| Abstract |
Rare earth element (REE) behaviour has been studied in hydrothermally altered rocks from four New Zealand geothermal systems (Broadlands, Kawerau, Tauhara and and compared with two Australian Palaeozoic systems (Mount Aubrey and Conway). The results show that the REE display similar behaviour in systems of different ages. Subparallel REE patterns are characteristic of rocks which are weakly altered or contain a diverse alteration mineralogy, whereas straight trends without anomalies are present in rocks which contain albite) assemblages, and bowed trends occur in strongly silicified rocks with minor clay and pyrite. In general, hydrothermally altered rocks display lower REE contents and less pronounced than fresh rock. REE behaviour during alteration is controlledby alteration intensity, rock permeability, and type of minerals formed. was probably present as which accounts for its differential behaviour. |