Photo of Mr Lawrence Carter

Mr Lawrence Carter

Postgraduate

Email:

PhD Project: Exsolution depth and migration pathways of mineralising fluids in porphyry deposit-forming magmatic systems

Porphyry copper deposits provide around 75% of the world's copper and are an important source of gold and other metals [1]. One aspect of porphyry deposit models that is poorly understood is whether the mineralising fluids from which they form are derived from: (i) high-level copper-rich porphyry magmatic stocks, (ii) feeder chambers at mid-upper crustal levels, (iii) a lower crustal magma reservoir, or (iv) a combination of these, possibly with a transcrustal magma-mush zone [2]. The high level porphyry stock is often assumed to be the fluid source as it is invariably mineralised and can usually be temporally and texturally linked to the mineralisation. However, it is unlikely that enough fluid could be derived from such a limited magma volume. It seems probable that much of the fluid comes from a deeper source, possibly 5 to 15 km, although how fluids are transported from such depths is poorly understood. 

The aim of my PhD is identify textural and chemical evidence for the exsolution depth(s) and migration pathways of mineralising fluids in porphyry systems. This is important because it is now generally recognised, through extensive global surface mapping, that the majority of exposed surface porphyry systems and their related deposits have been found. This is prompting research into new exploration tools for deposits too deep to be identified using remote sensing techniques, covered in barren or weakly altered rocks, or which may require expensive geophysical and drilling methods.

The deposits chosen as case studies are in the Yerington District, Nevada, USA, where due to tectonic tilting there is the rare opportunity to study well exposed sections through porphyry systems up to palaeo-depths of ~6km [3]. This study will be amongst the first to determine in detail the depths of fluid exsolution, and therefore the sources of mineralisaing fluids within the district whilst also assessing the mechanisms by whihc fluids migrate from depth in sufficient volume and time scale to generate economic porphyry deposits. It is hoped that this approach will inform models for porphyry deposit formation and lead to the development of new exploration tools for blind deposits and as such aid in their discovery. 

This project is funded through the NERC GW4+ initiative with additional funding from the Natural History Museum (NHM). I am supervised by Prof Ben Williamson (CSM) and co-supervised by Dr Robin Armstrong (NHM). Prof Kathy Cashman (Bristol) and Dr Robin Shail (CSM) are additional supervisors. I am also part of the Ore Deposits and Critical Metals Research Group at CSM.

 

Professional History

  • 2017 - present: CC Geoscience Ltd - Director & Consultant Geologist to the resources industry.

  • 2017: BP - Operations Geologist, Schiehallion Field. 

  • 2016 - 2017: BP - Wellsite Geologist, North Sea and West of Shetland.

  • 2015 - 2016: BP - Production & Well Planning Geologist, Clair Field.

  • 2015: IMERYS - Intern Geotechnical Engineer, UK Kaolin Platform

  • 2013: BP - Intern Exploration Geologist, Namibian Exploration.

  • 2012: IMERYS - Intern Production Geologist, UK Kaolin Platform.

 

Academic Qualifications

  • MSc Mining Engineering (Distinction), 2015 (Camborne School of Mines). Sponsored by SRK Consulting Ltd. Working with IMERYS, for my dissertation I performed a geotechnical assessment of current excavations and the proposed life of mine excavation design for Melbur Pit, and recommendations therein.

  • BSc (Hons) Applied Geology (1st Class), 2014 (Camborne School of Mines). Working with BP, my dissertation investigated the conjugate margin of the South Atlantic - implications on petroleum systems therein.

 

Honours and Awards

  • University of Exeter Dean's Commendations; 2013, 2014, 2015 - In recognition of outstanding academic performance.

  • CSMA's John Brook & John Trounson Prizes, 2015 - Awarded for best performance in management modules and best overall performance amongst the MSc cohort.

  • Excellence in Cornwall Postgraduate Scholarship, and further support from SRK Consulting Ltd for my MSc degree.

  • Richard Pearce Gold Medal, 2014 - awarded for best overall performance in cohort.

  • Martyn Nicholas Costello Memorial Prize, 2013 - For best overall academic result (2nd year Geology)

  • Mineralogical Society Student Award, 2013 - Best aggregate mark in mineralogical modules.

  • CSM Trust's Highest Achiever Award, 2012.

  • CSM Undergraduate Scholarship, 2011.

 

Affiliations

  • Camborne School of Mines Association.

  • Member of Society of Economic Geologists.

  • Member of the Mineral Deposits Study Group.

  • Member of the Mineralogical Society of Great Britain. 

 

[1] Sillitoe, R. H., 2010. Porphyry copper systems. Economic Geology, 105: 3-41.

[2] Cashman, K. V., Stephen, R. J. and Blundy, J. D., 2017. Vertically extensive and unstable magma systems: A unified view of igenous processes. Science, 355: 1280.

[3] Dilles, J. H., Einaudi, M. T., Proffett, J. and Barton, M. D., 2000. Overview of the Yerington porphyry copper district: Magmatic to non-magmatic sources of hydrothermal fluids, their flow paths, alteration effects on rocks, and Cu-Mo-Fe-Au Ores. SEG guidebook vol. 32.