Sn mineralisation-related slushy textures in the Heemskirk Granite in Western Tasmania, Australia
Hong, W and Cooke, DR and Zhang, L and Fox, N, Sn mineralisation-related slushy textures in the Heemskirk Granite in Western Tasmania, Australia, Future Understanding of Tectonics, Ores, Resources, Environment and Sustainability Abstracts, 2-5 June, Townsville, Australia (2013) [Conference Extract]
The Carboniferous Heemskirk Granite that crops out on the western coastline of Tasmania is associated with numerous Sn, Cu, Pb-Zn-Ag and rare Ni deposits in the Heemskirk and Zeehan mineral fields. This granite contains two main phases, the White and the Red granites. We have identified several main variants of slushy magmatic-hydrothermal textures dominated by quartz and tourmaline in the Heemskirk Granite. Tourmaline orbicules consisting of tourmaline and quartz are intensively developed near the contact between the White and Red granites, and also common on the margin of the White Granite, adjacent to the surrounding Proterozoic metasedimentary rocks. Tourmaline patches are smaller than the orbicules in size, and contain smoky quartz phenocrysts intergrown with coarse-grained tourmaline and feldspar. Tourmaline-filled miarolitic cavities are more common in the Red Granite, in which prismatic tourmaline crystals radiate outwards from the core of the cavities and are typically intergrown with minor quartz. Quartz-tourmaline veins typically have sub-vertical orientations and have penetrated from the White Granite into the overlying Red granite along joints and fractures. These textures, together with domains of unidirectional solidification textures (USTs, also known as comb-layer quartz) pervasively occurring in the roof zone and on the margin of the White Granite, are interpreted to be the products of magmatic-hydrothermal volatile exsolution from a late stage crystallising melt during the emplacement of the intrusion and migration into the roof zones and neighboring wallrocks. The textures also provide evidence for the origins of the ore deposits that occur within and around the granite batholith.