VOLATILE SOURCE OF THE SIBERIAN TRAPS AND THE CONTAMINATION OF SULFUR

Emplacement of the Siberian Traps large igneous province (~252.28 ± .011 Ma) appears to have triggered the end-Permian extinction ~251.941 ± .371 Ma when 90% of terrestrial and 75% of marine species went extinct. Assimilation of the underlying sedimentary basin, containing evaporite units, is the likely volatile source that contributed to the extinction.

The objective of this research is to measure the diffusion of sulfur released from anhydrite during dissolution in a basaltic magma, quantify the rates of sulfur contamination, and measure anhydrite saturation. Experiments were preformed to simulate assimilation during Siberian Traps magmatism by using a dike composition from the Central Atlantic Magmatic Province and a mixture of compressed anhydrite powder and anhydrite crystals (0.5-2.0 mm in length). Experimental conditions range from 1100-1450 °C at a constant pressure of 6 GPa and durations ranging from 600 to 7200 seconds. We are also investigating the dominant sulfur species in the melt at different oxygen fugacities to determine if there is an effect on the diffusivity. Anhydrite dissolution will also be analyzed to determine how pressure, temperature, and oxygen fugacity affect the S concentration within the melt. Preliminary results for anhydrite saturation at high oxygen fugacity in the basaltic melt at 1250°C demonstrate a minimum sulfur concentration in the melt at sulfate saturation of ~15,000 ppm.

Understanding the rate at which contamination of the basaltic magmas by evaporites occurs will not only allow for the construction of a model that can predict the rate of volatile uptake within a magmatic system but will allow insight into how sulfur is stored and transported. The excess sulfur problem and volatile fractionation associated with the production of bubble growth, both having important implications for magma degassing, can be further studied by analyzing the interactions between sulfur and basaltic magma. Further experimentation at lower temperatures and pressures will investigate fluid saturation and bubble growth to study the degassing of shallow intrusions and their potential contribution to volatiles released by the Siberian Traps.