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Dr. John Caulfield - Postdoctoral Research Fellow

John Caulfield

Contact Details

Email: caulfijo@tcd.ie

Tel: + 353 1 8961363

Office: Research Room B, Museum Building

 

Research

Mantle Geochemistry

I am interested in identifying and quantifying upper mantle chemical signatures to constrain mantle differentiation, melt generation and volatile budgets. Mantle xenoliths provide direct evidence for the chemical composition of the lithospheric mantle, and provide an important complement to the petrological inferences derived from volcanic sample suites. Samples are initially treated to careful micro-scale examination to establish mineralogy and key textures including phenocryst zoning, inclusions and resorption/dissolution features to help unravel magmatic histories. Sample suites are typically characterised using whole-rock major element XRF and trace element solution ICP-MS analysis, isotope ratio determinations via MC-ICP-MS and TIMS, in-situ EMP and LA-ICP-MS analysis of glass and minerals and SIMS analysis of glassy phenocryst hosted melt inclusions to determine volatile contents. I use partial melting and mass balance models to investigate the transfer of incompatible elements and volatile species between the mantle and the crust, the nature and extent of coupling between mantle reservoirs and the implications for geodynamic models. The use of Uranium-series isotope analyses (U-Th-Ra) provide additional insight into the timescales on which these geological processes operate.

Currently, I am developing novel ICP-MS and ICP-OES techniques for the routine analysis of the halogens (F, Cl, Br and I) and other volatile elements in glasses and mineral phases hosted in mantle derived sample suites. These techniques will be used to characterise proto-Icelandic basalts and kimberlites from South Greenland in order to improve our understanding of the storage and transport of volatiles in the mantle.

Explosive Mafic Volcanism

Large scale explosive mafic eruptions are important because of the large volumes of sulphur- and halogen-rich gases they release into the atmosphere. Eruption triggers and cycles are often more complex and unpredictable than their silicic counterparts. Furthermore, the reconstruction of mafic ignimbrite forming eruptions is often very challenging due to high eruption temperatures that can lead to poor preservation of primary fragmentation features. Accordingly, these eruptions are best characterised through combining detailed volcanic facies and dating studies with rigorous micro-imaging and geochemical analysis techniques. Radiocarbon dating, major and trace element analysis, and melt inclusion volatile determinations are all vital data sources that, together with field observations and data, offer unique insights into eruption triggers, timing and dynamics at mafic volcanic centres.

Chemical Weathering

I am interested in the chemical denudation of bedrock lithologies and the quantification of its impact on ground and surface water chemistry. The integration of mineralogical, geochemical and hydrochemical data allows important constraints to be placed on the nature and scale of groundwater flow in aquifers. Using this multi-disciplinary approach, it is possible to establish groundwater baseflow hydrochemical fluxes that provide valuble natural baseline data for environmental assessment studies.

Students

I currently co-supervise two students:

Brendan Hoare (Trinity College Dublin) – Halogens in the West Greenland sub-continental lithospheric mantle

Donal O'Farrell (Trinity College Dublin) – Halogens in the proto-Iceland plume source mantle

Publications

Mark Reagan, Simon Turner, Heather Handley, Michael Turner, Christoph Beier, Caulfield, J.T., & David Peate. 210Pb-226Ra disequilibria in young gas-laden magmas. Scientific Reports 7, Article number: 45186 (2017) doi:10.1038/srep45186

Caulfield, J.T., Blichert-Toft, J., Albarède, F., and Turner, S.P. (2015). Corrigendum to “ Magma evolution in the primitive, intra-oceanic Tonga arc: Petrogenesis of basaltic andesites at Tofua Volcano” and “ Magma evolution in the primitive, intra-oceanic Tonga arc: Rapid petrogenesis of dacites at Fonualei Volcano” . Journal of Petrology 56, pp. 641-644, doi: 10.1093/petrology/egv009.

Caulfield, J., Chelliah, M., Comte, J-C., Cassidy, R., Flynn, R. (2014). Integrating petrography, mineralogy and hydrochemistry to constrain the influence and distribution of groundwater contributions to baseflow in poorly productive aquifers: Insights from Gortinlieve catchment, Co. Donegal, NW Ireland. Science of The Total Environment 500-501, pp. 224-234, doi: 10.1016/j.scitotenv.2014.08.105.

Foley, F.V., Turner, S., Rushmer, T., Caulfield, J.T., Daczko. N.R., Bierman, P., Robertson, M., Barrie, C.D., Boyce, A.J. (2014). 10Be, 18O and radiogenic isotopic constraints on the origin of adakitic signatures: A case study from Solander and Little Solander Islands, New Zealand. Contributions to Mineralogy and Petrology 168:1048, doi: 10.1007/s00410-014-1048-9.

Caulfield, J., Turner, S., Arculus, R., Dale, C., Jenner, F., Pearce, J., Macpherson, C., Handley, H. (2012). Mantle flow, volatiles, slab-surface temperatures and melting dynamics in the north Tonga arc – Lau back-arc basin. Journal of Geophysical Research - Solid Earth 117, No. B11, B11209, doi: 10.1029/2012JB009526.

Cunningham, H., Gill, J., Turner, S., Caulfield, J., Edwards, L., Day, S. (2012). Rapid magmatic processes accompany arc – continent collision: the Western Bismarck arc, Papua New Guinea. Contributions to Mineralogy and Petrology 164, (5), pp. 789-804, doi: 10.1007/s00410-012-0776-y.

Caulfield, J.T., Turner, S.P., Smith, I.E.M., Cooper, L.B., Jenner, G.A. (2012). Magma evolution in the primitive, intra-oceanic Tonga arc: petrogenesis of basaltic andesites at Tofua volcano. Journal of Petrology 53, (6), pp. 1197-1230, doi: 10.1093/petrology/egs013.

Turner, S.P., Caulfield, J.T., Rushmer, T., Turner, M., Cronin, S., Smith, I.E.M. (2012). Magma evolution in the primitive, intra-oceanic Tonga arc: petrogenesis of dacites at Fonualei volcano. Journal of Petrology 53, (6), pp. 1231-1253, doi: 10.1093/petrology/egs005.

Turner, S., Caulfield, J., Turner, M., Van Keken, P., Maury, R., Sandiford, M., Prouteau, G. (2012). Recent contribution of sediments and fluids to the mantle’s volatile budget. Nature Geoscience 5, (1), pp. 50-54.

Caulfield, J.T., Cronin, S.J., Turner, S., Cooper, L.B. (2011). Mafic Plinian volcanism and ignimbrite emplacement at Tofua volcano, Tonga. Bulletin of Volcanology 73, (9), pp. 1259-1277, doi: 10.1007/s00445-011-0477-9.

Caulfield, J.T., Turner, S., Dosseto, A., Pearson, N.J. & Beier, C. (2008). Source depletion and extent of melting in the Tongan sub-arc mantle. Earth and Planetary Science Letters 273, (3-4), pp. 279-288.

PhD. Thesis (2010): Nature and timing of Magma Genesis at Tofua volcano, Tonga. Macquarie University, 164 pp.

MSci. Thesis (2005): Origin and evolution of the Bau Granite, Sarawak, Borneo. Durham University, 112 pp.


Last updated 31 July 2017 nmcginle@tcd.ie.