Waiau Basin Cretaceous-Tertiary heavy minerals

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Smale, D. 1985 Waiau Basin Cretaceous-Tertiary heavy minerals. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report SL 12 23 p.

Abstract: Heavy minerals from Tertiary sediments in the Waiau Basin suggest that most of the western sediments were derived locally from adjacent basement rocks of the Fiordland Complex. A greater proportion of semi- opaque debris in the eastern sediments suggests derivation from the Takitimu Mountains or Longwood Range. Ilmenite, magnetite, biotite, sphene, epidote, and hornblende are widespread in the sediments and in the basement rocks, though hornblende and biotite tend to fluctuate sidely. Only the Sand Hill Point Formation, while still being dominantly Fiordland-derived, was not derived from the immediately adjacent basement. The distinctive minerals aegerine-augite and riebeckite occur only near the upper Lill Burn. Impoverishment of apatite in the eastern part of the basin is probably due to solution through acid weathering. Factor analysis suggests that in two major sampled area (Lill Burn and Track Burn) an epidote-sphene assemblage contributed sediment to coal measures. In approximately Whaingaroan times the epidote-sphene assemblage was replaced by an impoverished ilmenite-zircon assemblage. Because this is the reverse of the situation in coal measures studied elsewhere in Southland and in Canterbury, the ilmenite-zircon assemblage was probably inherited from the provenance area rather than the result of intrastratal solution