Ajax Project
Gold was first discovered in 1851 at Wombat flat as prospectors searched through the creeks and streams heading to inland Victoria. By 1855 alluvial diggings had spread across the region with Daylesford town centre spring to prominence from the early 1860s.
In 1854 the first hard rock reef opened out was the Mauritius “Kidd’s Gully” mine. Soon after production from Burdon’s reef at Doctor’s Gully realised 2 oz to the ton. At this time Addis and Brook opened the Cornish reef with the production quoted as 3 oz/ton.
By 1856 the Daylesford auriferous belt is had been recognised as a significant gold field It is described as “approximately one mile in width and can be traced for several miles north and south”. The belt comprises many north-south trending reefs including Ajax, Rising Star, Specimen Hill, Colliers, Freemans, Wombat Hill, Cornish, Fear Not, Crown, St George, Eugenie and Hepburn. The earliest reference identified so far suggests mining on the Ajax line of reefs started around 1857.
By the 1860s the Connells and Nuggety Ajax reefs between Connells Gully and Tipperary point as well as Packers Reef on the Dry diggings and Frenchman’s, Steels Pioneer and Humbug reefs at Yandoit were all in production. Unfortunately, the Yandoit reefs proved poor and by 1861 largely shut down.
The ore of the goldfield generally was largely treatable through traditional gravity methods however in the literature there is reference to the treatment of pyritic ore using a chlorination process starting around the 1870’s. As enough of the ore had proved to be refractory but worth recovering, the Daylesford Pyrites Company (“Daylesford Pyrites Works”) using a 30 ft long furnace and grinding mills to treat ore was established. The works was reputed to be reasonably efficient using the “Newbury Vautin Improved Rapid Chlorination Process for Gold Extraction”.
Fortunes started to shift and late in the 1870s the Cornish mine fell into partial decline and by the 1880s was not considered profitable, and attention shifted to the 1886 Rising Star line. Whilst most mining was in decline sporadic production continued and in 1903 an English company took control of Cornish Hill. They were able to turn a profit from the mine until the First World War. The shifting fortunes of the main lode systems within the Daylesford goldfield seems to have migrated from one line to another and as one became unfavourable, a second became more profitable.
As a more profitable mine, the Ajax company continued well towards the First World War and in fact by 1911 Ajax Co was running a 20 head battery and at North Nugget, a 10 head battery. In 1914 a disastrous fire at the Ajax/North Nuggety destroyed winding engine and housing as well as boilers and compressing plant. Given the mine was still considered highly profitable, new equipment was installed over the old Ajax shaft and the mine continued working well into the 1920s. The Ajax mine attracted neighbours at Nugget Ajax, Ajax North, Ajax South, and Christian Ajax and the importance of the lode structure was well established.
For Ajax mining at depth was starting to compete with water influx. The mine was also struggling for materials and labour and by around 1917, most of the mines on the Ajax lines only continued to engage in minor prospecting. Reportable ore grade and production started to diminish. A year later the Ajax Company discovered a new line of reef however this was short-lived and Ajax North became largely unprofitable in development operations confining its production to taking out remnant stopes.
Ajax and Ajax North closed initially by 1926, however mining continued in Daylesford and in 1939 the most prolific and high-grade producer at 33 dwt/ton is the Maxwell Consolidated working to the 600 ft level.
The gold mining as elsewhere faltered during the First World War. A resurgence again in gold from Daylesford in the 1930s was driven by the Maxwell Consolidated. Its success revived the interest in the Ajax mine also but was short lived, Sporadic attempts to reopen the Ajax Consolidated occurred up until around 1947. The poppet head was eventually pulled down in 1979 and the shaft closed forever.
Today some of the original town centre is now submerged beneath Lake Daylesford (an historical dredging pond now rehabilitated as a feature in Daylesford township). The community however lives on and is a thriving tourist destination bustling with cafes, restaurants, and crafts shops. The township along with sister town, Hepburn, now promote the natural spring water found in the area and many tourist ventures often refer to the glorious gold mining days that built the town.
Many of the historical workings are now covered over or have collapsed. While evidence of some shafts remain as small openings in the countryside, most are too dangerous to easily access and will require substantial rehabilitation works to make safe. There is expectation that some point of entry will eventually be opened, and the historical mine can again be accessed for exploration purposes.
