Glen Wills Geology

Location Plan

Granted tenements EL 3916 and MIN 4921 cover the entire historically defined high-grade Maude and Yellow Girl group of mines and many peripheral mines adjacent to and along strike from this centre of production. Geographical isolation and high treatment costs due to historic mining and processing methods dictated only ore of very high grade was treated. Therefore, the potential exists for significant remaining ore of similar grade below the limits of the old workings and also extensions along strike. The need to access very high grade ore in the past is likely to have resulted in poor testing of the reef selvages within the altered sediments and the granite.

Disseminated gold targets are therefore a potential and are supported by the excellent drill results achieved since 2004 confirming the degree of shearing and alteration noted in underground exposures.

The potential for large-tonnage moderate-grade mineralisation exists within the Mt Wills granite and adjacent schistose sediments at its contact. The interplay between the dominant NNE fault sets and the brittle granite host appears to have resulted in the development of large bodies of quartz stockwork within the granite.

Exploration History

The area has had a long history of gold exploration and mining, dating back to the 1850s. Glen Wills was one of the major early goldfields in the North-East of Victoria that included the Mt Elliot, Dart, Harrietville, Bright, Wandiligong, Freeburgh, Beechworth and Bethanga goldfields.

Earlier modern day exploration focused on tin as well as gold. In the neighbouring goldfields of late 1970s-1980s, explorers targeted large stockwork or disseminated gold as well as alluvial gold. These included Gippsland Minerals NL (EL 126), Essex Minerals Company (EL 621) and Goldfields Exploration Pty Ltd (EL 1023). One of the most significant works undertaken at Glen Wills occurred in 1972 when Aurora Minerals NL refurbished the main 5 level access and internal shaft to the 9 level. This allowed access to mapping and bulk sampling of portions of the lower levels. This work concluded that the known shoots continue with depth. Citing corporate reasons Aurora Minerals NL withdrew from the agreement in 1974. Subsequent to this Aberfoyle Exploration carried out regional exploration for tin (1979-80).

More recently, companies including Bendigo Gold (EL 3163), Nickelseekers (EL 1553), Poseidon (EL 3244) and CRA Exploration within EL’s 2131, 2132, 2143 (areas north of the Glen Wills area) and EL 2146 have explored Mt Wills and Glen Wills together with areas to the north such as Mt Unicorn (Dart Area) for both disseminated gold in granite-associated gold enriched haloes, and gold in hydrothermal vein systems. Copperfield Gold NL drilled the upper levels of the Maude and Yellow Girl during 1987-88 under a farm in agreement with Swan Resources Ltd and other parties.

Regional Geological Setting

The Glen Wills goldfield is located in the eastern part of the Lachlan Fold Belt, in the Omeo Structural Zone. The Omeo zone (containing the Omeo Metamorphic Complex) extends north from Cassilis to the Hume Weir and into New South Wales. It is dominated by a basement of deformed Ordovician turbidites intruded by numerous granite plutons. Many of the sedimentary rocks have been metamorphosed to schist, gniess and migmatite.

All these rocks were severely deformed and metamorphosed during the Benambran Orogeny in the Early Silurian Period. The rocks were tightly folded, regionally metamorphosed and S-type granites intruded. Further, though less intense, deformation took place in the Late Silurian (Bindian), Middle Devonian (Tabberabberan) and Early Carboniferous (Kanimblan). The Tabberabberan event is thought to have resulted in crenulation cleavage, kink folds and brittle deformation. It also probably caused reactivation of pre-existing faults.

Geological Model

After completion of the Pre-Drill model, the extensive diamond drilling completed since 2004 has tested the validity of the model at many points. In general the faults and mineralised positions interpreted from the historic information have been reliable.

Drilling has revealed down dip extensions and strike extensions to known portions of mineralisation and has highlighted other potential mineralised structures for future testing.

Petrology

A petrological study was undertaken on several samples from three diamond drill holes. The study indicated that gold is paragenetically late (after pyrite and arsenopyrite) and probably deposited coevally with galena, chalcopyrite and carbonate, interstitial to quartz.

Gold was associated predominately with pyrite-arsenopyrite and solid solution gold within arsenopyrite and (arsenian) pyrite could be significant.

The most significant mineralisation occurs in the later phase of veining and associated hydrothermal brecciation. The emplacement is considered to be typical of the orogenic gold style of mineral deposit system. The alteration-mineralisation is late or post-tectonic stage, after peak metamorphism and regional deformation and after emplacement of the muscovite granite suite.

Mineralising fluids are likely to have been of moderate temperature (~300-350 deg C) near neutral, slightly reducing and introducing CO2, S, As and Au into the site of mineralisation. The siting of the mineralisation was favoured by late structures (maybe dilational) formed under brittle conditions at relatively shallow crustal depths.

Glen Wills Geology » Synergy Metals Limited » Projects

ASX Quotes