Abstract The seldom-described potassium-bearing phosphate minerals taranakite and leucophosphite occurs as veins, crusts, and alteration pools in jointed basalt of a sea stack and in basaltic breccia of Green Island off the Otago coast. All occurrences are microcrystalline aggregates. Electron microprobe analyses of taranakite reveal compositions very similar to the ideal formula. In contrast, leucophosphite analyses are lower in potassium and richer in titanium and aluminium than previously studied occurrences. Both localities host seabird populations and it is inferred that bird guano supplied both the phosphorus and potassium essential to these minerals. Aluminium, iron, and titanium, on the other hand, are probably derived from the basalt host rock.
Keywords phosphate minerals; taranakite; leucophosphite; soils; guano; Cooks Head Rock; Green Island; Otago
R02047 Received 21 October 2002; accepted 14 February 2003; published 30
April 2003
© Journal of the Royal Society of New Zealand, Volume 33, Number
1, March 2003, pp 487-495
PDF file of entire paper: Print-quality (2655K) | screen-quality (98K)