Magmatic zoning in apatite: a monitor of porosity and permeability change in granites

Apatites from the Shap Granite, northern England, are strongly zoned, reflecting multiple generations of growth and dissolution. Such chemical zoning is most readily displayed in cathodoluminescence images and correlates well with trace element variation determined using LA-ICP-MS analyses. The zone...

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Bibliographic Details
Published in:Contributions to mineralogy and petrology 2003-08, Vol.145 (5), p.568-577
Main Authors: Dempster, T. J., Jolivet, M., Tubrett, M. N., Braithwaite, C. J. R.
Format: Article
Language:English
Subjects:
Crystallography
Fracture zones
Geochemistry
Granite
Magma
Mineralogy
Mixing processes
Permeability
Petrology
Porosity
Stratigraphy
Trace elements
Zoning
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Summary:Apatites from the Shap Granite, northern England, are strongly zoned, reflecting multiple generations of growth and dissolution. Such chemical zoning is most readily displayed in cathodoluminescence images and correlates well with trace element variation determined using LA-ICP-MS analyses. The zoned apatites provide a detailed record of the changing scales of permeability during progressive crystallisation within the magma chamber. Early periods of apatite growth are preserved within cores and represent both early growth within a magma chamber dominated by vigorous mixing processes and inherited grains with significantly different chemistries. The main phase of apatite growth within the magma was strongly controlled by the presence of adjacent biotite phenocrysts and is characterised by fine scale oscillatory zoning, followed by the growth of a thin rim of relatively uniform composition. The chemical evolution of the later phases of apatite growth and the stratigraphy of the zoning appear to record late stage crystallisation within progressively more isolated interstitial melt pockets. [PUBLICATION ABSTRACT]
ISSN:0010-7999
1432-0967
DOI:10.1007/s00410-003-0471-0