Asthenosphere-induced melting of diverse source regions for East Carpathian post-collisional volcanism

Abstract

The occurrence of post-subduction magmatism in continental collision zones is a ubiquitous feature of plate tectonics, but its relation with geodynamic processes remains enigmatic. The nature of mantle sources in these settings, and their interaction with subduction-related components, are difficult to constrain using bulk rocks when magmas are subject to mixing and assimilation within the crust. Here we examine post-collisional magma sources in space and time through the chemistry of olivine-hosted melt inclusions and early-formed minerals (spinel, olivine and clinopyroxene) in primitive volcanic rocks from the Neogene-Quaternary East Carpathian volcanic range in Călimani (calc-alkaline; 10.1-6.7 Ma), Southern Harghita (calc-alkaline to shoshonitic; 5.3-0.03 Ma) and the Perșani Mountains (alkali basaltic; 1.2-0.6 Ma). Călimani calc-alkaline parental magma compositions indicate a lithospheric mantle source metasomatised by ~ 2% sediment-derived melts, and are best reproduced by ~ 2-12% melting. Mafic K-alkaline melts in Southern Harghita originate from a melt-and fluidmetasomatised lithospheric mantle source containing amphibole (± phlogopite), by ~ 5% melting. Intraplate Na-alkaline basalts from Racoș (Perșani) reflect small-degree (1-2%) asthenosphere-derived parental melts which experienced minor interaction with metasomatic components in the lithosphere. An important feature of the East Carpathian post-collisional volcanism is that the lithospheric source regions are located in the lower plate (distal Europe-Moesia), rather than the overriding plate (Tisza-Dacia). The volcanism appears to have been caused by (1) asthenospheric uprise following slab sinking and possibly south-eastward propagating delamination and breakoff, which induced melting of the subduction-modified lithospheric mantle (Călimani to Southern Harghita); and (2) decompression melting as a consequence of minor asthenospheric upwelling (Perșani).

Tectonics, Dynamics, and Plio‐Pleistocene Magmatism in the Central Tyrrhenian Sea: Insights From the Submarine Transitional Basalts of the Ventotene Volcanic Ridge (Pontine Islands, Italy)

“…Although many characteristics described for the postcollisional magmatism in these areas are largely similar to those inferred for the regional subduction-related, postcollisional volcanism in the Italia peninsula (Peccerillo, 2017, and references therein), the features of the TD4B and VR TR basalts recovered in the central Tyrrhenian basin differ from both the Na-alkaline parental melts having OIB-type signature (Bracco Gartner et al, 2020) and those having IAB-type signatures (Di Giuseppe et al, 2018). Indeed, TD4B and VR volcanics, (i) are not Na-basalts but weakly silica-saturated K-basalts, hy-to weakly ne-normative, evolving toward peralkaline differentiated and (ii) are geochemically similar to the orogenic-type magmas of the central-eastern Tyrrhenian area (Conte et al, 2016).…”

“…The occurrence of HKCA/KA and TR/Na-alkaline rock-series associated in space and in time is relatively common worldwide. It results as an effect of post-subduction magmatism in convergent/collisional zones where a variety of petrogenetic and geodynamic constraints concur to determine differences among the parental magma compositions of different magma series (Bracco Gartner et al, 2020;Bursik, 2009;Carminati et al, 2010;Chaussard & Amelung, 2014; Di Giuseppe et al, 2018 and references therein). The nature of mantle sources in these settings is strongly dependent by their interaction with subduction-related components and with its relation with geodynamic processes, both of which are difficult to constrain; moreover, magmas in these settings are often subject to mixing and assimilation within the crust (e.g., Beccaluva et al 2013;Conticelli et al, 2015;Conticelli et al, 2009aConticelli et al, , 2009bMazzeo et al, 2014).…”

Estimates of the Temperature and Melting Conditions of the Carpathian‐Pannonian Upper Mantle From Volcanism and Seismology

“…This value is slightly lower than, but probably within error of, previous estimates, that is, 2–3% (Harangi et al., 2015) or 1–4% (Seghedi et al., 2004). For Perşani, the calculated melt fraction is only slightly smaller than the 1–2% estimated from trace elements in olivine‐hosted melt inclusions from Racoş, a lava flow in Perşani (Bracco Gartner et al., 2020).…”

“…sourced from the asthenosphere and that some were modified by interaction with the lithospheric mantle during ascent (Embey-Isztin, Harangi et al, 2015;Seghedi et al, 2004). Trace element concentrations in melt inclusions in olivines from Perşani show averages that coincide with whole-rock data (Bracco Gartner et al, 2020), demonstrating that (near-)primary melt characteristics were largely preserved in the bulk lavas.…”

New geochemical and geochronological data on the Cenozoic Veneto Volcanic Province: Geodynamic inferences

“…Noteworthy, the importance of slab tears in controlling a) convective mantle cells around slabs and b) triggering of magmatic occurrences variously influenced (or even not influenced) by subduction related fluids has been convincingly proposed by Faccenna et al (2007). Such process seems to be effective to explain the Cenozoic spatio-temporal association of volcanic products having distinct magmatic affinity in and around the Italian peninsula (e.g., Southern Tyrrhenian, Sicily; Bianchini et al, 2008;De Ritis et al, 2019;Barreca et al, 2020), as well as to explain the occurrence of post-collisional intraplate magmatism in other areas of the world, e.g., in the Western Anatolia (Dilek and Altunkaynak, 2009;Prelević et al, 2015) and East Carpathian (Bracco Gartner et al, 2020).…”