Building a terrestrial planet: Chromium isotope constraints on metal-silicate differentiation

New insights into the formation of planets from metal isotopes in meteorites.

Terrestrial Planet

Figures: (Left) An early differentiation of terrestrial planets (i.e., planetesimals) into metallic core and silicate mantle/crust (from Granshaw, Portland State Uni). (Right) Coexisting phases of metallic alloys (Fe-Ni-Cr) and silicates (olivines) in stony-iron meteorite or pallasite (credit to Nagy, NASA). View larger image.

Terrestrial planets, such as Earth, Mars and Venus, experienced an early metal-silicate differentiation, which in turn led to the formation of the planets’ metallic core and outer silicate mantle, and eventually crust. Representative samples recording such metal-silicate differentiation processes are not accessible on Earth, but specific group of meteorites also called stony-irons or pallasites (see Figure) provide unique archives of these early differentiation processes from other planetary objects in the Solar System.

This project aims to investigate stable chromium isotope variations (53Cr/52Cr ratios or δ53Cr values) in coexisting metallic and silicate phases sampled from a set of stony-iron meteorites, to further constrain (i) the magnitude of Cr isotope fractionation during metal-silicate segregation, and also (i) the redox conditions (or O2 fugacity) during early planetary differentiation (see Bonnand & Halliday, 2018, Nat. Geosci, 401-405). Acquired Cr isotope data will be complemented by detail mineralogical and elemental analysis of meteorite fragments, and results interpreted in terms of early planetary differentiation and core formation on terrestrial planets.

The project will involve both laboratory work and fieldwork, where the latter will sample distal impact ejecta from Ediacaran (~580 Ma) Acraman crater exposed in Flinders Ranges, and Cr isotope analysis of these materials, coupled with analysis of main group of meteorites (chondrites, achondrites, stony-irons) will provide clues on the origin and composition of the Acraman asteroid (i.e., impactor).  


Dr Juraj Farkas

Supervisors

Dr Juraj Farkas, Professor Martin Hand and Associate Professor Victor Gostin

Research area: Mineral and energy systems, Tectonics and solid earth processes, Palaeoclimatology, Palaeontology and palaeoenvironments, Environmental geochemistry

Recommended honours enrolment: Honours in Geology

Tagged in Honours projects - Geology, Honours Projects - Juraj Farkas, Honours Projects - Martin Hand, Honours projects - Victor Gostin