The Goldmember Gold Project is a contiguous package of exploration licenses located in the Eastern Goldfields district of Western Australia and consists of two (granted) ELs and six applications which total 1,414 km2 .  Buxton Resources Ltd (BUX) has defined a gold in soils anomaly within this package over a 5 km2 area.  BUX is seeking a partner for follow-up drill testing and further systematic gold exploration on this Project.

 

Location

The Goldmember Project is located some 80km northeast of Norseman, on the Widgiemooltha 250,000 sheet and partially intersecting the abandoned Madoonia Downs pastoral lease.  The bush is characterized by variably dense malley scrub with occasional eucalypt stands and fringing salt lakes.  Heading north from the Eyre Highway, 4WD access is facilitated via a network of “Woodline” logging-era tracks and tramway formations.

 

Figure 1: Goldmember location map

 

Tenure

The tenement package (all ELs) presently forms a contiguous area of 1,414 km2 held 100% outright by BUX.  Two licenses were recently (Jan 2020) granted without Native Title objection.  These amount to 140 blocks for 408 km2 and have a commitment of $140,000 per annum.  The 6 surrounding applications consist of 354 blocks for 1,006 km2.

 

Geology

Goldmember is situated along the southeastern margin of the Eastern Goldfields Superterrane (EGS), part of the Archean Yilgarn Craton. The NNW trending Ockerburry Fault System, which defines the boundary / suture between the Kalgoorlie and Kurnalpi Domains, is located central to the Project area. To the east and south of the Project lie highly strained rocks that define the structurally reworked margin with the Albany-Fraser Orogen.

 

The oldest rocks, and the host of the targeted gold mineralisation, consist of Archean granitic and metasedimentary rocks and include the southernmost extent of the turbiditic ~2660 Ma Belches Late Basin. This is a 10-12km thick sedimentary package which represents a large reservoir of fluids which were available to contribute to the principal EGS gold mineralizing events.

 

The Project area is fringed by syenite intrusions. Elsewhere in the EGS, these syenites have a strong spatial and temporal relationship with gold mineralisation. The presence of these intrusions is particularly important because their geochemistry indicates high heat flow from mantle derived fluids and as such indicates proximity to a trans-lithospheric fluid pathway (Smithies et al 2018). These crustal scale structures can therefore allow for the transfer of gold from the mantle to the upper crust. Most Archean rocks encountered by BUX on surface are granitic and exhibit very low strain, however gnessic fabrics were described by ASARCO in metasedimentary / metavolcanic rocks. These metasediments are interpreted to be the lowest part of the Belches Sub Basin that has been sampled in this area. The higher strain in the Late Basin is evident from isoclinal folding in banded iron formations close to the ASARCO drilling and the relatively high lateral metamorphic gradients are a key Archean gold prospectivity indicator

 

A swarm of Paleoproterozoic dykes are also evident in the magnetics, including the Binneringerie and Jimerlana dykes which flank the Project area to the north and south.

 

An angular unconformity separates these Archean rocks from the overlying Woodline Sub-Basin - a Paleoproterozoic sequence of gently dipping, greenschist facies shales, quartzites and conglomeratic sedimentary breccia. The resistant quartzites form the Woodline Hills – the most prominent landscape feature in the area.

 

A thin (0-50m) veneer of transported unconsolidated sandy colluvium and alluvium obscures virtually all Archean rocks and several paleochannels valleys with associated salt lake fringe the Project.  The regolith material has been intensely calcretised.

Figure 2: Buxton's proprietary geological interpreation of the Goldmember Project area utilised geophysical coverage and the latest understanding of the geodynamic evolution of the Eastern Goldfields Superterrane to extrapolate between the sparse drilling and surface exposures / sampling.

