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Petrochemical characteristics of felsic veins in mantle xenoliths from Tallante (SE Spain): an insight into activity of silicic melt within the mantle wedge

By
Yohei Shimizu
Yohei Shimizu
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Shoji Arai
Shoji Arai
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Tomoaki Morishita
Tomoaki Morishita
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Hisayoshi Yurimoto
Hisayoshi Yurimoto
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Fernando Gervilla
Fernando Gervilla
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Published:
January 01, 2004

Felsic and related veins within mantle-derived peridotite xenoliths from Tallante, Spain, were examined in order to understand the mantle-wedge processes related to the behaviour of Si-rich melt. The thickest part of the vein has a quartz diorite lithology, and is composed mainly of quartz and plagioclase, with pyroxenes, hydrous mineral, apatite, zircon and rutile present as minor phases. The thinner parts are free of quartz and predominantly composed of plagioclase. Orthopyroxene always intervenes between the internal part (plagioclase ± quartz) and host peridotite, indicating that it is a product of interaction between silica-oversaturated melt and olivine. This indicates that a sufficiently high melt/wall rock ratio enabled the melt to retain its silica-oversaturated character.

The quartz diorite part has adakite-like geochemical signatures, except for negative Ba, Rb Eu and Sr anomalies, and positive Th and U anomalies. These negative anomalies indicate that fractionation of plagioclase and hydrous minerals was achieved between the upper most mantle and the slab melting zone. The shape of the rare-earth element (REE) pattern of clinopyroxene in quartz diorite is strikingly similar to that of clinopyroxene phenocrysts from Aleutian adakites. However, the former has one order higher REE contents than the latter, except for Eu which shows a prominent negative spike. This feature was caused by the precipitation of large amounts of plagioclase and small amounts of clinopyroxene from a fractionated adakitic melt before and during solidification. This adakitic melt was produced by partial melting of a detached and sinking slab beneath the Betic area in the Tertiary.

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GSA Special Papers

The Fifth Hutton Symposium on the Origin of Granites and Related Rocks

S. Ishihara
S. Ishihara
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W.E. Stephens
W.E. Stephens
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S.L. Harley
S.L. Harley
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M. Arima
M. Arima
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T. Nakajima
T. Nakajima
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Geological Society of America
Volume
389
ISBN print:
9780813723891
Publication date:
January 01, 2004

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