Improved understanding of the behaviour of mercury and other trace metals in basaltic magmas

Thesis

Volcanic degassing is one of the major emission sources in nature for atmospheric mercury, and the only one able to directly reach the stratosphere and troposphere. The actual magnitude of these emissions remains uncertain, due to the difficulties of accurately measuring the Hg from active volcanoes and the lack of published mercury analysis in volcanic rocks. It is critical to improve our knowledge on volcanic Hg behaviour and emissions to be able to establish the impact of these in the current and past atmospheric mercury budget. For that purpose, we need to understand how the volatility of mercury is affected under different conditions in a degassing volcano. This thesis attempts to overcome the difficulties of obtaining in-situ mercury analysis by producing, at high temperatures and pressures basaltic melts doped in mercury and other volatiles. There is no prior experimental record on mercury at high-temperature, due to the high volatility of this element, therefore, I have tested several experimental conditions and materials to counteract the evaporation of mercury during the synthesis of the glass and/or sulfide. These involve single-capsule and double-capsule assemblies. Additionally, I have performed a series of sulfide-silicate partitioning experiments for pressures ranging from 0.5 GPa to 2 GPa. These experiments seek to determine the pressure effect on the distribution of Ag, Cd, Co, Cr, Cu, Ga, Ge, In, Pb, Se, Sb, Tl, V, and Zn between both phases, and thus enhance the existing partitioning model that only considers melt and sulfide composition and temperature, as parameters.

Authors: Garcia Ramos, L

• Type of award: MSc by Research
• Level of award: Masters
• Awarding institution: University of Oxford
• Language: English
• Keywords: volcanic glass; volatility; high-temperature; degassing; mercury; synthetic glass; trace-elements; piston-cylinder; high-pressure; magmas; concentration; volcan; Hg
• Subjects: Geochemistry; Earth sciences; Geology; Experimental petrology; Volcanology