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Gum Creek East Gold Project




The Gum Creek East Project model has been updated and currently includes the tenements E53/1965, E53/1946, E53/1398 and E53/1879.  These tenements lie on the eastern margin of the productive Gum Creek greenstone belt which is highlighted by Banded Iron Formations (BIF) hosting significant gold deposits and gold mineralisation. The Gum Creek East Project has two major segmented BIF horizons over 9kms with only part of this formation (approximately 700 metres) being tested by drilling. It has been established in field mapping that outcrops of BIF continue north and south of a mineralised area in two horizons. The two horizons occur approximately 180 metres apart and it is likely that they are the part of a major mineralised shear zone, interpreted by Szoke (2003) as an extension of the regional shear zone known as the Victory Well Shear.
Location and Access
The Gum Creek East project tenements are located approximately 700 kilometres north-north-east of Perth and 600 kilometres north-north-west of Kalgoorlie-Boulder in Western Australia in the East Murchison Mineral Field. Access to the tenements is provided by the Yeelirrie-Meekatharra gravel road 75 kilometres north of the Leinster (Refer: Figure 1). From a road junction 10 kilometres east of Youno Downs station, an old haulage road heads north for 25 kilometres to the PSI-Omega mine site area and from this point the Gum Creek East Project can be reached continuing on the haulage road and tracks including a boundary fence line track on E53/1965.
Regional Geology

 The Gum Creek East tenements are situated at the north eastern end of the Gum Creek greenstone belt which extends a distance of about 110 kilometres with an average width of 20-25 kilometres. The belt is a north-north-west striking southerly plunging syncline with an axial plane dipping east. The synclinal geology is complicated with the occurrence of a series of strike parallel secondary faults which has created several localised anticlinal structures within the larger synformal structure.  An important anticlinal structure at the southern end of the greenstone belt is the Gidgee Anticline which hosts several operating gold mines.
 The Gum Creek East Project appears to be on the eastern limb of a secondary anticlinal structure dipping steeply to the east. It is thought the project is enclosed by a secondary anticline or on the western limb of a smaller syncline (after Szoke 2003). Szoke indicated in his report that regionally there are three shear zones covering the entire length of the Gum Creek greenstone belt. These are the Wilson Shear Zone, the Victory Well Shear Zone and the Gidgee Shear Zone. The three shear zones are host to several gold mines including the Gidgee mines on the Gidgee Shear; the German Well mines on the Victory Well Shear; and the Montague, Wilsons, Omega-PSI and Toedter mines on the Wilsons Shear. Szoke’s interpretation is that the gold mineralised shear zone on the Gum Creek East project is the extension of the Victory Well Shear which has been offset to the east by the Wilson Shear.

Local Geology

At the Gum Creek East project, gold is present in banded iron formations (BIF's) and quartz veins within mafic rocks. In addition to the main outcropping BIF horizons, there is a number of smaller discontinuous BIF’s in the hanging wall and footwall rocks. The main mineralised BIF where a shaft and previous exploration has occurred is traceable north and south of the shaft for over three kilometres and it has a thickness of up to a maximum of 10 metres. The BIF strikes at 20 degrees magnetic north and dips steeply at approximately 80 degrees to the east. Magnetic data indicates this strike is maintained southwards with this main outcropping BIF horizon crossing the western boundary of E53/1398. A more central or second parallel BIF horizon continues south in a segmented form crossing the southern boundary of exploration licence E53/1946 (Refer Figure 2).

Exploration Summary

Exploration has been carried out on the prospect area since the 1980's International Gold and Minerals NL carried out rock chip sampling and drilling in the sulphide bearing BIF on former prospecting licence P51/2572.  The area was first rock chip sampled in 1987 with significant gold values including 6.55g/t, 5.27g/t, and 4.45g/t. The drilling delineated thirty intersections of the main BIF on 22 lines returning 23 grades above 0.5g/t over one metre. On line 14 drill hole GC14_3 intersected gold assay values ranging from 49.8g/t to 116g/t at 44 metres which was the target of further drilling in 2002. However, the drilling adjacent to the collar of GC14_3 14 years later indicated that the intersection in GC14_3 was of limited extent and did not warrant a mining operation. In the same drilling programme however, another hole (Hole E) was drilled approximately 10 metres south of the shaft adjacent to the main BIF horizon. This vertical hole returned significant assay results at a shallow depth of 11m @ 3.25g/t Au from 9 metres.

