A study of detrital heavy minerals in the taramakau catchment

Abstract

A systematic survey of the detrital heavy minerals from thp granites, schists and Torlesse rocks of the Taramakau catchment has been carried out. Samples were taken from small feeder streams within source rocks, at various stages downriver to the mouth, and from the beaches.The mixing proportions in the lower river of euhedral and rounded zircon, from the granite and schist respectively, were used to derive the relative contributions of these rocks to the detrital ilmenite and magnetite. Beach-sand accumulation is considered in relation to provenance and persistence. The schists contribute most of the ilmenite, along with garnet, sphene and epidote, and minor rutile, tourmaline, tremolite and pumpellyite.In the lower Taramakau River a buried suite of additional granitic minerals not carried in the present river bed — cassiterite, monazite, uraninite and thorite — has concentrated above the “Blue-Bottom” (Miocene mudstone). There is little direct evidence on the source of these minerals, but they may have been derived from a part of the Hohonu Range now completely eroded. The heavy minerals in the present-day sediments of the adjacent Arahura and Hokitika rivers are essentially similar to those of the Taramakau, and so do not modify the Taramakau beach-sand suite, despite longshore drift from the south. © 1979 Taylor & Francis Group, LLC.