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Book Chapter

Trace-element distribution between coexisting aqueous fumarole condensates and natrocarbonatite lavas at Oldoinyo Lengai volcano, Tanzania

By
Alexander J. Teague
Alexander J. Teague
Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK, and Institute for Mineralogy and Petrology, ETH Zurich, CH-8092 Zürich, Switzerland
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Jacob Hanley
Jacob Hanley
Department of Geology, Saint Mary's University, 923 Robie Street, Halifax, Nova Scotia, B3H3C3, Canada, and Institute for Mineralogy and Petrology, ETH Zurich, CH-8092 Zürich, Switzerland
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Terry M. Seward
Terry M. Seward
Institute for Mineralogy and Petrology, ETH Zurich, CH-8092 Zürich, Switzerland
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Frederik Reutten
Frederik Reutten
Laboratory of Inorganic Chemistry, Department of Chemistry, ETH Zurich, CH-8093 Zürich, Switzerland
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Published:
June 01, 2011

Fieldwork was conducted in the active north crater of Oldoinyo Lengai volcano, Tanzania. Gases, aqueous fumarole condensates, and freshly erupted natrocarbonatite lavas were collected from several hornitoes associated with the same eruptive center and are considered to represent genetically related products of the same shallow magma chamber. Apparent trace-metal mineral-mineral partition coefficients were derived for the major carbonate phases, gregoryite and nyerereite, and several accessory phases within the fresh lava samples. Trace metals display an affinity for the accessory minerals.

Textural information suggests that fluorite and coexisting sylvite are also present interstitially as quenched immiscible salt melts, and that any trace metals present may be scavenged from the carbonatite by the immiscible separation of these salt phases. Gas condensate analyses from the fumaroles associated with the eruption reveal further partitioning of trace elements into the vapor phase. Chalcophile elements show particularly high volatility, and this implies either gas release prior to sulfide formation or the decomposition of sulfides prior to eruption.

The strong partitioning of metals into the halogenide and vapor phases has broad implications for the mobility of trace elements in the mantle source, the genesis of exotic mineralization associated with other carbonatites, and the ability of fumarole condensates to carry a direct chemical signature from their parent magma.

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Contents

GSA Special Papers

Volcanism and Evolution of the African Lithosphere

Luigi Beccaluva
Luigi Beccaluva
Dipartimento di Scienze della Terra, Università di Ferrara, Italy
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Gianluca Bianchini
Gianluca Bianchini
Dipartimento di Scienze della Terra, Università di Ferrara, Italy
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Marjorie Wilson
Marjorie Wilson
School of Earth & Environment, The University of Leeds, Leeds, UK
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Geological Society of America
Volume
478
ISBN print:
9780813724782
Publication date:
June 01, 2011

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