The Hf–Nd isotopic composition of marine sediments

Variable sediment flux in generation of Permian subduction-related mafic intrusions from the Yanbian region, NE China

“…The subducted marine sediments generally contain more radiogenic Hf than Nd as a result of 'zircon effect' (e.g., Carpentier et al, 2009;Vervoort et al, 2011), and the slab fluids also show such a Hf-Nd isotopic decoupling (e.g., Kogiso et al, 1997;Aizawa et al, 1999). The subarc mantle metasomatized by either the subducted sediments or slab fluids will contain more radiogenic Hf than Nd as observed in the Indian Ocean-type mantle.…”

“…Hf and Nd concentrations of DM are assumed to be somewhat lower than primitive mantle (Sun and McDonough, 1989). The Nd-Hf isotopic compositions of the subducted sediment component are assumed from the global marine sediments (Vervoort et al, 2011), while the Nd and Hf concentrations are estimated from the average global subducted sediment (GLOSS, Plank and Langmuir, 1998). The bulk partition coefficients (K D ) during sediment melting are estimated with a residual mineral assemblage of garnet + pyroxene + K-rich mineral (e.g., phengite) + Al-rich mineral (e.g., zoisite and allanite) with no or little plagioclase (Hermann and Spandler, 2008;Guo et al, 2014).…”

“…The incorporation of such terrestrial sediments into the mantle could create magmas with more radiogenic Nd than Hf . By contrast, marine sediments, which have been widely considered as recycled crustal components in arc magmas, generally contain more radiogenic Hf than Nd (Bayon et al, 2009;Vervoort et al, 2011). Therefore, Hf-Nd isotope decoupling can also provide important constraints on crustal recycling process in subduction zones.…”

Did diamond-bearing orangeites originate from MARID-veined peridotites in the lithospheric mantle?

“…The eHf i value is identical to that of zircon from the same sample, and is equivalent to an offset from the global Hf-Nd isotope array 48 of DeHf ¼ À 3.3 (Fig. 8).…”

Formation of mafic magmas through lower crustal AFC processes — An example from the Jinan gabbroic intrusion in the North China Block

“…Guo et al, 2013;Zhang et al, 2002); Cenozoic basalts (Chen et al, 2009). The terrestrial array is referred to Vervoort et al (2011). O isotopic compositions to those of perovskite crystallized in the early Paleozoic Mengyin kimberlites (Yang et al, 2009) and have Zr, Nb, Nd and Hf concentrations similar to primitive mantle estimated by Sun and McDonough (1989). The metasomatic carbonatite is assumed to have similar Nd and Hf isotopic compositions and trace element concentrations to those of Mesozoic Zibo igneous carbonatites (Ying et al, 2004 and this study).…”