Skip Navigation


Journal of Petrology Advance Access originally published online on September 25, 2006
Journal of Petrology 2007 48(1):3-42; doi:10.1093/petrology/egl052
This Article
Right arrow Full Text Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow Supplementary data
Right arrow All Versions of this Article:
48/1/3    most recent
egl052v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Toothill, J.
Right arrow Articles by Tindle, A. G.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© The Author 2006. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

A Complex Petrogenesis for an Arc Magmatic Suite, St Kitts, Lesser Antilles

J. Toothill1, C. A. Williams2, R. MacDonald1,*, S. P. Turner3, N. W. Rogers2, C. J. Hawkesworth4, D. A. Jerram5, C. J. Ottley5 and A. G. Tindle2

1Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK
2Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, UK
3Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109, Australia
4Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK
5Department Of Earth Sciences, University of Durham, Durham DH1 3LE, UK

RECEIVED FEBRUARY 3, 2005; ACCEPTED AUGUST 24, 2006


  Abstract

St Kitts forms one of the northern group of volcanic islands in the Lesser Antilles arc. Eruptive products from the Mt Liamuiga centre are predominantly olivine + hypersthene-normative, low-K basalts through basaltic andesites to quartz-normative, low-K andesites. Higher-Al and lower-Al groups can be distinguished in the suite. Mineral assemblages include olivine, clinopyroxene, orthopyroxene, plagioclase and titanomagnetite with rarer amphibole, ilmenite and apatite. Eruptive temperatures of the andesites are estimated as 963–950°C at fO2 ~ NNO + 1 (where NNO is the nickel–nickel oxide buffer). Field and mineral chemical data provide evidence for magma mixing. Glass (melt) inclusions in the phenocrysts range in composition from andesite to high-silica rhyolite. Compositional variations are broadly consistent with the evolution of more evolved magmas by crystal fractionation of basaltic parental magmas. The absence of any covariation between 87Sr/86Sr or 143Nd/144Nd and SiO2 rules out assimilation of older silicic crust. However, positive correlations between Ba/La, La/Sm and 208Pb/204Pb and between 208Pb/204Pb and SiO2 are consistent with assimilation of small amounts (<10%) of biogenic sediments. Trace element and Sr–Nd–Pb isotope data suggest derivation from a normal mid-ocean ridge basalt (N-MORB)-type mantle source metasomatized by subducted sediment or sediment melt and fluid. The eruptive rocks are characterized by 238U excesses that indicate that fluid addition of U occurred <350 kyr ago; U–Th isotope data for mineral separates are dominated by melt inclusions but would allow crystallization ages of 13–68 ka. However, plagioclase is consistently displaced above these ‘isochrons’, with apparent ages of 39–236 ka, and plagioclase crystal size distributions are concave-upwards. These observations suggest that mixing processes are important. The presence of 226Ra excesses in two samples indicates some fluid addition <8 kyr ago and that the magma residence times must also have been less than 8 kyr.

KEY WORDS: Sr–Nd–Pb isotopes; U-series isotopes; crystal size distribution; petrogenesis

*Corresponding author. E-mail: r.macdonald{at}lancaster.ac.uk


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer:
Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.