The tenement is located north of Elginvale in the South Burnett region and largely covers Triassic volcanics and sediments of the Esk Trough and Palaeozoic serpentinites and metasediments in the east. These rocks have been intruded by various Triassic diorite to granodiorite intrusive.
The EPM area is considered prospective for porphyry style Au-Cu mineralisation and several gold and copper prospects occur in the eastern part of the EPM
A NW striking lenticular ~4km wide block of Carboniferous aged ‘lower plate’ metamorphic rocks is located between the large Triassic-aged Station Creek Adamellite (231 Ma) and the boundary of the Esk Trough. The two main units are Gobongo Metamorphics consisting of phyllites & mica schists, and the Widgee Metamorphics with greenstones and metabasalts. Mt Mia Serpentinite outcrops in the Jimmy’s Scrub and Kabunga areas. The metamorphic block is
extensively faulted, and intruded by at least two small Triassic-aged porphyry diorite intrnsives and several dykes. Remnant Triassic-aged andesitic volcanics overlie basement rocks to the north.
The area is structurally complex but is dominated by two N/W faults with cross-faults or subsidiary structures consistently orientated N/E. The gold field appears to be bounded by, and contained within, the two N/W trending structures and all known mineralisation trends N/E. Dykes generally strike either N/W or N/E and at Kabunga prospect, a N/E trending andesite dyke is associated with gold mineralisation. The Golden Sunset prospect and associated porphyry appears to be developed at the intersection of the Mt Clara Thrust fault and the southern-most N/W strike-slip fault.
A soil sampling survey in 1998 indicated best Au soil values were on the hilltop at the northern end with a max of 1.26 g/t Au and two rock chips of nearby altered country rock assaying 1.66 & 0.697 g/t Au. A large zone of disseminated quartz stringer mineralization/stockworks may exist at this site. The andesite dyke is altered by pyritisation only on the hilltop.
The Jimmy’s Scrub prospect is contained within dioritic porphyry close to the contact with serpentinite. Two historical adits are partly caved and no historical records exist for the production
A sheeted vein set of gossanous quartz veins were intersected by 5 drill-holes carried out by United Reefs in 1988. 3 RC holes (JS/1-3) and 2 diamond holes (JS/4 and 5) were drilled to intersect high grade zones. RC holes JS/1-3 were drilled to 59m, 41.5m and 50m depth respectively and were assayed for Au, Ag, Cu, Zn and As.
JS/1 finished in 4.23g/t Au from 58-59m.
JS/2 was assayed to 23m; and JS/3 intersected a massive sulphide zone at 33-34m assaying 11.9g/t Au, 25g/t Ag and 4.48%Cu and ended in 1.05g/t Au.
Mapping by United Reefs indicate a porphyry intrusive about 1 km E/W and about 600m wide N/S. Due to incomplete assaying of drill-holes, the exact number of veins intersected is vague but between 5 and 8 veins across 110m length could be reasonable. Best assay across 1 m was over 11 g/t Au. A resource was announced by the United Reefs of 3,000 t @ 10 g/t Au. The resource is still open at depth and along strike.
Best assays from orientation rock samples collected from mineralised porphyry and vein assemblages at Jimmy’s Scrub historic workings included the following:
• 115g/t Au, 55g/t Ag, 0.9% Cu and 810ppm Bi from gossanous ironstone;
• 14.1g/t Au, 11g/t Ag and 2.85% Cu from cupriferous and sulphidic quartz veins;
• 1.5-10.9g/t Au, 4-6g/t Ag, 0.2% Cu and up to 1110ppm Bi from veins at the adit working face and floor fines.
The most easterly indicators of gold mineralisation within the Kabunga area consist of a tensional quartz vein striking N/E in schists for 1km. The line is proximal to the Station Creek batholith and consists of one bulldozed scrape in quartz and 2 shafts. No historical records, 5 rock chips assayed averaged 0.5 g/t Au in 1998. Mineralisation on this line is considered weak.
The Kabunga workings (adits and shafts) extend N/E for a strike length of 1 km and mineralisation is developed in quartz veins along the eastern margin of a porphyry diorite dyke, with a magnetite lode on its western margin, and in subsidiary structures intersecting with the main dyke.
Historical reports indicate gold is patchy but coarse, the drainage system is known for its’ small nuggets and alluvial gold. Tourmaline alteration has been reported from this prospect. At least 10 shafts and adits dot the hillside. Old reports indicate the presence of coarse gold flakes in loam and small quartz stringer veins on the hilltop.
Located approximately 50 km. north-east of Nanango, and just south of the border between the Nanango and Gympie Mining Districts, the Kabunga area contains numerous old mines and alluvial workings. The date of discovery is not known, but the location received a second breath of life in 1936. Sometimes referred to as Gobongo, the Kabunga workings are located at the head of Gobongo Creek, a tributary of Baramba Creek, in the Parish of Manumbar, County Fitzroy.
The activities were confined to a small area of metamorphic rocks, and consisted of mica, chlorite, talc, serpentine, actinolite, and sillimaite, schists, phyllites, greenstone, quartzite, gneiss, jasper and slates. These rocks are intruded, both in the eastern and southern portions of the area, by a coarse grained biotite-granite, which has caused more intense metamorphism of the series. The occurrence, in the schists near the granite margin, of large quartz tourmaline reefs containing gold values is a peculiar feature of the field.
The Miss Blackburn P.A., pegged by Messrs. R. Blackman and L. Clements, is located in the north-eastern comer of State Forest Reserve R. 97. Two reefs, striking north-north-east to south-south-west and dipping in a west-south-west direction, were opened up by means of costeans for a length of 30 m. The reefs occupy two roughly parallel fissures separated by crushed schistose formation. Government assays of samples, from the costeans, showed returns from a trace up to 2.5 ozs. per tonne.
