Volatile transport of metals in the andesitic magmatic-hydrothermal system of White Island
Volcanic gases observed at active volcanoes originate from the magma at depth. These volatiles exsolve as a result of decompression, crystallization and cooling of the silicate melt. The transport of metals in a magmatic volatile phase arises from complexation with the main volatile species, sulfur...
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Victoria University of Wellington
2017
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ftvuwellington:oai:researcharchive.vuw.ac.nz:10063/6730 2023-08-15T12:43:15+02:00 Volatile transport of metals in the andesitic magmatic-hydrothermal system of White Island Mandon, Céline Seward, Terry 2017 http://researcharchive.vuw.ac.nz/handle/10063/6730 en_NZ eng Victoria University of Wellington http://researcharchive.vuw.ac.nz/handle/10063/6730 http://creativecommons.org/licenses/by/3.0/nz/ Creative Commons GNU GPL Allow modifications Allow commercial use White Island Magmatic-hydrothermal system Metals text Doctoral 2017 ftvuwellington 2023-07-25T17:27:21Z Volcanic gases observed at active volcanoes originate from the magma at depth. These volatiles exsolve as a result of decompression, crystallization and cooling of the silicate melt. The transport of metals in a magmatic volatile phase arises from complexation with the main volatile species, sulfur and halides. Composition of the magma, temperature, pressure and redox state have thus strong implications on metal mobility in these environments. Moreover, a variety of interactions and phase separations can affect these fluids after exsolution from the parental magma. This thesis aims at constraining the volatile transport of trace metals at White Island, a subduction-related magmatic-hydrothermal system, through a characterization and metal budget of the magmatic reservoir and the different atmospheric discharges. The metal content of the reservoir, as well as the effects of degassing and magma mixing on the magma are explored through the study of ejecta from the 1976-2000 eruptive cycle. CO₂, SO₂ and H₂O are degassing from a mafic melt at ~ 5 km depth, regularly feeding a shallower and evolved reservoir at ~ 800 m. Average contents of 164 ppm of Cu, 73 ppm of Zn, 12 ppm of Pb and 0.4 ppm of Au and Ag were detected in melt inclusions. A fraction of these metals partition into the exsolving aqueous fluid. Onset of magnetite crystallization may trigger exsolution of sulphide melt, found to contain around 30 wt% of Cu, and as much as 36 wt% Ni, 21 wt% Ag, 0.10 wt% Au in small inclusions, representing a considerable source of metals available for an aqueous fluid phase upon resorption. The volatile transport of metals is indicated by their enrichment in a variety of discharges at the surface. The hyperacidic waters of the crater lake absorb metals from the magmatic gases injected at subaqueous vents. Concentrations of ~ 12 ppm of As and Zn, 6 ppm of Cu and Pb were observed. Hydrolysis of the host rock by the reactive waters is responsible for the high cation contents of the fluids. Precipitation of secondary minerals ... Doctoral or Postdoctoral Thesis White Island Victoria University of Wellington: ResearchArchive Crater Lake ENVELOPE(-60.667,-60.667,-62.983,-62.983) White Island ENVELOPE(48.583,48.583,-66.733,-66.733) |
institution |
Open Polar |
collection |
Victoria University of Wellington: ResearchArchive |
op_collection_id |
ftvuwellington |
language |
English |
topic |
White Island Magmatic-hydrothermal system Metals |
spellingShingle |
White Island Magmatic-hydrothermal system Metals Mandon, Céline Volatile transport of metals in the andesitic magmatic-hydrothermal system of White Island |
topic_facet |
White Island Magmatic-hydrothermal system Metals |
description |
Volcanic gases observed at active volcanoes originate from the magma at depth. These volatiles exsolve as a result of decompression, crystallization and cooling of the silicate melt. The transport of metals in a magmatic volatile phase arises from complexation with the main volatile species, sulfur and halides. Composition of the magma, temperature, pressure and redox state have thus strong implications on metal mobility in these environments. Moreover, a variety of interactions and phase separations can affect these fluids after exsolution from the parental magma. This thesis aims at constraining the volatile transport of trace metals at White Island, a subduction-related magmatic-hydrothermal system, through a characterization and metal budget of the magmatic reservoir and the different atmospheric discharges. The metal content of the reservoir, as well as the effects of degassing and magma mixing on the magma are explored through the study of ejecta from the 1976-2000 eruptive cycle. CO₂, SO₂ and H₂O are degassing from a mafic melt at ~ 5 km depth, regularly feeding a shallower and evolved reservoir at ~ 800 m. Average contents of 164 ppm of Cu, 73 ppm of Zn, 12 ppm of Pb and 0.4 ppm of Au and Ag were detected in melt inclusions. A fraction of these metals partition into the exsolving aqueous fluid. Onset of magnetite crystallization may trigger exsolution of sulphide melt, found to contain around 30 wt% of Cu, and as much as 36 wt% Ni, 21 wt% Ag, 0.10 wt% Au in small inclusions, representing a considerable source of metals available for an aqueous fluid phase upon resorption. The volatile transport of metals is indicated by their enrichment in a variety of discharges at the surface. The hyperacidic waters of the crater lake absorb metals from the magmatic gases injected at subaqueous vents. Concentrations of ~ 12 ppm of As and Zn, 6 ppm of Cu and Pb were observed. Hydrolysis of the host rock by the reactive waters is responsible for the high cation contents of the fluids. Precipitation of secondary minerals ... |
author2 |
Seward, Terry |
format |
Doctoral or Postdoctoral Thesis |
author |
Mandon, Céline |
author_facet |
Mandon, Céline |
author_sort |
Mandon, Céline |
title |
Volatile transport of metals in the andesitic magmatic-hydrothermal system of White Island |
title_short |
Volatile transport of metals in the andesitic magmatic-hydrothermal system of White Island |
title_full |
Volatile transport of metals in the andesitic magmatic-hydrothermal system of White Island |
title_fullStr |
Volatile transport of metals in the andesitic magmatic-hydrothermal system of White Island |
title_full_unstemmed |
Volatile transport of metals in the andesitic magmatic-hydrothermal system of White Island |
title_sort |
volatile transport of metals in the andesitic magmatic-hydrothermal system of white island |
publisher |
Victoria University of Wellington |
publishDate |
2017 |
url |
http://researcharchive.vuw.ac.nz/handle/10063/6730 |
long_lat |
ENVELOPE(-60.667,-60.667,-62.983,-62.983) ENVELOPE(48.583,48.583,-66.733,-66.733) |
geographic |
Crater Lake White Island |
geographic_facet |
Crater Lake White Island |
genre |
White Island |
genre_facet |
White Island |
op_relation |
http://researcharchive.vuw.ac.nz/handle/10063/6730 |
op_rights |
http://creativecommons.org/licenses/by/3.0/nz/ Creative Commons GNU GPL Allow modifications Allow commercial use |
_version_ |
1774299350254485504 |