| Autor: |
Jean Cotten, Gaëlle Prouteau, Joseph Cotten, F G Sajona, René C. Maury |
| Rok vydání: |
2008 |
| Předmět: |
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| Zdroj: |
Island Arc. 9:487-498 |
| ISSN: |
1038-4871 |
| DOI: |
10.1111/j.1440-1738.2000.00296.x |
| Popis: |
Pliocene–Quaternary adakites and spatially and temporally associated niobium-enriched basalts (the latter thought to be derived by melting of slab melt-metasomatized mantle) from the Philippine island arcs have been selected for analysis of high field strength elements (HFSE). All these samples have nearly constant and chondritic Zr/Hf ratio (36.5) and slightly infrachondritic Nb/Ta ratio (14.7). We interpret adakitic magmas to be derived from the partial melting at approximately 900°C of subducted mid-ocean ridge basalts (MORB) crust, with rutile and/or ilmenite as residual minerals. Melting calculations show that, under these conditions, slab melts should have suprachondritic Nb/Ta ratios. The obvious discrepancy with our data is attributed to insufficient knowledge of rutile-melt partition coefficients for HFSE. Consequently, abnormal Nb/Ta or Zr/Hf ratios cannot be considered as potential markers of slab melting processes in island arcs. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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