Metasomatic interactions between slab-derived melts and depleted mantle : insights from xenoliths within Monglo adakite (Luzon arc, Philippines)

• Main Authors: Grégoire, M., Jego, S., Maury, R. C., Polvé, Mireille, Payot, B., Tamayo, R. A., Yumul, G. P.
• Format: Text
• Language: English
• Published: 2008
• Subjects: Mantle xenoliths; Luzon arc; Metasomatism; Dunite; Trace elements; Adakite; Kamchatka
• Online Access: http://www.documentation.ird.fr/hor/fdi:010042728

The Monglo adakite contains mafic and ultramafic xenoliths, which probably originated from the mantle section of an Early Cretaceous supra-subduction zone ophiolitic complex located within the Luzon are crust. Spinel-bearing dunites are dominant among this xenolith collection and display evidence for three episodes of subduction-related melt percolation. The first one is evidenced by an undeformed clinopyroxene characterized by convex-upwards REE pattern. This clinopyroxene crystallized from a calc-alkaline basaltic magma, likely formed in the Cretaceous supra-subduction setting of the ophiolite. Then, two metasomatic events, evidenced by orthopyroxene-rich and amphibole-rich secondary parageneses, respectively, affected most of the spine) dunites. The opx-rich paragenesis is related to the circulation within the dunitic upper mantle of hydrous slab-derived melts similar to those affecting the mantle peridotite xenoliths from Papua New Guinea and Kamchatka. Finally the amphibole-rich veins are related to the interaction between the studied dunite xenoliths and the host adakite or an adakitic melt similar to it.