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January 2013 - December 2021
November 2011 - January 2013
September 2006 - August 2011
Publications
Publications (33)
Plate tectonics plays a vital role in the evolution of our planet. Geochemical analysis of Earth's oldest continental crust suggests that subduction may have begun episodically about 3.8 to 3.2 billion years ago, during the early Archaean or perhaps more than 3.8 billion years ago, during the Hadean. Yet, mantle rocks record evidence for modern-sty...
A collection of 61 xenocrystic and 12 eclogite xenolith-derived diamonds from the 600 Ma Lahtojoki kimberlite in central Finland has been investigated. Calculated pressure and temperature conditions for the diamondiferous eclogites are in excess of 5.5 GPa and 1300°C, suggesting residence depths greater than 180 km, near the base of the Karelian cr...
Olivine-free metasomatic mantle-derived xenoliths, frequently recovered from kimberlite and lamprophyre intrusions on the continents, are seldom described from oceanic settings. We report the mineralogy, geochemistry and Sr-Nd-Hf-Pb-Os isotopic compositions of a unique K-rich, hydrous mantle nodule sourced from a 34 Ma ultramafic lamprophyre (alnöi...
Eclogite mantle xenoliths from various kimberlite occurrences on the Kaapvaal craton show evidence for depth- and redox-dependent metasomatic events that led to variable base metal sulphide and incompatible element enrichments. Eclogite xenoliths from the Roberts Victor, Jagersfontein, Kimberley (Kamfersdam) and Premier kimberlites were investigate...
The nature of the deep calcium geochemical cycle through time is unresolved, in part due to the dearth of information about the calcium isotope composition of Archean recycled oceanic crust. Remnants of such ancient oceanic crust are preserved in the form of cratonic mantle eclogites, brought to surface as xenoliths in kimberlite magma eruptions. T...
Kimberlite-borne xenolithic eclogites, typically occurring in or near cratons, have long been recognized as remnants of Precambrian subducted oceanic crust that have undergone partial melting to yield granitoids similar to the Archaean continental crust. While some eclogitized oceanic crust was emplaced into cratonic lithospheres, the majority was...
Multiple sulphur isotopic compositions of sulphides from Kaapvaal craton mantle eclogites allow to elucidate the recycling of sulphur into the deep Earth and to differentiate between recycled crust and mantle origins of eclogite-hosted sulphides, including the precious metals that they capture. We present multiple sulphur isotope ratio measurements...
The central region of the Kaapvaal craton is relatively understudied in terms of its lithospheric mantle architecture, but is commonly believed to be significantly impacted by post-Archean magmatism such as the ca. 2056 Ma Bushveld large igneous event. We investigate a collection of 17 eclogite xenoliths from the Cretaceous Palmietfontein kimberlit...
The cratonic lithosphere-asthenosphere boundary is commonly invoked as the site of sheared peridotite and megacryst formation, a well-recognized petrologic assemblage whose genetic relationships-if any-remain poorly understood. We have undertaken a comprehensive petrology and Sr-Nd-Hf-Ca isotope study of sheared peridotite xenoliths and clinopyroxe...
The cratonic lithosphere–asthenosphere boundary is commonly invoked as the site of sheared peridotite and megacryst formation, a well-recognized petrologic assemblage whose genetic relationships – if any – remain poorly understood. We have undertaken a comprehensive petrology and Sr-Nd-Hf-Ca isotope study of sheared peridotite xenoliths and clinopy...
Kimberlite magmatism has occurred in cratonic regions on every continent. The global age distribution suggests that this form of mantle melting has been more prominent after 1.2 Ga, and notably between 250–50 Ma, than during early Earth history before 2 Ga (i.e., the Paleoproterozoic and Archean). Although preservation bias has been discussed as a...
Kimberlite and carbonatite magmas that intrude cratonic lithosphere are among the deepest probes of the terrestrial carbon cycle. Their co-existence on thick continental shields is commonly attributed to continuous partial melting sequences of carbonated peridotite at >150 km depths, possibly as deep as the mantle transition zone. At Tikiusaaq on t...
