By the end of the program, the zone of high-grade soil anomalism, up to a stunning peak assay of 74,997 parts per million (ppm) uranium oxide, was expanded to about 800m by 100m.
The overall anomalism parallels the alignment of the prominent fault escarpment that marks the western boundary of a de-magnetised granitic plateau, which is interpreted as a deep-seated thrust fault, bounded by three large converging secondary faults.
The setting is considered favourable for high-grade uranium mineralisation, with the granite likely thrust over the neighbouring sedimentary group at depth.
The sediments may contain reduced graphitic horizons, which often feature high-grade uranium mineralisation where they interact with oxidised uranium fluids rising through deep-seated faults.
Globally recognised glaciologist Dr Martin Ross last year conducted a review of the surface geology at Falls Lake, which concluded that the high-grade uranium hits in soils were likely to be locally derived, rather than being glacially transported from a remote location.
Infiniโs phase one drilling program focused on the high-grade uranium-in-soil results identified at Falls Lake.
Drilling targeted geological structures within the demagnetised granitoids of the north-south trending escarpment and its inferred underlying thrust fault, where the granitoid overrides the underlying carbonate sediments.
Elevated lanthanum, cerium, sodium oxide and potassium analytical results from the drill core point to a structurally focused hydrothermal alteration system analogous to other shear-hosted uranium deposits.
The analogues include the Valhalla deposit in Australiaโs Mount Isa region and at the Caetitรฉ (Cachoeira) mine in Brazil, the countryโs only uranium producer.
The hydrothermal alteration at Infiniโs Falls Lake prospect is especially prominent in one of the drill holes.
More than 50 samples from Infiniโs phase one diamond drilling program returned anomalous values up to maximums of 920ppm lanthanum, 1785ppm cerium, 11 per cent sodium and 65,700ppm potassium.
Infini Resources chief executive officer Rohan Bone said: โCompletion of Infiniโs phase 1 drill program at Portland Creek is a significant step for the company. Proving that uranium mineralisation above background levels exists in the system gives us confidence to proceed with phase 2 drilling targeting significant uranium mineralisation.โ
Infiniโs Portland Creek project is on the southwestern margin of the Long-Range Mountain Inlier, which is considered a prospective area for structurally controlled uranium mineralisation along shear zones at or near major lithological boundaries.
These structural features provide favourable conduits for the flow and emplacement of mineralised fluids.
The company has collected structural data from 1622 televiewer measurements from three of its six drill holes, indicating a regionally coherent structural fabric.
Interpretation of the directions of three distinct foliation populations observed in the televiewer data suggest they could represent opposing limbs of a recumbent fold structure โ possibly indicative of a thrust plane โ or that they may represent overprinting from two separate ductile deformation events.
Significantly, albitisation alteration and coincident enrichment in light rare earths and sodium occur within and/or up to 5m away from the logged shear and fault zones.
Most importantly for the program, interpretation shows the drill holes were largely sub-parallel to the dominant shear orientation, rather than piercing the thrust plane.
This means the primary structural target remains untested but while drilling did not intersect the primary structural target, the program gave the company a better understanding of the Falls Lake prospect, which will help it design its next program.
Infini is already planning its next round of diamond drilling program at Portland Creek in the third quarter of the year, which will be managed by Infiniโs in-country exploration manager Nick Mitchell.
Overall results from the prospect include massive uranium grades in soil and rock chip samples, strong radiometric signatures and solid aeromagnetic and coherent structural interpretations, while the phase one drill core analyses support the shear-hosted model.
The data so far paints an encouraging picture of the potential for an extensive shear-hosted uranium model.
For the upcoming phase two program, Infini will refine its drill hole orientations to intersect the most likely prospective shear plane and attendant faults, which comprise the inferred structural target and its plumbing system.
Is your ASX-listed company doing something interesting? Contact: mattbirney@bullsnbears.com.au
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