• Ironbark Gold Limited (Ironbark) and Monaro executed a Heads of Agreement covering the Captains Flat Project in August 2006. The agreement will enable Ironbark Gold to earn a 75% interest in the project subject to it meeting amongst other conditions, all expenditure commitments for the next 2 years and the completion of a positive feasibility study. Ironbark Gold is managing all exploration activities.

• The JV agreement with Ironbark Gold Limited was amended in May 2008 to accommodate the entry of NSW Base Metals Ltd, a wholly owned subsidiary of the international company Glencore Group.  Monaro’s position in the JV remains unchanged. 

• Ironbark completes air core drilling of Lake George tailings dumps. Ironbark estimates that there could be in excess of 2 million tonnes of this material in and around the old mine workings.

• Mine data compilation of Lake George Mine and other prospects in progress

Setting

Exploration Licence No. 6381 is underlain Silurian volcanics and sediments of the Hoskinstown Group which occur over a 39km strike length and 3km width. These rock units are prospective for Volcanogenic Massive Sulphide (VMS) deposits and host the now closed Lake George Mine.

Based on an earlier assessment by Monaro Mining NL of the previous exploration of the licence area, it was concluded that nine prospect areas have favourable mineral potential, and recommendations were made for their further assessment.

Figure 1: Location of project and main prospects

Location

The Project area covers an area of approximately 239 square kilometres surrounding the old mining town of Captains Flat, which is located about 60 kilometres southwest of Canberra (Figures 1 and 2).

Geology

The exploration licence covers a centrally located, narrow north-trending belt of the Hoskinstown Group which is of Silurian age. The Hoskinstown Group occurs in a north-plunging syncline which is located within a graben bounded on the west by the Narongo reverse fault and flanked on the east and on the west by the Foxlow Beds which are of Ordovician age.

The Hoskinstown Group consists of the Copper Creek Shale with Rutledge Quartzite Member, overlain by the Kohinoor Volcanics which includes the mineralised Keatings and Elliots Shale Members. These units are in turn, overlain by the Captains Flat Formation.

The Kohinoor Volcanics consists of interbedded and interfingered units of andesitic, dacitic and rhyodacitic volcanics and pyroclastics of crystal, crystal lithic and lapilli tuffs, agglomerates, rhyolitic lavas, shales and volcanic cherts and sinters. Shale lenses are relatively rare but several, including the Keatings Shale Member and the Elliots Shale Member contain pyrite and economically important quantities of copper, lead and zinc sulphide mineralisation. These shale units are believed to represent quiescent periods during the eruptive sequence.

The Kohinoor Volcanics have a gradational boundary with the overlying Captains Flat Formation which consists of a sequence of interbedded shale, lithic tuff, thin basalt, dacite and sandstone.
The Foxlow Beds and Hoskinstown Group are intruded by Early Devonian adamellites and granodiorites of the Sapling Flat Igneous Complex.

Mineralisation

The Kohinoor Volcanics host a base metal deposit of economic significance at the old Lake George Mine. At this mine, three elongated lode shoots that are conformable with the Elliots, Central and Keatings shale lenses were mined.

Figure 2: Township of Captains Flat.
Looking south-east over tailings dumps

The base-metal lodes reportedly had a total outcropping strike length of approximately 800 metres, extended to a depth of 600 metres and were up to 20 metres thick. They consisted of massive banded pyrite, sphalerite, galena and chalcopyrite, in decreasing order of abundance, with minor tennantite, arsenopyrite and gold. Laterally, the mineralisation passed into a peripheral zone of dolomite, chert and jasper. Stratigraphically beneath the lodes to the west, there is an altered zone with silica and stringer mineralisation of vein and disseminated pyrite and minor chalcopyrite with gold.

Mining History

The Lake George Mine was first worked during the period of 1882 to 1899 for a recorded production of 26.7 tonnes of silver, 16,100 ounces of gold and 3,841 tonnes of copper from 114,560 tonnes of ore. Minor production from the Federal Mine and from the Vanderbilt Hill workings are probably included with that of the Lake George Mine.

Figure 3: Looking northerly along main ridge line with old ore
storage bin on LHS of photo. Rehabilitated (green) tailings ponds are located in mid-distance.

