Zinc isotope fractionation in sediment-hosted Zn-Pb deposits
Dr. Jamie Wilkinson & Dr Dominik Weiss
AIM To determine the extent and controls of zinc isotope variation in sediment-hosted Zn-Pb ore deposits as a
potential tool for mineral exploration.
BACKGROUND Our knowledge of the controls of zinc isotope variation in hydrothermal systems is limited to just a
few studies of ore deposits (Mason et al., 2003; Wilkinson et al., 2005; Kelley et al., in revision) and modern submarine
systems (John et al., 2008). The data that exist show that almost the entire terrestrial range of zinc isotope
compositions is observed within such systems implicating hydrothermal processes as a major control of isotopic
fractionation. The generation of systematic patterns attributed to Rayleigh fractionation processes during sphalerite
precipitation provides a potential useful tool in the exploration for mineral resources.
OBJECTIVES The principal objective of the study is to
determine the Zn isotopic variability of sphalerite and
trace Zn in altered rocks in sediment-hosted ore
systems. These results will be used to test models of
isotopic fractionation and evaluate the potential for
fingerprinting ore signatures and targeting mineral
exploration.
METHODS Logging and sampling of drillcore and
underground mine exposures will be carried out in the
Irish Zn-Pb orefield and potentially other districts. The
study will utilise wet chemistry laboratory facilities
located in the Department. Chemical analyses will be
Aerial view of the Red Dog mine, Brooks Range, Alaska. New data carried out using ICP-AES and ICP-MS instruments, and
have shown that there are important variations in Zn isotope isotope measurements will be made using the
compositions in this district that could help to locate further Zn-Pb Department’s Nu Plasma multi-collector ICP-MS
resources.
located in the Royal School of Mines Building.
Experiments will be carried out to refine existing analytical methods and improve the accuracy and precision of
isotope data. Sample characterization will be carried out using optical microscopy and scanning electron microscopy.
Trace metal distribution and quantification will be determined by proton induced X-Ray emission (PIXE) in
collaboration with CSIRO in Melbourne, Australia.
WIDER IMPLICATIONS The research will help advance the currently limited understanding of transition metal
fractionation in hydrothermal systems and the development of a new tool for mineral exploration.
STUDENT PROFILE We are looking for a well-qualified and highly motivated Earth Sciences/Geology graduate with a
strong interest in geochemistry and hydrothermal mineralization. Experience of geochemical analytical methods
would be an advantage.
TRAINING The successful student will join a vibrant research group in geochemistry at Imperial College. The student
will receive training in field sampling, laboratory best practice, sample preparation methods, inductively-coupled
plasma atomic emission and mass spectrometry and data reduction methods. Training also will be given in
characterization techniques including reflected and transmitted light petrography, scanning electron microscopy and
PIXE analysis. Courses in isotope geochemistry, fluid geochemistry and mineralising processes and transferable skills
will be available.
FURTHER INFORMATION If you are interested in the project and would like to have further details please contact
Jamie Wilkinson at [email protected]
REFERENCES
John, S.G., Rouxel, O.J., Craddock, P.R., Engwall, A.M., and Boyle, E.A., 2008, Zinc stable isotopes in seafloor
hydrothermal vent fluids and chimneys: Earth and Planetary Science Letters, v. 269, p. 17-28.
Kelley, K.D., Wilkinson, J.J., Chapman, J.B., Crowther, H.L., and Weiss, D.J., in revision, Zinc isotopes in sphalerite from
base metal deposits in the Red Dog district, Northern Alaska: Economic Geology.
Mason, T.F.D., Weiss, D.J., Chapman, J.B., Wilkinson, J.J., Tessalina, S.G., Spiro, B., Horstwood, M.S.A., Spratt, J., and
Coles, B.J., 2005, Zn and Cu isotopic variability in the Alexandrinka volcanic-hosted massive sulfide (VHMS) ore
deposit, Urals, Russia: Chemical Geology, v. 221, p. 170-187.
Wilkinson, J.J., Weiss, D.J., Mason, T.F.D., and Coles, B.J., 2005, Zinc isotope variation in hydrothermal systems:
Preliminary evidence from the Irish Midlands ore field: Economic Geology, v. 100, p. 583-590.