Barite-fluorite mineralisation at Thomson Hill, Wangapeka Valley, Nelson

Abstract

Abstract Barite occurs as irregular veins cutting Ordovician marble of the Mount Arthur Group; as encrustations on surface boulders of lower Tertiary grit; and as occasional residual boulders within a solifluxion deposit, possibly a terra rossa, which mantles the marble and the associated rocks. Minerals accompanying the barite include quartz, fluorite, adularia, pyrite, muscovite, and jarosite. Brief chemical and optical data are given for barite, adularia, and jarosite, and the petrography of the vein rocks is described and illustrated. The veins, which are probably of low-temperature hydrothermal origin, are believed to be upper Paleozoic in age, and to have been formed during the later stages of evolution of the Separation Point Granite. The barite deposits are shown to be of uneconomic size to warrant a treatment plant. Of the several outcrops of barite known only one has an appreciable amount readily available (about 3,000 tons of crude are). Nearly all the barite rock contains greater or smaller amounts of other minerals, particularly quartz and fluorite, so that for most uses any rock worked would require beneficiation.