The Barrambie Belt has a history of high-grade gold production having produced some 27,339 ounces of gold from 34,233 tonnes of ore (24.8 g/t). The Doherty’s Project consists of three groups of historical mine workings; the Doherty’s, Old Camp and South Shear mines. Previous exploration and underground mine developments at the Doherty’s workings have identified high grade gold mineralisation over a distance of 51 metres at 100 metres depth. In April 2005 a deposit continuation at depth for Doherty’s of 26,700 t @ 23.8 g/t Au was estimated by consultants Geological Investigations Pty Ltd. The data for this estimate is being obtained and a revised 2012 JORC compliant resource estimate will be made. The quartz vein filled shear which hosts the gold mineralisation does appear to be consistent and further diamond drill based exploration should be targeted on this narrow but high grade structure.
The Company plans to further evaluate the known high-grade gold mineralisation and to carry out exploration over the Project with the object of discovering further mineralised structures. The project is located within 100 kms of both the Gidgee and Sandstone mills and provides an opportunity for toll milling.
The Doherty’s Project is situated at the southern end of the Barrambie Greenstone Belt that comprises felsic volcanoclastics, minor greenstone metasediments and banded iron formation (BIF) all of which have been intruded by felsic porphyry and granites. The Barrambie Greenstone Belt is a northwest trending belt in the granite gneiss terrain of the East Murchison. All lithologies at Barrambie contain gold mineralisation, including gabbro, granite, felsic volcanics and sedimentary rocks. Many deposits discovered to date contain a significant portion of supergene gold, and the higher grade zones are typically sulphide bearing quartz veins.
Within the tenement area the exposed rock types comprise felsic volcanoclastic and metasediments that are intruded by porphyry and mafics. The felsic rocks are banded and schistose and intercalated with the felsics are banded iron formation (BIF), which contain grey chert and magnetite bands with minor pyrite. The BIF forms a prominent north- westerly-trending ridge through the tenement. Overlying these rocks are fine-grained quartz-eye tuffs.
Gold mineralisations at Doherty’s occurs in north trending, flat easterly dipping quartz filled shears and also have developed on an anticlinal fold that plunges at 30 degrees to the north west.
In 2010 Classic Minerals drilled four reverse circulation drill holes for a total of 374 metres. The holes ranged in depth from 85 to 95 metres and were targeted at known gold mineralisation at the northern end of the tenement adjacent to the Scheelite North Dohertys gold occurrence.
Samples were submitted as 5 metre composites for analysis with two interesections returned. DRC07 returned 5m @ 7.08 g/t Au from 60-65 metres and DRC08 returned 5m @ 3.64 g/t Au from 60-65 metres. Reanalysis of these composite samples as 1m samples is now occuring.
There are three groups of gold workings located within the project area, namely, Doherty’s, Old Camp and South Shear. Gold mineralisation is hosted by quartz-filled shears in altered albite porphyry. The dominant sulphide is pyrite with traces of chalcopyrite and scheelite. The mineralised gold reefs are developed along quartz veins in NS shears adjacent to BIF at Doherty and South Shear. Gold at Doherty also occurs in an anticlinal crest and fold limbs plunging at 30º to the north-northwest. The workings have been investigated by systematic shallow RAB drilling. The geometry of the structures suggest a northerly plunge direction of the gold mineralisation and these should be tested down dip and plunge of the known higher grade shoots, which have intersections up to 1.55 m at 84.4 g/t Au.
Doherty’s has been investigated by RAB, RC, and Diamond Core drilling and the South Shear workings by RAB drilling. Shallow RAB drilling encountered anomalous gold to the west of the main lode system and this area was testing by RC drilling with positive results. Isoclinal folding in the area suggests the possibility of repetitive sub parallel lodes and anomalous results in the RAB drilling may support this. A geophysical interpretation by Geoscience geophysical consultants located 6 targets within the tenement and these will be investigated by geochemistry and where warranted, drilling.
The obvious potential in the area is the down dip and down plunge potential of the main gold mineralised structure. The grades returned to date are encouraging and based on the results further drilling should extend the known gold mineralisation. Deeper diamond drilling is the recommended approach for advancing the project followed by resource estimation and economic analysis.
Compiling of old exploration data showed that accurate collar and downhole surveys had not been undertaken on all rC holes, some of which intersected the high grade gold bearing quartz vein. Arrangements were made to have these holes accurately downhole surveyed in February, so accurate plans and cross-sections can be drawn up, and then additional drilling planned. Some holes were blocked at depth, and others were fully surveyed. An accurate survey of hole collars, and a topographic survey will be undertaken in the immediate area of the old workings at Doherty mine, in case an open cut pit is considered.