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Iceland: What we know and what we don’t

Gillian R. Foulger

Durham University, U.K.

Rift to Ridge ‘07 meeting, 28-29 June 2007National Oceanography Centre, Southampton

Invited keynote talk

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What we know and what we don’t is person-dependent

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Is Iceland hot?

• T = 93˚C (Ribe et al., 1995)

• T = 0-200˚C (Foulger et al., 2000)

• T = 70-190˚C (Herzberg et al., 2007)

• T = 270˚C (Langmuir et al., 1992)

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Is the Iceland “hotspot” a spot?

Centre of “the” Iceland plume

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• “How does a hotspot influence the

development of an oceanic basin…”

• How does breaking the law affect crime?

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Other plume diagnostics

• Precursory uplift

• Initial LIP

• Time-progressive volcanic chain

• Deep mantle seismic anomaly

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Upliftcontemporaneous, fast, permanent

Jones (2005)

0-200 m0 - 200 m

500-800 m

400-900 m 420-620 m

180-425 m

0-100 m

380-590 m

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LIPNot one, but two

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• Iceland LIP started ~ 30 Ma• Area = ~ 500,000 km2

LIP # 2

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Time-progressive chain

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Seismic anomaly

Ritsema et al. (1999)model of Bijwaard & Spakman (1999)

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Now I’ve got that off my chest, let’s turn to some problems

1. Complex spreading

2. An Easter-type trapped microplate?

3. Composition of the crust and mantle

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1. Complex spreading

• How?

• Why?

• What is the way forward?

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1. Complex spreading

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1. Complex spreading

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1. Complex spreading

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2. A trapped microplate beneath Iceland

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3. Composition of crust and mantle

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3. Composition of crust and mantle

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3. Composition of crust and mantle

IcelandShelf

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3. Composition of crust and mantle

• mantle-lowercrust ~ 100 kg/m3

• Composition unknown• Source of Icelandic lavas partly recycled

surface materials– crust?– lithosphere?– how much? ~ 10%? (Sobolev et al., 2007)– where does microplate fit in?

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• “To summarise the current state of

knowledge…”

• We know a lot, but understand little

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http://www.mantleplumes.org/Resources

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