Information about open system magma chambers derived from textures in magmatic enclaves; the Kameni Islands, Santorini, Greece

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doi: 10.1017/S0016756805001172
Authors:Holness, Marian B.; Martin, V. M.; Pyle, D. M.
Author Affiliations:Primary:
University of Cambridge, Department of Earth Sciences, Cambridge, United Kingdom
Volume Title:Geological Magazine
Source:Geological Magazine, 142(6), p.637-649. Publisher: Cambridge University Press, London, United Kingdom. ISSN: 0016-7568
Publication Date:2005
Note:In English. 54 refs.; illus., incl. 1 table, sketch map
Summary:Post-caldera eruptions of Santorini, Greece, over the past 3000 years resulted in the formation of the Kameni Islands, which comprise a series of compositionally similar dacitic lava flows. Each lava flow has a distinct population of partially-crystalline mafic enclaves, which we propose were derived from the break-up of a layer of replenishing magma responsible for triggering the eruption. Five of the recent flows (erupted in 1570, 1939, 1940, 1941 and 1950) include enclaves of essentially identical andesitic bulk compositions, which formed by crystallization of originally aphyric melts prior to eruption. Detailed examination of angles subtended at the junctions between pairs of plagioclase grains demonstrates that enclaves from each flow have a characteristic textural signature, with distinct differences in the extent of quench-related modification of the original population of dihedral angles formed by impingement of growing grains. These variations suggest that the temperature difference between the host dacite and the replenishing andesite at the time of layer overturn and eruption differed between flows. The uniformity of major element compositions of both the replenishing magma and the host dacitic lava flows demonstrates that the critical parameter in determining the timing of layer-overturn is the pre-eruptive H2O content of both host dacite and replenishing magma. We suggest that the replenishing magma responsible for two of the three eruptions in the period 1939-1941 was significantly wetter than that responsible for the later 1950 eruption. The enclaves with the least amount of quench-related modification occur in the 1570 flow. We suggest that in this case the intruding magma was relatively dry.
Subsections:Igneous rocks; Volcanology
Subjects:Calderas; Crystallization; Dacites; Eruptions; Igneous rocks; Inclusions; Kinetics; Lava flows; Magma chambers; Magmas; Magmatism; Microscope methods; Mineral composition; Models; Petrography; Spectra; Volcanic features; Volcanic rocks; Volcanism; Volcanoes; Water; X-ray fluorescence spectra; Aegean Islands; Cyclades; Europe; Greece; Greek Aegean Islands; Mediterranean region; Santorin; Southern Europe; Thera; Kameni Islands; Nea Kameni Island; Palaea Island
Coordinates:N362400 N362400 E0252700 E0252700
Abstract Numbers:06M/1167
Record ID:2006021477
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Cambridge University Press, Reference includes data from GeoScienceWorld, Alexandria, VA, United States
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