EL007330 is located in the Bendigo Structural Zone of the Tasman Fold Belt and covers the north-trending Muckleford Fault. The basement lithology comprises interbedded slates, siltstones and sandstones turbiditic sequences of the Ordovician Castlemaine Group that have undergone east-west compression during the Benambran Orogeny. Limb thrusts propagating from bedding parallel layer slip planes formed as fold lock up approached. The folds form part of larger scale anticlinoria which form broad, gently plunging dome and basin structures. The Daylesford Goldfield is located at the culmination of such a dome on the Daylesford Anticlinorium. Major west-dipping reverse faults are interpreted as listric faults. The regional north-northwest trending Muckleford Fault passes 3 km west of Daylesford and truncates the Daylesford Anticlinorium west of its hinge. (Gough, 2013) Widespread orogenic gold mineralisation associated with faulting occurred during the late stages of deformation. (Arden, 1997)
Underground mapping in several mines by the GSV has shown an alternating sequence of shale and sandstone horizons. In practice these may sometimes represent shale horizons up to 2 metres wide, sandstones that may be massive channel deposits up to 10 metres thick, or alternatively they may represent upward fining sand dominated turbidite units mapped individually or as groups of units with similar characteristics.
Folds in the area are upright with axial planes dipping steeply to the east, with wavelengths varying from over 500 metres to less than 50 in some places. The fold pattern appears to be far less regular than that observed in the mineralised corridors of the Bendigo or Castlemaine goldfields. Although faulting may in part explain this irregularity, it appears likely that significant variation in wavelength does exist, as shown on several traverses that have been mapped in detail by the GSV.
Larger amplitude folds appear more likely to host significant mineralisation, with the Ajax line associated with one of the broadest fold limbs in the area. Examination of the available mine plans, combined with the relationship between the faulting and bedding, strongly suggests that the overall plunge of the Ajax anticline is to the south in the Ajax South (14°S) (Macdonald, 2006)
The Ajax mines worked a series of nine stacked reverse fault hosted lodes that dip between 45o and 90o to the west (Whitelaw and Baragwanath, 1923). The faults strike oblique to bedding and consists of laminated quartz that is highly mineralised in places. Mineralisation appears to occur in ‘shoots’ within these fault systems which have been identified to potentially correspond with favourable lithology. In the case of the Ajax line, the shoots are associated with sandstone containing thinner beds of slate (Whitelaw and Baragwanath, 1923). These lodes have a variable thickness along strike. The following lode thickness in the Ajax Mine have been estimated by Whitelaw and Baragwanath, 1923:
- Ajax Lode: 1 foot to 6 feet. ( 0.3-2m)*
- MacMillan’s Lode: 3-10 feet.( 1-3m)*
- North Lode: 1 to 4 feet.0.3-1.3m)*
* subsequent search of the literature has identified the lode thicknesses exceed Baragwanath’s initial observation and this increased thickness from the literature search has been used in developing the models
These faults are only payable in the eastern limb of the anticlines although limited exploration has occurred in the western limb where these faults are reported to be parallel to the bedding with little or no quartz (Arden, 1997). There is the potential for mineralisation in the western limb where these faults become bedded in dark shale units directly after intersecting. This style of mineralisation is commonly seen in the Ballarat goldfields.
Figure West dipping faults in the Ajax ((Whitelaw and Baragwanath, 1923)
At the Nuggetty and North Nuggetty Ajax mines, sub-horizontal tensional veins, known locally as ‘flat makes’ occur. These veins are up to 90m in width, 2m thick were mined for 340m north and south (Baragwanath, 1923). These veins border the west dipping faults and probably formed in a response to movement along them (Mahar, 2002) In the Ajax line, these veins increase in abundance where the lithology is dominated by thick sand beds which is considered to a reflection of the competency of these units (Mahar, 2002). There is potential for local gold enrichment at the intersection of the east and west dipping faults (Whitelaw and Baragwanath, 1923).
The Flat Makes have not been included in the Exploration Target and are seen as an opportunistic target at this stage. The breakdown of production between the West Dipping faults and Flat Makes has never been completed to the best of Red Rock Australasia’s knowledge. This is one of the tasks that will be completed during the literature search.
