Colloquium: Mike Krawczynski

Mike Krawczynski

Postdoctoral Research Associate, Department of Earth, Environmental, and Planetary Sciences, Case Western Reserve University 

Abstract: Understanding the amount of dissolved H₂O in subduction zone magmas at depth is of critical importance to model the buoyancy, viscosity, and mixing of magmas in the crust. In addition, mass balance calculations of hydrogen flux through subduction zones are a principle source of uncertainty in the budget of volatile element addition to the earth's mantle. Traditional methods of estimating pre-eruptive water contents of magmas have been limited by the storage capacity of trapped melt inclusions, and/or by the coexistence of mineral assemblages stable at relatively-low water contents. In this talk I present a new experimentally calibrated method for evaluating pre-eruptive H₂O contents of subduction zone magmas using amphibole mineral chemistry. This hygrometer is applied to primitive lavas from Mt. Shasta, CA and shows evidence for extreme dissolved water contents in mantle melts emplaced in the lower crust.