Bynoe Lithium Project

PROJECT HIGHLIGHTS

The Bynoe Project occurs within the Pine Creek orogen, which includes the Bynoe Pegmatite Field, one of three fields within the 180km long Litchfield Pegmatite Belt, extending from Darwin Harbour to the north, to the Windgate Mountains to the south.

  • Project located approximately 38km southwest of Darwin in the Northern Territory
  • Target is lithium-bearing spodumene pegmatites and gold

EXPLORATION POTENTIAL

The Bynoe Pegmatite field is one of the most prospective areas for lithium in the NT and has many similarities to Greenbushes in WA, one of the world’s largest spodumene deposits.

The Bynoe Lithium Project tenement (EL30897) is surrounded by the extremely large tenement holdings of Core Lithium Ltd’s Finnis Lithium Project which has announced to the ASX a total mineral resource inventory of 14.7 Mt at 1.32% LiO2 of which includes 7.6 Mt in the Measured and Indicated Mineral Resource category [1]. The Finnis Lithium Project is at a very advanced stage of development having completed a definitive Feasibility Study in April 2019 [2]

[1] Core Lithium ASX Announcement 10 February 2021
[2] Core Lithium ASX Announcement 17 April 2019

Bynoe Li and Au Project – Geological plan modified from Frater (2005)
Bynoe Li and Au Project location plan showing proximity to Core Lithium’s Finnis Lithium Project and LCT pegmatite occurrences

PROPOSED EXPLORATION PROGRAM & BUDGET

Sampling of weathered bedrock by previous explorers has shown to be a very effective exploration tool and should be expanded to get systematic cover of the tenement.  The different sample media should not present a problem in the data interpretation as each of the different sample type datasets can be normalised.

The results of geological mapping, which helped determine the dimensions and orientations of the known pegmatites, coupled with the previous systematic geochemical sampling on a 200 m x 50 m grid, should provide sufficient detail to define the pegmatite swarms.

Similar to the recommendations for the lithium exploration at Lake Johnston, consideration should be given to the application of hyperpectral remote sensing data obtained from satellites as these are known to work particularly well in identifying specific Li-bearing silicate minerals such as spodumene

EXPLORATION PROGRAM – YEAR 1

Based on previous exploration and nature of the pegmatite occurrences within EL30897, the following exploration program is proposed.

  • Preparation of regolith maps from satellite imagery and ground mapping to determine the optimum sampling method for each regolith type,
  • Undertake an orientation geochemical programme to determine the vertical variation in elemental content with depth and regolith characteristics,
  • Complete a soil sampling program on a 200 m x 50 m grid over the areas determined viable for soil sampling and not included in previous sampling surveys,
  • Complete the systematic sampling programme with RAB drilling where soil sampling is deemed to be ineffective,
Bynoe Lithium Project priority target areas

GEOLOGICAL SETTING

The Bynoe Li and Au Project is located within the Bynoe Pegmatite Field which is part of the much larger Litchfield Pegmatite Belt.  The Bynoe Pegmatite Field is the largest of the pegmatite fields within the Litchfield Pegmatite Belt being some 70 km in length and 15 km in width.  Over 100 rare-element pegmatites are known to occur within the field either as clusters, in groups or as single bodies.  The pegmatites are hosted in metasedimentary rocks of the Burrell Creek Formation and Welltree Metamorphics proximal to the Two Sisters Granite

Frater (2005) reported that the individual pegmatites range in size from a few metres wide and tens of metres long, to larger bodies tens of metres wide and hundreds of metres long, and that the trends of the pegmatite swarms are usually conformable to the regional schistosity, but dips are variable, with local transgressive relationships common.

Locally, the Leviathan Group pegmatites (predominantly located within the excised MLN1148) generally occur within pelitic rocks.  The pegmatites are often tabular or pod-like, steeply dipping (predominately to the east), and striking generally north-northeast.  The pegmatites are zoned with three to five zones which are not concentric or even.  The typical mineralogy of the greisens is quartz-variable micas-cassiterite (± tantalum).  Although not definitive, lithium analyses from greisen material are generally more elevated from other non-greisen samples.

The pegmatites have been subjected to pervasive kaolinite alteration at the Bynoe Project.  The depth of the kaolinite alteration is at least to 22 m as defined in the earlier RC drilling by Corporate Development Resources (Corporate) in 1997.  This will have implications for lithium exploration as the lithium will be depleted in the weathered pegmatite resulting in more subtle geochemical anomalies

PREVIOUS EXPLORATION

The Bynoe area was historically mined for cassiterite that formed within LCT pegmatites.  The mining was mostly small scale with few production records.

