Ioneer Ltd (“Ioneer” or the “Company”) (ASX: INR, NASDAQ: IONR) announced the latest core drill results at the Rhyolite Ridge Lithium-Boron Project located in Nevada, USA, finding lithium grades well above the average of previous estimates.
Results for its newly identified “Shelf Zone” in the southeast section of the South Basin, an area outside of the Tiehm’s buckwheat critical habitat, show the average lithium grades at more than 20% higher than the comparable Mineral Resource average. The findings demonstrate the project’s unique mineralogy, flexibility in commencing operations, and the company’s continued commitment to minimize potential impact to Tiehm’s buckwheat alongside its $2.5 million voluntary conservation investments to date, including the 2023 opening of its dedicated greenhouse.
“Rhyolite Ridge continues to surprise with its unique lithium-boron mineralogy. The southeast section of the South Basin allows us to begin our work providing these critical energy transition materials.” said Bernard Rowe, Managing Director, Ioneer. “Importantly, these findings further demonstrate Rhyolite Ridge and Tiehm’s buckwheat can co-exist, and we remain committed to providing these necessary materials while conserving the plant’s critical habitat for pollinators. We look forward to the anticipated conclusion of the federal permitting process and Record of Decision in the coming months and beginning construction in 2025 on the United States’ first new lithium mine in almost fifty years.”
Ioneer previously announced an updated South Basin Mineral Resource Estimate on April 30, 2024, but results for the final 12 drill holes were not included in the estimate. Highlights from the Shelf Zone drill program, completed in January 2024, include:
- SBH-132: 19.9m at 2070ppm lithium and 11,716ppm boron from 66.8m
- SBH-135: 25.9m at 2153ppm lithium and 10,443ppm boron from 44m
- SBH-137: 17.6m at 2503ppm lithium and 523ppm boron from 96.6m
- SBH-139: 20.7m at 2039ppm lithium and 9,752ppm boron from 79.9m
South Basin and the Shelf Zone
Ioneer’s three-dimensional modelling of detailed ground gravity and magnetic data coupled with drill hole information revealed the South Basin is made up of four main sub-basins.
The sub-basins are separated by faults and folds that have either uplifted or down-dropped the sedimentary layers that host lithium and boron mineralisation. An uplifted block in the southeast portion of the South Basin referred to as the “Shelf Zone” was the primary focus of the most recent drilling. The Shelf Zone measures approximately 1500 x 750 m and until recently, was largely undrilled.
The Shelf Zone represents a highly prospective area due to:
- the shallow depth of the mineralized units,
- the sediments sub-crop beneath unconsolidated gravel,
- lithium grades are consistently higher than the Resource average,
- sediments are relatively flat lying to gentle dipping, and
- the entire area lies outside of Tiehm’s buckwheat critical habitat.
Within the area of the Shelf Zone, mineralised units lie within 30 metres of the surface and are covered by unconsolidated gravel. The mineralised units dip to the east at shallow angles which is likely to prove favourable for mining. The uplifted block that separates the Shelf Zone from the deeper mineralised units to the west is well defined by gravity and magnetic data and has been confirmed with multiple drill hole intersections.
Rhyolite Ridge Site Geology and Overview
Sedimentary layers containing lithium and boron were deposited into the lakebed at Rhyolite Ridge approximately six million years ago. The lake formed within a closed structural basin measuring approximately 2 km by 6 km (South Basin). Over time, the lake filled with sediments and was eventually drained of water. The initially soft, sedimentary layers were turned into solid rock over time. Today, the sedimentary rocks are up to 300m in thickness, can be subdivided into 11 separate units and are almost entirely concealed beneath a 20m thick layer of unconsolidated gravel.
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About Ioneer
Ioneer Ltd is the 100% owner of the Rhyolite Ridge Lithium-Boron Project located in Nevada, USA, the only known lithium-boron ore deposit in North America and one of only two known such deposits in the world. The Definitive Feasibility Study (DFS) completed in 2020 confirmed Rhyolite Ridge as a world-class lithium and boron project that is expected to become a globally significant, long-life, low-cost source of lithium and boron vital to a sustainable future.
In September 2021, Ioneer entered into an agreement with Sibanye-Stillwater where, following the satisfaction of conditions precedent, Sibanye-Stillwater will acquire a 50% interest in the Project, with Ioneer maintaining a 50% interest and retaining the operational management responsibility for the joint venture. In January 2023, Ioneer received a conditional commitment from the U.S. Department of Energy Loan Programs Office for up to $700 million of debt financing. Ioneer signed separate offtake agreements with Ford Motor Company and PPES (joint venture between Toyota and Panasonic) in 2022 and Korea’s EcoPro Innovation in 2021.
