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Making wealth: Using detailed field analysis, novel experiments and high end microscopy to elucidate how gold is made?

Dr Rob Chapman (SEE), Dr Thomas Mueller (SEE), Dr David Banks (SEE), Dr Sandra Piazolo, (SEE), Dr Taija Torvela, (SEE), Dr Dan Morgan (SEE)

Contact email: r.j.chapman@leeds.ac.uk

Summary

Natural gold, precipitated from hydrothermal systems exhibits a wide range of particle sizes and mineralogical features. The causes of these characteristics are not understood, and indeed the degree of mineralogical heterogeneity within gold particles has only recently been recognised. In this project you will study in detail a gold locality in Western Ireland where different generations of quartz veins exhibit different concentrations and size ranges of natural gold. Geological characterization of this mineralization during fieldwork will constrain the P-T-X conditions used in the design of novel laboratory experiments in which synthetic auriferous mineral assemblages will be ‘grown’. The characteristics of the gold produced will be examined using the same methodologies routinely employed to characterise natural gold both from this and other localities worldwide. 

Natural gold occurs in a wide range of particle sizes, ranging from the extremes of large (multi kg) nuggets to ‘invisible’ gold within quartz, but gold particle size is not indicative of economic potential, and the reasons for this  counter intuitive relationship are unclear.  You will investigate this relationship between gold particle size, depositional conditions, and mineral substrates in the first systematic study of its kind.  

Polished sections of natural gold may show local concentrations of metals such as Ag or Cu, as zones or tracks. The boundaries of such features may be diffuse, or sharp which has been interpreted as variation in the conditions of mineralization, or possible thermal history post deposition. In addition, the presence of inclusions of other minerals may constrain the environment of precipitation.  However, the significance of all these features remains speculative in the absence of experimental data in which the characteristics are replicated under controlled conditions

The focus will be on high (>200ºC) hydrothermal systems containing  low Cl, low CO2 fluid in which gold is transported as the bisulphide complex, and silver as the chloride complex. Such regimes are prevalent in orogenic gold systems, intrusion related gold systems and the porphyry- epithermal environment. Gold may precipitate in response to changes in P, T or through change in pH or fS2.  We aim to correlate gold composition and textures with the environment of precipitation to allow interpretation of the features observed in natural gold particles in the extensive collections at Leeds.  This aspect of the research seeks to illuminate the conditions under which these gold particles formed, allowing future exploration programs to target the source more effectively.  

You will be supported by a team of academics whose range of expertise underpins the project.  In particular you will be involved in the design of the first experiments to systematically synthesise hydrothermal gold according to a range of P-T-X-t regimes. The possibilities to contribute to our basic understanding of the characteristics of natural gold and the implications for interpretation of gold from different geological systems is both wide ranging and of great general value to both academic and industrial communities. There is also the possibility to focus on a particular aspect of the study as it develops. Examples could be the relationship between other metals in the fluid and gold composition, experimental studies which replicate catastrophic changes in P-T-X associated with tectonic activity, or developing a tool for exploration, or the influences of conditions of formation on the crystalline microstructure of metallic gold. The final supervision team will reflect the chosen direction of the student. The proposed project provides a platform for post-doctoral employment either in an industrial or academic arena

You will join a vibrant community of researchers active in a wide range of geoscience disciplines within both the Institute of Applied Geosciences and the Institute of Geophysics and Tectonics. The programme of external speakers and internal seminars is well established and postgraduate students are fully involved.  Your academic home will be the Ores and Minerals Group, (OMG) (https://www.facebook.com/Ores-and-Mineralization-Research-Group-OMG-1155557114600278) which currently supports five post graduate students. OMG students benefit from the networking opportunities provided by the activities of the Leeds Chapter of the Society for Economic Geology, (for example Leeds has a strong staff and student presence every year at the Vancouver Exploration Roundup), and the extensive industry, academic and alumni networks of supervisors. 

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Related undergraduate subjects:

  • Chemistry
  • Earth science
  • Earth system science
  • Geological science
  • Geology
  • Geoscience
  • Materials science
  • Natural sciences
  • Physical science