Vancouver — Junior
In recent years, the company has been busy acquiring tenements in the East Kimberley region, known for its platinum and palladium potential. Thundelarra now holds prospects that range from the grassroots stage to the more advanced Eileen Bore prospect, where drilling returned 35 metres grading 0.46 gram palladium and 0.15 gram platinum per tonne, plus 0.78% copper and 0.17% nickel.
The company has focused its platinum group metal (PGM) exploration on the Palaeoproterozoic Halls Creek Orogenic belt in East Kimberley. This belt is recognized as one of the most extensively mineralized mafic-ultramafic associations in Australia. In excess of 180 orthomagmatic PGM and nickel-copper occurrences have been recorded from numerous mafic-ultramafic intrusions.
Thundelarra decided to search for structurally controlled hydrothermal PGM mineralization similar to the bulk tonnage Lac des les deposit, near Thunder Bay, Ont. The company selected targets by compiling data from past exploration programs, in which base metal sulphides with favourable geochemistry were discovered but not sampled for PGMs. During the 1970s, potential Lac des les type mineralization would have been identified as a low-grade copper-nickel prospect, and little or no PGM sampling would have been performed. During the 1980s, PGM exploration was focused on Bushveld-type targets and other reef styles of mineralization.
Thundelarra’s East Kimberley PGM project consists of nine exploration licences covering 773 sq. km. These include the Eileen Bore, Corkwood, Panton, Sally Malay, Billymac Yard, Lamboo, Nine Mile Intrusive and Moola Bulla properties.
Field exploration programs are to begin on the East Kimberley PGM projects in late June. Initial work will concentrate on Thundelarra’s tenements adjacent to the Panton Sill resource.
A description of the company’s tenements is as follows:
Eileen Bore property
This property hosts three prospects — Eileen Bore, Alice Downs and McIntosh — and covers the western margin of the McIntosh igneous complex, as well as small mafic-ultramafic intrusions in the Tickalara metamorphics that extend along the northeast-striking Alice Downs fault system. The fault zone hosts extensive PGM and copper-nickel occurrences along its strike length. The fault corridor represents a major crustal lineament that appears to control the strike of the intrusions and is thought to be partially coeval with the emplacement of the intrusions.
The Eileen Bore prospect covers a poorly exposed metasedimentary and metavolcanic package of the Tickalara metamorphics close to the Alice Downs fault. The metamorphics are intruded by sulphide-bearing mafic and ultramafic rocks, including pyroxenites and peridotites. Mineralization is hosted in a 70-metre-wide hornblendite unit.
Previous work by Australian-based Anglo American included four drill holes, with the best intercept returning 10 metres grading 1.35% copper and 0.4% nickel. Later, Australian company Geopeko drilled 100 metres to the north and hit 38 metres grading 0.9% copper and 0.34% nickel. In 1986, Dry Creek Mining performed 353 metres of rotary-air-blast (RAB) drilling and cut 35 metres grading 0.46 gram palladium, 0.15 gram platinum, 0.78% copper, 0.17% nickel and 0.17 gram gold. The depth and strike extensions of this mineralized zone remain untested, and Thundelarra is uncertain if fresh bedrock was drilled.
About 6 km to the north is the Alice Downs prospect, which is on strike with, and adjacent to, the Alice Downs fault. The prospect hosts the Tickalara metamorphics, which are intruded by pyroxenite and peridotite rocks that are enveloped by an extensive metagabbro. The three main anomalies on the prospect — Shiraz, Cabernet and Malbec — extend more than 2 km along strike.
Mineralization consists of nickel-copper sulphides in the ultramafics and minor copper in the gabbro. Previous drilling intersected 16 metres grading 1.4% nickel and 0.94% copper. Chip samples returned anomalous gold and platinum. No palladium assays were reported.
The nearby McIntosh prospect, discovered in 1971, hosts a sheared gabbro that exhibits copper staining. The copper mineralization was interpreted to be re-mobilized and upgraded into fault zones. No PGM assays were performed, though the prospect is at only an early stage of exploration.
Other properties
The Corkwood North tenement covers the northern extension of the Alice Downs fault system. The property is at the grassroots stage and hosts a few copper-nickel showings in small intrusives. Only two samples were tested for PGMs, and both returned strongly anomalous values.