In 2011 a vertical hole, GCRC02 drilled 100 metres south of the shaft, intersected significant mineralisation of 5m @8.65g/t from 82m - 87m, then in 2015 as part of the Government Co - funded Exploration Incentive Scheme (EIS), RC drilling intersected a gold mineralised structure between the shaft and the vertical drill hole GCRC02, extending the mineralisation 20 metres to the south of drill hole GCRC09. Drill intersections included GCRC07 11m @1.9g/tAu from 49m including 3m @ 6.1g/t from  56m, GCRC15 12m @ 1.7g/tAu from 38m including 2m @ 6.53g/tAu from 47m, GCRC17 5m @ 11.7g/tAu from 95m including 3m @ 18.5g/tAu from 96m. The higher-grade mineralised structures intersected in the drilling were within a highly magnetic host rock with quartz veining and the transition from non-magnetic rock to magnetic host rock was clearly defined occurring both entering and exiting the high-grade gold mineralised zones.

A close spaced ground magnetic survey was carried out in 2016 on exploration licence E53/1398 as a result of the high-grade gold structure/s being discovered within the strong magnetic iron host rock. The survey conducted by Southern Geoscience Consultants "SGC" was conducted at 10 metre spacings within former Prospecting Licence P51/2572 and at 25 metre spacings in the exploration licence E53/1398.

In the 2017 -2018 reporting period the Round 15 Co-Funded drilling programme consisting of RC drill holes GCRC20 - GCRC30 was carried out. GCRC20 (vertical) and GCRC21(-60deg.) tested for gold mineralised structures associated with the intersection in drill hole GC14_3 at 44 metres assumed to be in the hanging wall of the main BIF and directly east of the shaft. Additional drilling including drill holes GCRC23 and GCRC24 were designed to intersect mineralised structures in the hanging wall of the main BIF approximately 70metres and 110 metres south of vertical drillhole GCRC09 however drilling indicated that the hanging wall BIFs were not significantly mineralised, possibly because of the thin true widths and the segmented distribution of the BIF along strike which is apparent on the surface and probably repeated at depth. Drilling of GCRC23 and GCRC24 was therefore deepened to intersect the main BIF and drill hole GCRC28 was designed to intersect the apparent south plunge of the higher-grade mineralisation approximately 3 metres south of drill hole GCRC09. The drill holes targeting the hanging wall BIFs and main BIF indicated that the main BIF was mineralised at depth and had extended the strike length of mineralisation south of the shaft to approximately 380 metres (Refer: Figure 3).  

Drill holes GCRC22, GCRC25 - GCRC27, and GCRC30 were drilled to intersect the eastern BIF horizon which consisted of thin segmented banded iron outcrops approximately 150 metres east of the main mineralised BIF horizon and shaft. Vertical drill hole GCRC22 intersected significant sulphides (80-90%) from 73 metres to 89 metres which was considered significant and further geophysical work was therefore considered warranted.

 In 2017 rock chip samples were collected from BIF outcrops on the Gum Creek East Project tenements from the northern tenement E53/1965 to the southern boundary of E53/1946 a distance of approximately 9kms.
 Geological mapping and sampling was continued in 2018 -2019 to assess the BIF areas where rock chip sampling was anomalous in base metals and gold. Work carried out included a soil and lag orientation survey across the main BIF immediately south of the shaft on E53/1398 followed by rock chip and lag sampling programmes at selected outcrops of the 2 BIF horizons.  Rock chip sample results   located areas of the anomalous BIF horizons which targeted the surface lag sampling lines in the programme.

Geological mapping and rock chip sampling was carried out in the 2019 - 2020 in areas where results were considered anomalous from previous rock chip and lag sampling programmes in 2017- 2019. From the work done 4 target areas have been established (Refer: Figure 4). 

In the northern area of Target 1  gold assays were low, however, assays in the base metals Pb, Cu, Zn were anomalous associated with an interpreted north west structure. Mapping and a ground 'truthing' investigation indicated a significant area of quartz scree with the structural geology interpreted from photo imagery (Landgate Aerial Imagery). The investigation indicated evidence of quartz veining in a north south trend of approximately 480m. The presence of significant quartz scree indicates a complex of quartz filled structures with probable mineralisation occurring at depth.

