Graymare Gold Project 

• A huge area of unexplained gold mineralisation
• Fosterville analogies
• Only 2 known drill holes in the whole project area
• Over 60 historical mines &100 linear kilometres of alluvial gold

Project

The Graymare Gold Project comprises two granted contiguous EPMs, covering 199 sub-blocks amounting to 654x km².  The project is situated 40 km west of Warwick and north-west of Stanthorpe in south-east Queensland, covering the central and southern portions of the Warwick Goldfields (Figure 26 ).  Access to the area for field work is straightforward with the area generally open, subject to sheep and cattle grazing with some easily traversed forestry.  A good network of mostly gravel roads exists throughout the area, which is serviced by the townships of Stanthorpe (the base of operations) and Warwick.  The project is within a three hour drive from Brisbane.

The Graymare Gold Project encompasses a number of goldfields including the Pikedale goldfield in the south and Canal Creek goldfield in the west of the project area . 

The principal exploration target in the EPMs is bulk, low-grade gold of the orogenic and intrusive-related classes, which are discussed in detail below, but other gold deposit styles such as skarn-hosted gold and Carlin-style gold cannot be discounted.  Several areas of gold mineralisation are to be investigated and prospective areas have been identified at Kaffir Chief, Blackfellow, Mountain Maid, Telegraph, Providence and Camp Hill.

 Regional Geology

The Stanthorpe-Texas area is part of the New England Province (the southernmost structural province of the New England Fold Belt in Queensland) and comprises three structural units: the Silverwood Block, the Texas Block and the New England Batholith.

The oldest exposed rocks in the area belong to the Early Devonian Rosenthal Creek Formation, which consists entirely of sedimentary rocks (sandstone, mudstone, chert, intra-formational conglomerate and limestone).  The widespread Texas Beds are a thick sequence of flysch-like, regularly interbedded, volcaniclastic turbidites (lithic sandstone and mudstone) with minor chert, jasper, intra-formational conglomerate, acid to intermediate volcanics and limestone (Figure 26). Limestone lenses crop out mainly in the Texas area.  According to Geoscience Australia the age of the Texas Beds has been reported as old as Silurian (423 Ma) to as young as upper Carboniferous (Namurian; 315 Ma).  Authors in the Geology of Queensland (2013, p451) prefer a lower Carboniferous, Visean age (330-346 Ma).

The Texas Beds are intensely deformed and have been interpreted to be an imbricated stack of fault slices (Flood and Fergusson 1984), formed as the accretionary wedge of a subduction complex.  Dips are generally steep to vertical and beds are overturned in many places. Between Texas and Stanthorpe, the Texas Beds lie in an arcuate fold structure (orocline) approximately 75 km wide.  The strike of the Texas Beds is north to north-west with a series of west-north-west trending fault zones and anastomosing fault sets, which locally produce extensional east-trending structures, some of which are proven sites for gold mineralisation.

Permian rocks are confined to small inliers, outliers and fault-bounded basins; in places they unconformably overlie the Texas Beds. The Early to Middle Triassic Stanthorpe Granite crops out extensively to the east of the EPMs.

Gold Mineralisation

All the observed historical hard-rock gold deposits are interpreted to be syn-tectonic quartz-carbonate veins within slates, indurated shale and greywacke which are locally pyritic and have suffered slate-grade metamorphic deformation.  Records show that the auriferous reefs were small but very rich.  They were worked by small parties, and were generally abandoned at about 30 m depth, at the contact of the primary pyrite and arsenopyrite-bearing mineralisation.  Quartz veins and fissure fillings, strongly faulted in part, hosted the pyrite-gold mineralisation. 

Gold production was confined to reef mining but a reliable record of actual production is not available. 

Alluvial gold deposits are extensive throughout the tenement package.  The sources of many of these alluvial workings have never been traced.  Historical records report multiple quartz vein occurrences which were known to be gold-bearing but were not worked and could have been one of the sources for the alluvial gold.  Some alluvial gold areas were never reported or recorded by the QGS and consequently were forgotten until discovered by modern exploration.

The extensive alluvial mining in the west of the tenement area, in the Canal Creek Goldfield, had only a few hard-rock occurrences that were worked, and the geologists and miners stated “that the gold was derived from pyrite, sometimes observed in the middle of weathered pyrite crystal lattices” (de Havelland 1987).  Within these goldfields and clusters of mines, QMines has located several historical mines and prospects and zones of prospective rock formations associated with both hard-rock and alluvial gold mineralisation.

Previous Exploration

Drilling on the tenements has been very limited.  Saracen Minerals NL in 1989 tested two abandoned mine sites within the project area by drilling five holes for a total of 197 m.  The outcomes were disappointing with only low grade gold assays although it is possible that the positioning of the holes may have been sub-optimal

There were several EPMs held in the district by the ‘majors’ during the period 1987-1991. This was a difficult time for explorers, after the stock market crash of 1987 and it marked a period in which exploration was poorly funded: several international companies withdrew from Australia and Australian-based companies reduced or ceased exploration. This might explain why projects were not supported and would account for the scarcity of exploration drilling.  Table 9 details previous exploration work.

QCM concludes that although exploration concepts were generally valid, very little progress was made by previous explorers, other than to provide some good geochemical sampling and some geology and geophysical information, which has allowed QMines to analyse to its advantage the prospectivity of its EPM holding.  

Table 9:  Historical Exploration Activity from the 1970s to the Present Day.

Exploration Models for the Texas Beds

The Texas Beds are prospective for several types of gold mineralisation.  Figure 27 gives examples of the types of gold mineralisation which are considered relevant for the gold mineralisation currently known about for the Texas Beds.

