The role of carbon from recycled sediments in the origin of ultrapotassic igneous rocks in the Central Mediterranean

Abstract

The Central Mediterranean region is one of the most important areas on Earth for studying subduction-related potassic and ultrapotassic magmatism, derived from partial melting of the metasomatised lithospheric mantle wedge. In this region, leucite-free (i.e., lamproite) and leucite-bearing (i.e., kamafugite, leucitite, and plagioleucitite) ultrapotassic rocks closely occur, in a time-related progression, linked to the evolution of both the mantle source and the regional tectonic regime. Time- and space-related magmatism migration followed the roll-back of the subducting slab and the anticlockwise drift of the Italian Peninsula. Leucite-free silica-rich lamproites are restricted to the early stage of magmatism and are associated with ultrapotassic shoshonites and high-K calc-alkaline volcanic rocks. Leucite-bearing (i.e., Roman Province) rocks are erupted consistently later than lamproite-like and associated shoshonitic rocks, with post-leucititic volcanism occurring in the late stage of volcanic activity with eruption of alkali-basaltic to latitic and trachytic rocks, often after major caldera-forming events. Present-day ultrapotassic volcanism is restricted to the Neapolitan area. Central Mediterranean potassic and ultrapotassic rocks are extremely enriched in incompatible trace elements with variable fractionation of Ta, Nb, and Ti in comparison to Th and large ion lithophile elements (LILE). They are also variably enriched in radiogenic Sr and Pb and unradiogenic Nd. The main geochemical and isotopic signatures are consistent with sediment recycling within the mantle wedge via subduction. A twofold metasomatism, induced by the recycle of pelitic sediments and dehydration of lawsonite-bearing schists generates the early metasomatic events that enriched the mantle wedge from which leucite-free ultrapotassic rocks (i.e., lamproite) were generated. Recycling of carbonate-rich pelites played an important role in the shift to silica-undersaturated ultrapotassic rocks (kalsilite- and leucite-bearing) of the classic ‘Roman province’

Conservation of 87 Sr/ 86 Sr isotopic ratios during the winemaking processes of ‘Red’ wines to validate their use as geographic tracer

“…On the other hands, vineyards from hills are characterised by substrata made up by Mesozoic to Tertiary sedimentary rocks (limestone, marlstone, sandstone; Critelli et al, 2007). 87 Sr/ 86 Sr determined on rocks and soils sampled from substrata of the vineyards of production of the wines considered in this study are well within the ranges of measured 87 Sr/ 86 Sr for volcanic and sedimentary rocks of the Cesanese area and of the Italian peninsula in general (Boari et al, 2009a;2009bConticelli et al, 2015. Marchionni et al (2013) has shown that at a very large scale 87 Marchionni et al (2013) have also shown that in some cases 87 Sr/ 86 Sr variability in wines is larger than expected from the analyses of the geological substratum (i.e., rocks).…”

“…In addition to wine, must, and grape, volcanic and sedimentary bedrocks along with soils from the vineyards of grape production have been sampled to verify the 87 Sr/ 86 Sr of the geological substrata of the Cesanese area in comparison with the available data for similar rocks (Conticelli et al, 2010(Conticelli et al, , 2015Boari et al, 2009a,b). In addition the 87 Sr/ 86 Sr from rocks and soil of the vineyards substrata are necessary to assess the existing relationships with the Sr isotope composition of wines.…”

The Vesuvius and the other volcanoes of Central Italy

“…In Italy ultrapotassic rocks are associated in time and space with calcalkaline lamprophyres, shoshonitic and high-K calc-alkaline volcanic rocks, and at Monticchio monogenetic field, within the Lucanian Magmatic Province, with carbonatite-like rocks (Avanzinelli et al, 2009;Conticelli et al, 2010aConticelli et al, , 2015a.…”

“…These rocks have variable enrichment in K 2 O. No definitive boundary between ultrapotassic groups and shoshonitic series has been drawn on the K 2 O vs. silica diagram (Peccerillo & Taylor, 1976); in some cases shoshonites are classified as ultrapotassic rocks (e.g., Conticelli et al, 2010bConticelli et al, , 2011Conticelli et al, , 2015a and they fall within the field of transitional group IV ultrapotassic rocks ( Fig. 2) according to the classification scheme of Foley et al (1987).…”

“…1). Indeed, the Roman province is characterised during the early phases of the magmatism (600-300 ka; Conticelli et al, 2010aConticelli et al, , 2013Conticelli et al, , 2015a by silica undersaturated ultrapotassic rocks dominated by leucite crystallisation with less sanidine and kalsilite. The Roman province shows a twofold age distribution with Latian volcanoes (districts) that ended their parossistic to lava emission at around 50 ka, whilst activity in the Neapolitan district (e.g., Somma-Vesuvius, Campi Flegrei, Procida and Ischia volcanoes) continued during the Holocene with last lava flow of 1944 AD.…”