Previous drilling had established the Target 2 area with significant drill intersections and gold assays in rock chip, soil and lag sampling programmes The early programmes in 1987 has been followed up with 3 programmes of drilling conducted in 2011, 2015, and 2017 which concluded that significant gold mineralisation could be present associated with a gold mineralised lineation plunging approximately 40deg. south from the shaft working.  Soil and lag sampling as an orientation survey was carried out in a 20m x10m pattern across the main BIF south of the shaft, indicating a variability of gold mineralisation with assay values ranging   from 10ppb to 72ppb in the soils and from 37ppb - 102ppb in the surface scree samples. The variability of the gold mineralisation has been shown in the limited drilling programmes adjacent to and south of the shaft including rock chip sampling programmes.

 In the Target 3 area the main focus has been on the Disruption zone where quartz veined structures are prominent trending North West, East West and North East directions.  The Target 3 area has been highlighted by elevated values in gold and base metals in rock chip sampling programmes with results peaking at 1.63g/tAu and  1.07g/tAu.  Anomalous results are in the range from 23ppb to 1.63g/t with consistent elevated values in Cu and Ni.

  Mapping has shown the occurrence of NNW and ENE structures with strong east west structures such as a quartz reef trending 290deg. at 7028343N and a significant "boulder size" quartz reef trending 264deg. at 7028415N.  It is thought that this structure reflects the axial plane of a possible east west fold structure and that east west creek systems form part of the east west axial plane structures as shear structures.  South of Target 3 a prominent east west creek is located at the contact of a quartz scree zone which is interpreted to connect with Specimen Creek to the west and further south at Target 4 a west north west creek appears to connect with the south east BIF trend from the Omega open pit.

Recent Interpretation

The recent interpretation of the Target Areas 2 & 3 including field investigations indicates a system of fold like structures which is assumed to be part of a larger fold plunging south. The recent photographic interpretation and a field investigation indicates the presence of crosscutting structures which are possibly reflected in the creek systems. East west and north west trends appear to be the more prominent structural trends. Stoke (2003) interpreted that the prospect was a southerly plunging syncline with the axial plane dipping east, however the structural geology was complicated with the occurrence of a series of strike parallel secondary faults creating several localised anticlinal structures. Gold mineralisation therefore is complicated particularly near to the surface, occurring on a secondary structure such as the limb of a secondary fold within the eastern limb of the synclinal south plunging fold.
Target 4 has been based on at least one line of historic drilling for which assay results have not been found. The drilling could have been part of a programme trying to discover an extension of the Omega Pit.  With the BIF horizon directly adjacent to the western boundaries of E53/1879 and E53/1946 a small area of 400m x 400m was recommended by the owner of the licence as a target area to test.

MLEM Geophysics Survey

A Transient Electromagnetic (MLEM) survey was completed over the four target areas by Vortex Geophysics during September 2020. Geophysical support with respect to survey planning, data QC and modelling have been supplied by Southern Geoscience Consultants (SGC), with the aim of these surveys to identify strong conductive sulphide-rich mineralisation which may contain gold.  The surveys successfully identified anomalies of interest that are consistent with bedrock conductors. The anomalies have been modelled, target vectors and the results are discussed below.

Data QA / QC was conducted by SGC as the survey progressed. For each station, the locations of the readings were checked along with the noise levels and repeatability of the secondary decay curves for each component of the measurement. As each area was completed, a summary of the results was sent to the client representative.
Vortex Geophysics successfully completed the MLEM surveys as planned, the data is of very good quality and was completed in good time given the highly variable access and ground conditions (vegetation, terrain etc). MLEM survey lines were planned to use 200m line spacing and 100m station spacing as shown below in Figure 5.

The survey results for target area 1 highlighted a strongly conductive feature positioned on the southern margin of the survey block as shown in Figure 6. The profiles for the southern three lines (7032100N, 70331900N and 7031700n – Figure 7) are diagnostic of the response caused by a bedrock conductor dipping moderately to the east-southeast. Maxwell plate modelling of these three lines is shown in Figure 8, the model profile for line 7031700N (ie the strongest response is shown in Figure 9).

