G. Rosatelli

Is there a mantle plume below Italy

Some of the most diverse igneous rocks found on Earth occur along the length of Italy and in many of the islands in the southeastern Tyrrhenian Sea, all the result of Cenozoic magmatism. Magmas extremely rich in alkalis, particularly potassium, and many undersaturated with respect to silica, were erupted, as well as others of calc-alkalic affinity (see legend in Figure 1). Their origin has been the subject of heated debate, and there is still no general consensus about how they formed. Most attribute them to subduction-related processes (see Beccaluva et al. [2004] for a review); others consider them to be the result of within-plate magmatism [e.g., Vollmer, 1976; Lauecchia and Stoppa, 1996]. Still others consider magmatism the result of a deep, mantle upwelling within a slab window coupled with mixing between isotopically different reservoirs [Gasperini et al., 2002].

Intrusive calcite-carbonatite occurrence from Mt. Vulture volcano, southern Italy

Abstract Intrusive calcite-carbonatite ejecta (sovite) in the lowermost tephra layers of the Mt. Vulture alkaline mafic-ultramafic volcano (Upper Pleistocene), is the first intrusive carbonatite sample from southern Europe. The sovite is of coarse granularity and shows some textural and mineralogical layering. It is mainly formed of calcite (up to 3.5 wt.% MgO, and 0.53 wt.% SrO), less dolomite (average 18.2 wt.% MgO, and up to 2.1 wt.% SrO), spinel (60 wt.% Al2O3, 26.5 wt.% MgO, 10.7 wt.% FeO) and olivine (Fo99). Perovskite and apatite have been found only as microlites. Intergranular vugs are scattered throughout the rocks and small composite inclusions occur in calcite. The mineral chemistry, high temperature melt inclusions, overall isotopic compositions, and the REE distribution are consistent with a primary igneous origin. Compared with world average sovite compositions, the Vulture sovite has lower LILE and HFSE but Rb, Sr, Th and U are high. The REE abundance is typical of carbonatites, having an LREE/HREE value of ~100. The δ13C ( 4.8% SMOW) is in the range for mantle-derived carbonatites. The 143Nd/144Nd (0.512648±15) and 87Sr/86Sr (0.705978±10) ratios show close similarity between the sovite and the Vulture alkaline mafic rocks. The sovite ejecta are interpreted as a crystallization product of carbonate ultramafic liquid. In common with many shallow-level carbonatites from other localities, the recrystallization of rather pure Mg-calcite, the presence of dissolution vugs and the depletion of some HFSE and the relatively high δ18O values, suggest that a secondary process, such as hydrothermal leaching, affected the rock.

Crystal chemistry of phlogopite from Vulture-S. Michele Subsynthem volcanic rocks (Mt. Vulture, Italy) and volcanological implications

Abstract Volcanic activity at Mt. Vulture lasted about 750 ka and produced SiO2-undersaturated volcanic rocks that can be classified as old (~700 ka), intermediate (~600-550 ka), and young (~130 ka). The intermediate deposits consist of pyroclastic falls and flows and lavas with compositions ranging from phonolite to foidite. A recent revision of the stratigraphic setting allowed these deposits to be classified into one synthem (the Barile Synthem) and further subdivided into four subsynthems (Toppo S. Paolo, Rionero, Vulture-S. Michele, and Ventaruolo). In the present investigation, trioctahedral micas from sample VUT191 in the Vulture-S. Michele Subsynthem are considered. The host rock has modal diopside (20.2%), analcime (22.8%), plagioclase (27.8%), haüyne (5%), phlogopite (8.9%), and magnetite (6.3%). The micas were studied using chemical (EPMA, C-H-N, SIMS), structural (SCXRD), and spectroscopic (Mössbauer) methods. EPMA of 36 crystals from thin sections and 6 discrete crystals selected for the structural analysis showed remarkable compositional variability, as follows (in wt%): SiO3 = 33.14-38.01, Al2O3 = 15.56-20.45, MgO = 13.02-20.81, FeOtot = 6.34-14.08, TiO2 = 2.34-6.02, K2O = 6.03-9.48, Na2O = 0.50-0.78, and BaO = 0.89-4.06; all crystals proved to be phlogopite. Elemental C-H-N analyses yielded H2O = 2.86 ± 0.36 wt%. The water content was also determined by SIMS on two single crystals, labeled VUT191_2 and VUT191_19, which yielded values of 3.81 ± 0.12 and 1.72 ± 0.08 wt% H2O, respectively. Mössbauer investigation showed that all the iron in VUT191 mica is octahedral with Fe2+ = 25.5% and Fe3+ = 74.5%, confirming that Vulture micas are particularly Fe3+-rich, as also found from previous investigations. Structure refinements using anisotropic displacement parameters were performed in space group C2/m and converged at 1.89 ≤ R ≤ 3.17, 2.09 ≤ Rw ≤ 3.43%. All of the analyzed micas belong to the 1M polytype but exhibit remarkable variations in the c parameter from 10.1569(4) to 10.2458(4) Å. The chemical and structural parameters indicate that the studied micas can be divided into two groups: the first encompassing strongly dehydrogenated micas affected mainly by Ti-oxy [VIM2+ + 2(OH)- ↔ VITi4+ + 2O2- + H2] and M3+-oxy [VIM2+ + (OH)- ↔ VIM3+ + O2- + ½H2, with M3+ = Fe3+, Al3+] substitutions. The second group consist of samples in which vacancy-bearing mechanisms, 2 VIM2+ ↔ VITi4+ + VI□ and 3VIM2+ ↔ 2VIM3+ + VI□ occur.

