Clay minerals formed from micas and chlorites in some New Zealand soils

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Abstract
Clay mineralogical differences between eight soils in South Island, New Zealand, are related to differences in climate, vegetation, and formation time. Alteration of chlorite follows the sequence chlorite→interlayered hydrousmica→chlorite-swelling chlorite→chlorite-vermiculite, with increased weathering leading to the destruction of the chloritic layers. Mica (muscovite) follows two alteration sequences depending on the overlying vegetation. Under tussock grassland the sequence is mica→mica-vermiculite→mica-beidellite→beidellite. This sequence is also followed under beech forest, together with the sequence of mica→vermiculite→beidellite, with pedogenic chlorite forming when the pH is > 4·5. All but one of the interstratified products (the interlayered hydrous mica) appear to be based on a 1:1 regular interlayering of the two components.