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Theme 6

Subduction, the Mantle Wedge and Arc Volcanism: Early to Present-day Earth

Don Baker, McGill,
Benoit Villemant, IPGP, France,

Co-hosted sessions

SESSIONS

6a. Earth’s deep carbon cycle

(co-hosted by Themes 6, 3 and 4)

Co-convenors:
Erik Hauri (Carnegie Institution of Washington) - ehauriciw.edu
Juske Horita (Texas Tech University) - juske.horitattu.edu

The deep Earth contains multiple carbon-bearing reservoirs, but the forms, ages, sizes, and distributions of the carbon in these deep-Earth reservoirs have been only vaguely discerned, and the abundance of carbon in each reservoir is poorly known. The interface and interconnection between the surficial and deep-Earth carbon cycles include volcanoes on continents, ocean islands, mid-ocean ridges and convergent margins, and the altered oceanic crust recycled into the deep Earth at subduction zones. Volcanic eruption and degassing deliver carbon-bearing volatile compounds from the deep-Earth into the atmosphere, and the cycle is completed by returning carbon-rich organic, inorganic, and biological materials in near-surface sediments and altered oceanic crust into the Earth's interior at subduction zones. The balance of delivery and return fluxes of carbon from the surface to the interior is so poorly known that we don't even know if the net flux of carbon is into - or out of - the Earth's interior. This session will invite papers describing research results from geochemistry, experimental petrology and geodynamic modeling that address these fundamental issues in the Earth's deep carbon cycle.

6b. The dynamics of volcanic excess degassing: from source to surface

Co-convenors:
Séverine Moune (Université Clermont-Ferrand) – s.mouneopgc.univ-bpclermont.fr
Glyn Williams-Jones (Simon Fraser University) - glynwjsfu.ca
Pierre Delmelle (University Catholique de Louvain) - pierre.delmelleuclouvain.be

SESSION MERGED with 6f

6c. Crystals and glasses as archives of volcanic processes

(co-hosted by Themes 6 and 3)

Co-convenors:
Marc-Antoine Longpré (GEOTOP & McGill University) - m-a.longpremcgill.ca
Valentin Troll (Uppsala Universitet) - valentin.trollgeo.uu.se
John Stix (GEOTOP & McGill University) - john.stixmcgill.ca
Steffen Kutterolf (IFM-GEOMAR) - skutterolfifm-geomar.de

Volcanic eruptions are the consequence of processes that occur in subterranean magma plumbing systems. The study of quenched melt (matrix glass and glass inclusions) and crystals erupted at the Earth’s surface provides a powerful means of reconstructing these sub-volcanic processes. Coupled with advances in thermodynamic modelling and experimental petrology, this approach also allows better estimates of the physico-chemical conditions prevailing in magmatic systems. This session aims to bring together researchers who use the composition of crystals and glasses (major, trace and volatile elements, as well as isotopes) to unravel pre- and syn-eruptive magmatic processes, magma chamber conditions, and the evolution of volcanic systems. We are particularly interested in contributions that investigate eruption trigger mechanisms using petrological and geochemical data.

Keynote speaker:
Jon Blundy (University of Bristol), Jon.Blundybristol.ac.uk
Fidel Costa (Earth Observatory of Singapore), fcostantu.edu.sg

6d. What is the nature of subduction records preserved in Earth’s upper mantle?

Co-convenors:
Amy Riches (University of Alberta) - arichesualberta.ca
Chris Dale (University of Durham, UK) - christopher.daledurham.ac.uk
Helen Williams (University of Durham, UK) - h.m.williams2durham.ac.uk

Basaltic materials provide indirect evidence of mineralogical and isotopic heterogeneity in Earth’s mantle, and studies of mantle lithosphere support the notion that basalt source regions may be lithologically complex. However, the origin, extent, and nature of this heterogeneity remains poorly understood. Initiation of ‘modern’ subduction during the Archean has had a significant impact on the evolution of Earth’s upper mantle, but the effects of these processes are not yet well constrained. This session will address the nature of subduction signatures incorporated into lithospheric and asthenospheric mantle environments over geological time. We seek contributions that encompass studies of mantle-derived melts, mantle xenoliths, and ultramafic massifs at a variety of analytical scales, and focus on; 1) comparisons between subduction signatures in ancient and modern-day settings; 2) information derived from mantle materials exhumed in a variety of abyssal and continental settings; and 3) chemical and statistical assessment of proposed links between subduction processes and major crust-mantle differentiation events.

Keynote speaker:
Othmar Müntener (Université de Lausanne), othmar.muntenerunil.ch

6e. From crystallization to exsolution: the origin and fate of magmatic volatiles and the magmatic-hydrothermal transition in ore-forming systems.

