Wide palaeovalley confirmed in initial drilling at Lake Throssell SOP project

The air-core programme, which commenced in late November, was designed to test the basal aquifer within the interpreted 46 km palaeovalley target derived from the ground gravity surveys.

The drill programme is being carried out by Ausdrill with a track-mounted air-core rig with 16 holes completed for 1806 m to a maximum depth of 130 m.

The drilled holes are located in the northern portion of the central tenement E38/3065 and have confirmed the presence of a broad palaeovalley system approximately 100 m deep.

Preliminary interpretation based on visual inspection of drill samples suggests that the palaeovalley system comprises multiple aquifer zones with a thick upper sequence of lacustrine1 clays and sequences of polymictic medium-coarse grained rounded to angular lithic clasts (e.g. gravels and rock fragments) occurring towards the base of the sequence.

These zones are likely to have the highest porosity/permeability within the palaeovalley sequence and may therefore host the most significant brine resources. These gravel-dominated zones occur in sequences of between a few metres and up to 9 m thick, inter-bedded with silt and clay-dominated zones, and are present across the deep sections of the palaeovalley.

Importantly, the palaeovalley appears to be at least 1 km wide and may be up to 3 – 4 km wide in places.

Preliminary field analysis of salinity from the air-core drilling completed to date is comparable to the salinities encountered within the surficial aquifer, where previous hand and rotary drilling programmes encountered brine with high grades of up to 14 800 mg/L SOP. Brine samples collected have been submitted for analysis, with results expected in 2021.

Following a significant rain event where approximately 80 mm of rain fell in 48 hours, the drilling programme has been temporarily suspended. The programme is expected to re-commence when weather and access conditions improve.

The lakes of the north-eastern goldfields are known to experience these sporadic heavy rain events, most commonly during the summer months when the north of Australia encounters tropical lows and cyclones. Some of these weather systems carry southward and can deposit large volumes of water in a short period of time.

With the lakes being the collection point for much of the surface run-off, conditions can deteriorate quickly, but can also recover quickly as the water seeps into the aquifers or evaporates, with daytime temperatures reaching highs of more than 45°C and approximately 3 m of evaporation/yr.

Trigg Mining’s Managing Director, Keren Paterson, said: “We are very encouraged by these early results from the maiden air-core drilling programme at Lake Throssell, which build on the high-grade results encountered in the surficial aquifer and continue to show Lake Throssell has the potential to be a significant new sulfate of potash project. As soon as weather conditions permit, we anticipate recommencing the drilling programme to continue to delineate this exciting high-grade SOP discovery.”

Read the article online at: https://www.worldfertilizer.com/potash/11012021/wide-palaeovalley-confirmed-in-initial-drilling-at-lake-throssell-sop-project/