Early reports suggest that careful prospecting on the surface may reveal further rich patches . The D. D., G.M.L. 1771, pegged by Tomison and party, is situated on portion 1337 and the reef strikes east-south-east to west-north-west Several shafts and drives were sunk, with the best results obtained from shaft No. 1 (the most southerly), although values rapidly dropped from 24 m. downwards. The shoot of gold-bearing stone is described as being very narrow and confined to the western porphyrite-schist contact, the reef, in the dyke itself and at the eastern contact, being practically barren. Small rich patches of gold could be found along the western contact, but it is thought that they would be small and not economical to mine on a large scale.
The Birthday Gift, G.M.L. 1775, pegged by Mr. M. J. McNamara and Mr. E. Morgan and sons, was situated in portion 1337, about 50 m. west of the D. D. The country rock is chlorite schist and the reef strikes north-north-east to south-south-west and dips in an east-south-east direction. It consisted of quartz, ironstone gossan and rather massive hematite at the surface, altering to quartz, magnetite, chalcopyrite and pyrites below the water level, which is at about 6 m. No. 1 shaft was sunk vertically on the reef, which was passed through and subsequently intersected by crosscutting in an east-south-east direction at a depth of 7.92 m. A sample from this section assayed at only a trace of gold a metre or so to the south on No. 1 shaft an underlie shaft was sunk to 4.26 m. The reef at the outcrop assayed a yield of almost 1 oz. of gold per tonne over a width of 45 cms., and at the bottom it returned (by assay) 4.49 grams of gold and 5 ozs. of silver per tonne. Shaft No. 2 was sunk to a ec of 4.5 m. and the reef returned (by assay) 19 grains of gold per tonne. No. 3 shaft was sunk to a depth of 4 22 m. exposing the reef at that depth. Again, the assay revealed only low (9 grains) gold values. Shaft No. 4, -siach was sunk to 7.92 m., and a 3.6 m. drive in a south-westerly direction at the bottom of this, failed to reveal ne reef.
Prospecting Area No. 1228, taken up by Mr. E. J. Tyrie, was situated on Timber Reserve 2492, 120 m. west of portion 928. What appears to be a continuation of the porphyrite dyke, exposed in the D. D. workings, outcrops about 30 m. west of the workings. Following good loams from a small gully south of the area, Mr. Tyrie located several small 'mullocky leaders' carrying low gold values. A pothole and deep costean opened up a few of these small veins, which the prospector hoped would unite at depth and form a reef of workable size. The man was advised that it was improbable that the veins (small clay filled joints) would meet at depth, and to discontinue sinking. Coarse colours of gold can be found over a wide area here and the opinion, of the visiting geologist, was that this is due to the erosion of numerous small veins of unworkable size.
Mr. Tyrie was considered to have been the most successful alluvial worker on the field, during the second rush of the 1930s. He worked the creek intermittently over a period of fifteen months, and won 17-18 ozs. of gold from his claim on Gobongo Creek, in portion 2491, below Morgan's Claim. Prospecting Area No. 1225, opened by Mr. E. Morgan, is situated in Timber Reserve 2492, 300 m. south of P.A. 1228. The country rock is mica-schist, striking north-east to south-west and dipping 20 deg. in a southeasterly direction. A porphyrite dyke extends from the D. D. workings to this area. The prospector found loams in the area and sank a pothole and two costeans, both in the porphyrite and schist, but failed to locate any reef. It is not clear if such a reef was ever located. Before reef mining, Mr. Morgan and his sons had worked the alluvial in Gobongo Creek, on a bend in the north-east comer of portion 2491, for a year. During that time they had earned gold at the rate of 6d. to 8s. per week, per man. One nugget, found by Morgan (sen.) weighed 2.36 ozs.
Hopkins' P.A. is situated in portion 1337, about 240 m. north of the D. D. The country rock is schist and quartzite, striking north 10 deg. east to south 10 deg. west. Hopkins obtained coarse particles of gold in the loam and on sinking found numerous small quartz veinlets in the schist, but it appears that these were barren. The visiting geologist, at the time, suggested that the small veins did shed alluvial gold, but Hopkins had sunk on a barren section. He had added that it was unlikely a reef of workable size would be found. The original workings, known as Old Kabunga, are situated on a small branch of Gobongo Creek, in portion 1337. Two main lines of reef were exposed practically at right angles to each other. In No. 1 shaft the reef, 1.37 m. wide, has a direction of east-south-east to west-north-west, and dips steeply in a south-south-west direction. No. 2 shaft, the northern adit and southern adit are probably all on the same line of reef, having a general direction of north-north-east to south-south-west. This latter reef, where exposed in the adits, has an average width of about 15 cm. At the outcrop it consists of quartz and ironstone gossan. The ore on the old dumps consists of quartz, iron pyrites and copper pyrites. In the southern adit, a small vein intersects this reef almost at right angles. At the intersection of the two was a lens of ore 4.26 m. in length, having an average width of 30 cm. This intersection was removed by later holders of the lease, Messrs. B. Hammer, J. Anderson and party. They advised that about 2 tonnes of the ore returned 4 ozs. of fine gold It was recommended that further prospecting be carried out to locate a large reef that could exist in the area. Other alluvial claims (worked during 1935-36) in the area included Mr. R. Bundi's on Gobongo Creek, in the north-eastern comer of portion 2491. From this claim, Bundi is said to have found 7 ozs. of gold won in three months of a twelve month period.