A number of companies have explored the Tarnagulla Goldfield and surrounds since the 1970's. However, drilling & underground development was dominantly focused around existing mines on the Poverty Reef, New Chum Reef (Cambrian) and Great Western Reef.

Three parallel "lines-of-reef" exist in the central Tarnagulla Goldfield; the main Poverty Line, the Great Western Line (to the west) and the Growlers Line (to the east). Further out, "satellite" gold centres exist. To the north Arnold, north-east, Llanelly (New Chum Reef / Cambrian Mine, Sandstone Reef); to the east the Hellas - Corfu Line; further east on the Loddon River the Poseidon deep lead mines and underlying reefs; to the south-east Mother Chisholms Reef and the Laanecoorie Reefs (Kangaroo, American and Specimen Reefs) and to the south-west the Waanyarra (Jones Creek) centre.

All of the above reefs occur within MIN 4756 / EL 3640, EL 4541, EL 4542, EL 4992 and surrounding EL 4214 held by Ironbark Mining Pty Ltd, a wholly owned subsidiary of Castlemaine Goldfields Ltd.

Outside of the Poverty-Line-of-Reef, only limited shallow RC percussion drilling and rare shallow diamond drilling has been carried out. There are only two deep shafts in the field (Prince of Wales Shaft, Poverty Reef - 314m, Yorkshire Shaft, Watts Reef - 353m).

Exploration and mining by Reef Mining N.L. (1994 - 2000) was focussed mainly on the Poverty Reef. Some widely spaced reconnaissance drilling along the Poverty-Line-of-Reef was also carried out, along with limited reconnaissance drilling on adjoining lines.

During August-September 2005, Alexander Resources Ltd (now Castlemaine Goldfields) drilled three diamond drill holes, into the North Watts Reef. Although a 20m wide alteration zone with mineralised quartz veining was intersected, gold assay results were low.

Castlemaine Goldfields Ltd completed (Nov 2006 - February 2007) a 1261m reconnaissance drilling program (RC / Diamond), on 100m traverses, along the "Poverty-Line-of-Reef", north of the actual Poverty Reef. The northern and southern margins of Stoney Reef and Young Australian Reef and the northern extrapolation of Watts Reef (Yorkshire Mine area) were targeted. Nothing of obvious economic interest (to a depth of 150m - 250m) was intersected, however, information gaps exist between the Poverty Reef and Stoney Reef (200m) and at North Watts Reef which hold potential for relatively shallow discoveries. The intensity of quartz spur veining and associated alteration in the drillholes was encouraging. Based on this round of 100m spaced drill traverses, the Stoney Reef and Young Australian Reef Segments do not host large dilation zones at their northern and southern margins similar to the Poverty Reef (Bonanza Shoot size; 100m + strike length), to a depth of 250m from surface. Smaller shoots (Nick O' Time Shoot size) may exist between the 100m drill traverses and larger dilation zones may exist at greater depths (below 250m) across this prolifically mineralised line of reefs.

Historically the highest gold yields have been from the Poverty-Line-of-Reef, therefore a succession of explorers have concentrated exclusively on that line. Castlemaine Goldfields have commenced a study of the broader potential of the Tarnagulla region, within their 216 sq km tenement holding. To date 82 gold-bearing quartz reefs have been researched, which generally occur along en echelon, north-south lineal zones ("lines-of-reef").

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Conceptual cross section looking north at the major structural elements of the greater Tarnagulla goldfield. Note the sediments which cover the Poseidon and Campbelltown faults.

The structural setting is being analysed to determine which of these "lines" is likely to be in the most favourable position (narrow highly productive zones occur in most major fields in central Victoria). The historic (central) Tarnagulla Goldfield may not be the richest part of the region (although it was outcropping and therefore easily found). The reefs are in the same position, relative to the Campbelltown Fault, as the Ballarat Goldfield. The Poseidon reefs are largely obscured by alluvial cover and are the source of extraordinarily rich alluvial gold nugget yields.

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