Oxygen isotope evidence for slab melting in modern and ancient subduction zones

Continental flood basalts derived from the hydrous mantle transition zone

“…The melt inclusion data imply that these CFBs were mainly derived from an olivine-free pyroxenite-dominated source with high water content (4450 p.p.m.). These observations show that the low d 18 O end-member melt most likely originated from hydrothermally altered oceanic gabbros 30,32 . Furthermore, from the systematic regional trend presented in Fig.…”

“…Variations in oxygen isotopes in the mantle source are ultimately related to surface water-rock interaction [29][30][31] . The oxygen isotopes of primary melts are therefore sensitive to contributions from hydrothermally altered recycled components.…”

Neoarchean siliceous high-Mg basalt (SHMB) from the Taishan granite–greenstone terrane, Eastern North China Craton: Petrogenesis and tectonic implications

“…This clearly demonstrates that a greater proportion of sedimentary-and/or basaltic-derived slab melts have been involved in their generation Pearce and Peate, 1995;Bédard, 1999). Several studies have established that the enriched nature of most Cenozoic high-Mg rocks, including high-Mg andesites and boninites, can be attributed to a contribution from slab-derived melts (Kay, 1978;Cameron et al, 1983;Pearce et al, 1992;Yogodzinski et al, 1994;Shimoda et al, 1998;Tatsumi, 2001;Bindeman et al, 2005;König et al, 2010). Furthermore, the coeval occurrence of boninites with high-Mg andesite and slab melt-related rocks (e.g., adakites) has been recognized in some present-day arcs (e.g., Tonga, Falloon et al, 2008;IzuBonin-Mariana Fore-arc, Pearce et al, 1992), providing evidence of slab melt-related enrichment.…”

“…Recent oxygen isotope studies show that Archean TTGs show identical oxygen isotopic compositions to modern adakites. This also suggests that melting of subducted oceanic slabs was much more common in the Archean than today (Bindeman et al, 2005). With respect to the petrogenesis of TTGs with low-Mg and Cr and Ni values, it is possible the higher geothermal gradients in the Archean mantle led to flat subduction with no or very thin mantle wedge above the slab at the initial stage of subduction.…”

Oxygen isotope and trace element geochemistry of zircons from porphyry copper system: Implications for Late Triassic metallogenesis within the Yidun Terrane, southeastern Tibetan Plateau

“…signature (8‰-10‰; Gregory and Taylor, 1981;Muehlenbachs, 1986) which reflecting low-temperature slab-seawater interaction, and the lower gabbroic part of the slab have low δ 18 O values (3‰-5‰) owing to high-temperature exchange with percolating water (Magaritz and Taylor, 1974;Cocker et al, 1982;Hart et al, 1999). The marginally shifted PDL zircon δ 18 O values (increment of~1‰) require the fortuitous mixtures of 18 O-rich and 18 O-poor parts of the slab, which is not to be generally expected (Eiler, 2001;Bindeman et al, 2005). Secondly, the temporally, spatially, and universality features of the high δ 18 O mantle settings are still unclear, and only some case studies revealed that prolonged enrichment of high δ 18 O melt/fluids from the partial melting of subducting oceanic slab would led to enrichment of the mantle oxygen isotope signatures (e.g., Bindeman et al, 2004;Auer et al, 2009;Johnson et al, 2009;Martin et al, 2011).…”