The Bynoe Li and Au Project covers extensions to the Leviathan Group of mines mineralisation which was discovered by in 1886.  A mine and battery were established shortly after with a recorded production of 13 t of tin concentrate between 1886 and 1890 (Frater, 2005).  The tin mineralisation proved to be patchy and the leases were abandoned in 1909.

Renewed interest in the region commenced after 1980 when the price for tin reached $17,000 remaining high until 1985 when the price declined.  Exploration completed by the main explorers in the area is summarised below:

  • 1983-1990
    Greenex Resources
    Greenex explored the Leviathan area between 1983 and 1990 resulting in the re-location of over 20 of the pegmatites that had been worked at the turn of the century.  Tonnes and grade estimates (non-JORC) were made for Ta2O5 and SnO2 in weathered pegmatites and alluvials for five groups of deposits including the Leviathan Group.
  • 1984-1992
    Corporate Development Resources
    In 1992 Corporate held the Leviathan leases and estimated a total pegmatite resource (non-JORC) of 81,900 m3 of mineralisation with estimated grades up to 1 kg/m3 SnO2 (Carthew, 1996).
  • 2001
    Julia Corporation Ltd (Julia)
    In 2000 Julia negotiated an option to explore the Leviathan ground with Corporate Development.  Julia carried out costeaning and RC drilling programme, targeting several of the larger Leviathan pegmatites.  In total, over thirty pegmatites have been discovered in the Leviathan area.
  • 2007-2012
    Haddington Resources Ltd (Haddington)
    Haddington on behalf of Arnhem Resources Pty Ltd and Australian Tantalum Pty Ltd explored the area during 2007-2012 principally for tantalum.  Haddington completed programmes of rock-chip and soil sampling combined with RAB drilling.  In the course of the exploration the first lithium prospect in this part of the Bynoe Pegmatite Field was located at the 7-Up Prospect.
Location of previous sampling within and adjacent to EL30897
Image of Li from RAB and Soil Sampling overlain by results of termite mound sampling
Distribution of Li-Libs, Rb, K & Cs from termite mound sampling geochemistry

RECENT EXPLORATION

Location of previous sampling within and adjacent to EL30897

Image of Li from RAB and Soil Sampling overlain by results of termite mound sampling

Distribution of Li-Libs, Rb, K & Cs from termite mound sampling geochemistry

Lithium Australia NL, (LIT) 2019.

LIT collated all of the previous sampling data into a database that could be used to create geochemical images of the various elements associated with LCT pegmatites.

The most widespread and systematic sampling data was the Haddington saprock sampling programme, completed in 2006.  The Haddington data consisted of complementary surface and RAB data, based on the likely thickness of soil coverage, on a 400m x 100m grid.  Surface sampling was conducted above a topographic height of 45m above sea level where the depth of soil cover was from 0 to 0.5m deep.  RAB Drilling was used to collect samples below the 45m ASL contour where the thickness of transported cover was greater.  The RAB holes had an average depth of less than 3m, and a maximum of 10m within EL30897.  Each sample was analysed for arsenic, beryllium, caesium, lithium, niobium, phosphorous, rubidium, tin and tantalum.

LIT collected samples from termite mounds as an orientation programme in 2019, and to expand the geochemical footprint without resorting to drilling.  Sampling of termite mounds has been used in many parts of the world in the past and while most effective for deposits containing chemically resistant minerals such as gold, tin, tantalum and tungsten, the method has also been used for base metal exploration.  The LIT sampling procedure involved collecting broken-off pieces of termite nest from the ground below the nest, at intervals of approximately 200 m along traverses.  A total of 210 samples were collected.

The termite mound samples were analysed in the field using laser-induced breakdown spectroscopy (LIBS) which has been in development for the geochemical analysis of lithium with US-based SciAps Inc, a field portable analytical product manufacturer, and LIT, working in collaboration for the past two years.  The advantage of LIBS is that it is able to detect very light elements such as boron, beryllium and lithium which cannot be determined by portable XRF units.  The LIBS termite mound sampling results, when compared to laboratory analysed RAB and soil lithium results, are sufficiently encouraging to be used as a ‘fit for purpose’ first pass, cost effective exploration method.  The method can be used to generate priority targets for RAB drilling

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