Diffusive fractionation of trace elements and their isotopes in silicate melts
Authors
Holycross, Megan
ORCID
Loading...
Other Contributors
Watson, E. Bruce
Issue Date
2017-08
Keywords
Geology
Degree
PhD
Terms of Use
This electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
Full Citation
Abstract
PART I and II: To assess the influence of diffusion on the trace element composition of magmatic systems, we determined the mobilities of 21+ trace elements (including transition metals, high field strength elements, low field strength elements and rare earth elements (REE)) in basaltic (part I) and hydrous rhyolitic (part II) melts. High temperature, high pressure experiments were executed in a piston-cylinder apparatus using simple diffusion couple assemblies. The resulting trace element concentration gradients developed in all experimental materials were simultaneously characterized using laser ablation ICP-MS. Diffusivities of the lanthanides in basaltic melt decrease monotonically from lanthanum to lutetium at a given temperature. Trace element diffusivities in hydrous rhyolitic melt cover nearly two orders of magnitude at a single temperature. The considerable differences among the measured trace element diffusion coefficients indicates that there is the potential for significant diffusive fractionation effects to develop in natural silicate magmas. The new data for trace element diffusion in melts is used in kinetic models to explore how diffusive fractionation occurs in “interrupted” processes in systems that have not yet reached equilibrium. Results indicate that diffusion in silicate melt is an effective mechanism to significantly fractionate trace elements from one another and produce anomalies in REE concentrations as diffusive boundary layers develop across melt-melt and crystal-melt interfaces.
Description
August 2017
School of Science
School of Science
Department
Dept. of Earth and Environmental Sciences
Publisher
Rensselaer Polytechnic Institute, Troy, NY
Relationships
Rensselaer Theses and Dissertations Online Collection
Access
Restricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.