Moytirra:

a new type of

hydrothermal vent

Prof. Andy Wheeler, University College Cork, Ireland

& the VENTuRE survey scientific team

Irish-British multidisciplinary expedition Partner institutes:

Uni. Coll. Cork (IRE) Nat. Oceanog. Centre (UK) Nat. Uni. Ire, Galway (IRE) Uni. Southampton (UK) Geol. Surv. Ireland (IRE)

Funded by the NDP Shiptime grant-aid programme, via the Irish Marine Institute, & National Geographic Television

Hydrothermal vents or “black smokers”

Motivation - to discover the only know vent field between Azores and Iceland - to explore the relationship of hydrothermal fluid venting to volcanic and tectonic structures. - and to test vent biogeography models

A recently discovered black smoker 3000m deep in the middle of the Atlantic

Fast to intermediate spreading - <40 mm a-1) - volcanically controlled & basaltic Slow spreading to ultra-slow - > 40 mm a-1) - as above & tectonically controlled & ultramafic

Buck et al. 2005 http://www.divediscover.whoi.edu/ridge/infomod.html

The mid-Atlantic Ridge

8km

Courtesy Bram Murton, NOC

Seamount summit

AVR crest: conical pillow lava volcanoes

Primary eruptive slopes often exceed 60°

Courtesy Bram Murton, NOCS

Lava tubes feed the massive flows that and cover the

axial floor and onlap the AVR flanks.

Lava tubes

Courtesy Bram Murton, NOCS

Hunting the plume

A suspected hydrothermal

plume was found over the

central-eastern flank of the

AVR in 2008

The first views of a newly discovered hydrothermal vent system

18m high Balor chimney

The Formorians

Mag Mell – old, organ pipe forest

Unique hydrothermal vent location

Tectonically controlled

Basalt-hosted massive sulphides with bacterial mats indicative of defuse flow

Dian Cecht – a squat, complex vent system

Chimney composition

XRF mosaic of area scanned (~50mm x 30mm) Copper

Iron

Zinc

Calcium

Strontium

Sulphur

Lead

Molybdinum

Arsenic

8km

Where is the heat source?

1. The only know hydrothermal vent know between Iceland and the Azores 2. A new hydrothermal vent setting: Tectonically controlled and basalt hosted Uniquely on the median valley wall

Conclusions

Thank-you for listening……

Wheeler, A. J., B. Murton, J. Copley, A. Lim, J.

Carlsson, P. Collins, B. Dorschel, D. Green, V. Nye,

J. Benzie, A. Antoniacomi, M. Coughlan, K. Morris

(2013), Moytirra: Discovery of the first known

deep-sea hydrothermal vent field on the slow-

spreading Mid-Atlantic Ridge north of the Azores,

Geochemistry, Geophysics, Geosystems, 14,

doi:10.1002/ggge.20243.