 

 

Geophysical Interpretation

Filtered aeromagnetic and gravity imagery reveal structural complexity within this granitic basement that is not immediately obvious from statewide imagery.  For example, several structural features which likely controlled sedimentation in this basin are defined in the aeromagnetic imagery and represent important features to prioritize further exploration.  Additionally, the filtered magnetics define a series of oblate and relatively late intrusions which cross-cut locally de-magnetised and variably iron-bearing host granites. Highly magnetic intrusions surround the project area.  These distinctive patterns can be reconciled with Yilgarn geodynamic evolution models whereby older “High Ca” granites (moderate mag) are overprinted initially by “Low Ca” granites (low mag) and then by syenites / mafic granites (high mag).  A NE trending gravity gradient strikes through the center of the Project which appears to juxtapose contrasting Archean rocks (both granites and sediments) and to also coincide with the approximate position and preserved alignment of the Woodline Sub-Basin.

 

The aeromagnetic / radiometric dataset is from a 2012 government survey, 100m line spaced, 50m flight height, east-west lines.  The gravity database consists of 4km spaced GSWA survey conducted in 1998.

 

 

Gold Prospectivity Indicators

Greenstones are absent within the Project area and this has limited the model-driven gold exploration in the area.  However, the nearby and relatively recent discoveries of gold at Tropicana and at the granite hosted Woodcutters gold deposits represent non greenstone hosted economic gold deposits with subtle regolith and geophysical expression.  Therefore, the old maxim “gold is where you find it” should be borne in mind.  The presence of a regionally statistically significant accumulation of gold in calcrete defined at Goldmember by Anglo (discussed below) requires a relatively proximal source which may or may not turn out to be an economic gold deposit

 

Accordingly, the regional-scale drivers of the orogenic gold mineral system which are represented at Goldmember are presented as follows…

  1. A source of gold and energy as indicated by mantle derived granitic intrusions
  2. A significant secondary fluid reservoir, as indicated by the Belches late basin metasediments.This large basin represents both;
    • a secondary source of gold and, probably more significantly,
    • a second fluid that can mix-with and contribute to destabilization of gold in source (mantle derived) fluids in chemical / physical traps.
  3. A “permissive” structural setting as represented by;
    • the intersection between the NNW trending Ockerburry Fault System and the NE trending gravity gradient
    • the margin of the Belches late basin (a post volcanic turbiditic basin)
    • complex structures as revealed by filtered magnetics.The demagnetization patterns evident in the relatively older granitic basement provide camp scale evidence of alteration by fluid flow

 

 

Historical Exploration

Despite the reasonably good vehicular access and proximity to both Norseman and Kambalda, there has been extremely limited work undertaken within the Project area. The only meaningful contributions are summarized below…

 

1969-1970       ASARCO Australia Pty Ltd

ASARCO targeted fossilised placer uranium. Exploration consisted of mapping, mechanical auger sampling and nine stratigraphic percussion drill holes with two diamond tails. This diamond core is preserved in the WA core library. These diamond-tailed holes both penetrated the Proterozoic unconformity (albeit in the percussion interval) below which a variably altered Archean gnessic phyllite, quartzite, felsic porphyry and biotite gneiss was intersected. Alteration consisted of bleaching and clotty chloritization which hosted small blebs of pyrite, pyrrhotite and chalcopyrite. Anomalous gold (highest 0.32 ppm Au) was reported from three holes. Heron Resources later assayed 31 core samples for a suite of 56 elements. The Heron data indicates the phyllite is distinctly “mafic” (high Mg-Fe-Cr-Ni-Sc) but otherwise no obviously anomalous geochemistry is evident.

 

2006-2009       Cullen Resources Ltd

Cullen conducted orientation calcrete sampling on E15/933 that was described in ASX quarterly reports & company presentations but not reported to DMIRS (this work was presumably undertaken while the license was in application). Cullen defined a gold anomaly which trends northeast over approximately 7 km, with a maximum concentration of 9.8 ppb Au. This anomaly is centered approximately 10 km ENE of Jeffery anomaly and appears to have been replicated by subsequent Anglo auger sampling. Cullen did report geochemical results from their northern license E28/1662 where up to 9.4 ppb Au was returned from surface calcrete.

