GD6.6/GMPV53/MPRG20/PS9.2/SM6.12

The deep mantle, plumes, and chemical heterogeneity: structure, dynamics, and evolution (co-organized)
Convener: Stephane Labrosse  | Co-Conveners: Daniel Frost , Christine Thomas , Ulrich Hansen , John Tarduno , Paul Tackley 
Oral Programme
 / Thu, 06 May, 13:30–17:00  / Room 31
Poster Programme
 / Attendance Fri, 07 May, 13:30–15:00  / Hall A
This session is organised along three distinct themes:

(i) Structure, dynamics and evolution of the lowermost mantle and the core:
The lower mantle and the core are the source of some of the most important processes occurring in the interiors of the Earth and the terrestrial planets. In the last decade, tremendous progress has been made in understanding the structure, dynamics, and mineralogy of this central region of the Earth. Our perception of the base of the mantle, for example, has been altered dramatically through the discovery of ultra low velocity zones, thermo-chemical domes and the post-perovskite phase, while research on the Earth’s core has led to the generalisation of self-consistent dynamo models, the discovery of the inner core structure and its possible dynamical implications. The interactions between the core and the mantle have also been subject to great attention, and some exotic scenarios have been proposed to explain the magnetic signature of other terrestrial planets and asteroids. The essential aim of this session is to debate the structure, dynamics and evolution of the deepest parts of the Earth from the varying view points of mineral physics, seismology, geodynamics, geochemistry, and planetary sciences, through the presentation of the most recent discoveries and models.

(ii) Mantle plumes- observations, models, and their importance throughout Earth history:
Although small-scale, local processes can result in magmatism, mantle plumes are predicted to arise from the thermal boundary layers and their existence is supported by a plethora of observations and modeling studies. We invite contributions in geochemistry, geodynamics, seismology, mineral physics, paleomagnetism and other relevant fields that present new observations and modeling results bearing on mantle plumes and their relationship to Earth structure and evolution. Suggested topics include (but are not limited to), plumes and long-term cooling of the mantle, chemical vs. thermal plumes, plume heat transport, mantle plume comparative case histories, mantle plumes and large-scale structure near the core-mantle boundary, mantle plumes and plate motions, and superplumes.

(iii) Structure and evolution of chemical heterogeneities in the Earth's mantle:
The origin, preservation and evolution of isotopic heterogeneities in the terrestrial mantle remain fundamental questions on the efficiency of mixing and therefore structure of the mantle system. Seismic tomography provides a view of the large-scale structure within the mantle today, while geochemical analyses show evidence of all scales of heterogeneities, ranging from global down to microscopic. Numerical simulations of mantle convection investigate the chemical and physical evolution of the mantle over its lifetime, employing constraints imposed by processes of magmatic differentiation and convective homogenization. Some of the open question in this context are: What is the present-day state of mantle heterogeneity and how has it evolved through time? Do the compositions of mantle melts adequately reflect the heterogeneity of mantle-source compositions, or are they primarily controlled by mixing processes in magma chambers? What is the role of “layered” as opposed to “whole-mantle” convection? Are there physically distinct geochemical reservoirs in the mantle, or are the heterogeneities chaotically distributed throughout the mantle? What are the dimensions of such heterogeneities? Is the concept of distinct geochemical “reservoirs” and geochemical “end-member” compositions appropriate for describing the geochemistry of the mantle? We invite contributions that provide new insights into the nature of the terrestrial mantle and particularly those that integrate one or more of the subdisciplines of geochemistry, fluid dynamics, seismology and petrology