Mixed deposits of complex magmatic and phreatomagmatic volcanism: an example from Crater Hill,Auckland, New Zealand |
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| Authors: | B F Houghton C J N Wilson M D Rosenberg I E M Smith R J Parker |
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| Institution: | (1) Institute of Geological and Nuclear Sciences, Wairakei Research Centre, Private Bag 2000, Taupo, New Zealand, NZ;(2) Department of Geology, University of Auckland, Private Bag 92019, Auckland, New Zealand, NZ |
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| Abstract: | A series of alternating phreatomagmatic ("wet") and magmatic ("dry") basaltic pyroclastic deposits forming the Crater Hill
tuff ring in New Zealand contains one unit (M1) which can only be interpreted as the products of mixing of ejecta from simultaneous
wet and dry explosions at different portions of a multiple vent system. The principal characteristics of M1 are (a) rapid
lateral changes in the thicknesses of, and proportions in juvenile components in individual beds, and (b) wide ranges of juvenile
clast densities in every sample. M1 appears to have been associated with an elongate source of highly variable and fluctuating
magma : water ratios and magma discharge rates. This contrasts with the only other documented mixed (wet and dry) basaltic
pyroclastic deposits where mixing from two point sources of quite different but stable character has been inferred.
Received: July 11, 1995 / Accepted: February 13, 1996 |
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| Keywords: | Explosive volcanism Magmatic Phreatomagmatic Crater Hill Basalt |
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