Phenocrystic fluorite in peralkaline rhyolites, Olkaria, Kenya Rift Valley.

Lancaster Environment Centre

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Phenocrystic fluorite in peralkaline rhyolites, Olkaria, Kenya Rift Valley. / Marshall, A. S.; Hinton, R. W.; MacDonald, Raymond.
In: Mineralogical Magazine, Vol. 62, No. 4, 01.08.1998, p. 477-486.

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

Author

Marshall, A. S. ; Hinton, R. W. ; MacDonald, Raymond. / Phenocrystic fluorite in peralkaline rhyolites, Olkaria, Kenya Rift Valley. In: Mineralogical Magazine. 1998 ; Vol. 62, No. 4. pp. 477-486.

Bibtex

@article{e6943f79178543278a623c04f6d4f272,

title = "Phenocrystic fluorite in peralkaline rhyolites, Olkaria, Kenya Rift Valley.",

abstract = "The first occurrence of phenocrystic fluorite in a peralkaline rhyolite is reported from Quaternary lavas (agpaitic index 1.11-1.37) erupted from the Greater Olkaria Volcanic Complex, Kenya. Fluorite compositions are almost stoichiometric, with 0.65-1.49 REE + Y oxides. Relative to coexisting glass (melt), the fluorites are enriched in REE, Y and Sr, are strongly depleted in all other trace elements and concentrate MREE relative to LREE and HREE. Y partitions into fluorite more strongly than the HREE. Fractionation of fluorite in its modal abundance would not significantly affect the REE abundances in the residual liquids, nor result in stronger Sr depletion. The P, T and composition conditions which stabilize fluorite in rhyolitic magmas are still obscure.",

author = "Marshall, {A. S.} and Hinton, {R. W.} and Raymond MacDonald",

year = "1998",

month = aug,

day = "1",

language = "English",

volume = "62",

pages = "477--486",

journal = "Mineralogical Magazine",

issn = "0026-461X",

publisher = "Mineralogical Society",

number = "4",

}

RIS

TY - JOUR

T1 - Phenocrystic fluorite in peralkaline rhyolites, Olkaria, Kenya Rift Valley.

AU - Marshall, A. S.

AU - Hinton, R. W.

AU - MacDonald, Raymond

PY - 1998/8/1

Y1 - 1998/8/1

N2 - The first occurrence of phenocrystic fluorite in a peralkaline rhyolite is reported from Quaternary lavas (agpaitic index 1.11-1.37) erupted from the Greater Olkaria Volcanic Complex, Kenya. Fluorite compositions are almost stoichiometric, with 0.65-1.49 REE + Y oxides. Relative to coexisting glass (melt), the fluorites are enriched in REE, Y and Sr, are strongly depleted in all other trace elements and concentrate MREE relative to LREE and HREE. Y partitions into fluorite more strongly than the HREE. Fractionation of fluorite in its modal abundance would not significantly affect the REE abundances in the residual liquids, nor result in stronger Sr depletion. The P, T and composition conditions which stabilize fluorite in rhyolitic magmas are still obscure.

AB - The first occurrence of phenocrystic fluorite in a peralkaline rhyolite is reported from Quaternary lavas (agpaitic index 1.11-1.37) erupted from the Greater Olkaria Volcanic Complex, Kenya. Fluorite compositions are almost stoichiometric, with 0.65-1.49 REE + Y oxides. Relative to coexisting glass (melt), the fluorites are enriched in REE, Y and Sr, are strongly depleted in all other trace elements and concentrate MREE relative to LREE and HREE. Y partitions into fluorite more strongly than the HREE. Fractionation of fluorite in its modal abundance would not significantly affect the REE abundances in the residual liquids, nor result in stronger Sr depletion. The P, T and composition conditions which stabilize fluorite in rhyolitic magmas are still obscure.

M3 - Journal article

VL - 62

SP - 477

EP - 486

JO - Mineralogical Magazine

JF - Mineralogical Magazine

SN - 0026-461X

IS - 4

ER -

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