Lenard Shelf Projects

Location & Access

The Lennard Shelf Project is situated approximately 30km southeast of Fitzroy Crossing on the Lennard Shelf in the Kimberley and West Kimberley Mineral Fields of Western Australia.

Access to the area is via the Great Northern Highway, which links to the coastal towns of Derby and Broome and then by station tracks (see Figure 2 below). A map of the Lennard Shelf project with surrounding historical projects is included in Figure 3 below. 

Pillara East

Local Geology & Mineralisation

The Pillara East Sub-Project covers an extensive area on the eastern margin of the Margaret Embayment, extending from Pillara Range and Virgin Hills in the south to Mount Pierre and Piker Hills in the north and to the Horsespring Range in the northeast. This area includes limestone platform highs on tilted fault blocks and intervening shale-dominated basins.

The area is an eastern extension of the historical Pillara Mine now held by Chinese mining company, Northwest Nonferrous International Investment Company Limited (see Figure 4 below).

At Pillara East, mineralisation occurs as sulphidic breccias, veins and minor replacement along a set of N-NNE trending faults, developed as dilational Riedel splays from the major NE-trending structures of the Pillara Relay Zone. The main host structures, the Western and Eastern Faults, define an extensional graben. Mineralisation also occurs within numerous synthetic and antithetic splays to these faults and in broad breccia bodies developed in the hanging wall of the faults, reaching maximum dimensions at splay junctions. Mineralisation is best developed where structures displace a structurally favourable, competent fenestral limestone unit.

Previous Exploration

The first exploration undertaken at Pillara East was in 1973 by Amax Exploration (Aust) Inc., which carried out reconnaissance and detailed geological mapping, gossan sampling, reconnaissance stream sediment sampling, IP surveys and RAB drilling (22 holes).

In the 1980s, in addition to geological mapping, aerial photography and photo lineament interpretation, gravity (4.2 line-kilometres) and induced polarisation (15.8 line-kilometres) surveys, stream sediment sampling, BHP drilled 66 holes. The majority of the BHP drilled diamond drill holes were vertical and appeared to be targeting either stratigraphic hosted mineralisation within the Pillara Formation or holes were located over mapped structures across the project area to assess the down dip potential of the structures.A summary of the significant drilling results (>1% Zn+Pb) from the Amax Exploration and BHP drilling is set out below.

For further details, see section 3.4.3 of the Independent Geologist’s Report at Annexure C. 

Prospectivity & Work Plan

Data compilation has defined two obvious targets associated with ENE trending, steep SE dipping faults where historic drill holes have intersected significant Zn and Pb. Another series of Zn-Pb targets occurs along the regional NW trending Home Range and Virgin Hill Faults.

Previous exploration has been primarily focussed on stratigraphic drilling targeting the occurrence of shallow granitic basement and the Pillara Formation, along with the north trending structures. The data assessment and interpretation of the aerial imagery suggests the ENE trending structures are a favourable orientation for mineralisation and provides further upside within the project area with several obvious ENE structures that remain untested.

It is proposed that the exploration program should involve a detailed mapping, surface geochemistry sampling, 3D-IP survey over the target area to confirm the location of the targets and to model the target depth, followed by drilling.

Prices Hill

Local Geology & Mineralisation 

Prices Hill is situated at the NW end of the Emanuel Range and is an area of outcropping Pillara Formation with strong geochemical response in stream sediment sampling. The ranges are dissected by a set of N- to NNE-trending faults within the Prices Hill Relay Zone, which transfers movement between Cadjebut-Pinnacle Fault zone and the Virgin Hills Fault zone to the north.

Previous Exploration

BHP completed wide-spaced grid drilling during 1980s but failed to intersect any significant mineralisation. 

During 1997, three lines of IP survey were conducted by Western Metals Ltd over the northern margin of Prices Hill and led to the discovery of an anomalous gossan (Cappa’s Gossan) at the NE edge of the outcropping limestones, in the footwall of the NE-trending splay of the Cadjebut Fault. The IP anomaly over the structure suggested a shallow source less than 100m. Mapping suggested a main WNW -dipping structure with an E-dipping antithetic structure to the west and extensive gossanous breccias over 50-100m between the structures. The survey outlined a number of very high phase anomalies that remain untested.  Subsequently, during 1998, two additional drillholes were drilled at Prices Hill (within the E04/2504 – PHD023 and 027) to test a combination of structural, geochemical and geophysical targets arising from a program of mapping, soil sampling and IP surveying. Both drillholes failed to intersect Zn (+/-Pb) mineralisation.

Prospectivity & Work Plan

Three lines of IP were surveyed over Prices Hill where mapping and sampling has shown the presence of anomalous gossans associated with north trending structures. Some anomalism was reported from the IP survey, within a highly polarisable background response.

Results of drilling at Prices Hill were generally mixed. Although a well-developed structure with strong marcasite mineralisation was defined at Cappa’s Gossan, base metal mineralisation appears very weak. However, marcasite may represent a halo to base metal mineralisation and limited deeper testing is warranted. Structural and Lower Dolomite targets elsewhere at Prices Hill have not produced any significant base metal mineralisation. It is possible that the Gap Creek Formation provided the main hydrothermal fluid pathway in this area and that structural and/or stratigraphic pinch-outs of this formation represent the best target.

