Mineral Physics Institute
Summer Scholars Program

Justin Wood
Rutgers University
Geology Major
Mentor: Baosheng Li and Qiong Liu

What is the density of carbonate melts in relation to silicate liquids at pressure?

Carbonatites are igneous rocks with at least 20% of their volumes composed of carbonate (CO 3 2- ) minerals and are found almost exclusively at continental rift zones. This composition causes carbonatites to be highly reactive to earth's atmosphere, which is why samples are most often plutonic in origin (save for natrocarbonatite lava at the world's only carbonatite volcano, Ol Doinyo Lengai). Although they are volumetrically less common than other forms of igneous rocks, carbonatites are of great interest to geologists. They are key agents in mantle alteration due to their high molarity of incompatible trace elements and high mobility. Additionally, they are of economic importance since they are good repositories of rare earth elements, fluorite, phosphate, zirconium, and other incompatible elements. However, the physical properties of these melts are poorly known.

In our experiment, high pressure density data will be obtained using the falling-sphere method in order to ascertain whether carbonatites rise (erupt), sink, or achieve neutral buoyancy in the mantle at pressures of 4GPa and greater. Specifically, potassium carbonate (K 2 CO 3 ) will be chosen for experimentation since its thermodynamic properties (necessary to calculate the equation of state) are already available in literature and it will not incongruently melt like the more common magnesium and calcium carbonates. Density will be calculated after first determining the compressibility or bulk modulus of K 2 CO 3 and the pressure dependence of the bulk modulus, which is derived from fusion curve analysis.