Carbon dioxide bearing melt inclusions within a gold-mineralized felsic granite

摘要

Disseminated gold mineralization at Timbarra forms flat-lying ore bodies constrained beneath a fine-grained carapace within the core of a zoned 249-252 Ma I-type granite. Emplacement at mesozonal levels (～7km) resulted in the development of a late stage volatile bearing (carbon dioxide-rich, chlorine-poor) magmatic fluid that was constrained by lithostatic conditions beneath a fine-grained 'quenched' carapace. The magmatic-hydrothermal fluids that ponded below the carapace formed unidirectional solidification textures (USTs), pegmatite lenses, miarolitic cavities, interconnected miarolitic cavities (IMTs) and vein-dykes. These variably gold-mineralized magmatic-hydrothermal transition textures contain carbon dioxide-bearing melt inclusions and low-salinity carbon dioxide-rich aqueous inclusions, whereas moderate to high-salinity aqueous inclusions are completely absent. The detection of carbon dioxide within melt inclusions using laser Raman spectroscopy is a significant observation supporting a magmatic origin for carbon dioxide in intrusion-related gold deposits.