Multiple subduction imprints in the mantle below Italy detected in a single lava flow

Post-collisional magmatism reflects the regional subduction history prior to collision but the link between the two is complex and often poorly understood. The collision of continents along a convergent plate boundary commonly marks the onset of a variety of transitional geodynamic processes. Typical responses include delamination of subducting lithosphere, crustal thickening in the overriding plate, slab detachment and asthenospheric upwelling, or the complete termination of convergence. A prominent example is the Western-Central Mediterranean, where the ongoing slow convergence of Africa and Europe (Eurasia) has been accommodated by a variety of spreading and subduction systems that dispersed remnants of subducted lithosphere into the mantle, creating a compositionally wide spectrum of magmatism. Using lead isotope compositions of a set of melt inclusions in magmatic olivine crystals we detect exceptional heterogeneity in the mantle domain below Central Italy, which we attribute to the presence of continental material, introduced initially by Alpine and subsequently by Apennine subduction. We show that superimposed subduction imprints of a mantle source can be tapped during a melting episode millions of years later, and are recorded in a single lava flow

Is the Permian–Triassic Mass Extinction Related to the Siberian Traps?

Abstract: The Siberian Traps are believed to play an essential role in the Permian–Triassic extinction event, although the link between these events is unclear. Plume ascent, its interaction with the lithosphere, and crustal rocks are considered as sources of volatile components that trigger mass extinction. Reliable estimations of the volumes of gases released during the basalt magma degassing that formed typical traps are few. In this work, the volatile contents in the parental melt of the Southern Maslovsky intrusion, which is a part of the PGE–Cu–Ni Maslovsky deposit in the Norilsk district in the Northwest Siberian Platform, were determined. The studied intrusion belongs to the ore-bearing Norilsk intrusive complex, which is coeval to the Morongovsky–Mokulaevsky Formations of the Siberian flood basalt province. The objects of this study were 8 silicate-melt inclusions in olivines from picritic gabbro-dolerites and 68 inclusions in clinopyroxenes, and 2 inclusions in olivines from olivine-bearing gabbro-dolerites. The composition of the parental melt in terms of major and trace element abundances was close to the main stage of the platform magmatism. The average volatile contents in melt inclusions were as follows: 4500 ppm H2O and Cl 1333 ppm, followed by trace amounts of F 387 ppm, S 743 ppm, CO2 1279 ppm, and B 4.18 ppm, typical of within-plate magmas. In addition, the contacts of igneous rocks with sedimentary deposits (carbonate-terrigenous rocks and coals) demonstrate the occurrence of narrow zones of alteration and the absence of a significant volume of gases that could influence the process of species extinction. There is no strict evidence of the influence of the Siberian traps on the Permian–Triassic mass extinction

Mantle Sources of Recent Anatolian Intraplate Magmatism: A Regional Plume or Local Tectonic Origin?

We present an extensive study of rehomogenized olivine-hosted melt inclusions, olivine phenocrysts, and chromian spinel inclusions to explore the link between geodynamic conditions and the origin and composition of Pliocene–Quaternary intraplate magmatism in Anatolia at Kula, Ceyhan-Osmaniye, and Karacadağ. Exceptional compositional variability of these products reveals early and incomplete mixing of distinct parental melts in each volcanic center, reflecting asthenospheric and lithospheric mantle sources. The studied primitive magmas consist of (1) two variably enriched ocean island basalt (OIB)-type melts in Kula; (2) both OIB-type and plume mid-ocean ridge basalt (P-MORB)-like melts beneath Toprakkale and Üçtepeler (Ceyhan-Osmaniye); and (3) two variably enriched OIB-type melts beneath Karacadağ. Estimated conditions of primary melt generation are 23–9 kbar, 75–30 km, and 1415–1215 °C for Kula; 28–19 kbar, 90–65 km, and 1430–1350 °C for Toprakkale; 23–18 kbar, 75–60 km, and 1400–1355 °C for Üçtepeler; and 35–27 kbar, 115–90 km, and 1530–1455 °C for Karacadağ, the deepest levels of which correspond to the depth of the lithosphere-asthenosphere boundary in all regions. Although magma ascent was likely facilitated by local deformation structures, recent Anatolian intraplate magmatism seems to be triggered by large-scale mantle flow that also affects the wider Arabian and North African regions. We infer that these volcanics form part of a much wider Arabian-North African intraplate volcanic province, which was able to invade the Anatolian upper plate through slab gaps