(co-hosted by Themes 4 and 6)

Co-convenors:
Jake Hanley (Saint Mary's University, Nova Scotia, Canada) - jake.hanleygmail.com
Jim Webster (American Museum of Natural History) - jwdamnh.org

The volatile content of ore-forming magmas and the process of fluid phase separation in magmatic-hydrothermal systems is a critical process in the genesis of a wide variety of ore deposits. This session is intended to bring together researchers who describe experimental, field, and theoretical-based studies of the evolution of volatiles in ore-forming magmas, their interaction with ore metals, the formation of free volatile phases at the magmatic-hydrothermal transition, and overall, the role that these processes plan in generating fluids capable of forming metallic ore deposits.

6f. Volatiles and their role in petrogenetic, intrusive and eruptive processes in subduction zones

Co-convenors:
Georg Zellmer (Academia Sinica-Taiwan) - gzellmerearth.sinica.edu.tw
Susanne Straub (Lamont-Doherty Earth Observatory) - smstraubldeo.columbia.edu
Marie Edmonds (University of Cambridge, UK) - me201cam.ac.uk
Jon Blundy (University of Bristol, UK) - Jon.Blundybristol.ac.uk
Séverine Moune (Université Clermont-Ferrand) – S.Mouneopgc.univ-bpclermont.fr
Glyn Williams-Jones (Simon Fraser University) - glynwjsfu.ca

The volatile cycle at subduction zones is a key to the processes involved in the petrogenesis, ascent, storage, and eruption of arc magmas. Volatiles (H₂O, CO₂, Li, B, F, Cl, S) control the flux of slab components into the mantle wedge, are responsible for melt generation through lowering the solidi of the involved materials, and determine the crystallizing phase assemblages in the overriding crust as well as influencing redox conditions. During magma transport and storage, degassing may induce rapid crystallization and stalling of magmas at depth, to form viscous crystal mushes and plutonic bodies. On the other hand, volatiles carried within ascending melts may also play a role in driving the remobilization and subsequent eruption of previously degassed and stalled intrusives. Finally, the rate and extent of degassing during magma decompression, and its effects on magma rheology, control eruption style and the occurrence and environmental impacts of explosive arc volcanism.

The volatile cycle and mass budget associated with subduction zones has changed through geological time and varies spatially in modern subduction zones. We invite all contributions that elucidate and quantify such variations and their effects on the magmatic and volcanic processes operating in modern and ancient arcs, as well as their implications for subduction zone geochemical budgets. We welcome studies involving experimental petrology, melt and fluid inclusion work, mineral hygrometry and analysis of water in nominally anhydrous minerals, direct measurements of volatiles in gases at active arc volcanoes, combinations of such methods, and any other techniques that may provide insights into this broad topic.

Keynote speakers:
Hiroshi Shinohara (Geological Survey of Japan, shinohara-haist.go.jp
Paul Wallace (University of Oregon), pwallaceuoregon.edu
Invited speaker:
James Webster (American Museum of Natural History), jdwamnh.org

Co-hosted sessions:

Please note that for abstract submission purposes, the following sessions and their respective descriptions appear in their primary Theme assignments (numbers in red or before the title).

3c.- Deep cycles of volatiles in terrestrial planets through time

Co-convenors: R. Dasgupta/Rice, N. Shimizu/WHOI and M. Mookherjee/Bayreuth
(co-hosted by Themes 3 and 6)

3g.- Melts, glasses and magmas

Co-convenors: Daniel Neuville/IPGP, Cristina de Campos/Munich, Akio Suzuki/Tokyo and Kelly Russell/UBC
(co-hosted by Themes 3, 4 and 6)

4i.- Mass transfer processes at the mantle-seawater interface

Co-convenors: Dionysis Foustoukos/Carnegie and Michael Bizimis/South Carolina
(co-hosted by Themes 4 and 6)

5d.- Recycling of continental crust into the mantle: evidence and observations from ocean margins, the crust and the mantle, modern and ancient.

Co-convenors: David W. Scholl/USGS and Kent Condie/New Mexico Tech
(co-hosted by Themes 5 and 6)

5e.- Extraction of crust from the mantle through time: from the Archean to the present

Co-convenors: Othmar Müntener/Lausanne, Oliver Jagoutz/MIT, Jean Bédard/GSC and Steve Parman/Brown
(co-hosted by Themes 5, 3 and 6)

5f.- Characterizing mid- to lower-crustal flow related to orogenic processes

Co-convenors: Félix Gervais/Polytechnique, Montréal, Dan Gibson/SFU and Laurent Godin/Queen’s
(co-hosted by Themes 5 and 6)

9f.- Innovative geochemical approaches to understanding geothermal systems

Co-conveners: Nathalie Vigouroux/Alterra Power Corp., BC, A.E. Williams-Jones/ McGill and Glyn Williams-Jones/Simon Fraser University
(co-hosted by Themes 9 and 6)

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