Twenty Seven Co Ltd (ASX:TSC) is buoyed by promising early lithium exploration results from the North Rover tenement in WA’s central Yilgarn that have prompted global mining group Rio Tinto (ASX:RIO) to exercise its option to farm-in to the non-gold rights.
Rio Tinto Exploration (RTX), a wholly-owned subsidiary of Rio, has elected to exercise the option over exploration licence E57/1134 at the northern end of TSC’s Rover Project near Sandstone.
This follows TSC entering a binding term sheet with RTX in March 2022 with RTX paying an initial A$25,000 upfront for an exclusive initial six-month option to explore North Rover for non-gold minerals.
Pegmatite unit identified
During the initial six months, RTX identified a sub-cropping weathered pegmatite unit that may be prospective for lithium (spodumene) and tantalum mineralisation, with an area prioritised for follow-up drill testing.
This has led to RTX exercising its option to earn an 80% joint venture interest in the non-gold mineral rights on E57/1134 by sole funding A$5 million of non-gold exploration.
“Positive early results”
Executive chairman & CEO, Mark Caruso said: “We are encouraged that RTX has opted to exercise its option to farm-in and advance the North Rover Project in WA.
"The positive early results of first stage exploration has indicators that warrant the drill testing to assess the sub outcropping pegmatite target in the northern area of the tenement for potential lithium mineralisation.
"Securing the support of a global miner such as Rio Tinto demonstrates the underlying potential of the North Rover Project, and we look forward to working closely with the RTX exploration team during the farm-in.”
Rover Project location map.
Exploration activities
Stream sediment, soil and rock chip sampling were undertaken by RTX in the area of interest to better assess the potential for the pegmatite to host lithium (spodumene) mineralisation.
Exploration activities during the option period from April to September 2022 were focused on the northern section of the North Rover Project area and comprised:
- Review of historical exploration information and satellite imagery.
- Acquisition and review of existing airborne magnetic-radiometric survey data.
- Field reconnaissance mapping undertaken via walked traverses that identified an area of interest containing sub-cropping weathered pegmatite and banded aplite.
- Collection of 23 stream sediment samples from mostly first-order drainages from the identified area of interest, which were assayed for a broad element suite.
- The collection of 51 soil samples in a notional 100 x 50-metre grid over the catchment with the highest stream sediment tantalum anomalism that were assayed for a broad element suite.
- Collection of 12 rock chip samples from selected weathered pegmatitic rubble within the area of interest that were assayed for a broad element suite.
Drilling being planned
On the basis of the sampling results, in particular coherent tantalum and related geochemical anomalism over an area of the interpreted pegmatite unit, RTX believes that drill testing of the pegmatite unit to test for potential spodumene mineralisation is warranted.
RTX is planning to conduct an initial drill program of 500-1,000 metres to investigate the interpreted pegmatite unit in early 2023, subject to land access consents and clearances.
TSC retains all gold mineral rights in respect of North Rover.
RTX and TSC caution that due to the significant chemical and physical weathering at surface, which has leached many alkaline elements such as lithium, caesium and rubidium, the interpretation of geochemical anomalism for spodumene is relatively uncertain and the drill targets should, therefore, be considered high risk.