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Gradual and selective trace-element enrichment in slab-released fluids at sub-arc depths
The geochemical signature of magmas generated at convergent margins greatly depends on the nature of fluids and melts released during subduction. While major- and trace-elements transport capacity of ultrahigh pressure (UHP) hydrous-silicate melts has been investigated, little is known about solute...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Nature Publishing Group UK
2019
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6841933/ https://www.ncbi.nlm.nih.gov/pubmed/31704982 http://dx.doi.org/10.1038/s41598-019-52755-9 |
Sumario: | The geochemical signature of magmas generated at convergent margins greatly depends on the nature of fluids and melts released during subduction. While major- and trace-elements transport capacity of ultrahigh pressure (UHP) hydrous-silicate melts has been investigated, little is known about solute enrichment and fractionation in UHP (>3.5–4 GPa) solute-rich aqueous fluids released along colder geothermal gradients. Here, we performed in situ LA-ICP-MS trace-element analyses on selected UHP prograde-to-peak fluid inclusions trapped in a kyanite-bearing quartzite from Sulu (China). The alkali-aluminosilicate-rich aqueous fluid released from the meta-sediments by dehydration reactions is enriched in LILE, U, Th, Sr, and REE. Inclusions trapped at increasing temperature (and pressure) preserve a gradual and selective trace-element enrichment resulting from the progressive dissolution of phengite and carbonate and the partial dissolution of allanite/monazite. We show that, at the investigated P-T conditions, aqueous fluids generated by dissolution of volatile-bearing minerals fractionate trace-element distinctly from hydrous-silicate melts, regardless of the source lithology. The orogenic/post-orogenic magmas generated in a mantle enriched by metasomatic processes involving either solute-rich aqueous fluids or hydrous-silicate melts released by the slab at UHP conditions can preserve evidence of the nature of these agents. |
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