Abstract
The placer deposit at Barrytown, New Zealand, has been worked for gold and is known for high levels of ilmenite that has not been exploited. Other heavy minerals are present but have not been well characterized, which is the purpose of this research. Sand grains were separated into the density fractions and the heavier fractions analyzed by laser ablation ICP-MS for elemental composition and by scanning electron microscopy (SEM) EDS in whole grains and polished sections. Grain size distributions were determined from SEM images of polished grain mounts. Elemental associations have been identified with different minerals. A wide range of ore minerals, or potential useful industrial minerals, have been shown to be present largely as individual sand grains. These include gold, ilmenite, garnet, zircon, monazite, allanite, uraninite, thorite, cassiterite, wolframite, scheelite, and columbite. The ilmenite contains many inclusions, consisting of silicates and phosphates and 100–400 ppm Nb. Scandium is found to be present in zircon at 100–600 ppm along with 3000 ppm Y. Monazite is depleted in Eu relative to chondrite and contains Ga and Ge at 1000–3000 ppm. Because the sand grains are mostly individual minerals, it is suggested that separation may be possible using a combination of density, electrostatic and magnetic methods to obtain almost pure mineral fractions. This knowledge should inform decisions on potential exploitation of the resource.
Highlights
IntroductionThe placer deposits (beach sands) of heavy minerals at Barrytown on the West Coast of the SouthIsland of New Zealand have been known for many years [1,2,3]
The placer deposits of heavy minerals at Barrytown on the West Coast of the SouthIsland of New Zealand have been known for many years [1,2,3]
Some studies have been done to investigate the mineralogy of the ilmenite, but little has been done on the other potentially valuable minerals since a wide-ranging study in the 1940s from the South Island, New Zealand, beach sand deposits and gold dredge concentrates [5]
Summary
The placer deposits (beach sands) of heavy minerals at Barrytown on the West Coast of the SouthIsland of New Zealand have been known for many years [1,2,3]. There has been very little published on the detailed mineral compositions including solid solution components and the nature and extent of inclusion impurities This gap in knowledge has been partly filled with a comprehensive recent study on the garnet composition in this and related deposits [4]. Some studies have been done to investigate the mineralogy of the ilmenite, but little has been done on the other potentially valuable minerals since a wide-ranging study in the 1940s from the South Island, New Zealand, beach sand deposits and gold dredge concentrates [5]. The ilmenite has a relatively low titanium content of 45–47% TiO2 because of the relatively high levels of inclusions, the ilmenite matrix is closed to stoichiometric FeTiO3 , with 52.6% TiO2 , 47.3% FeO [6]. The iron within the ilmenite is mostly as Fe2+ with little present as Fe3+
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