Orogenic pyritic gold turbidite deposits

The term “orogenic gold” was introduced originally by Groves et al. (1998) in recognition of the fact that quartz-carbonate vein gold deposits in greenstone and slate belts, including those in banded iron formations, have similar characteristics and have formed by similar processes. Originally, the orogenic model applied strictly to syn-tectonic vein-type deposits formed at mid-crustal levels in compressional or transpressional settings, i.e. as syn-orogenic deposits. However, the term has been progressively broadened to include deposits that are post-orogenic relative to the processes at their crustal depth of formation.

Sediment hosted intrusive-related gold deposits

These deposits consist of disseminations, stockworks or sheeted veinlets of quartz and feldspar, within the thermal aureole above a roof zone of a reduced ‘I’-type granite.  Associated mineralogy to the gold can be arsenic, antimony, bismuth and molybdenum sulphides and tungsten minerals.  These deposits are related to deep crustal faults and type deposits are Muruntau in Uzbekistan (175 million ounces of contained gold) and Telfer in Western Australia (> 20 million ounces of contained gold).

Skarn deposits

These stratabound replacement deposits consist of disseminations and veins of gold or copper/gold mineralisation associated with porphyry-related mineral fluid migration away from the intrusive centres into preferred host rocks, e.g. calcareous and/or volcaniclastic sediments.  The best example in eastern Australia are the Big and Little Cadia gold deposits in NSW which contain approximately 500,000ozs.  Key to the deposits are the presence of major intrusive complexes cutting across permeable and replaceable calcareous rocks in conjunction with appropriate structural controls focusing the mineral fluid flow (Figure 28).

There is the possibility of finding skarn deposits in the Herries Range, because granitoids may have intruded the limestone horizons within the Texas Beds.  Marble deposits (metamorphosed limestones) are scattered throughout the Texas Beds.  Other examples of skarn deposits in Eastern Australia include the Red Dome and Mungana gold mines in far north Queensland with combined resources of 2.4 million ounces gold (not including mined sections) and the Bau gold mine of Sarawak Malaysia (585,000ozs gold).

Graymare Gold Project   Exploration Opportunities

QCM’s initial evaluation of the Graymare Gold Project has identified several prospective zones for gold .

• Palgrave Goldfield - Mountain Maid - Madam Ross - Telegraph zone
• Pikedale Goldfield - KC mine  and Star of the East mine cluster
• Camp Hill- Rabbit Fence - Whinge Hill zone
• Puddler - Hunts Gully - Mascot mine cluster
• Hunters Gully - Mount Burrabaranga zone
• Durikai zone

Palgrave Goldfield - Mountain Maid - Madam Ross - Telegraph zone

The two largest historical mines are situated in this gold district.  Mapping by previous explorers shows the mines are 3 km apart on differing postulated anticlinal structures (Hearder 1987).  The workings at both Mountain Maid and Madam Ross were in multiple high-grade vein systems with the Mountain Maid workings striking for a distance of at least 650 m and Madam Ross for 750 m (Hearder 1987).

Pikedale Goldfield- Kaffir Chief & Star of the East Mine Cluster

This is a group of six known hard-rock gold mines, and the Blackfellow gully was mined for both alluvial and hard-rock gold.  The mines hosted high-grade gold vein systems in pyritic slates and greywacke sandstones.  At the Kaffir Chief gold mine a report compiled by Kay (1978), described an underground sampling program conducted by the Queensland Mines Department, which returned average gold grades in the bottom section of the mine of 14.9 g/t gold with a high of 207 g/t gold from an existing pillar. 

Puddler - Hunts Gully - Mascot Mine Cluster

An 8 km long zone incorporates thirteen hard-rock gold mines and prospects and extensive alluvial gold workings at the Puddler, Hunts Gully and Two Lizards.  The mines were small; the largest of the hard rock mines was the Mascot gold mine in the south of the zone where the mineralised reef was 550 m in strike length (Hearder 1987). 

Hunters Gully- Mount Burrabaranga Zone

Eight creeks with anomalous gold values, with pan concentrate values ranging from 3.7 g/t gold to 236 g/t gold (Saracen 1989), drain a northerly trending elevated sand-covered ridge within undulating forested terrain.  The ridge extends for more than 5 km.  Alluvial gold workings are scattered throughout the zone but no hard-rock occurrences have been identified. 

Durikai Zone

The Durikai prospect is a 5 km long zone that is drained by six gold-anomalous creeks and gullies.  Pan-concentrate sample results ranged from 0.5 g/t gold to 22 g /t gold (Saracen 1989) in this part of the Herries Range.  Pyritic shales and greywackes are known to be exposed in the area.  No exploration has been conducted along the zone.

Conclusions & Recommendations

The Graymare Gold Project contains an abundance of gold mineral occurrences, as both high-grade, small, hard rock workings and more widespread alluvial gold workings.  The Texas Beds of the New England Orogen are considered prospective for large-scale intrusion-related gold deposits and possibly sediment-hosted gold deposits. 

QCM has proposed the following exploration programme:

• A full data compilation exercise should be undertaken to establish what work has been done and what were the outcomes of that work. This is to include a substantial review of geophysical and satellite data with a view to better understanding the geology of the area. The output from this work should be in the form of a digital summary map that can be used for assessing anomalous areas defined by previous explorers and aid further targeting of exploration work.
• Geological reconnaissance and rock-chip sampling of anomalous zones identified from the data compilation exercise.
• Stream and soil geochemical follow-up sampling, ground-checking

The aim is that the above work can progress exploration to identify areas for more detailed follow up including ground-based geophysical surveys and possibly drill testing.