Cauldron Energy Ltd (ASX:CXU) has successfully resolved the core recovery issues that have plagued its underground drilling at the Blackwood Gold Joint Venture Project in Victoria over recent months.
Drilling is now progressing well with drill core recoveries of more than 90%, following assistance from specialist drilling technical advisors.
Background
Over the past several months, Cauldron has trialled several conventional drilling systems from smaller to larger diameter holes in an attempt to improve core recovery at Blackwood.
The initial drill contractor used LTK48 (35mm core) conventional diamond drilling but only achieved recoveries of up to 60%, which risked missing the discrete target ore zones.
The current boom in the Victorian gold industry has resulted in difficulties sourcing experienced diamond drill operators, consequently delaying the completion of the planned contract metres.
Cauldron has also experienced similar challenges in sourcing personnel and also long lead times on equipment, again delaying drilling operations at the Tyrconnel.
Subsequent in-house drilling using the larger diameter LTK60 (45mm core) conventional system, readily available over the 2021 Christmas period, similarly suffered from insufficient core recoveries and hole collapses in the sheared target areas.
Blackwood Gold Project and planned drilling location map.
The current drill program, which commenced over Easter 2022, utilises a triple tube NQ3 system that has proven successful and provided the required core recoveries from the target areas being drilled.
It has involved sourcing experienced pneumatic diamond drillers and modifying the existing Kempe drill rig to fit the larger diameter coring bits and barrel (for an outer hole diameter of 75mm).
Again, lingering supply effects from the COVID pandemic have impacted the program which, in addition to personnel availability issues, has prevented continuity of drilling until now.
Thanks to the various inputs from external drilling advisors Stephen Poke, E-Drill Australia (Tasmania), and Tony Collins at East West Drilling & Mining Supplies (Victoria), Cauldron has now found the right drilling personnel and the right diamond coring system, returning more than 90% core recoveries.
This system is enabling Cauldron to continue operating in a manner that minimises environmental and community impacts for all current and future operations.
“Found the right diamond coring system”
Cauldron executive chairman Simon Youds said: “Drilling at Blackwood has been challenging and delayed by macro events.
“However, we are pleased to report that we have now successfully found the right drilling personnel and the right diamond coring system, giving us nearly 100% core recovery in most of the individual runs.
“This provides us with confidence that the next planned drillholes, targeting areas historically shown to host high grades will obtain the samples required to define the zone being drilled.
“By understanding the nature of these areas not mined in earlier operations, it may be possible to calibrate non-invasive geophysical techniques to pinpoint similar structural zones across the significant Blackwood tenement package held by Cauldron which was extensively mined in the 1860s.”
Targeting historical high-grade zones
Sample recovery is vital in this geological environment because of the narrow-vein style, high-grade but highly faulted and sheared nature of the reefs.
Cauldron’s work on the structural setting has shown that there are multiple cross-cutting faults throughout the tightly folded rock sequence in this part of the Blackwood Gold Project.
Drilling into such structurally complex areas is often difficult and can miss these narrow targets if the incorrect sample recovery system is used.
Achieving more than 90% sample recovery is, therefore, critical to enabling the successful definition of these discrete, narrow, high-grade ore zones as reported historically within the region.
The current recoveries now allow the geology team to confidently target these historical high-grade zones.