Magmatic hydrothermal ore deposits are associated with subduction zones, indicating that subduction zone magmas contain the necessary ‘ingredients’ to form copper-sulfide-rich ore deposits. However, the distribution of crustal ore deposits above subduction zones is sporadic, and continental arc magmas are typically depleted in economically important metals. It remains unclear which crustal/mantle processes predispose some subduction-zone magmatic systems to be associated with ore deposits compared to others, and why only some arc volcanoes release voluminous poisonous sulphur-rich gases.
Popocatépetl volcano is one of the most dangerous and active volcanoes in Mexico, located 70 km from Mexico City. It is characterised by extremely high SO2 emission rates and exhibits a wide range of eruption styles including highly explosive Plinian events, lava dome growth and explosive vulcanian activity.
This project will investigate the link between magma source composition, magma mixing, sulfide crystallisation, eruption style and processes that contribute to the formation of economically-important ore deposits. In particular, the project will explore whether the partitioning behaviour of economically important sulfide-hosted elements during sulfide fractionation limits the proportion of sulphur that is lost to the atmosphere during volcanic eruptions.
The student will analyse and produce chemical maps of minerals and melt inclusions from an NHM collection of specimens from the last 40 kyr of activity at Popocatépetl using recently-developed LA-ICP-MS (OU) protocols and EPMA (NHM, Birkbeck). Element diffusion should illuminate the timescales of magmatic processes. Data will be modelled to reconstruct the magmatic behaviour of chalcophile elements and determine their relation to sulphur degassing.