Dr Melissa Murphy

Mel MPost Doctoral Research Associate

Email: Melissa.Murphy@earth.ox.ac.uk

Research Profile

My research primarily focuses on the application of non-traditional stable isotope systems (lithium and uranium) to understand their geochemical cycling in a range of low temperature surficial environments.

This project will primarily focus on the application of ‘stable’ 238U and 235U isotopes (δ238U) to reconstruct palaeoredox conditions during intervals of source rock formation in ancient oceans using archives from the sedimentary record that may preserve a seawater signature, such as black shales and marine carbonates.

Li isotopes (δ7Li) will be explored as a tracer of silicate weathering processes, both in the modern environment (during estuarine mixing and in the large permafrost-dominated Lena River that drains into the Arctic Ocean) and in the past (to evaluate models linking changes in weathering regimes to organic carbon burial during carbon cycle perturbation events).

During my PhD at Macquarie University, Australia, I investigated the behaviour of uranium isotopes (U-series, δ238U and 236U/238U) during low temperature uranium ore formation processes, with the aim to assess their potential use as a tracer of redox processes, and ultimately as an exploration tool.

Publications:

Pogge von Strandmann, P.A.E., Burton, K.W., Opfergelt, S., Eiríksdóttir, E.S., Murphy, M.J., Einarsson, A., Gislason, S.R., 2016. The effect of hydrothermal spring weathering processes and primary productivity on lithium isotopes: Lake Myvatn, Iceland. Chemical Geology.

Murphy, M.J., Froehlich, M.B., Fifield, L.K., Turner, S.P., Schaefer, B.F., 2015. In-situ production of natural 236U in groundwaters and ores in high-grade uranium deposits. Chemical Geology 410, 213-222.

Murphy, M.J., Pogge von Strandmann, P.A.E., Porcelli, D., Ingri, J., 2014. Li Isotope Behaviour in the Low Salinity Zone During Estuarine Mixing. Procedia Earth and Planetary Science 10, 204-207.

Murphy, M.J., Stirling, C.H, Turner, S.P., Schaefer, B.F. and Kaltenbach, A., 2014. Redox-controlled fractionation of 238U/235U during low temperature uranium mineralisation. Earth and Planetary Science Letters. 388, 306-317.

Portner, R.A., Daczko, N.R., Murphy, M..J., and Pearson, N.J., 2011. Enriching mantle melts within a dying mid-ocean spreading ridge: Insights from Hf-isotope and trace element patterns in detrital oceanic zircon. Lithos, 126, 355-368.

Portner, R.A., Murphy, M.J., and Daczko, N.R., 2011. A detrital record of lower oceanic crust exhumation within a Miocene slow-spreading ridge: Macquarie Island, Southern Ocean. Geological Society of America Bulletin, 123, 255-273.