Exploring intrusive processes through the crystal cargo of volcanic rocks: The case of lava flows from Taranaki volcano, New Zealand
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Date
2024-11
Open Access Location
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier B V
Rights
(c) The author/s
CC BY
CC BY
Abstract
The present-day edifice of Taranaki volcano, New Zealand, is largely made up of lava flows extruded over approximately the last 8 kyr. The crystal cargo of plagioclase, pyroxene and amphibole in these lavas displays varied major, minor, and trace element zoning patterns, pointing to long and complex crystal growth histories. Crystal zoning patterns do not vary systematically between stratigraphic units, and multiple patterns are seen within the same sample over very short length scales. Intracrystalline elemental variations reveal mineral-melt interactions, which result in repeated resorption and recrystallisation in varied environments. Variable degrees of undercooling are evidenced by clinopyroxenes, with most crystals displaying sector zoning (ΔT < 50 K), while others only show concentric zoning, which suggests very low ΔT. The common occurrence of resorbed cores within the crystals and the prevalence of glomerocrysts indicate antecrystic and/or xenocrystic origins and crystal aggregation processes. We hypothesise that the repeated intrusion of melts into the crustal basement of Taranaki volcano has resulted in the formation of a heterogeneous subsolidus plutonic to supersolidus mushy (∼15–55 vol% crystals) system that interacts with intruding melts from the mantle. These interactions result in disaggregation of crystal clots from the plutonic intrusives and remobilization of the crystals through various sub-environments of small ephemeral mush pockets. Eruption-triggering injections of melt then pick up these crystals with varied growth histories to be extruded
Description
Keywords
Plutonic basement Mush pockets Antecrysts Xenocrysts Remobilisation, Plutonic basement, Mush pockets, Antecrysts, Xenocrysts, Remobilisation
Citation
D'Mello NG, Zellmer GF, Ubide T, Caulfield J, Usuki M, Iizuka Y, Kereszturi G, Procter JN, Stewart RB. (2024). Exploring intrusive processes through the crystal cargo of volcanic rocks: The case of lava flows from Taranaki volcano, New Zealand. Chemical Geology. 667.