Spherulite crystallization induces Fe-redox redistribution in silicic melt.

Lancaster Environment Centre

Research output: Contribution to Journal/Magazine › Journal article › peer-review

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Spherulite crystallization induces Fe-redox redistribution in silicic melt. / Castro, Jonathan M.; Cottrell, Elizabeth; Tuffen, Hugh et al.
In: Chemical Geology, Vol. 268, No. 3-4, 30.11.2009, p. 272-280.

Research output: Contribution to Journal/Magazine › Journal article › peer-review

Harvard

Castro, JM, Cottrell, E, Tuffen, H, Logan, A & Kelley, KA 2009, 'Spherulite crystallization induces Fe-redox redistribution in silicic melt.', Chemical Geology, vol. 268, no. 3-4, pp. 272-280. https://doi.org/10.1016/j.chemgeo.2009.09.006

APA

Castro, J. M., Cottrell, E., Tuffen, H., Logan, A., & Kelley, K. A. (2009). Spherulite crystallization induces Fe-redox redistribution in silicic melt. Chemical Geology, 268(3-4), 272-280. https://doi.org/10.1016/j.chemgeo.2009.09.006

Vancouver

Castro JM, Cottrell E, Tuffen H, Logan A, Kelley KA. Spherulite crystallization induces Fe-redox redistribution in silicic melt. Chemical Geology. 2009 Nov 30;268(3-4):272-280. doi: 10.1016/j.chemgeo.2009.09.006

Author

Castro, Jonathan M. ; Cottrell, Elizabeth ; Tuffen, Hugh et al. / Spherulite crystallization induces Fe-redox redistribution in silicic melt. In: Chemical Geology. 2009 ; Vol. 268, No. 3-4. pp. 272-280.

Bibtex

@article{7e3c0d4f25014ff09f72a4302318761c,

title = "Spherulite crystallization induces Fe-redox redistribution in silicic melt.",

abstract = "Rhyolitic obsidians from Krafla volcano, Iceland, record the interaction between mobile hydrous species liberated during crystal growth and the reduction of ferric iron in the silicate melt. We performed synchrotron µ-FTIR and µ-XANES measurements along a transect extending from a spherulite into optically distinct colorless and brown glass zones. Measurements show that the colorless glass is enriched in OH-groups and depleted in ferric iron, while the brown glass shows the opposite relationship. The color shift between brown and clear glass is sharp, suggesting that the colorless glass zone was produced by a redox front that originated from the spherulite margin and moved through surrounding melt during crystallization. We conclude that the most likely reducing agent is hydrogen, produced by magnetite crystallization within the spherulite. The Krafla flow dramatically captures redox disequilibrium on the micoscale and highlights the importance of hydrous fluid liberation and late stage crystallization to the redox signature of glassy lavas.",

keywords = "Obsidian, spherulite, oxidation-reduction, FTIR, iron, hydrogen, XANES",

author = "Castro, {Jonathan M.} and Elizabeth Cottrell and Hugh Tuffen and Amelia Logan and Kelley, {Katherine A.}",

note = "The final, definitive version of this article has been published in the Journal, Chemical Geology 268 (3-4), 2009, {\textcopyright} ELSEVIER.",

year = "2009",

month = nov,

day = "30",

doi = "10.1016/j.chemgeo.2009.09.006",

language = "English",

volume = "268",

pages = "272--280",

journal = "Chemical Geology",

issn = "0009-2541",

publisher = "Elsevier",

number = "3-4",

}

RIS

TY - JOUR

T1 - Spherulite crystallization induces Fe-redox redistribution in silicic melt.

AU - Castro, Jonathan M.

AU - Cottrell, Elizabeth

AU - Tuffen, Hugh

AU - Logan, Amelia

AU - Kelley, Katherine A.

N1 - The final, definitive version of this article has been published in the Journal, Chemical Geology 268 (3-4), 2009, © ELSEVIER.

PY - 2009/11/30

Y1 - 2009/11/30

N2 - Rhyolitic obsidians from Krafla volcano, Iceland, record the interaction between mobile hydrous species liberated during crystal growth and the reduction of ferric iron in the silicate melt. We performed synchrotron µ-FTIR and µ-XANES measurements along a transect extending from a spherulite into optically distinct colorless and brown glass zones. Measurements show that the colorless glass is enriched in OH-groups and depleted in ferric iron, while the brown glass shows the opposite relationship. The color shift between brown and clear glass is sharp, suggesting that the colorless glass zone was produced by a redox front that originated from the spherulite margin and moved through surrounding melt during crystallization. We conclude that the most likely reducing agent is hydrogen, produced by magnetite crystallization within the spherulite. The Krafla flow dramatically captures redox disequilibrium on the micoscale and highlights the importance of hydrous fluid liberation and late stage crystallization to the redox signature of glassy lavas.

AB - Rhyolitic obsidians from Krafla volcano, Iceland, record the interaction between mobile hydrous species liberated during crystal growth and the reduction of ferric iron in the silicate melt. We performed synchrotron µ-FTIR and µ-XANES measurements along a transect extending from a spherulite into optically distinct colorless and brown glass zones. Measurements show that the colorless glass is enriched in OH-groups and depleted in ferric iron, while the brown glass shows the opposite relationship. The color shift between brown and clear glass is sharp, suggesting that the colorless glass zone was produced by a redox front that originated from the spherulite margin and moved through surrounding melt during crystallization. We conclude that the most likely reducing agent is hydrogen, produced by magnetite crystallization within the spherulite. The Krafla flow dramatically captures redox disequilibrium on the micoscale and highlights the importance of hydrous fluid liberation and late stage crystallization to the redox signature of glassy lavas.

KW - Obsidian

KW - spherulite

KW - oxidation-reduction

KW - FTIR

KW - iron

KW - hydrogen

KW - XANES

U2 - 10.1016/j.chemgeo.2009.09.006

DO - 10.1016/j.chemgeo.2009.09.006

M3 - Journal article

VL - 268

SP - 272

EP - 280

JO - Chemical Geology

JF - Chemical Geology

SN - 0009-2541

IS - 3-4

ER -

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