Previous diamond drilling has indicated that mineralisation extends into surrounding sandstone wall rock that contains little to no quartz veining. Petrographic examination of the sediments revealed visible free gold associated with disseminated pyrite aggregates containing an assemblage of arsenopyrite, pyrite and lesser copper, lead and zinc.
Reef Styles
West dipping shears/ reverse faults
These structures form a series of subparallel fault in the eastern limb of anticlinal folds seen in both the Ajax and Cornish lines. On the Ajax lines seven main loads have been worked: Blacksmiths, nuggetty Welcome, Western, Ajax, McMillan’s and Ajax North the reefs are separated by approx. 20 – 50 meters and have sinuous sub parallel traces. Where the faults cross the fold hinge, the structure tens to develop a dilatant zone which leads to a thickening of the reef at this point.
Associated quartz reef varies from a few centimetres to over 10 meters however most available information suggest in the rage 1 – 3 metres but can be upwards of 6 metres in part.
East dipping faults
East dipping structures are rarely seen in these mines. These structures are associated with more laminated quartz as bedding parallel slip faults and often end up linking structures from within the east facing limb of the fold
Flat Makes
These flat lying veins most likely as a form of tension gash vein system were reported to be persistent over several hundreds of meters long strike up to 20 to 50 m in width and from 0.5 to 2m thick. In the determination of this exploration target, the flat makes have not been taken into consideration. The presence of the flat makes will serve to provide additional upside to the project should mining commerce.
Mineralogy
Gold is hosted in the quartz veins and in the immediate wall rock as alteration adjacent to the main quartz filled structures. Generally dominated by pyrite with lesser arsenopyrite, sphalerite and galena and rare chalcopyrite. Arsenic concentrations appear to be significantly lower than at Bendigo and more similar to the deposit at Ballarat. Early processing of the ore seems to suggest that whilst free milling was a major component, the establishment of the Daylesford Pyrites Works to process ores would imply some refractory ore is present. This is presumed to be most likely in the wall rock alteration halos.(Bravo, 2001)
Production
Total gold production from the Daylesford goldfield to date is estimated in excess of 1.29 million ounces. Primary gold production amounts to 795,254 ounces.
Two major lines of workings dominated historical production namely the Ajax and Cornish lines with production figures of 657,343 @14.8g/t and 523,429@ 10.8g/t respectively. These lines count for nearly 70% of the production. The ajax lines was clearly the bigger producer and at a notably higher grade. The deepest mines at Daylesford identified to date is the Ajax shaft at 370m and the New Cornish at 404m. Outside of the two main lines of lode, several other mines produced significant amounts of gold including the Rising Star Mine (78,458 oz), Maxwell Consolidated (21,989 oz) and the Specimen Hill Mine (35,801 oz). (MacDonald, 2006)
Recent exploration restarted around mid 1990s when two RC holes of a lager program (RC2 & 5 aggregating 170 m) were drilled to test results from the channel sampling at the South Star Extended Prospect. Although the drilling intersected significant zones of quartz veining, no significant gold grades were returned, the peak result being 3m @ 0.07 g/t Au from 12 m in RC5. Two diamond holes (RD12 & 17 aggregating 467.2 m) were drilled to test for westerly dipping auriferous reefs in the South Cornish and Argus areas south of Daylesford. Hole RD12 intersected several quartz reefs associated with shear zones and carbonaceous shale and slate. Hole RD17 was drilled to follow up anomalous gold results from Nord surface sampling and shallow RC drilling. Designed to intersect surface mineralisation at depth, the hole intersected several auriferous reefs. The South Cornish mine was worked to a maximum depth of about 110 m (360 feet), well above RRG’s high grade intersections in RD12.
During the same period, an airborne magnetic and radiometric survey was flown at 100 m line spacing. Results from the survey identified NNW trending fold closures that are intersected or displaced by NE trending structures.
During 1996 a further A five-hole (513 m) RC drilling program (RC7 – 11) was completed to test anomalies identified by further channel sampling at the South Star Extended Prospect. No significant assays were reported. A six-hole (467 m) RC drilling program (KID1 – 6) was completed at the Keep it Dark Prospect to test gold anomalies identified by Nord Resources in 1988. Most holes intersected bleached sandstone and siltstone with abundant quartz veining and sericite–pyrite alteration.
