Register now After registration you will be able to apply for this opportunity online.
This opportunity is not published. No applications will be accepted.
An olivine perspective on the genesis of diamondiferous lamproites
Olivine lamproites are volcanic rocks that host major diamond deposits. Their genesis is commonly attributed to partial melting of enriched lithospheric mantle. This project will employ the composition of olivine in lamproites worldwide to understand if their source is in the convective mantle
Olivine lamproites are mantle-derived volcanic rocks that occur in stable continental areas and host major diamond deposits. They are highly enriched in K and other mantle-incompatible trace elements, which, combined with radiogenic Sr and unradiogenic Nd and Hf isotope compositions, suggest derivation from enriched (i.e. metasomatised) lithospheric mantle sources. However, some isotopic studies suggest that an asthenospheric (i.e. convective) mantle component occurs in these rocks, which is consistent with the presence of diamonds derived from the lithosphere-asthenosphere boundary in some olivine lamproites. The aim of this project is to understand the origin and source location of olivine lamproites, which has important implications for the petrology of mantle-derived magmas and the formation of diamond deposits.
This question will be addressed by examining the texture and composition of olivine in olivine-lamproites from worldwide localities (southern Africa, India, Australia, north America, Russia). Olivine includes both mantle-derived and magmatic parts, which can therefore be employed to track the source composition and melt evolution of olivine-lamproites as recently done for kimberlites by Giuliani and coworkers.
The petrography of olivine-lamproites will be first examined by optical microscopy and the texture and composition of olivine will be then studied by scanning electron microscopy (SEM) and electron probe micro-analysis (EPMA).
All the samples for this project are already available in house. However, additional samples could be collected during field work in South Africa in October 2020, which will be a complementary part of this project. This trip will include visits to diamond mines as well as kimberlite and olivine-lamproite volcanoes at Kimberley, and to the unique diamond and mantle rock collection housed in the Mantle Room (University of Cape Town).
Project supervisors: Dr Andrea Giuliani, Prof Max Schmidt, Prof Peter Ulmer
Olivine lamproites are mantle-derived volcanic rocks that occur in stable continental areas and host major diamond deposits. They are highly enriched in K and other mantle-incompatible trace elements, which, combined with radiogenic Sr and unradiogenic Nd and Hf isotope compositions, suggest derivation from enriched (i.e. metasomatised) lithospheric mantle sources. However, some isotopic studies suggest that an asthenospheric (i.e. convective) mantle component occurs in these rocks, which is consistent with the presence of diamonds derived from the lithosphere-asthenosphere boundary in some olivine lamproites. The aim of this project is to understand the origin and source location of olivine lamproites, which has important implications for the petrology of mantle-derived magmas and the formation of diamond deposits. This question will be addressed by examining the texture and composition of olivine in olivine-lamproites from worldwide localities (southern Africa, India, Australia, north America, Russia). Olivine includes both mantle-derived and magmatic parts, which can therefore be employed to track the source composition and melt evolution of olivine-lamproites as recently done for kimberlites by Giuliani and coworkers. The petrography of olivine-lamproites will be first examined by optical microscopy and the texture and composition of olivine will be then studied by scanning electron microscopy (SEM) and electron probe micro-analysis (EPMA).
All the samples for this project are already available in house. However, additional samples could be collected during field work in South Africa in October 2020, which will be a complementary part of this project. This trip will include visits to diamond mines as well as kimberlite and olivine-lamproite volcanoes at Kimberley, and to the unique diamond and mantle rock collection housed in the Mantle Room (University of Cape Town).
Project supervisors: Dr Andrea Giuliani, Prof Max Schmidt, Prof Peter Ulmer
see project description
see project description
Andrea Giuliani office NW D 76.2 email: andrea.giuliani@erdw.ethz.ch
Andrea Giuliani office NW D 76.2 email: andrea.giuliani@erdw.ethz.ch