Pb and Sr diffusion in Ca and Ti Perovskite

Christopher Beyer, Ralf Dohmen, Sumit Chakraborty

Collaboration: Hans-Werner Becker, RUBION

CaTiO₃ perovskite is a common matrix mineral in silica-undersaturated ultrapotassic igneous rocks, such as kimberlites, lamproites and carbonatites (Chakhmouradian 2006; Mitchell 2002). Kimberlite is of particular interest, because it is well-known for its high yield of diamond-bearing xenoliths from Earth’s upper mantle. However, it is difficult to date kimberlites because zircons and titanites, which are commonly used for U/Pb and Pb/Pb chronometry, are usually absent (Tappe and Simonetti 2012).

CaTiO₃ is a potential candidate mineral that has proven its usefulness for determining the age of ultrapotassic rocks (Kramers and Smith 1983). Although, perovskite U/Pb and Pb/Pb chronometry has been frequently used in recent years, closure temperatures of different isotopic systems in this mineral are still unknown. In addition, perovskite is used in Sr isotopic studies and diffusion data are also necessary for for that.

In this project we want to determine the diffusion coefficients and closure temperatures for Pb and Sr diffusion in CaTiO₃ perovskite using Rutherford Backscattering (RBS) on synthetic CaTiO₃ single-crystals annealed at different T-fo2 conditions to better constraint time-temperature histories of silica undersaturated rocks.

REFERENCES

Chakhmouradian AR (2006). High-field-strength elements in carbonatitic rocks: geochemistry, crystal chemistry and significance for constraining the sources of carbonatites. Chem Geol 235: 138-160

Kramers J, Smith C (1983). A feasibility study of U− Pb and Pb− Pb dating of kimberlites using groundmass mineral fractions and whole-rock samples. Chem Geol 41: 23-38

Mitchell RH (2002). Perovskites: modern and ancient 

Tappe S, Simonetti A (2012). Combined U–Pb geochronology and Sr–Nd isotope analysis of the Ice River perovskite standard, with implications for kimberlite and alkaline rock petrogenesis. Chem Geol 304: 10-17