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• 1. [Article] The potential influence of database configuration on the derivation of trace element partitioning expressions for clinopyroxene

  Decades of experimental work has illustrated the high degree to which the partitioning of most elements is dependent on phase composition, temperature and pressure. In order to quantitatively describe ...

  Citation × Citation Citation Abstract Copy Title: The potential influence of database configuration on the derivation of trace element partitioning expressions for clinopyroxene Author: Cunningham, Jennifer L. Decades of experimental work has illustrated the high degree to which the partitioning of most elements is dependent on phase composition, temperature and pressure. In order to quantitatively describe clinopyroxene partitioning it is required to derive expressions using theoretical constraints calibrated with experimental data. The experimental database available for such an analysis has grown considerably in the past decade, both in number of experiments and the range of compositional and experimental conditions. Our research focused on the compilation of this newly available experimental clinopyroxene data as part of the ongoing update of the Geochemical Earth Reference Model (GERM) partition coefficient database. Previous versions of GERM provided a summary of partitioning information from the literature. In this current update, data on phase composition and experimental conditions are being added. Our analysis suggests there are great differences in numbers of experiments between different elements, as well as in the distribution of pyroxene composition, melt composition, and experimental temperature and pressure for each element, all of which may have a significant effect on calibration. Understanding the characteristics of the database we are working with when deriving numerical expressions will help us avoid mistakes in application and provide helpful guidelines for future experimental designs. Title: The potential influence of database configuration on the derivation of trace element partitioning expressions for clinopyroxene Author: Cunningham, Jennifer L. Decades of experimental work has illustrated the high degree to which the partitioning of most elements is dependent on phase composition, temperature and pressure. In order to quantitatively describe clinopyroxene partitioning it is required to derive expressions using theoretical constraints calibrated with experimental data. The experimental database available for such an analysis has grown considerably in the past decade, both in number of experiments and the range of compositional and experimental conditions. Our research focused on the compilation of this newly available experimental clinopyroxene data as part of the ongoing update of the Geochemical Earth Reference Model (GERM) partition coefficient database. Previous versions of GERM provided a summary of partitioning information from the literature. In this current update, data on phase composition and experimental conditions are being added. Our analysis suggests there are great differences in numbers of experiments between different elements, as well as in the distribution of pyroxene composition, melt composition, and experimental temperature and pressure for each element, all of which may have a significant effect on calibration. Understanding the characteristics of the database we are working with when deriving numerical expressions will help us avoid mistakes in application and provide helpful guidelines for future experimental designs. Close

• 2. [Article] Quantification of the temperature, pressure and compositional dependence of trace element partitioning : an experimental and theoretical study

  The thermodynamic history of the Earth is preserved in the trace element record created through igneous processes. The ability to interpret that record depends on the accuracy and precision of numerical ...

  Citation × Citation Citation Abstract Copy Title: Quantification of the temperature, pressure and compositional dependence of trace element partitioning : an experimental and theoretical study Author: Cunningham, Jennifer Lynn The thermodynamic history of the Earth is preserved in the trace element record created through igneous processes. The ability to interpret that record depends on the accuracy and precision of numerical models that connect igneous processes with their geochemical consequences. This project answers three major questions concerning the relationship between trace element partitioning and the processes that influence it. One: using a common igneous mineral, clinopyroxene, as a base, how complete is the dataset on which our understanding of this relationship relies? Two: what are the dangers involved with basing models on experiments that contain higher than natural concentrations of trace elements? Three: how accurate and precise is the current numerical model that describes this relationship, and can it be improved? This project determined that the data contain gaps at high pressures and temperatures, are limited for felsic rock compositions, and are lacking for hydrous conditions. A set of experiments conducted on plagioclase feldspar crystallization from a base MORB composition containing various levels of dopants at below wt% levels reveals the presence of non-Henry's Law partitioning behavior through the disruption of the phase equilibria of the system. Lastly, the current clinopyroxene/melt rare earth element partitioning model (Wood and Blundy, 2003) is shown to reasonably, though less than ideally, describe the relationship between igneous processes and their trace-element partitioning results using the thermodynamics of the system. The accuracy was improved through adding a regression, which is based on the major element concentrations of the clinopyroxene and melt to the original numerical expressions. Title: Quantification of the temperature, pressure and compositional dependence of trace element partitioning : an experimental and theoretical study Author: Cunningham, Jennifer Lynn The thermodynamic history of the Earth is preserved in the trace element record created through igneous processes. The ability to interpret that record depends on the accuracy and precision of numerical models that connect igneous processes with their geochemical consequences. This project answers three major questions concerning the relationship between trace element partitioning and the processes that influence it. One: using a common igneous mineral, clinopyroxene, as a base, how complete is the dataset on which our understanding of this relationship relies? Two: what are the dangers involved with basing models on experiments that contain higher than natural concentrations of trace elements? Three: how accurate and precise is the current numerical model that describes this relationship, and can it be improved? This project determined that the data contain gaps at high pressures and temperatures, are limited for felsic rock compositions, and are lacking for hydrous conditions. A set of experiments conducted on plagioclase feldspar crystallization from a base MORB composition containing various levels of dopants at below wt% levels reveals the presence of non-Henry's Law partitioning behavior through the disruption of the phase equilibria of the system. Lastly, the current clinopyroxene/melt rare earth element partitioning model (Wood and Blundy, 2003) is shown to reasonably, though less than ideally, describe the relationship between igneous processes and their trace-element partitioning results using the thermodynamics of the system. The accuracy was improved through adding a regression, which is based on the major element concentrations of the clinopyroxene and melt to the original numerical expressions. Close