New high-grade discovery at Lake Throssell Sulfate of Potash project

The results from the helicopter-supported rotary drilling programme have confirmed the presence of a high-grade surficial aquifer over an extensive area, with favourable host lithologies.

The drilling programme comprised 26 holes drilled to an average depth of 6.5 m (maximum of 10 m), with a total of 77 brine samples collected at various depths down-hole.

The samples taken cover the extent of the playa area and returned grades of up to 14 500mg/l SOP (14.5 kg/m3), with an average grade of 11 300 mg/l SOP. These results compare favourably to the shallow hand auger sampling undertaken late in 2019, which returned grades of up to 14 800 mg/l – providing further evidence that Lake Throssell is a high-grade, potentially large-scale SOP project.

When combined with results from the initial hand auger survey, 90% of the total holes drilled across the playa lake surface to date have reported a maximum SOP grade exceeding 10 000 mg/l.

The brine chemistry was also consistent with earlier results and exhibited favourable characteristics for solar evaporative concentration and lower waste salts, with a low Na:K ratio and a high SO4 concentration. The results also suggest that the down-hole potassium grade profile remains consistent within individual drill holes.

Many of the holes encountered strong brine-flows seen in units with increased gypsum content and silty sand channels. Layers of crystalline gypsum, ranging in grain size from fine to coarse (≥10 mm), were evident within the majority of holes above ~5 m depth (~80% of holes drilled), inter-layered with silty clays.

The gypsum layers were up to ~20 cm thick in some holes and were often associated with good to very good brine recharge rates. Minor channel deposits (sands and gravels) were also identified in three holes, with one hole (LTAG19) containing a clay/silt supported sand interval of at least 1.3 m with rounded pebbles up to 30 mm dia.

Crystalline gypsum and channel deposit material are known to have high porosity and permeability and have the potential to contain significant brine volumes with good flow rates. As part of the programme, two holes were designed to test the characteristics of the sedimentary sequence within the islands (LTAG04 and LTAG05), confirming a lack of brine flow within these areas.

Modelling of the surficial aquifer has commenced and will be combined with the forthcoming results of the infill gravity survey and the air-core drilling programme planned to target the potentially large basal aquifer hosted within the interpreted palaeochannel to underpin the project’s maiden Mineral Resource estimate – which will be Trigg Mining’s second Mineral Resource estimate since listing late last year.

Trigg Mining’s Managing Director, Keren Paterson, said: “These are exciting results which strengthen our conviction that we have a unique opportunity in front of us to rapidly delineate a high-quality, high-grade SOP deposit at Lake Throssell by the end of this year, providing the foundation to create a sustainable, long-term business that is highly geared to one of the world’s fastest growing markets.”

“The recent helicopter-supported drilling programme has reinforced the positive indications provided by the initial auger results reported last year, building significant momentum in our 2020 exploration programme ahead of the planned upcoming air-core drilling program.

“We have also recently completed the in-fill gravity survey, with the data currently being processed. This will give us a much clearer picture of the entire tenement and help us to refine the locations for the air-core programme which, subject to receipt of final approvals, we are hoping to commence later this quarter. This will underpin the estimation of a maiden Mineral Resource estimate for Lake Throssell.”

Read the article online at: https://www.worldfertilizer.com/project-news/10082020/new-high-grade-discovery-at-lake-throssell-sulfate-of-potash-project/