 

2006-2010       Epsilon Energy Ltd

Epsilon targeted sandstone hosted Uranium and coal within the paleochannel sediments located on the southeastern corner of the Project area. An Air Core drilling programme was undertaken in 2009 which consisted of 2,535 metres in 49 vertical drill holes and which targeted a north-south palaeo-drainage system revealed by an airborne Tempest™ EM survey flown during August 2007. Drill holes varied from 12m to 91m deep with holes terminating in bedrock or basal granitic gravels. Gold was part of the multi-element suite and all results were below the relatively high detection limit of 0.2 ppm (ME-MS41 method ALS Laboratories, Perth).

 

2007-2014       Newmont Exploration Pty Ltd

Newmont targeted orogenic gold as part of their Woodline Project in JV with Sipa Exploration NL and Comet Resources Limited. Newmont’s work was concentrated to the east however a small area of overlap exists within the far northeast of the Goldmember project area where first pass auger and 16 air core holes were drilled.

 

2009-2012       AngloGold Ashanti Australia Ltd       

AngloGold Ashanti also targeted orogenic gold as part of their extensive Viking Project. The principal exploration programs consisted of mechanical auger sampling which targeted the most acid (HCl?) reactive carbonate material within a maximum depth of 7m. 10,940 samples have been compiled from digital WAMEX records from Anglo’s sampling within the Buxton licenses. These results define a broad 7 ppb anomaly which BUX immediately pegged as E 15/1719 and E28/2922. The four largest gold anomalies cover approximately 70 km2. Anglo drilled a small number of air core holes in the far western and south eastern portion of the Project area without intersecting anomalous gold. Neither Anglo nor any other previous explorer have drill tested the Jeffery anomaly.

 

Anglo’s 2010 auger sampling targeted the most calcium-rich part of the regolith profile as evidenced by Ca abundances which are substantially higher than BUX’s soil samples (despite the practically identically laboratory methods used - aqua regia digest with ICP finish). Since calcrete is highly capable of trapping gold moving through the regolith in surficial groundwaters, Anglo’s work is therefore considered to be highly prone to lateral dispersion effects and can be interpreted in a similar way as stream sediment samples whereas BUX’s soils are likely to detect in-situ bedrock gold enrichment.

Figure 3: Summary of historical exploration at Goldmember

 

 

BUX Exploration Programs

Desktop compilation and analysis of WAMEX data by BUX in May 2019 identified the regionally anomalous gold levels in Anglo mechanical auger sampling – a large but subdued anomaly.  The source of this gold has not been located and none of this anomalous area has been followed-up with air core or other drilling methods. 

 

BUX’s subsequent exploration approach has consisted of field reconnaissance and a blanket geochemical soil sampling program over the two granted licenses. 

 

Soil Sampling

Three soil sampling programs have been conducted; the Phase 1 soil program involved an 11-sample orientation program which aimed at evaluating four low level gold methods from the Intertek laboratory.  This work successfully repeated the background / anomalous pattern of gold results from the Anglo auger sampling.  The aqua regia analysis method AR25/eMS was selected for the subsequent soil analyses.

 

The Phase 1 orientation work was followed by 1-km spaced grid pattern soil sampling (Phase 2 - 413 samples) and subsequent infill soil sampling (Phase 3 - 345 samples).  All BUX soil sampling has followed an identical and simple procedure whereby approximately 4kg of -4mm sample was collected in the field from a shallow (10-20 cm) hole.  A total of 758 samples, including 60 quality assurance samples (site duplicates & replicates plus corresponding “original” samples), have been collected by BUX during Phases 2 & 3.

 

This work has resulted in the definition of the soil gold anomaly herein termed “Jeffery” which is described in more detail below.  Additionally, several other broad low-level multielement anomalies are present in the soils data which should be considered for follow-up exploration.

