Ankerite carbonatite from Swartbooisdrif, Namibia: The first evidence for magmatic ferrocarbonatite

Abstract

Although general accounts of carbonatites usually envisage Ca-Mg carbonate melts evolving by fractional crystallization to Fe-rich residua, there is longstanding concern that ferrocarbonatites may actually be products of hydrothermal rather than magmatic processes. All previously published examples of ankerite- and/or siderite-carbonatites fail to show one or more of the isotopic criteria (all determined on the same sample) thought to be diagnostic of crystallized magmatic carbonate liquids.