Zenith Minerals (ASX:ZNC) has reported lithium recoveries of up to 90% from the Burro Creek Clay Project in Nevada, comparable to nearby deposits. Permitting is in progress for resource drilling of the Burro Creek lithium clay target. The target contains a near surface, thick, flat lying and very extensive clay zone with high-grade assays to 1650 ppm Li.
- Lithium recovery of 90% from Burro Creek clays using simple acid leach, with acid consumption comparable to competitor lithium clay project in Nevada (*Rhyolite Ridge ASX-GSC);
- Initial lithium recoveries up to 75% using an alternate calcine-water leach method similar to that proposed for major competitor lithium clay project in Mexico (*Sonora TSX-BCN);
- Permitting in progress for resource drilling of the Burro Creek lithium clay target;
- Near surface, thick, flat lying and very extensive clay zone with high-grade assays to 1650 ppm Li.
Zenith Minerals Limited (“Zenith” or “the Company”) is very pleased to advise that results of initial, sighter level metallurgical testwork on lithium clays from the Burro Creek project in Arizona (Figure 1), funded by its joint venture partner Bradda Head Ltd have returned highly encouraging lithium recoveries.
Leach testwork was conducted by metallurgical consults JE Litz and Associates LLC in conjunction with Hazen Research Inc at their respective testwork facilities in Colorado. A bulk sample taken from outcropping, lithium bearing clays now confirmed by recent XRD testwork to contain the smectite clay mineral variety saponite-hectorite, was subjected to a number of tests under variable laboratory conditions.
High lithium recoveries of 90% were achieved in three leach tests using sulphuric acid at a temperature of 800 C. Acid consumption was similar to that of raw ore from the Rhyolite Ridge lithium project in Nevada owned by Global Geoscience Limited (ASX:GSC- market capitalisation $A210 million) as documented in a release dated 1st June 2017.
Additional initial testwork using alternate leaching methods as proposed for the Sonora lithium clay project located in Mexico owned by Bacanora Minerals Limited (TSX:BCN – market capitalisation $C175 million) has also been completed. Calcined clay from Burro Creek with various additives was leached by water and up to 75% lithium recovery has been achieved to date.
Background on the Burro Creek Project Arizona
On the 10th November the Company announced that it had secured an exclusive option to acquire a 100% interest in the Burro Creek lithium clay project located in central western Arizona, USA. Located in an active mining district, Freeport McMoRan’s operating Bagdad porphyry copper mine is located 10km from the Burro Creek project.
Initial surface sampling by the Company of the lithium clay exposures (reported 10th November 2016) returned results including: 20m @ 818ppm Li, 5m @ 1090ppm Li and 15m @ 930ppm Li & 50m @ 785 ppm Li.
Follow-up sampling results were announced to the market on the 13th January 2017. Results from that follow-up program returned generally higher-grade lithium results over greater widths (Figure 3).
- Results from composite channel sampling of zones where the full clay thickness is exposed in the field included: 33.6m @ 980ppm Li; whilst,
- Zones where lithium bearing clay zones are not fully exposed and are locally obscured by transported rubble and alluvium included: 15m @ 1427ppm Li and 15m @ 920ppm Li; 2.5m @ 1300ppm Li, 3.5m @1120ppm Li and 1.5m @ 1210ppm Li. These results represent only a portion of the lithium clay horizon and drilling or trenching is required to test the full thickness of the lithium bearing units; and
- Grab samples of relict drill spoil from shallow holes drilled during a small, historical program to test the clay for industrial purposes returned results including: 1650ppm Li and 1290ppm Li. Encouragingly these are among the highest grades returned from Zenith’s sampling to date and may indicate that surface sampling is understating the true lithium grade. True widths for these zones are unknown and follow-up drilling is required.
- A trial geophysical survey using passive seismic technique supports Zenith’s geological interpretation of extensive flat lying, near surface lithium bearing clays.
The lithium bearing clay zone is a near surface, flat lying horizon extending over 1700m by 1000m within the eastern project leases and a further 800m by 600m within the western lease areas. Observations from mapping and sampling programs indicate that the clay horizon generally has a true thickness greater than 30 m where it is exposed in gullies within gently undulating, poorly vegetated hills that comprise the eastern project area. Previous drilling to test the clay quality for industrial uses intersected clay units over thicknesses up to 20m in the western half of the project area, notwithstanding that drilling did not penetrate the full thickness of those clay beds which are up to 50 m thick in outcrop in the eastern area. The Company therefore concludes that there is excellent potential for large tonnages of lithium bearing clay within the Burro Creek project.