Plumes and Their Role in Whole Mantle Convection and Recycling

Pico, the Azores

17–21 September 2008

Conveners:

Christoph Beier

Macquarie University, Dept. of Earth and Planetary Sciences, Room 216, Building E5B, Sydney NSW 2109, Australia,

Tracy Rushmer

Macquarie University, Dept. of Earth and Planetary Sciences, Key Centre Geochemical Evolution and Metallogeny of Continents, Room 423, Building E7A, Sydney NSW 2109, Australia,

Simon Turner

Macquarie University, Dept. of Earth and Planetary Sciences, Room 215, Building E5B, Sydney NSW 2109, Australia,

Elizabeth Widom

Miami University, Dept. of Geology, 114 Shideler Hall, Oxford, Ohio 45056, USA,

Zilda Franca

Universidade dos Açores, Departamento de Geociências, Apartado 1422, 9501-801 Ponta Delgada, Portugal

DESCRIPTION AND OBJECTIVES

The model of rising mantle plumes and hotspots from the core-mantle boundary first invoked by W.J. Morgan (1971, Nature, v. 230, p. 42–43) has been used for the establishment of geochemical and geophysical models, but the model of mantle plumes is a matter of intense and active debate. Despite the ongoing controversy about the existence of mantle plumes and their possible connection to the lower mantle or even core-mantle boundary, the existence of melting anomalies in Earth’s upper mantle cannot be denied. The main topic of this conference requires the existence of mantle plumes largely independent of their origin and therefore differs from earlier meetings. Instead of aiming to solve the outstanding issue of whether mantle plumes exist we focus on the geophysical and geochemical aspects of well-established mantle plumes–melting anomalies, such as the Azores.

There is increasing evidence that some mantle plumes rise from the core-mantle boundary and accordingly there is much interest in the role they play, not only in whole mantle convection, but also in the recycling of near surface materials. The buoyancy flux of mantle plumes varies by a factor of three or more, and much study has concentrated on the high flux Hawaiian plume. The Azores plume provides an interesting contrast because of its low buoyancy flux and the large variation in radiogenic and stable isotopes in erupted products. Additionally, it has long been suggested that the Azores reflect melting in the presence of volatiles as well as elevated temperatures. Thus, whilst the Azores plume cannot transport as much heat as Hawaii, it may contain the best evidence for recycling of materials subducted beneath an arc. Several recent studies have suggested that this may have occurred ca. 2.5–3 Ga, making the Azores unique in providing evidence for Archaean subduction and very long-term storage of this material in the mantle. In the light of the importance and impact of mantle plumes to the geodynamic evolution and behavior of Earth’s mantle, it is important to bring together geochemists, experimentalists, modelers, and seismologists in particular who have expertise in the Azores and other mantle plumes.

We will discuss our present understanding of mantle plumes and, based on their existence, which issues still need to be resolved. The meeting will convene at the Azores Hotel Aldeia da Fonte, in Pico, Azores, and will involve three days of presentations and two days of field observations. Participants should plan on arriving on Pico on Tuesday, 16 September.

PROPOSED ITINERARY

The field trips on Pico and on Faial will cover the most frequent eruption styles and tectonic features in the Azores and may provide the ideal overview for conference participants. Depending on interest, we would also like to offer a pre- or post-meeting field trip to the island of São Miguel. This island is unique in many aspects (e.g., tectonics, geochemistry) and would provide a unique opportunity for participants to gain an understanding of the tectonics, geology, and geochemistry, and to collect samples.

ATTENDEES AND ESTIMATED COST

Participation of graduate students is especially encouraged, and partial support to attend the meeting is being actively sought by the organizers. Participants must make their own travel arrangements to and from the Azores. The registration fee will be confirmed by the end of April, and it will cover six nights hotel lodging (16–21 Sept.), meals, guidebook, and all transportation (e.g. ferries) while on the Azores. Airfare is not included.

REGISTRATION APPLICATIONS AND INFORMATION

Interested persons should send a letter of application by e-mail to by 25 June 2008. The letter should include a brief statement of the applicant’s research interests and the relevance of those interests to the focus of the conference. Please also indicate if you are interested in a pre- or post-meeting field trip to the island of São Miguel.

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