logistics options for exporting phosphate. This includes a slurry pipeline to transport the phosphate to one of a number of coastal locations, where it would be dewatered and loaded onto a coastal barging operation with transhipment to bulk carriers, in a process similar to existing operations at Port Karumba or Port Bing Bong. The potential slurry pipeline distances range from 220 km to 374 km.

Highland Plains is also only 68 km from existing infrastructure at the Century Zinc Mine where New Century Resources is producing zinc concentrate from a tailings retreatment operation. This mine already has in place mains power, a beneficiation plant and an existing slurry pipeline to transport product to Port Karumba for export via a barge with transhipment to a larger vessel in the Gulf of Carpentaria.

Figure 2: Highland Plains Phosphate Project Plan View

Figure 3: Highland Plains Phosphate Project Section View

Highland Plains JORC Resource Estimates

The Inferred Resources (JORC 2004) reported on 31 January 2012 are:

WMT Zone 14 million tonnes at 20% P₂O₅ with a 15% P₂O₅ cut-off
Total Resource 53 million tonnes at 16% P₂O₅ at a 10% P₂O₅ cut-off.

NB the WMT Zone is a sub-set of the total resource.

Impurities

All phosphate deposits have varying levels of impurities. Previously reported work at Highland Plains has indicated impurity levels for a 22.9% P2O5 (un-beneficiated) rock as being:

C (0.2%); S (0.06%); F (1.82%); Cl (112ppm); Cd (4ppm); U (38ppm). The levels of these contaminants could be considered low.

Pb: A limited number (74) phosphate bearing sample pulps were assayed for further trace elements including Pb (POZ Quarterly Report to ASX dated 1 October 2012). Elevated lead values occurred in isolated areas at the base of the lower phosphate beds where they directly overlie basement Proterozoic rocks; this effect is possibly related to post-mineralisation groundwater movement concentrating lead at the geological unconformity. These areas of elevated lead could potentially be mitigated through selective mining practices.

Further drill and assay work is required to model the impurities within the overall resource.

Highland Plains Phosphate Metallurgical Flotation Testing

Highland Plains Bulk Sampling High Grade Phosphate at Surface

Further work

The Company is seeking a strategic investment partner to progress the project through feasibility studies and into production. Further work would include:

Further drilling and assay work to upgrade the deposit to a JORC (2012) Indicated and Inferred Resource
Metallurgical pilot plant testing of bulk samples for phosphate grade enhancement and reduction of impurities
Geological modelling of areas containing elevated impurities
Further logistical studies and modelling
Mine planning
Budgeting, planning and timelines to production
Publishing a Scoping Study leading into a full Bankable Feasibility Study

References

¹Maiden JORC Resource at Highland Plains; POZ/GIB ASX Release dated 31 March 2009
²Quarterly Report; POZ/GIB ASX Release dated 29 October 2009
³Metallurgical Update (#4); POZ/GIB ASX Release dated 19 Mar 2010
⁴Quarterly Report; POZ/GIB ASX Release dated 29 July 2010
⁵Quarterly Report; POZ/GIB ASX Release dated 29 Oct 2010
⁶Further Positive Results from Metallurgical Testing (#2); POZ/GIB ASX Release dated 21 Dec 2010
⁷Quarterly Report; POZ/GIB ASX Release dated 1 October 2012

The Information in this report that relates to the previously reported Highland Plains Mineral Resource and previously reported Highland Plains exploration and metallurgical data is based on information compiled by Jim Richards who is a member of the Australasian Institute of Mining and Metallurgy and a Member of the Australian Institute of Geoscientists. Jim Richards is a director of Gibb River Diamonds Limited and has sufficient experience which is relevant to the style of mineralisation and type of deposit under consideration and to the activity which they are undertaking to qualify as a competent Person as defined in the December 2004 Edition of the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves. Mr Richards consents to the inclusion in this report of the Information, in the form and context in which it appears.

The Highland Plains Mineral Resource Estimates (MRE)’s were prepared and first disclosed under the JORC Code 2004. It has not been updated since to comply with the JORC Code 2012 on the basis that the information has not materially changed since it was last reported. The Company confirms that the form and context in which the Competent Person’s findings are presented here have not been materially modified.