The Corkwood South tenement hosts several small and intrusive pipes, plugs and sills. In one area, nickel sulphide exploration identified a 1-km zone hosting six gossan horizons across a width of 100 metres. The gossans were sampled and found to contain up to 9.1% copper. Only two samples of PGMs were made, and these returned 0.82 gram platinum and 0.26 gram palladium. One drill hole intersected massive pyrite-chalcopyrite mineralization but was completed only to a depth of 59 metres.
The Panton property hosts the Robin Well and Big Ben prospects. The former covers 61 sq. km and is 3 km west of the Panton Sill deposit (2 million tonnes grading 6.02 grams combined platinum, palladium and gold per tonne). The tenement hosts several poorly exposed mafic-ultramafic sills that have a strike length of 14 km. The basal portions of these pyroxenite and peridotite bodies are gossanous and assay up to 2.7% copper and 4.2% nickel. They have not been tested for platinum metals, though chromite-magnetite seams were identified by past workers.
The Big Ben prospect covers the Big Ben intrusive, a faulted offset of the Panton Sill. It is a 1,500-metre-thick sequence of ultramafic cumulate rocks that include dunites and iherzolites that are overlain by a 500-metre-thick sequence of norite, gabbro and anorthosites. Very little historical work has been performed on the property, but Thundelarra recently identified PGM-rich chromitite horizons that returned 1.25 grams palladium and 0.73 gram platinum per tonne.
The Sally Malay property hosts two prospects: Bulldust Flat and Spring Creek. The project is still at the grassroots stage and covers several small intrusives that form part of the complex which hosts the nearby Sally Malay nickel sulphide deposit (3.8 million tonnes grading 1.79% nickel, 0.73% copper and 0.1% cobalt). Very little PGM exploration has been performed.
The Bulldust Flat prospect, discovered in 1971, hosts base metal mineralization in thin norite intrusives. Pitting and trenching returned 17 metres grading 0.51% copper and 0.26% nickel. Two drill holes returned lower grades. The property was not assessed for PGMs. The Spring Creek prospect consists of sulphide anomalies that appear to relate to the Sally Malay sulphide system.
The 97-sq.-km Billymac Yard project hosts the Juries, Paperbark and Billymac Yard intrusions, which form part of the contiguous Corridor gabbro and the Black Hills Yard troctolite bodies. The Corridor gabbro is an extensive dyke-like gabbro measuring 1-3 km wide. The gabbro intrudes fault zones and is thought to represent a feeder system for magma chambers. Early work identified gossans, in the Billymac Yard area, that assayed up to 5% copper and 0.5% nickel. The gossans occur at the basal contact of a differentiated gabbro, norite and an ultramafic complex. Limited drilling returned up to 0.19% copper and 0.15% nickel over 26 metres.
The Black Yard troctolites have been little-explored, except for a 1968 stream-sediment survey that returned high nickel values. The troctolites are prospective for Voisey’s Bay-style nickel mineralization.
The Lamboo project covers 59 sq. km and comprises the poorly exposed eastern portion of the Lamboo igneous complex.
In the 1970s, work on the western part of the
intrusive identified up to 2.5 grams per tonne PGMs associated with chromitites hosted in a serpentinized peridotite. Later work, focused on the exposed chromitite horizons, defined extensive platinum metal, nickel and copper mineralization.
Historical work included soil sampling, trenching and four drill holes. Chip samples from a large shear zone that truncates the eastern margin of the intrusive returned up to 1.7 grams per tonne platinum. About 400 metres to the north, another chip sample assayed 0.225 grams palladium. Thundelarra says these results suggest a potential for structurally hosted, remobilized (Lac-des-les-style) mineralization along the fault corridor.
The Dusty Bore prospect lies over a faulted portion of the Lamboo intrusive. The only past work carried out was regional stream sampling, which returned an anomaly grading 0.4 gram platinum and a 0.06 gram palladium.
The Nine Mile Intrusive property covers 58 sq. km and is 30 km northeast of the Billymac area.
