Orion Gold NL
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WA - Fraser Range

Fraser Range Project, WA

Fraser Range Nickel-Copper & Gold Project

The Fraser Range Nickel-Copper & Gold Project comprises almost 4,500km2 of granted tenements and applications spanning the rich Fraser Range and Tropicana mineral belts in Western Australia.

The Tropicana belt hosts the world-class Tropicana Gold Mine, operated by AngloGold Ashanti and Independence Group, which is one of the most significant new gold discoveries of the past decade and is now in commercial production.

The Fraser Range belt has recently risen to international prominence with the discovery of the world-class Nova-Bollinger nickel-copper-cobalt deposit by Sirius Resources (ASX : SIR).

This area is now one of Australia’s hottest exploration districts, based on its strong potential to host repeats of the Sirius Resources' Nova-Bollinger Ni-Cu discovery. Despite being located just 250km east of Kalgoorlie, very little exploration has been conducted historically due to the presence of thick sand cover and lack of infrastructure.

Orion's Fraser Range tenement package includes the Peninsula Project and the Cundeelee Project, which host both Nova-style nickel-copper-PGE targets and Tropicana-style gold targets.  The tenements were acquired from Mark Creasy, one of Australia’s best known prospectors, and unlisted company Kamax Resources in 2013.

 

Deposit Model

Orion's primary target in the Fraser Range are magmatic hosted nickel-copper deposits.  These deposits are formed during the intrusion, emplacement and cooling of mafic-ultramafic magmas followed by later uplift.  The schematic diagram below shows some of the characteristics of these deposits, as well as the processes and elements required to form them.  Key elements include:

  • Ni-Cu concentrations elevated above the average content of mafic-ultramafic intrusions (a function of the Mg content of the intrusion)
  • Ni-Cu hosted by magmatic sulphide minerals
  • Sulphides formed during emplacement of intrusions and concentrated by magmatic processes
  • Interactions with "country rock" especially sulphur bearing seditments can also play a role in formation of deposits by sulphur saturating the magma.  This process is called crustal contamination.

To measure these key indicators a combination of geological, geochemical and geophysical datasets are required to be acquired and interpreted.  Certain datasets may have limitations in some situations, e.g. under recent cover.  Orion has developed a systematic exploration methodology to test its Fraser Range landholdings to ensure the most efficient and cost-effective exploration of its project area.

 

History

Nickel exploration was carried out by Western Areas NL at the Peninsula Project between 2000 and 2006. Scout RC drilling by Western Areas yielded intersections of gabbronorite and other mafic units which were interpreted to represent differentiated mafic intrusives.

Drilling in the three holes also yielded nickel values of >0.1% nickel in hard rock. This exploration pre-dated the recent Nova discovery and was not conducted in that context, although Peninsula is one of the few confirmed differentiated mafic intrusives in the Fraser Range geological province, with a similar rock composition to Nova. Significantly, while aeromagnetic and ground gravity data was collected, no EM surveys (airborne or ground) were carried out.

 

Orion's Exploration

Since acquiring the project, Orion has carried out airborne and ground EM surveys, ground surveys and reprocessed historical aeromagnetic data. This has enabled the Company to identify those areas most likely to be underlain by mafic-ultramafic intrusions. Interface drilling at a number of these target areas has been used to confirm the presence of mafic-ultramafic intrusions as well as collect bedrock samples for high precision multi-element geochemical analysis. 

Detailed geochemical analysis and interpretation assisted by an expert in the field, Professor Reid Keys of Monash University, has concluded that the intrusive mafic and ultramafic bodies intersected are all dervied from the same magma source at depth.

  

Extended spidergrams from the HA2 & Pennor Prospects, demonstrating the co-magmatic nature of the mafic-ultramafic intrusives intersected in drilling.

Importantly these bodies are Ni-Cu-Co bearing, including a best result to date of 80m at 0.11% Ni in OPRC008, with bnoth geochemical data and petrogrphic inspections confirming that the metlas are hosted in sulphides.  Encouragingly the suplhide grains that were intersected have been calculated to contain high metal tenors leading the Orion exploration team to the conclusion that any massive suplphide accumulations which are discovered are likely to be high grade deposits.

 

Geochemical plots from HA2 RC drillling both confirming that Ni-Cu is present as sulphides.  The Ni vs Mg plot (LHS) demonstrates that, Ni is present in elevated concentrations based on Mg content and the Cu vs S (RHS) shows a strong correlation between these elements.

Geochemical data has also confirmed that crustal contamination has occurred during uplift and emplacement of these intrusions.  This is particularly important as this process can trigger formation of sulphides in a dynamic melt, which can then be concentrated by other magmatic processes.  Conversely sulphides formed as a result of magma colling, can often become trapped in solidifying rock before gravity or other processes can cause them to accumulate and to coalesce into immiscible massive sulphide melts. 

 

Geochemical plot of Nb / Th ratio vs Th / Yb ratio, both normalised using average concentrations in primitive magmas.  Nb / Th ratios decrese with crustal contamination.  Th / Yb ratios increase with crustal contamination.

In order to focus exploration efforts, in particular, high powered ground EM surveys within the large Orion tenement holding, the Company has executed a closely spaced ground gravity survey and processed the data using gravity inversion techniques to effectively locate the high density mafic-ultramafic intrusions that are the hosts for magmatic Ni-Cu mineralisation and therefore our primary targets. 

 

Orion's tenement holding in the Fraser Range depicated on regional gravity image and the area of the lage scale, high resolution gravity inversion modelling completed in May 2015.

 

Gravity Inversion Model indicating bodies with SG of 3.0g/cm3 and above, which is characteristic of mafic intrusive bodies in the Fraser - Albany belt.

 

The results of this survey are shown in the figure above, with the red shapes denoting areas where the sub-surface density is best modelled with SG's of 3.0 and above.  This density corresonds to the density measured for mafic intrusions elsewhere in the Fraser Belt.  Consequently these are high priority targets in the Company's current exploration programs.

Data from the Company's drilling programs has enabled the robustness of the gravity modelling to be assessed independently and in general there is good correlation between the location of mafic-ultramafic intrusions intersected in drilling and the locations predicted by the gravity model, based on drilling to date.

Importantly, the modelling indicates the presence of a significant dense body at depth beneath the project area, with the bodies closer to surface emerging as apophyses from this larger body.

This fits with the general deposit model  discussed earlier, where the mafic-ultramafic intrusions intersected near surface show evidence of having been extruded from larger staging chambers which lie at depth.

 

Orthogonal view of +2.85g/cm3 surface from gravity model showing a large staging chamber with smaller intrusions emerging as apophyses to reach closer to surface.

 

 

 For the latest updates on exploration within the Fraser Range Project, please refer to our ASX Announcements