The geology and mineral deposits of the Moina-Lorinna area

The oldest rocks exposed in the area are quartzites and schists of the Dove Group which underwent considerable deformation during the Precambrian. Upper (?) Cambrian acid lavas, volcanics, greywackes, cherts, siltstones and quartzites comprise the Bull Creek Volcanics and the Lorinna Volcanics. These rocks were formed in an easterly extension of the Dundas Trough, north of the Tyennan Block. The Dove Granodiorite intruded these rocks along the southern margin of the Trough in Late Jukesian (?) times. The petrology of the Cambrian rocks is discussed in some detail and it is concluded that the acid lavas were derived from the same magma as the Dove Granodiorite. Ordovician rocks in this area consist of the Roland Conglomerate at the base, which is conformably overlain by the Moina Sandstone and the Gordon Limestone in turn. During the Tabberabberan Orogeny, these rocks were folded and faulted into northwesterly trending structures. The Dolcoath Granite intruded late in the Tabberabberan Orogeny causing some metamorphism of the country rocks. It is suggested the granite intruded as a northerly dipping, roughly tabular body. There may be a small cupola in the Stormont area. The majority of the mineral deposits in this area are genetically related to the Dolcoath Granite. A fairly distinct zone of wolframcassiterite deposits surrounds the northern part of the granite. Around this, is a zone of auriferous sulphides. The mineralogy of these two zones is described. Areas most likely to prove of economic importance are indicated together with suggested sites for a preliminary diamond-drilling programme.