22 March, 2012 – Seminar

When: 4pm on Thursday, March 22nd, 2012
Where: DIAS, Geophysics Section, 5 Merrion Square, Dublin 2, (library)

Speaker: Ms. Leila Hashim from Institut des Sciences de la Terre d’Orleans
Title: Experimental evidence for crustal melting underneath the Himalayan belt.

Abstract:

Seismic and magnetotelluric field campaigns carried out across the Himalaya and the Tibetan Plateau show widespread low velocity and low resistivity zones. Interpretation of these anomalous readings is still largely debated, either saline fluids or partial melts. Laboratory resistivity measurements on crustal rocks undergoing hydrous partial melting show that the electrical anomalies measured underneath the Himalayan range are best explained by emplacement of pure melt bodies and by partially molten rocks. These results imply a viscosity range of Log Viscosity= 4-12 Pa.s for the middle crust of the Himalaya-Tibetan orogenic system, which is several orders of magnitude lower than previously evaluated. This requires a revision of low-viscosity channel flow models and associated ductile extrusions.