By 1997, results of historical research were incorporated into 3-dimensional computer models of the Ajax and Cornish lines; and target zones identified based on this modelling. Seven mines have been incorporated into the model for the Ajax li ne – Ajax North, The Ajax Mine, Ajax Central, North Nuggetty Ajax, North Ajax, Nuggetty Trafalgar and Christenson’s Ajax were included in the models
Along with the Cornish line comprising the North Cornish, the Victorian Comish (Bonnards) and the New Comish (Mitchalls and Bonnards) mines. The modelling data has not been able to be located
In 1998 another two diamond drill holes (RD18 & 19 aggregating 1035 m) were drilled beneath the North Nuggetty, Ajax and Ajax Central Mines. Both holes intersected several weakly mineralised reef structures. Most of the gold is associated with narrow quartz veins, minor sulphides and structures. However some gold occurs in silty sandstone without any apparent veining, sulphides or structures. Best results were in RD19 with 9.1 m @ 9.18 g/t Au intersected.
Further in 1999, Seven soil samples and one rock sample were collected from the Ajax and Cornish areas respectively. Samples were analysed for an extended suite of elements including gold and platinum but did not return any high values.
Undeterred the exploration continued with four diamond holes (RD20 – 23) with RC pre-collars (aggregating 963 m) were drilled in the central part of the Ajax line. Arden (1999) reported that this showed “widespread gold mineralisation not solely restricted to (a) previously mined narrow zone within east-dipping sediments to the east of the Ajax Anticlinal Axis”.
Regionally exploration expended to see a detailed structural interpretation based on historic mining records and Landsat imagery was completed to identify targets for gold mineralisation.
This included re-evaluation of an unreported diamond drilling program at the Aurora Mine by Ajax Consolidated NL in 1951: • an RC program (5 holes, aggregating 277 m) at Eganstown by Dome Resources NL in 1988 and• an RC program (8 holes, aggregating 497 m) along the Cornish line by Nord Resources (Pacific) Pty Ltd between 1988–89. The only significant intersection from this program was 9 m @ 0.64 g/t Au from 52.0 m including 2 m @ 1.92 g/t from 56.0 m in 125 RC 6.
Ealy into 2001 further structural mapping of the Ajax Anticline and surrounding area by Thom (2000) revealed significant local variations in fold plunge, fold morphology and bedding. It was noted that the workings are associated with areas of intense folding and deformation in stark contrast to unworked areas north of the Ajax North mineshaft.
From early 2000’s until present day exploration remained largely office based and limited further reviews of previous mining activity historical data and previous exploration efforts were sporadically undertaken up until 2006. Nothing further was completed until Red Rock acquired the tenement in 2022 and reviewed all the historical data before developing detailed computer models for the mines, lithology and structural elements.
Whilst the eventual definition of economic quantities of gold within the historical Ajax mine is the wishful endgame, there are many hurdles and road blocks to navigate before then. At this early stage the area is under only an exploration licence, hence the drive is on understanding the geology (geoscience including geochemistry, lithology and structural elements of gold mineralisation) rather than any extraction or processing investigations. Understanding the geology better at a major mine site like Ajax will undoubtedly lead to developing a greater understanding of the geology of Victoria, as important as any other scientific study of the world around us. As the historical mine has been closed off and buried, since 1980s there is no physical access to the mine any more. Past production to implies that any remaining mineralisation available to study is at greater depth (below 300 metres down!). Consequently, drilling is the only tool available to physically continue to investigate the geology. Some theoretical work has already been completed including computer modelling. As a result, the relationship between the folded rocks, the faults and subsequent mineralising of some structures in preference to others is developing quickly. Testing this model through drilling is a critical next step.
The first phase drilling will allow Geoscientists to determine if the model is correct, specifically targeting pierce points in the models where hard data is lacking but thought is though to occur based upon current understanding.
The first low impact programme planned for the proof of concept, will determine the next step.
First phase drilling is anticipated in early 2023 but remains dependent upon complying with many social, economic, environmental and stakeholder considerations with any anticipated follow up drilling not planned before late 2023.
