Diffusive fractionation of lithium and boron isotopes in silicate melts: a tool to study degassing in ascending magmas
Final Report Abstract
In this study the diffusivity and kinetic fraction of Li and B in a rhyolitic melt composition was determined for H2O-contents that are quite typical for natural magmas. These data do fill a gap in knowledge and clearly document the strong effect of H2O dissolved in silicate melts on the transport kinetics of these two elements. Based on these results, time windows for ascent-speedometers could be established that range from seconds to hours for Li, and from hours to weeks or months for B, depending on H2O-content of the melt. By decompression experiments with various decompression rates the evolution of Li and B contents and isotopes during bubble nucleation and growth was determined and provided insights to realistic situations of natural magma ascent and eruption and the chemical variations around vesicles that can be expected. With these data the predictive quality of numerical models on the chemical evolution of degassing and ascending magmas was assessed to point out their strengths and limits.
Publications
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August 18-23, 2019, Li and B contents in silicate melts as tracers of volcanic degassing, Goldschmidt conference, Barcelona (Spain)
Spallanzani R., Cichy S.B., Wilke M., Koga K., Laporte D.
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October 01-05, 2019, Li and B contents in silicate melts as tracers of volcanic degassing, Silicate Melts Workshop, La Petite Pierre, Strasbourg (France)
Spallanzani R., Cichy S.B., Wilke M., Koga K., Laporte D.
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May 04-08, 2020, Li and B diffusivity in hydrated silicate melts: an experimental study, EGU General Assembly, online
Spallanzani R., Cichy S.B., Oelze M., Koga K., Wilke M., Fanara S., Sieber M.J.
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(2021), Pre-eruptive PTX fluid-conditions of the Afyon Volcanic Complex (Western Anatolia, Turkey): Studies of natural rocks and phase equilibria experiments. Lithos 398-399, 106297
Dogan-Kulahci G.D., Cichy S.B., Temel A., Spallanzani R.
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April 06-09, 2021, Experimental insights on lithium and boron behaviour during magma degassing, Alan Rittmann Conference, Italian Association of Volcanology, AIV, online
Spallanzani R., Cichy S.B., Koga K., Oelze M., Wilke M., Fanara S., Wiedenbeck M., Schmidt B.
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March 01-03, 2021, Lithium and boron mobility in degassing magma: an experimental study. EMPG-XVII Symposium online
Spallanzani R., Cichy S.B., Koga K., Oelze M., Wilke M., Fanara S., Wiedenbeck M.
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(2022) Experimental determination of lithium and boron diffusivity and isotopic fractionation in hydrated rhyolitic melts. Contributions to Mineralogy and Petrology vol 177 n. 74
Spallanzani R., Koga K., Cichy S.B., Wiedenbeck M., Wilke M., Schmidt B., Oelze M.
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(2022) Li and B in ascending magmas: an experimental study on their mobility and isotopic fractionation. PhD Thesis Universität Potsdam
Spallanzani R.