Mantle-derived eclogite and pyroxenite xenoliths from the Jurassic Voyageur kimberlite on the northern Slave craton in Arctic Canada were studied for garnet and clinopyroxene major and trace element compositions, clinopyroxene Pb and garnet O isotopic compositions, and garnet Fe3 +/ΣFe contents. The Voyageur xenoliths record a wide range of pressur...
A new high-precision 40Ar/39Ar anorthoclase feldspar age of 176.7±0.5Ma (2-sigma) reveals that small-volume alkaline basaltic magmatism occurred at the rifted SW margin of the Baltic Shield in Scania (southern Sweden), at a time of global plate reorganization associated with the inception of Pangea supercontinent break-up. Our combined elemental an...
Paleoproterozoic eclogite xenoliths from the Jericho and Muskox kimberlites located in the northern Slave craton, Canada, display geochemical and isotopic evidence of a recycled oceanic lithosphere origin. The eclogites comprise a diverse suite of kyanite- and diamond-bearing and bimineralic xenoliths that have a wide range of geochemical compositi...
Continental and oceanic mafic alkaline magmas have comparable major and trace element compositions that point towards similar P-T and volatile conditions during partial melting of their upper mantle source regions. While it is now widely accepted that OIB source regions must contain small amounts of recycled mafic components that contribute disprop...
Cratonic crust and underlying mantle roots are thought to have a shared history of growth and modification since the Archean. However, debate continues on whether their coupled growth was due to mantle plumes or early forms of subduction. Cratonic mantle eclogites are central to this debate and here we present evidence from two such xenolith suites...
It is now well established that the early continental crust was
formed by melting of basaltic lithologies such as amphibolite and eclogite. However, considerable uncertainty surrounds the geo- logic environment in which melting took place. Commonly invoked options range between melting at the underside of oceanic plateaus above mantle plumes or mel...
Diamonds from high- and low-MgO groups of eclogite xenoliths from the Jericho kimberlite, Slave Craton, Canada were analyzed for carbon isotope compositions and nitrogen contents. Diamonds extracted from the two groups show remarkably different nitrogen abundances and δ¹³C values. While diamonds from high-MgO eclogites have low nitrogen contents (5...
Diamonds are key to understanding the sources, speciation and cycling of carbon in the mantle, and together this information is crucial for the study of mantle redox processes. The carbon isotope composition of diamond provides essential information on both the source and redox-state dependent speciation of C reservoirs involved in diamond growth....
The high-MgO, diamond-bearing eclogites from the Jericho kimberlite in the northern Slave craton are unique in their high Mg# (82-87), high incompatible element contents, radiogenic Sr isotope ratios, and abundant diamonds (up to 20 modal %) that contain lower-Mg garnet inclusions (Mg#~54). As first noted by [1], these diamonds have the lightest ca...
A unique suite of diamond-rich eclogites from the Jericho kimberlite, Nunavut, Canada, has a uniform but unusual geochemical and isotopic composition that is unlike any other eclogite suite worldwide. Compared to other eclogite suites, garnets from Jericho diamond-bearing eclogites have high MgO (19.6–21.2 wt.%), Cr2O3 (0.28–0.60 wt.%), Sc (88–113...
A suite of diamond-rich eclogites from the Jericho kimberlite, Nunavut, has an unusual but uniform geochemical and isotopic composition that is unlike any other eclogite suite worldwide. Compared to other suites, garnets from most Jericho diamond-bearing eclogites have high MgO (19.6-21.2 wt.%), Cr2O3 (0.28- 0.60 wt.%), Sc (88-113 ppm) and Zr (32-3...
Some of Earth's most refractory peridotitic mantle is known to form the keel of the North Atlantic craton (NAC) beneath West Greenland and geochemical and isotopic evidence suggest that this cratonic root stabilized due to extensive 'shallow' melting during the Early Archean. The nature of the eclogitic component, however, was unknown until recent...