Development of UV-fluorescence spectroscopy as a tool for mineral exploration

A willemite rock glowing under flurescent light with a black background

A specimen of willemite (zinc silicate) photographed under UV light © The Trustees of the Natural History Museum, London

This project will define and understand the spectral fingerprints of minerals that can be used to discriminate between hydrothermal ore deposit environments and to vector within individual systems.

Background

Many minerals and organic materials fluoresce (emit light) under UV illumination and the fluorescence colour and intensity are a function of the activating frequency and the presence of trace element or molecular activators in the sample structure. In mineralogy, quantitative spectral determinations and the identification of activator elements are surprisingly scarce.

The aim of this project is to define spectral fingerprints of alteration minerals that can be used to discriminate between hydrothermal ore deposit environments, distinguish mineralized from barren systems and potentially to vector within individual systems.

Objectives

The project will focus on the acquisition of 3D UV-fluorescence spectra (emission intensity as a function of activation and emission wavelengths) of key alteration minerals and the development of Machine Learning algorithms to classify them.

Samples will be sourced from the ore and mineralogy collections at the Natural History Museum and from a field study site where selected minerals can be collected from a 3D framework around a well-constrained ore system.

In tandem, the minerals will be analysed using several techniques including electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry in order to identify trace element activators.

The student will also help to develop a workflow for routine acquisition of spectra and digital archiving of data on museum collections samples. Ultimately, we aim to develop a practical tool that can be simply applied in a core-shack environment in mineral exploration, in order to enhance the efficiency of mapping and interpreting hydrothermal systems.

This could potentially provide a much quicker and cost-effective solution to current targeting methods that rely on time-consuming chemical analysis of mineral samples.

An enhanced understanding of mineral chemical variation in hydrothermal minerals will feed into our overarching research goal to decrease the risk and environmental footprint of mineral exploration that seeks to discover the metals needed for the low carbon energy transition.

Methods

An initial literature review of UV-fluorescence properties of relevant alteration minerals will be used to identify key minerals for further investigation. The Natural History Museum Rocks and Minerals database will then be interrogated to locate suitable specimens for reference measurements.

A suitable field area will be identified, likely to be in collaboration with an industry partner, to act as an orientation study with spatially constrained sampling. Fieldwork will involve extensive mapping of the alteration domains and sampling.

Samples will be analysed using 3D UV-fluorescence (UV-F) scanning using a brand new fluorescence spectrometer located in the Imaging and Analysis Centre at the NHM. The same areas analysed by UV-F will then be imaged using optical hot-cathode cathodoluminescence, scanning electron microscopy backscattered electron and cathodoluminescence imaging, and analysed by electron microprobe and laser ablation ICP-MS for major, minor and trace elements. Spectral peaks corresponding to specific activators will be identified and spectra quantified in terms of absolute trace element abundances and trace element ratios. Data analytics, including machine learning approaches, will be applied to characterise complex 3D spectral datasets in relation to alteration mineral origin and/or spatial position classifications.

Wider implications

The research will provide new insights into the controls of UV activated fluorescence and potentially also photoluminescence in alteration minerals and will provide a thorough test of the applicability of such spectra for mineral exploration applications.

Who we are looking for

We are looking for a well-qualified and highly motivated Earth Sciences/Geology graduate who wishes to carry out a cutting edge PhD in economic geology/geochemistry/ spectroscopy and gain experience in a range of mineralogical and geochemical analytical methods. Excellence in geochemistry and mineralogy are essential; experience of microanalytical techniques and statistical data evaluation are desirable. A desire for involvement with the Imperial Student Chapter of the Society of Economic Geologists and outreach activities will be beneficial.

Training

The successful student will join the London Centre for Ore Deposits and Exploration (LODE) research group in the attractive environment of South Kensington, London, that includes researchers from Imperial College London and the NHM. The student will be based full time at the Museum and have the opportunity to work in the state-of-the-art analytical suite.

The student will receive training in field mapping, core logging and sampling, laboratory best practice, UV-fluorescence/ photoluminescence spectroscopy, cathodoluminescence, SEM techniques, laser ablation ICP-MS instrumentation and analysis, data reduction and analytics.

Attendance and presentation of results at major UK and international conferences will be supported in the research programme. All postgraduates in the Department of Earth Science and Engineering have access to workshops organised by the Graduate School of Engineering and Physical Science which include: personal organisation and effectiveness; thesis writing and completing the PhD; technical writing; teamwork; professional issues in science; research ethics; and presentation skills.

There are also optional courses in career planning, IT skills, media and entrepreneurship. Attendance at regular seminars on ore geology, geochemistry and the wider Earth Sciences is compulsory.

How to apply

Applications for the PhD are processed through the Natural History Museum.

To apply please send the following documents to the Postgraduate Office at postgradoffice@nhm.ac.uk:

  • Curriculum vitae.
  • Covering letter outlining your interest in the PhD position, relevant skills training, experience and qualifications for the research, and a statement of how this PhD project fits your career development plans.
  • Names of two academic referees.

The deadline for applications is 4 January 2021.

Apply for this project

Find out more about the Science and Solutions for a Changing Planet Doctorate Training Program and how to apply on their website

Application deadline: 4 January 2021

Any questions?

Natural History Museum

Main supervisor: Prof Jamie Wilkinson

Science and Solutions for a Changing Planet (SSCP) doctoral training partnership

This is a joint project between The Science and Solutions for a Changing Planet (SSCP) Doctoral Training Partnership at Imperial College London and The Natural History Museum.

Funded by