Metal source rocks for sediment-hosted ores
Dr. Jamie Wilkinson & Dr Dominik Weiss
AIM To determine the fertility of different rock types as metal sources for base metal ore deposits and their transition
metal isotope fingerprint.
BACKGROUND The debate concerning the origin of metals in hydrothermal ore deposits and the significance of
specific “source rocks” has been ongoing for 150 years. The recent development of new tools for the analysis of fluid
inclusions in ore deposits and novel isotope techniques have started to shed more light on this fundamental question
(e.g. Wilkinson et al., 2009a, b), with more significance being placed on the metal budget of
the rocks (or magmas) from which fluids are derived. However, little recent work has been
undertaken on the fertility of different rock types with respect to supplying ore metals to
hydrothermal systems and the mineralogical associations of these metals.
OBJECTIVES The principal objective of the study is to determine the trace metal content of
individual mineral phases within characteristic source rock types. Stepwise leaching and
possibly hydrothermal experiments will be used to determine metal extraction pathways
from these phases and isotopic characterisation (e.g. Pb, Zn, Cu, Fe) will be carried out to
fingerprint the different metal reservoirs.
METHODS The study will utilise wet chemistry laboratory facilities located in the
Department. Chemical analyses will be carried out using ICP-AES and ICPMS instruments,
and isotope measurements will be made using the Department’s Nu Plasma multi-collector
ICPMS 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 and trace metal distribution will be determined by proton induced X-Ray
emission (PIXE) in collaboration with CSIRO in Melbourne, Australia.
WIDER IMPLICATIONS The research will
Banded sphalerite ore
containing galena (grey)
and cemented by white
dolomite. Galmoy Mine,
Ireland.
represent a major contribution to the
understanding of the origin of metals in
hydrothermal ore deposits and to the
development of non-traditional stable
isotope geochemistry.
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
0.5mm
PIXE image showing distribution of zinc in greywacke. Chlorite is the principal host for the
metal in the matrix between the clastic grains.
in geochemistry at Imperial College. The student will receive training
in laboratory best practice, sample preparation methods, inductively-coupled plasma atomic emission and mass
spectrometry and data reduction methods. Training also will be given in sample 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 j.wilkinson@imperial.ac.uk
REFERENCES
Wilkinson, J.J., Stoffell, B., Wilkinson, C.C., Jeffries, T.E., and Appold, M.S., 2009a, Anomalously metal-rich fluids form
hydrothermal ore deposits: Science, v. 323, p. 764-767.
Wilkinson, J.J., Cooke, D.R., Weiss, D.J., Crowther, H.L., Coles, B.J., Jeffries, T.E., Ryan, C.G., and Laird, J., 2009b, Making
metal super-charged ore fluids: the key to hydrothermal base-metal ore formation? Proceedings of the 10th Biennial
SGA Meeting, Townsville, August 17-20, 2009.