The Burro Creek lithium clay project is located in central western Arizona, USA within an active mining district, Freeport McMoRan’s operating Bagdad porphyry copper mine is located 10km from the Burro Creek project. The Burro Creek project is subject to an exclusive option to purchase as detailed in Zenith’s ASX Release 10th November 2016.
Assay results from the maiden drill program at Burro Creek show that the higher-grade portion of the lithium bearing clay zone is a near surface, flat lying horizon extending over 900m by 400m within the eastern project state leases. Significant lithium rich drill intersections are detailed in Table 1 of (ASX Release dated 19th June 2018) and include:
- Hole BCRC18-01 – 22.9 metres @ 1088ppm lithium and 2.94% potassium from 4.68m depth, and 9.1 metres @ 1325ppm lithium and 3.04% potassium from 33.5 metres depth;
- Hole BCRC18-04 – 19.8 metres @ 1180ppm lithium and 2.23% potassium from 21.3 metres depth; and
- Hole BCRC18-14 – 24.4 metres @ 1361ppm lithium and 3.23% potassium from 19.8m depth.
Depending on the cut-off grade used the lithium mineralised portion of the clay averages 23 to 54 metres in thickness, whilst recent testwork indicates a bulk density of 1.6 to 1.8 g/cm3.
Recent mapping and surface sampling in the new Burro Creek western claims has identified further widespread, high-grade, flat-lying lithium clays at surface with two new areas identified each equal or greater in size to the zone of lithium mineralisation discovered in the current drill program. These two new areas will be the focus of future resource drilling (Figures 1 & 2).
Figure 1: Burro Creek Project Area Showing Lithium Clay Area Defined by Drilling and New Western Claim Area Targets
Figure 2: Burro Creek Drill Cross Section Showing Lithium Results
Based on the drilling activity noted above, and surface sampling and mapping in the western claim area Zenith and Bradda Head have estimated an Exploration Target1 for the Burro Creek project of 30-50 million tonnes at 1000 to 1100ppm lithium Li and 2% to 3% potassium. The upcoming maiden resource estimate will report on the eastern claim area only, representing approximately 1/3 of the Exploration Target1. It is expected that the western claim area targets will be the subject of a future drill campaign.
|Exploration Target1||Tonnes||Lithium Grade||Potassium Grade|
|Burro Creek Project||30 – 50 million||1000 to 1100ppm||2 to 3%|
1The potential quantities and grades are conceptual in nature and there has been insufficient exploration to date to define a Mineral Resource. It is not certain that further exploration will result in the determination of a Mineral Resource under the “Australian Code for Reporting Exploration Results, Mineral Resources and Ore Reserves, the JORC Code” (JORC 2012). The Exploration Target is not being reported as part of any Mineral Resource or Ore Reserve.
The Burro Creek lithium clay project in Arizona is comparable to other lithium projects in the USA and Mexico subject to resource and development studies.
Global Geoscience Limited (ASX:GSC – market capitalisation $A562 million as at 15th June 2018) recently announced 14th June 2018) it had secured funding ($A53million) to accelerate the development of its 100% owned Rhyolite Ridge lithium – boron project in Nevada USA. The project contains a Mineral Resource constrained by a starter pit – open pit shell of 26 million tonnes at 1400ppm lithium and 1.24% boron which the company’s pre-feasibility study is focussed on. 2For details refer to GSC – ASX Release 13th June 2018.
|South Basin Resource – Constrained Starter Pit Shell2||Tonnes||Lithium Grade||Boron Grade|
|Rhyolite Ridge – South Basin||26 million||1400ppm||1.24%|
Bacanora Minerals Limited (AIM:BCN – market capitalisation GBP116 million Source: BCN Corporate Presentation June 2018) are developing the Sonora lithium clay project in Mexico. An integrated plant has been designed at Sonora to initially process 1.1 Mt of ore per year, during Stage 1 of the Project, subsequently increasing to some 2.2 Mt per year at Stage 2, producing 17,500 tonnes per annum and 35,000 tonnes per annum of lithium carbonate, respectively. The plant design also includes a circuit to produce up to 30,000 tonnes per annum of potassium sulphate (K2SO4/SOP) product through a series of evaporation and precipitation stages (source Bacanora website accessed 15/06/18).
Metallurgical Testwork Results
Initial preliminary metallurgical testwork conducted on surface samples has provided encouraging results with calcine-water leaches recovering 89% lithium (ASX Release 1st May 2018) on Burro Creek clay samples using a similar method as being used in a pilot plant for the Sonora lithium clay project located in Mexico owned by Bacanora Minerals Limited.
These results are in addition to previous testwork (ASX Release 27th July 2017) that resulted in high lithium recoveries to 90% from simple acid leaching using a sulphuric acid leach at a temperature of 800C. Acid consumption in those tests was similar to that from tests on raw ore from the Rhyolite Ridge lithium project in Nevada reported on 1st June 2017 by Global Geoscience Limited.
Further metallurgical testwork has commenced on representative sub-surface clay samples from the recent drill program and will include a future focus on the potassium contained within the lithium bearing clays.
Data compilation, interpretation and geological modelling in progress leading to a maiden mineral resource estimate.