REGIONAL GEOLOGY
The Cethana and Dove River Tenements are contained within the northern portion Mt Read Volcanic Arc. This belt comprises Cambrian c500Ma Mt Read Volcanic and granitic rocks, which are overlain by Cambro-Ordovician sandstones and limestones. Many stratigraphic relationships within the Northern Mt Read Volcanics remain conjectural.
The Mt Read Volcanic Arc hosts world class ore deposits (eg: Rosebery), numerous other polymetallic VHMS-style deposits (eg. Que River) and volcanogenic copper and gold deposits (eg. Mt Lyell, Henty).
- Cambrian Volcanic Rocks
- Cambrian Intrusive Rocks
- Late Cambrian-Ordovician sedimentary rocks
- Devonian granite
- Structure
- Mineralisation
Cambrian Volcanic Rocks
Cambrian rocks in the vicinity of the Tenements are part of the Mt Read Volcanics. The units are tentatively correlated with the Sticht Range Beds, the Central Volcanic Complex and the Eastern Quartz-phyric Sequence.
The rocks hosting the Cethana magnetic anomaly are the Bull Creek Volcanics, a package of dacitic and andesitic volcanic and volcaniclastic rocks.
The Bull Creek Volcanics and, in particular, the Bull Creek porphyry have been tentatively correlated with the Bonds Range Porphyry to the west. By this interpretation the Bull Creek Volcanics could be considered correlates of the Eastern Quartz-phyric Sequence. Alternative correlations have been made with the Tyndall Group. The Tyndall Group is a late Cambrian volcanic package dominated by volcanic derived sediments.
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Cambrian Intrusive Rocks
The porphyritic Dove Granite crops out in three locations, two of which are contained in the Dove River area. The latest phase of the granite has a favourable chemistry as a more evolved source rock for metallic mineral deposits. The granites are intruded by late dykes, some of which also have favourable source rock chemistry. The margins of the granite are mineralised in the vicinity of the Devon Mine and an altered dyke has been identified in drill core at Cethana.
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Late Cambrian-Ordovician sedimentary rocks
Conglomerate and sandstone sequences are regionally unconformable on the Cambrian volcanic rocks. Late Cambrian sandstones overlying the target volcanic are known as the Moina sandstone, an equivalent of the Upper Owen Group of Western Tasmania. The Moina Sandstone is sometimes underlain by thick sequences of conglomerate, known locally as the Roland Conglomerate. The Ordovician Gordon limestone conformably and gradationally overlies the Moina Sandstone in areas of minimal erosion.
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Devonian Granite
The Dolcoath Granite crops out about 2km north of the Cethana tenements. Although outcrop is limited to one small window, gravity data indicates the granite occurs at less than 1km below the surface for some considerable distance west of the Forth River Valley.
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Structure
Cambrian rocks in the tenements have endured folding, uplift and erosion prior to deposition of the overlying sedimentary sequence. A subsequent phase of Devonian deformation resulted in widespread folding and thrust faulting prior to intrusion of the Dolcoath granite.
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Copper and gold-bearing vein from the Devon Mine, Dove River Tenement, Tasmania.
Mineralisation
The district is known for polymetallic mineralisation, including; W, Sn, Au, Bi, Pb and Zn. Most deposits are considered Devonian in age and related to intrusion of the Dolcoath Granite.
Cambrian mineralisation occurs at the Fire Tower prospect, located about 7km northeast of the Cethana tenements and several other prospects occur in Cambrian rocks (see Mining History)