Tracking the magmatic evolution of island arc volcanism: Insights from a high-precision Pb isotope record of Montserrat, Lesser Antilles


Cassidy, M., Taylor, R.N., Palmer, M.R., Cooper, R.J., Stenlake, C. and Trofimovs, J. (2012) Tracking the magmatic evolution of island arc volcanism: Insights from a high-precision Pb isotope record of Montserrat, Lesser Antilles. Geochemistry Geophysics Geosystems, 13, Q05003. (doi:10.1029/2012GC004064).

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Description/Abstract

The volcanic succession on Montserrat provides an opportunity to examine the magmatic evolution of island arc volcanism over a ∼2.5 Ma period, extending from the andesites of the Silver Hills center, to the currently active Soufrière Hills volcano (February 2010). Here we present high-precision double-spike Pb isotope data, combined with trace element and Sr-Nd isotope data throughout this period of Montserrat's volcanic evolution. We demonstrate that each volcanic center; South Soufrière Hills, Soufrière Hills, Centre Hills and Silver Hills, can be clearly discriminated using trace element and isotopic parameters. Variations in these parameters suggest there have been systematic and episodic changes in the subduction input. The SSH center, in particular, has a greater slab fluid signature, as indicated by low Ce/Pb, but less sediment addition than the other volcanic centers, which have higher Th/Ce. Pb isotope data from Montserrat fall along two trends, the Silver Hills, Centre Hills and Soufrière Hills lie on a general trend of the Lesser Antilles volcanics, whereas SSH volcanics define a separate trend. The Soufrière Hills and SSH volcanic centers were erupted at approximately the same time, but retain distinctive isotopic signatures, suggesting that the SSH magmas have a different source to the other volcanic centers. We hypothesize that this rapid magmatic source change is controlled by the regional transtensional regime, which allowed the SSH magma to be extracted from a shallower source. The Pb isotopes indicate an interplay between subduction derived components and a MORB-like mantle wedge influenced by a Galapagos plume-like source.

Item Type: Article
ISSNs: 1525-2027 (print)
1525-2027 (electronic)
Subjects: Q Science > QE Geology
Divisions: Faculty of Natural and Environmental Sciences > Ocean and Earth Science > Geochemistry
National Oceanography Centre (NERC) > Marine Geoscience
ePrint ID: 338932
Date Deposited: 17 May 2012 14:31
Last Modified: 14 Apr 2014 11:41
Research Funder: NERC
Projects:
The impact of submarine diagenesis of tephra on seawater chemistry
Funded by: NERC (NE/D004020/1)
Led by: Martin Ralph Palmer
24 July 2007 to 23 December 2009
URI: http://eprints.soton.ac.uk/id/eprint/338932

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