The Foxlow gold prospect has a recorded production of 40 ounces of gold in 1934 and 1936. The Lake George Mine was reopened in 1937 and up to the date of its closure in 1962 produced 406,418 tonnes of zinc, 243,851 tonnes of lead, 27,230 tonnes of copper, 236.4 tonnes of silver and 220,000 ounces of gold from over four million tonnes of ore (Figures 3 and 4).

Figure 4: Old ore storage bin depicting concrete footings of support infrastructure.

Review of Exploration Prospectivity

An initial review of the tenement concluded that there were nine prospect areas worthy of detailed assessment and exploration. These included the following:

Lake George Mine Area

This area lies in the Kohinoor Volcanics and it includes the Lake George Mine and any possible extensions to the known lodes, including the Keatings South Prospect, and the nearby Federal Mine and Copper Shaft and Copper Dam prospects.

It was concluded that there is potential for extensions and repetitions of the known massive base metal sulphide lodes, down dip and along strike. Also, in the stratigraphic footwall (in the feeder zone of the lodes), there is potential for structurally relocated copper and gold stringer mineralisation.

The Lake George Mine at Captains Flat was one of the earliest base metals mines to be developed in NSW. Exploration during and since mining has considered the possibility of new ore shoots both along strike and at depth. The extent of this drilling and the position of the now extracted ore bodies is depicted in Figure 5. Drill hole T29 is recorded as intersecting 2.44 metres of mineralisation with a grade of 3.9% Zn and 1.9% Pb, whereas T30 is recorded as hosting 1.22m with a grade of 12.4%Zn and 5.4% Pb. Another drill hole(T57) indicates a grade of 9% Pb within close proximity. These holes are the deepest (at approximately 945 metres) that have been drilled within the vicinity of the Lake George Mine and are spaced over a 300 metre strike length. Further detailed assessment of the geology and geophysics is required, but at this stage, the area directly below and to the south of these three drill holes presents itself as a viable drilling target. The potential for an orebody to occur at depth with similar grades to those encountered historically is considered to be reasonable and warrants testing.

Figure 5: Lake George Mine at Captains Flat illustrating Exploration Target Area.

Vanderbilt Hill

This base metal and gold prospect lies in the Kohinoor Volcanics adjacent to and to the east of the Lake George Mine and was originally mined as a gold prospect to a shallow depth. There have been several drilling programs and during the earliest campaigns, were focused on base metal mineralisation – no gold assaying was carried out. Some of this earlier diamond drilling, which targeted the Vanderbilt gossan is summarised as follows:

Later campaigns focused more on the gold potential of the prospect. A total of 15 percussion holes were completed over the prospect area during the late 1980’s and early 1990’s. The location of these holes is depicted in Figure 6 and a summary of the drilling is tabled below:

Drill holes VB-8 and VB-15 tested adjacent structures whereas the remaining holes were focused on the main Vanderbilt mineralised structure over a strike length of approximately 250-300 metres. These drill holes were orientated north-westerly and were angled at approximately 70 degrees.
These drill holes established the presence of a relatively broad band of gold and base metal mineralisation, with many of the drill holes being terminated in anomalous to high gold values.

Figure 6: Vanderbilt Hill Prospect showing
Soil and Near Surface gold zones and Exploration Targets

It is clear that the Vanderbilt “Deeps” (the zone below existing drill holes VB-7 to BB-11) presents as a strong gold exploration target. In addition, the strike extension of the structure that hosted the original mineralisation also requires investigation.

Jerangle Area

The Jerangle Prospect is located near the village of Jerangle, which is located approximately 30 kilometres south of Captains Flat. This area has base metal prospects that occur in the Kohinoor Volcanics near a faulted contact with the Foxlow Beds. Drilling programs to date have intersected VMS style mineralisation with anomalous and high grades of copper lead and zinc as well as skarn assemblages.

Mineralisation is hosted by a package of siltstones, shales, rhyolites, tuffs, quartz eye tuffs and agglomerates. The mineralisation occurs over a strike extent of 1.5 kilometres and is composed of Copper, Lead and Zinc and precious metals in the form of chalcopyrite, sphalerite and galena. Pyrite is a commonly associated with the above mineralisation and silver is the dominant precious metal.

