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Oxidized primary arc magmas: Constraints from Cu/Zr systematics in global arc volcanics
Arc volcanics are more oxidized than mid-ocean ridge basalts (MORB), but it is debated whether this is a mantle feature or a result of magmatic evolution. Copper, a sulfur-loving element, has been used to trace the behavior of redox-sensitive sulfur during mantle melting and infer similar redox stat...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American Association for the Advancement of Science
2022
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8942352/ https://www.ncbi.nlm.nih.gov/pubmed/35319995 http://dx.doi.org/10.1126/sciadv.abk0718 |
Sumario: | Arc volcanics are more oxidized than mid-ocean ridge basalts (MORB), but it is debated whether this is a mantle feature or a result of magmatic evolution. Copper, a sulfur-loving element, has been used to trace the behavior of redox-sensitive sulfur during mantle melting and infer similar redox states of sub-arc and sub-ridge mantle. Previous studies, however, neglected elevated sulfur contents in the sub-arc mantle, leading to underestimation of oxygen fugacities, and did not recognize systematic Cu variations in arc volcanics. Here, we show that the Cu/Zr ratio is a sensitive indicator that responds to sulfur content, oxygen fugacity, and extent of melting of the mantle. Because of higher mantle S contents, Cu systematics of arc magmas require one log unit higher oxygen fugacities of sub-arc than sub-ridge mantle. Low Cu contents of thick-crusted arc volcanics result from low extents of melting of sulfur-rich mantle, obviating the need for deep crustal sulfide fractionation, with substantial implications for the origin of porphyry-Cu deposits. |
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