Re-Os isotope studies of Mindanao adakites: Implications for sources of metals and melts

Dreher, S.T; Macpherson, C.G; Pearson, D.G; Davidson, J.P

Abstract

Whether the downgoing slab in modern subduction zones is able to melt is an important unresolved aspect of plate tectonics. Rare arc lavas with high Sr/Y ratios and low Y and heavy rare earth element concentrations, called adakites, are often attributed to melting of young subducted crust in subduction zones. Osmium isotopic data obtained for 13 adakite samples from Mindanao, Philippines, conflict with the slab-melting model. Ten of the samples have unradiogenic 187Os/188Os ratios inconsistent with partial melting of the ca. 50 Ma Philippine Sea lithosphere subducting beneath Mindanao. The Os isotope signatures are similar to those of young mid-oceanic-ridge basalts and normal arc rocks, consistent with a mantle source. In addition to implications for mass transfer in subduction zones, the apparent association of adakites with Cu-Au deposits makes understanding their origin, and that of the associated metals, economically interesting. This study suggests that a reevaluation is required of the slab-melting hypothesis in general, and that the metals associated with the Mindanao adakites come from the mantle.

Citation

Dreher, S., Macpherson, C., Pearson, D., & Davidson, J. (2005). Re-Os isotope studies of Mindanao adakites: Implications for sources of metals and melts. Geology, 33(12), 957-960. https://doi.org/10.1130/g21755.1

• Journal Article Type: Article
• Publication Date: 2005-12
• Deposit Date: Mar 13, 2007
• Journal: Geology
• Print ISSN: 0091-7613
• Electronic ISSN: 1943-2682
• Publisher: Geological Society of America
• Peer Reviewed: Peer Reviewed
• Volume: 33
• Issue: 12
• Pages: 957-960
• DOI: https://doi.org/10.1130/g21755.1
• Keywords: Adakites, Osmium, Philippines, Subduction.
• Public URL: https://durham-repository.worktribe.com/output/1576069