The intrusive complex is a poorly outcropping body that measures 2.5 by 8 km. On the western margin, an intense magnetic signature remains untested. Thundelarra says the property in unexplored and that further magnetic data should better define the magnetic feature.
The Moola Bulla property spans 52 sq. km and covers an entire mafic-ultramafic sequence that produces a magnetic anomaly that can be traced for 10 km.
Past exploration included drilling, which returned 3 metres grading 0.24 gram platinum from a weathered mafic sequence. In 1973, Australian Anglo American identified extensive nickel mineralization through trenching and pitting with up to 1.3% nickel in laterite.
In addition to its East Kimberley properties, Thundelarra also holds ground in the Southern Murchison region of Western Australia.
The Southern Murchison PGM projects consist of the Field Find tenements and the contiguous Baron project. The former, 420 km north of Perth, consists of 17 contiguous tenements covering 420 sq. km. Thundelarra has an option to buy a 100% interest in the tenements from FutureXone for shares or cash.
The area hosts an Archean-aged greenstone belt that is folded into a shallow, southeast-dipping anticline. The Fields Find ultramafic complex intrudes the core of the anticline. The complex comprises a 30-sq.-km area and consists of a sequence of pyroxenites, peridotites and various chromite-bearing cumulate rocks. About 70% of the property is covered by a transported laterite.
In 1998, chip sampling on the northern margin of the complex returned up to 1.83 grams per tonne PGMs from the Breakaway prospect. Follow-up soil sampling defined an anomalous zone that measured 1,800 metres long by 100-500 metres wide. Combined platinum and palladium values ranged between 20 and 456 parts per billion.
A limited RAB drill program returned 18 metres of 0.68 gram combined PGMs, 20 metres of 0.22% copper, and 16 metres of 0.24% nickel. The drilling defined a broad blanket of supergene mineralization that is believed to represent the near-surface expression of a primary sulphide body at depth.
Recently, reverse-circulation (RC) drilling at Fields Find returned broad zones of anomalous PGM mineralization. Hole 1 intersected 14 metres grading 0.92 grams platinum and palladium, whereas hole 2 cut 11 metres of 0.61 gram combined PGMs. Diamond drilling is now testing for primary PGM mineralization beneath the laterite.
The Baron project hosts the small Baron Rothschild gold resource, where, in 1999, Thundelarra discovered platinum mineralization at the Dauphin prospect while drilling a gold-in-soil anomaly.
The Dauphin prospect is 18 km east of the Fields Find property in the middle of the Baron project area. The Baron project consists of eight tenements spanning 176 sq. km, with the tenements contiguous with the Fields Find project.
Locally, the stratigraphy consists of sequences of fine-grained mafic and felsic volcanics with interbedded banded iron formations. The mafic-ultramafic sequence at the Dauphin prospect is still poorly understood, owing to poor outcrop exposure. RAB drilling intersected 7 metres grading 0.61 grams combined platinum and palladium and 25 metres grading 0.23 gram platinum and palladium. The best individual sample assayed 1.16 grams combined platinum and palladium. Recently, two RC holes were drilled for a total of 182 metres. Hole 3 cut anomalous PGM mineralization, which averaged 0.26 grams combined platinum and palladium over 26 metres.
Diamonds
The 652-sq.-km Phillips Range diamond project, in the Kimberley region, hosts the Aries diamondiferous kimberlite pipe, said to be the largest in Western Australia. The pipe’s best-quality gems were valued at US$150 per carat in 1993, and the average price realized for the 1,800 carats recovered was US$100 per carat. Systematic bulk sampling is now required to determine the pipe’s diamond distribution, as well as the grade of the various phases.
The property is expected to be joint-ventured by BHP Minerals, which is currently assessing 53 targets. Each will be ranked for later drill-testing. As things stand, Thundelarra holds a 95% interest in the property, with the remainder held by Australian-based Ragged Range Mining. BHP stands to earn a 60% interest by funding the project through to a full feasibility study within three years from the completion of a prefeasibility study. BHP is required to spend A$660,000 on exploration during 2001.
Thundelarra’s major shareholder is Ragged Range Mining, which holds a 27% interest in the company. Thundelarra has 43 million shares fully diluted.
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