Silica-rich lavas in the oceanic crust: experimental evidence for fractional crystallization under low water activity
International audience We experimentally investigated phase relations and phase compositions as well as the influence of water activity ( aH 2 O) and redox conditions on the equilibrium crystallization path within an oceanic dacitic potassium-depleted system at shallow pressure (200 MPa). Moreover,...
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ftunilorrainehal:oai:HAL:insu-03712931v1 2023-10-09T21:44:58+02:00 Silica-rich lavas in the oceanic crust: experimental evidence for fractional crystallization under low water activity Erdmann, Martin Koepke, Jürgen Centre de Recherches Pétrographiques et Géochimiques (CRPG) Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS) Institut für Mineralogie Hannover Leibniz Universität Hannover=Leibniz University Hannover German Research Foundation (DFG) 2016 https://insu.hal.science/insu-03712931 https://doi.org/10.1007/s00410-016-1294-0 en eng HAL CCSD info:eu-repo/semantics/altIdentifier/doi/10.1007/s00410-016-1294-0 insu-03712931 https://insu.hal.science/insu-03712931 BIBCODE: 2016CoMP.171.83E doi:10.1007/s00410-016-1294-0 Contributions to Mineralogy and Petrology https://insu.hal.science/insu-03712931 Contributions to Mineralogy and Petrology, 2016, 171, pp.83. ⟨10.1007/s00410-016-1294-0⟩ Crystallization experiments Phase equilibria Differentiation Dacite Fast-spreading mid-ocean ridge Oceanic plagiogranite [SDU]Sciences of the Universe [physics] info:eu-repo/semantics/article Journal articles 2016 ftunilorrainehal https://doi.org/10.1007/s00410-016-1294-0 2023-09-12T22:50:26Z International audience We experimentally investigated phase relations and phase compositions as well as the influence of water activity ( aH 2 O) and redox conditions on the equilibrium crystallization path within an oceanic dacitic potassium-depleted system at shallow pressure (200 MPa). Moreover, we measured the partitioning of trace elements between melt and plagioclase via secondary ion mass spectrometry for a highly evolved experiment (SiO 2 = 74.6 wt%). As starting material, we used a dacitic glass dredged at the Pacific-Antarctic Rise. Phase assemblages in natural high-silica systems reported from different locations of fast-spreading oceanic crust could be experimentally reproduced only in a relatively small range of temperature and melt-water content ( T ~950 °C; melt H 2 O < 1.5 wt%) at redox conditions slightly below the quartz-fayalite-magnetite buffer. The relatively low water content is remarkable, because distinct hydrothermal influence is generally regarded as key for producing silica-rich rocks in an oceanic environment. However, our conclusion is also supported by mineral and melt chemistry of natural evolved rocks; these rocks are only congruent to the composition of those experimental phases that are produced under low aH 2 O. Low FeO contents under water-saturated conditions and the characteristic enrichment of Al 2 O 3 in high aH 2 O experiments, in particular, contradict natural observations, while experiments with low aH 2 O match the natural trend. Moreover, the observation that highly evolved experimental melts remain H 2 O-poor while they are relatively enriched in chlorine implies a decoupling between these two volatiles during crustal contamination. Article in Journal/Newspaper Antarc* Antarctic Université de Lorraine: HAL Antarctic Pacific Contributions to Mineralogy and Petrology 171 10 |
institution |
Open Polar |
collection |
Université de Lorraine: HAL |
op_collection_id |
ftunilorrainehal |
language |
English |
topic |
Crystallization experiments Phase equilibria Differentiation Dacite Fast-spreading mid-ocean ridge Oceanic plagiogranite [SDU]Sciences of the Universe [physics] |
spellingShingle |
Crystallization experiments Phase equilibria Differentiation Dacite Fast-spreading mid-ocean ridge Oceanic plagiogranite [SDU]Sciences of the Universe [physics] Erdmann, Martin Koepke, Jürgen Silica-rich lavas in the oceanic crust: experimental evidence for fractional crystallization under low water activity |
topic_facet |
Crystallization experiments Phase equilibria Differentiation Dacite Fast-spreading mid-ocean ridge Oceanic plagiogranite [SDU]Sciences of the Universe [physics] |
description |
International audience We experimentally investigated phase relations and phase compositions as well as the influence of water activity ( aH 2 O) and redox conditions on the equilibrium crystallization path within an oceanic dacitic potassium-depleted system at shallow pressure (200 MPa). Moreover, we measured the partitioning of trace elements between melt and plagioclase via secondary ion mass spectrometry for a highly evolved experiment (SiO 2 = 74.6 wt%). As starting material, we used a dacitic glass dredged at the Pacific-Antarctic Rise. Phase assemblages in natural high-silica systems reported from different locations of fast-spreading oceanic crust could be experimentally reproduced only in a relatively small range of temperature and melt-water content ( T ~950 °C; melt H 2 O < 1.5 wt%) at redox conditions slightly below the quartz-fayalite-magnetite buffer. The relatively low water content is remarkable, because distinct hydrothermal influence is generally regarded as key for producing silica-rich rocks in an oceanic environment. However, our conclusion is also supported by mineral and melt chemistry of natural evolved rocks; these rocks are only congruent to the composition of those experimental phases that are produced under low aH 2 O. Low FeO contents under water-saturated conditions and the characteristic enrichment of Al 2 O 3 in high aH 2 O experiments, in particular, contradict natural observations, while experiments with low aH 2 O match the natural trend. Moreover, the observation that highly evolved experimental melts remain H 2 O-poor while they are relatively enriched in chlorine implies a decoupling between these two volatiles during crustal contamination. |
author2 |
Centre de Recherches Pétrographiques et Géochimiques (CRPG) Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS) Institut für Mineralogie Hannover Leibniz Universität Hannover=Leibniz University Hannover German Research Foundation (DFG) |
format |
Article in Journal/Newspaper |
author |
Erdmann, Martin Koepke, Jürgen |
author_facet |
Erdmann, Martin Koepke, Jürgen |
author_sort |
Erdmann, Martin |
title |
Silica-rich lavas in the oceanic crust: experimental evidence for fractional crystallization under low water activity |
title_short |
Silica-rich lavas in the oceanic crust: experimental evidence for fractional crystallization under low water activity |
title_full |
Silica-rich lavas in the oceanic crust: experimental evidence for fractional crystallization under low water activity |
title_fullStr |
Silica-rich lavas in the oceanic crust: experimental evidence for fractional crystallization under low water activity |
title_full_unstemmed |
Silica-rich lavas in the oceanic crust: experimental evidence for fractional crystallization under low water activity |
title_sort |
silica-rich lavas in the oceanic crust: experimental evidence for fractional crystallization under low water activity |
publisher |
HAL CCSD |
publishDate |
2016 |
url |
https://insu.hal.science/insu-03712931 https://doi.org/10.1007/s00410-016-1294-0 |
geographic |
Antarctic Pacific |
geographic_facet |
Antarctic Pacific |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_source |
Contributions to Mineralogy and Petrology https://insu.hal.science/insu-03712931 Contributions to Mineralogy and Petrology, 2016, 171, pp.83. ⟨10.1007/s00410-016-1294-0⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1007/s00410-016-1294-0 insu-03712931 https://insu.hal.science/insu-03712931 BIBCODE: 2016CoMP.171.83E doi:10.1007/s00410-016-1294-0 |
op_doi |
https://doi.org/10.1007/s00410-016-1294-0 |
container_title |
Contributions to Mineralogy and Petrology |
container_volume |
171 |
container_issue |
10 |
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1779315041574584320 |