 

Soil Sampling - Jeffery Anomaly

Jeffery is annular in shape, and measures about 4km x 2km elongated in a NNW direction.  The anomaly area of 5 km2 is defined by 114 BUX soil samples which return an average grade 5 ppb (~ 2 x background) and a maximum of 13.8 ppb Au (~ 5 x background).  A statistical correlation is apparent between Au, Ca, As, Cu +/- Sb and V.  The correlation between gold and calcium appears to weaken at higher gold grades.  Interpretation of magnetics indicates that this anomaly lies within a demagnetized zone adjacent to a large circular feature with several structural discontinuities evident in the magnetics. 

 

The Jeffery Anomaly lies along a drainage divide / hinterland and away from the valley bottom – a landscape setting where soil sampling is more likely to detect bedrock gold enrichment.

 

Opportunistic Rock Chip and Calcrete Sampling

Samples of calcrete were also collected where this material was abundantly evident in the soil sample (i.e. in the +4mm fraction).  This material has not been assayed apart from 13 samples within and around the Jeffery anomaly area.  Three calcrete samples within the 5 km2 anomaly area returned over 20 ppb Au with a maximum of 26.5 ppb Au.  The calcrete samples were also analyzed at Intertek by AR25/eMS. 

 

A total of 17 rock chips were also collected during the Phase 2 work.  Five rock chips of weathered granitic Archean rock were selected for whole-rock geochemistry and three samples of bucky quartz and apparent ferruginous laterite were submitted for fire-assay gold. 

Figure 4: Gridded gold-in-soil results from Buxton's recent surveying on E15/1719 and E28/2922

Figure 5:  Close-up of the gridded gold results from the Jeffery Anomaly area.

 

 

Discussion

Anglo targeted the most calcium rich part of the regolith profile as evidenced by Ca abundances which are substantially higher than those in BUX’s soil samples despite the very similar analytical approach.  Since calcrete is highly capable of trapping gold moving in the regolith system, Anglo’s work is considered to be highly prone to detecting lateral dispersion effects and should be interpreted in a similar way to stream sediment sampling programs, whereas BUX’s soils are likely to detect much more localized bedrock gold enrichment.  Concomitantly, it is likely that the BUX soil sampling approach may not be effective where the soil profile is thicker, e.g. in the lower parts of the drainage system.

 

BUX therefore believes that the Anglo work has detected a widespread dispersion pattern from a bedrock source of gold that is likely to be present in the Project area.  The Jeffery soil anomaly represents a candidate for the source of this gold.  Support for this interpretation is provided by the calcrete results, regolith setting, and structural / geodynamic context.  The Jeffery anomaly therefore constitutes a target for follow-up with air core drilling. 

 

Furthermore, the soils and auger data combined with relatively high quality radiometric and elevation datasets provide an excellent opportunity to evaluate the regolith setting and prioritise follow-up strategies for the remainder of the gold anomalies in the area, which may include reconnaissance electrical geophysics combined with interface drilling programs.

 

More detail is provided in BUX's Goldmember Technical Snapshot available here...

 

References

Goscombe, B., Blewett, R.S., Czarnota, K., Groenewald, P.B. and Maas, R., 2009. Metamorphic evolution and integrated terrane analysis of the eastern Yilgarn Craton: rationale, methods, outcomes and interpretation. Geoscience Australia, Record 2009/23. 270pp.

Krapež, B, Standing, JG, Brown, SJA and Barley, ME 2008, Late Archaean synorogenic basins of the Eastern Goldfields Superterrane, Yilgarn Craton, Western Australia: Part II. Kurnalpi Terrane: Precambrian Research, v. 161, p. 154–182.

Smithies, RH, Lu, Y, Kirkland, CL, Cassidy, KF, Champion, DC, Sapkota, J, De Paoli, M and Burley, L 2018, A new look at lamprophyres and sanukitoids, and their relationship to the Black Flag Group and gold prospectivity: Geological Survey of Western Australia, Record 2018/15, 23p.

Witt, WK, Ford, A, Hanrahan, B, and Mamuse, A, 2013, Regional-scale targeting for gold in the Yilgarn Craton: Part 1 of the Yilgarn Gold Exploration Targeting Atlas: Geological Survey of Western Australia, Report 125, 130p.