Late-magmatic mineral assemblages with siderite and zirconian pyroxene and amphibole in the anorogenic Mt Gibraltar microsyenite, New South Wales, Australia, and their petrological implications

► Unique occurrence of siderite as a magmatic mineral in peralkaline, igneous rock. ► Crystallisation at very low oxygen fugacity, possibly due to contamination with coal. ► Zirconium is camouflaged in pyroxene and amphibole rather than forming its own minerals. ► Alkali activity and oxygen fugacity control the behaviour of zirconium.