Accessory mineralogy of orangeite from Swartruggens, South Africa

Summary

¶Orangeite occurring as a complex series of dikes at Swartruggens (South Africa), is host to a diversity of accessory minerals, the most common of which are apatite, barite and calcite. Less common, but important phases are perovskite, wadeite, an unidentified Ca–Ti–Fe-silicate, strontianite, unidentified Ca-REE phosphate, zircon, rutile, titaniferous magnetite, quartz and diverse sulphides. The accessory minerals show wide variations in their mode in different segments of the dike suite as a consequence of crystal sorting during flow differentiation. Compositional data are given for apatite, barite, calcite, perovskite, wadeite and the unidentified Ca–Ti–Fe-silicate. The accessory mineral suite is similar to that found in lamproites but is sufficiently distinct in composition and paragenesis to preclude inclusion with that clan. Differences include the common presence of groundmass calcite, barite and serpentine in the orangeite and the absence of typomorphic minerals (leucite, sanidine, richterite) of the lamproite clan.