Diamonds illuminate the nature of Earth’s deep and dynamic carbon cycle
|Starts:||13:00 9 Mar 2021|
|Ends:||14:00 9 Mar 2021|
|What is it:||Seminar|
|Organiser:||Department of Earth and Environmental Sciences|
|Who is it for:||University staff, Adults, Alumni, Current University students|
|Speaker:||Dr Sami Mikhail|
Dr Sami Mikhail, Min Soc Distinguished Lecturer, University of St Andrews, joins us for a Department of Earth and Environmental Sciences seminar. Abstract below.
Carbon is omnipresent in the Earth system. The predominant mechanisms driving exchange between Earth’s layers are diffusion, volcanism, and chemomechanical mixing (i.e., plate tectonics). A minor technical issue is that >90% of Earth carbon is stored within the inaccessible interior (mantle + core). This means that tracing Earth’s planet-wide carbon cycle is challenging, to say the least. However, there are windows into Earth’s mysterious interior, and they’re made of diamonds. Diamond inclusions sample the otherwise inaccessible archive of Earth’s deep interior. The geochemical and petrological diversity of diamond inclusions reflects either pre-metasomatic upper mantle heterogeneity or metasomatism coeval with diamond formation. We focus on the origin of lithospheric garnet and clinopyroxene inclusions by simulating metasomatic reactions between eclogitic fluids and mantle peridotites at 5 GPa, 1000ºC, and across a range of redox conditions (logfO2 = -1 to -5 ?FMQ). Our results demonstrate that fluid-rock interaction can result in the formation of peridotitic, eclogitic, and websteritic silicates from a single fluid during a single metasomatic event. Ergo, the petrogenesis of diamond and their inclusions can be equivalent, and the apparently distinct silicate parageneses can share a kinship. In addition, we show that a pyroxenitic mantle source for oceanic basalts can be generated by the conversion of refractory peridotite to fertile websterite via fluid metasomatism.
Dr Sami Mikhail
Organisation: University of St Andrews
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