The role of subduction fluids and mantle sources in the petrogenesis of Eastern Lau Spreading Center magmas
Abstract
Mantle melting beneath island arcs and back-arc spreading centers is governed to the first order by the addition of water to the mantle wedge. The Eastern Lau Spreading Center (ELSC) becomes progressively more distant from the Tonga arc front toward the north and is thus an ideal natural laboratory to assess the influence of subduction-related fluids on mantle composition and melting processes. Our previous works on the ELSC have clearly identified different subduction components present in the Lau basin (Escrig et al., 2009) and characterized their relationship to mantle melting for the northernmost segment (Bézos et al., 2009). Thanks to new major element (N=153) and trace element (N=102) data, we can apply the approach developed for the northern ELSC to the entire ridge, and better characterize the effects of the subduction input on back-arc mantle petrogenesis. We also propose to integrate these new results with data available for the Tonga arc and discuss the absence of continuity in the spectrum of major elements compositions between arc and back-arc lavas. Such a difference has already been documented for the Mariana arc-back-arc system (i.e. respectively high vs. Low FeO contents). Boninitic lavas, which are a rare but important component of subduction zone magmatism, appear however to share some similarities with wet back-arc magmas (i.e. low TiO2 and FeO, and high H2O and SiO2 contents). We propose to discuss all these differences and similarities in the global context of the subduction factory.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.V41D2547B
- Keywords:
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- 1031 GEOCHEMISTRY / Subduction zone processes