The prospect has been subjected to two main drilling programs and a total of 17 percussion and diamond drill holes have been completed. The drilling has revealed broad zones of base metal mineralisation over the entire strike length. Highlights of this drilling include:

Many of the above intersections have been derived from broad zones of mineralisation suggesting the presence of an extensive mineralised system. A number of holes failed to reach target depth and some suffered poor recoveries. Mineralisation is open both along strike and at depth in many instances. During late 2006, Ironbark carried out a preliminary drilling program at Jerangle. The location of this drilling in relation to historical drill drill sites is illustrated in Figure 7.

Figure 7: Drilling targets outlined by Ironbark Gold Ltd at the Jerangle Prospect.

Three Reverse Circulation (RC) holes with diamond tails were completed for a drilled aggregate of 500 metres. However, the drilling program was abandoned because of unsatisfactory performance by the contracted drilling rig.

Ironbark Gold Ltd has indicated that the drilling program at Jerangle will be resumed towards the latter half of 2007. The next drilling program is to target the deeper down-dip extensions to previously recorded base-metal intercepts.

Other Areas

A number of other Prospects have been identified as being prospective for gold and or base metals. These prospects, which are briefly outlined below, will be followed up during the course of next calendar year.

Foxlow Gold Prospect

This gold prospect occurs in the Captains Flat Formation and it has a small recorded gold production. It was explored by Lake George Mines but recent explorers have not investigated the gold potential.

Bollards Prospect

This base metal and gold prospect occurs in the Copper Creek Shale. It has VMS and stringer mineralisation which was tested by only one drill hole.

Narongo Prospect

This prospect has gossans and old workings which are possibly in faulted Foxlow Beds. Two drill holes intersected anomalous gold, silver and base metals and highly anomalous tellurium. The presence of tellurium is unusual, and may indicate skarn mineralisation. Trace amounts of tellurium may occur in pyrite and larger amounts, of possible economic significance, may occur as gold, silver and bismuth tellurides.

Julita Prospect

This prospect has gossans which are possibly in faulted Foxlow Beds. Three drill holes intersected anomalous lead and zinc but the gossan zone was not tested.

Anembo Prospect

This prospect has gossans and old workings which occur on a faulted contact between the Kohinoor Volcanics and Foxlow Beds. The gossans are anomalous in copper and zinc and there have been several drilling programs by previous explorers that intersected anomalous and economic grades of lead and zinc mineralisation.

Bold Slate Ridge Prospect

This prospect occurs in a structurally complex area of the Kohinoor Volcanics and the Foxlow Beds and it has skarns and gossans which are anomalous in lead and zinc. It has not been tested by drilling.

Proposed Exploration Activities

The introduction of Glencore to the Joint Venture will help Ironbark to fund deeper exploration in the main Lake George Mine area.  Earlier deep drilling beneath the historical workings has intersected primary mineralisation which is thought to represent a possible continuation of the Lake George mineralisation.
In the short term, the joint venture partners aim to complete metallurgical studies, surveying and other work ahead of determining a definable resource on the lead and zinc bearing tailings dumps located near the Lake George Mine.  The tailings are deposited in two main dumps and are estimated to contain approximately 2.1Mt of material based on production records.  So far Ironbark drilled 154 air core holes totalling 2,533 metres on the Lake George Mine Tailings.  The significant results included*:

• LGD113: 3 metres at 6.9% zinc, 1.8% lead, 0.3% copper, 1.0 g/t gold and 27 g/t silver from 12 metres
  
  
• 
  LGD147: 3 metres at 5.3% zinc, 1.7% lead, 0.4% copper, 1.1 g/t gold and 25 g/t silver from 12 metres
  
• LGD117: 6 metres at 4.2% zinc, 1.5% lead, 0.4% copper, 0.9 g/t gold and 27 g/t silver from 12 metres
  
• LGD145: 6 meters at 4.6% zinc, 1.5% lead, 0.4% copper, 0.9 g/t gold and 24 g/t silver from 15 metres

* Samples taken in 3 metre composites, assays obtained from ALS Laboratories in Orange, NSW. All elements except gold were analysed using an Aqua Regia acid digestion followed by ICP; Gold was assayed using a fire assay and AAS

Metallurgical testing has also been carried out on a selection of the dump samples.  A JORC compliant resource of the zinc-lead-copper-silver-gold in the tailings will be estimated and released as soon as possible. 

In addition, numerous other prospects were identified within the same trend to the south, over a 50 kilometre strike.  The evaluation of these prospects is on-going.