From Arc Magmas to Ores (FAMOS)

Andes of northern Chile

View across the Ujina porphyry copper-molybdenum deposit in the high Andes of northern Chile. The volcanoes in the background straddle the Bolivian border and have summits above 5000 metres. No eruptions have been recorded since 1867 but these represent the active volcanic arc in the area. The porphyry deposits in the Collahuasi district formed in an earlier, Eocene-Oligocene magmatic epoch 37-34 million years ago. What made the Eocene-Oligocene arc so fertile for the formation of large ore deposits and why more recent magmas did not are the types of question being tackled in the FAMOS project.

The FAMOS (From Arc Magmas to Ores) project aims to develop new exploration tools to help locate metal resources in volcanic arcs by understanding the fundamental processes involved in cycling magmas, fluids and metals in these zones.

A new approach

The search for new ore deposits has to consider the 'ingredients', the processes and environments that favour their formation. Historically, most research has focused on the 'trap' in the Earth's shallow crust where the ore minerals are finally deposited.

The FAMOS project will focus deep in the Earth's crust, to probe the formation and evolution of the molten rocks (or magmas) that are ultimately responsible for some of the largest accumulations of metals on the planet.

How do metals accumulate in magma ?

Magmas are formed at subduction zones, where one tectonic plate descends beneath another, and where volcanoes and earthquakes are produced.

We will study the environments above subduction zones, associated with volcanic arcs. This is where the crust is thought to be full of mushy magma, rich in crystals and volatiles like water and carbon dioxide.

The key goal is to understand how the metals of interest are enriched in these magmas and then transferred to the water-rich liquids from which the ore minerals are finally deposited.

The analysis of natural minerals will be supported by high-pressure and -temperature experiments designed to simulate conditions found deep in the Earth’s crust.

We will also develop computer models to explore the physics of how mushy magmas and metal-rich fluids migrate through the Earth's crust on their way towards the surface.

What conditions led to the formation of ore deposits ?

A special set of conditions allow a typical arc magma to evolve to the point where an ore deposit can form.

We aim to identify when and where these conditions might have existed by analysing the chemical fingerprints in minerals, that lock-in information as they crystallise.

Apatite crystals

Microscopic cathodoluminescence image of apatite crystals (yellow) within pink-luminescent anhydrite from The Resolution porphyry copper-molybdenum deposit, Arizona, USA. Apatite can record a number of properties of the magma from which it grew and is one of the minerals to be studied in the project. © Matthew Loader

 

The team

A multidisciplinary team of researchers has been assembled from the fields of economic geology, igneous and metamorphic petrology, volcanology, geochemistry, numerical modelling and fluid dynamics.

The project also has a diverse group of international scientific collaborators and the support of several of the world’s largest mineral exploration companies.

We will be using a wealth of modern analytical tools hosted from nine universities and research institutes around the UK that enable most of the elements in the periodic table to be measured.

Bridging the divide

The project combines a desire to understand fundamental processes about our planet works - how metals, magmas and fluids are cycled through subduction zones - with  delivering outcomes that will benefit industry through improved exploration tools.

The project will bridge the divide between academic and applied research in a way that is not normally possible through projects funded entirely by industry or entirely by government agencies. This bridging activity lies at the heart of the Natural Environment Research Council’s (NERC) hghlight topic funding scheme.

Rosario mine

View of the Rosario mine, Collahuasi district, northern Chile. This is a typical porphyry-copper deposit mined by open pit methods. The pit is 2.3 kilometres across and the excavated waste rock and ore stockpiles have been deposited to the west of the mine.©Google Earth

 

Why do we need to look for new ore deposits ?

Society is dependent on a reliable supply of metals and minerals for economic growth, improved standards of living, and development of infrastructure.

These resources are derived from ore deposits - accumulations of useful minerals within the Earth’s crust - and have to be extracted by mining.

Although many deposits are already being mined, population growth means that even with increased recycling and resource efficiency, new deposits still need to be discovered.

This is increasingly difficult because most of the ores exposed at the Earth’s surface have already been found. This means that mineral exploration companies increasingly have to search for hidden deposits, concealed beneath up to a kilometre of barren rock.

New concepts, approaches and tools are now required for the location and extraction of ores, with minimal environmental impact and financial risk to investors.

Project summary

  • Focus: To develop new exploration tools for mineral resouces by understanding the processes by which metals are concentrated in magmatic arcs.
  • Funding: NERC
  • Start date: 1 May 2017
  • End date: 30 April 2021

Have a question for the FAMOS team?