The survey results for the Target Areas 2 & 3 highlighted a strongly conductive feature positioned towards the north-eastern end of Target area 2 as shown in Figure 10. The TEM profiles (7029050N, 7029250N and 7029450N – Figure 11) are diagnostic of the response caused by a bedrock conductor dipping steeply to the east-south east. Maxwell plate modelling for this anomaly is shown in Figure 12.  A single conductor plate was used to model the response on line 7029450N, and a second model (higher conductance and slightly deeper) was used to model the anomalies on lines 7029050N and 7029250N. The model profiles for these three lines are included in Figure 13.

Two MLEM profiles were completed in Target Area 4 where there is evidence of a strong conductor response in the southwest corner of the survey area (Figure 14 and Figure 15), however, the survey lines did not adequately extend or close-off the response to allow for modelling or interpretation.
Conclusion & Recommendations

Exploration over many years have identified several areas where drill testing should be carried out including:
  1. Infill drilling south of the shaft on E53/1398.
  2. North Target Plate Conductor Model 1 on E53/1965.
  3. Eastern BIF Plate Conductor Model 2 on E53/1398
  4. Boundary Anomaly Target Area 4 on E53/1879 and E53/1946.
(Refer: Figure 16)
Infill drilling is required south of the shaft to confirm the orientation and existence of a high-grade shoot and then develop a gold resource model. Planning of an infill programme has been carried out to a maximum depth of 120m, defining a south plunging (40deg. – 45deg.) high grade gold shoot or series of shoots. Based on the drilling already completed; approximately 1135m of drilling in 20 RC holes to varying depths has been proposed to give a completed drill intersection pattern of approximately 10m x 10m. The high-grade shoot/s gold mineralisation has been defined in a strong magnetic envelope at depth which has been shown to be the host rock or the main BIF horizon dipping easterly at 70 – 75deg. The interpretation made is that a high-grade shoot has a moderate plunge to the south as part of a fold system, suggested from the previous drilling and in part by the isoclinal folding of quartz veining in the weathered BIF.

In the Target 1 area, an EM Anomaly is apparent which has been modelled as a 900m long conductor plate with a width of 250m.  The centre of the top of the plate is at a depth of 70m and dips at the moderate angle of 45deg. This conductor is a new and significant anomaly which has never been drill tested under sand cover and it appears to be the continuation of the main BIF Horizon from the shaft area mineralisation on E53/1398. The occurrence of the conductor assumed to be sulphides and the host rock assumed to be BIF, it would appear possible that significant gold mineralisation is present.  It is recommended to drill test this conductor dipping at 45deg. to the east with proposed drill hole P4 (Refer: Figure 17)  and to intersect it at a vertical depth of 100m below surface.
The Target 2 Area east of the Shaft Area known as the Eastern BIF horizon has been modelled as two conductor Plates with depths to the centre top as vertical depths of 98m and 145m. Each plate is 500m in length and 250m – 280m in width dipping 75deg. to the east.  It is apparent that the top of each plate deepens to the south suggesting a plunge component to the mineralisation.  In drill hole GCRC22 which was a vertical hole within the plate boundary, 80% - 90% sulphides were intersected at a depth between 73m and 84m, however assay results indicated there was no associated gold mineralisation.  The ground magnetics survey conducted in 2016 indicated weak magnetism suggesting the host rock was not a BIF and the gold mineralised structure in a BIF was missed. The other suggestion is that gold mineralisation where the hole was drilled was deeper down as the top of the conductor plate was deeper down. It is recommended that the 2 conductor plates be drill tested with angled holes intersecting at depth where the stronger magnetics occur and probable BIF host rock. Three holes have been proposed (P1 – P3) intersecting the conductor at a vertical depth of between 200m and 250m (Refer: Figure 18).

Target Area 4 described as the Boundary Target has now been shown to host a strong EM anomaly in the south west corner of this area on the western boundaries of E53/1879 and E53/1946. (Refer: Figure 16).  This area was deemed to small an area to adequately produce a plate model even though there was a strong bedrock conductor response indicating further MLEM work was warranted. It is recommended to approach the neighbouring tenement owner.


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