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Geoscience Seminar: A record of deep crustal foundering from high-pressure xenoliths

Time: Tuesday, December 5; 4:00 pm - Place: 1673-118 - By Dr. Ellen Kooijiman, Senior Researcher, Head of Vegacenter, Swedish Museum of Natural History

01.12.2017 | Ann Eg Mølhave

Crustal foundering is an important mechanism in the differentiation and recycling of continental crust, but little is known about the timescale of foundering and its role in the dynamics of active margins and orogens. Lower crustal xenoliths erupted in the Pamir provide a unique opportunity to study the evolution of crust at mantle depths during an active continent-continent collision. We subjected 6 xenoliths to coupled in-situ U-(Th-)Pb geochronology and trace-element analysis of zircon, monazite and rutile by laser-ablation (split-stream) ICP-MS. The data record the history of the rocks at a million-year resolution and reflect the foundering of differentiated deep-crustal fragments into a metasomatized and less dense mantle wedge on a relatively short time scale. Through our new approach in constraining the burial history of rocks, we provided the first time-resolved record of this crustal recycling process.

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