The target area occurs in the northern portion of the tenement (Figure 7) and is associated with a number of IP targets that remain untested. It is proposed that the exploration program should involve a detailed mapping, 3D-IP survey over the target area to confirm the location of the targets and to model the target depth, followed by drilling.

Sadler Ridge

Local Geology & Mineralisation 

The tenement covers the central part of the Emanuel Range. The Gap Creek Formation is underlain by nodular shales of the Emanuel Formation which lie unconformably on Proterozoic granitic basement. The Gap Creek Formation is unconformably overlain by the Lower Dolomite unit of the Pillara Formation (now distinguished as the Cadjebut Formation) along the southwest edge of the Emanuel Range

Previous Exploration

Previous exploration includes gridding, Landsat imagery, soil, stream-sediment and ironstone sampling, mapping and geophysics undertaken by Esso in 1984/5. Geopeko conducted a drilling program in 1991 and 1992 in the northern portion of the tenement. Significant rock chip samples (>0.5% Zn+Pb) are shown below. Hole VHD-10 intersected 1m @ 0.14 Zn and 2.75% Pb from 207m. Fuller details of drilling results are contained in Appendix D of the Independent Geologist’s Report located at Annexure C to this Prospectus. 

Prospectivity & Work Plan

At Sadler Ridge, surface gossans occur within a broad zone of stromatolite-like carbonates at the contact of the Sadler and Gogo Formation. These comprise columnar and plumose carbonate masses growing in all directions into open space cavities or the sea floor. These may or may not be organic, but are interpreted to reflect expulsion of fluids onto the sea floor or into cavities close to the sea floor. Widespread barite occurs as probable replacements of this carbonate, although it could also be interpreted as a primary precipitate, and as remobilised veins. This style of stromatolite-like carbonate has now been recognised widely on the SE Lennard Shelf, in a similar setting and with a similar barite association. Ferruginous gossan at Sadler Ridge occurs as massive linear zones within the belt of stromatolite-like carbonate. Locally, it is seen to rim cavities within the ‘stromatolite’ system with a later spar fill. The gossans are weakly to moderately anomalous in base metals. The primary target area occurs in the north western portion of the tenement while a second area of interest located close to the southern tenement boundary.

Further work is required on the prospect to increase understanding of the origin and controls on the mineralisation and to determine appropriate follow-up exploration. The proposed exploration program involves a 3D-IP survey over the target area to confirm the location of the targets and to model the target depth, followed by drilling. Further mapping and rock chip sampling will be required around the southern area of interest to assess the mineralisation potential.

Oscar Range

Local Geology & Mineralisation 

Mapping at Oscar Range (ELA 04/2662) has delineated in detail the marginal slope (Nullara) – platform (Pillara) contact and the extent of gossanous zones in the marginal slope has been outlined. The Oscar Range Sub-Project consists mainly of fenestral-pelletal grainstone with locally documented oncolites, stromatoporoids, amphipora and silty beds, suggesting a shallow-water platform environment.

Previous Exploration

Work carried out during BHP’s tenure (1977-83) in the area included aerial photography, mapping, gravity profiling, stream sediment and rock chip sampling. Short resistivity depth soundings as well as percussion and diamond drilling were also carried out. Twenty-six percussion holes (4,592 m) and six diamond holes, BD1-BD6 (2,200 m) were drilled. BHP carried out further gravity and induced polarisation (IP) survey and further 11 diamond drill holes during the 1988-1993 period on the current tenement area.

The primary target area occurs in the north western portion of the tenement ELA 04/2662 associated with a number of outcropping gossans and a series of north east trending structures.  Rock chip sampling of the gossans in shows elevated Zn ranging up to 39.4% Zn. Historical drill holes were positioned to test the down dip potential of the gossans which were interpreted to be associated with north west trending structures. BHP drilled BD1 in 1981 which intersected 4m @ 4.12% Zn below Screaming Gossan. This was followed up by BD13 drilled by Billiton in 1990 to intersect 50m down dip of BD1. BD13 intersected 19m @ 2.6% Zn. BD15 was drilled by Billiton in 1990 to intersect 50m down dip of BD13, however failed to intersect any significant mineralisation. Further details are contained in Appendix E of the Independent Geologist’s Report located at Annexure C to this Prospectus. 

Prospectivity & Work Plan

The above referenced historical drill holes were orientated on a north-east trending plane (Figure 9), perpendicular to the BHP/Billiton interpreted orientation of the mineralised structures. Following the assessment of the Pillara East and Sadler Ridge projects, it is noted that mineralisation appears to be hosted by the north-east trending structures and the co-incident occurrence of these northeast trending structures across this target area, which suggest the host structure to mineralisation is orientated in the north-easterly direction. As historical drilling parallels this orientation, the north-east structural host orientation has not been tested and there remains scope for this area to host significant mineralisation.  The proposed exploration program involves detailed mapping and field checking of the hole positioning followed by 3D-IP surveys orientated to test the mineralisation potential of the north-east trending structures. Drilling will depend on the results of the 3D-IP survey.