Koornneef Janne M, Nikogosian Igor, van Bergen Manfred J, Vroon Pieter Z, Davies Gareth R
Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands.
Utrecht University, Budapestlaan 4, 3584 CD, Utrecht, The Netherlands.
Nat Commun. 2019 Jul 19;10(1):3237. doi: 10.1038/s41467-019-11072-5.
Recycling of Earth's crust through subduction and delamination contributes to mantle heterogeneity. Melt inclusions in early crystallised magmatic minerals record greater geochemical variability than host lavas and more fully reflect the heterogeneity of magma sources. To date, use of multiple isotope systems on small (< 300 μm) melt inclusions was hampered by analytical limitations. Here we report the first coupled Sr-Nd-Pb isotope data on individual melt inclusions from potassium-rich lavas from neighbouring Quaternary volcanoes in central Italy and infer the presence of a previously unidentified ancient lower crustal component in the mantle. We suggest derivation from Variscan or older basement included in the upper mantle by either delamination, sediment recycling, subduction erosion and/or slab detachment processes during Cenozoic subduction and collision of the western Mediterranean. The capability to determine isotope ratios in individual melt inclusions permits the detection of distinctive mantle contaminants and can provide insights into how geodynamic processes affect subduction recycling.
通过俯冲和拆沉作用使地壳再循环，这有助于地幔的不均一性。早期结晶的岩浆矿物中的熔体包裹体记录的地球化学变异性比寄主熔岩更大，并且更充分地反映了岩浆源的不均一性。迄今为止，由于分析上的限制，在小（<300μm）熔体包裹体上使用多种同位素体系受到阻碍。在此，我们报告了来自意大利中部相邻第四纪火山的富钾熔岩中单个熔体包裹体的首批耦合锶-钕-铅同位素数据，并推断在地幔中存在一个先前未识别的古老下地壳组分。我们认为它源自于在新生代西地中海俯冲和碰撞期间，通过拆沉、沉积物再循环、俯冲侵蚀和/或板块脱离过程而包含在上地幔中的华力西期或更古老的基底。测定单个熔体包裹体中同位素比值的能力能够检测出独特的地幔污染物，并可为地球动力学过程如何影响俯冲再循环提供见解。
