Hydrothermal association of pyrophyllite, kaolinite, diaspore, dickite, and quartz in the Coromandel Area, New Zealand

Abstract

Hydrothermal action has formed a clay deposit with a zone containing over 80% pyrophyllite and other zones containing kaolinite-dickite-quartz and kaolinite-diaspore from andesite in the Coromandel area New Zealand. The deposit was formed deep in the earth at pressures over 2,000 p.s.i. and temperatures above 335°C. The pyrophyllite in the deposits has the formula [Al(OH)2)]+0.1 Al2 [Si3.90Al0.10] O9.05(OH)2.10, and an X-ray diffraction pattern and differential thermogram similar to, but not identical with, those given in the literature. Dickite and lepidocrocite were identified in the deposits by X-ray diffraction techniques; diaspore by X-ray diffraction and optical techniques. © Taylor & Francis Group, LLC.