Hydrovolcanic vs Magmatic Processes in Forming Maars and Associated Pyroclasts: The Calatrava -Spain- Case History

The Calatrava Volcanic Field (CVF) of Castilla-La Mancha is characterised by numerous monogenetic volcanic centres, that erupted mainly foidites, melilitites and carbonatites (ultra-alkaline rock-association sensu, Le Bas, 1981) carrying abundant mantle xenoliths. At CVF, carbonatites have been described by Bailey et al. (2005) and Stoppa et al. (2011). Along with the volcanic field of Eifel of Germany, Limagne basin of France and Intra-mountain Ultra-alkaline Province (IUP) of Italy, the CVF encompasses the most numerous PlioceneQuaternary extrusive carbonatites in Western Europe in terms of dimension, number and size of volcanoes (Bailey et al., 2005; Bailey et al., 2006). Similar volcanic fields are ToroAkole and Bufumbira in Uganda (Bailey & Collier, 2000), the Avon district in Missouri (Callicoat et al., 2008), Mata da Corda in Brazil (Junqueira-Brod et al., 1999) and West Qinling in Gansu Province, China (Yu et al., 2003). In spite of abundant local studies (Gonzalez Cardenas et al., 2010; Peinado et al., 2009), the CVF has been mostly neglected by the international audience, although Bailey (2005) outlined the need for a long-term research program on CVF. This work focuses on the role of deep CO2 at CVF, which is considered an intrinsic component of carbonatitic mantle magmatism (Hamilton et al., 1979). Previous, studies of CVF volcanoes considered that the hydrovolcanism is a necessary and sufficient condition to explain the CVF volcanological features, and, as a corollary that the carbonate present in the pyroclastic rocks is remobilised limestones (e.g., Lopez-Ruiz et al., 2002). We propose an alternative hypotheses based on CO2 violent exolution and expansion germane to diatremic propagation of ultra-alkaline melts towards the surface and to dry-magmatic origin of the maars (Mattsson & Tripoli, 2011; Stoppa, 1996; Stoppa & Principe, 1998).

Phlogopite from the Ventaruolo subsynthem volcanics (Mt Vulture, Italy): a multi-method study

Abstract Volcanic activity at Mt Vulture lasted throughout the Middle Pleistocene and produced SiO2⃛ undersaturated volcanics. Deposits from the Monte Vulture stratovolcano have been classified into four subsynthems and clustered into the Barile Synthem. In the present investigation, trioctahedral micas from the uppermost units (the Ventaruolo Subsynthem) of the Barile Synthem are considered. The samples are labelled VUT187. The phlogopitic micas were separated from the host rock (an olivine-foidite) and underwent chemical (electron microprobe analysis - EMPA and C-H-N), structural (single-crystal X-ray diffraction) and spectroscopic (Mössbauer) investigations. The EMPA yielded: MgO (17.62-21.89 wt.%), FeOtot (5.98-9.78 wt.%), TiO2 (1.81-3.92 wt.%) and Al2O3 (14.47-17.98 wt.%), with H2O contents = 2.86 (±0.42) wt.% determined by C-H-N analyses. Mössbauer investigation provided [VI]Fe2+ = 12.6%, [VI]Fe3+ = 87.4%. The chemical and structural data are consistent with the occurrence of Ti-oxy, [VI]M2+ + 2(OH)- ⇌ [VI]Ti4+ + 2O2- + H2, and M3+-oxy substitutions, [VI]M2+ + (OH)- ⇌ [VI]M3+ + O2⃛ + ½H2, with M3+ = Fe3+, Al3+. In particular, Fe3+-oxy substitution has affected the Fe2+/Fe3+ ratio in the studied sample. This is probably due to the fact that interaction with underground water or a hydrothermal system may have altered the oxygen fugacity and raised the Fe3+ content of VUT187 phlogopite with respect to magmatic values.

Comment on Melluso et al. (2003) Reported data and interpretation of some wollastonite- and melilite-bearing rocks from the Central Apennines of Italy

Abstract Two distinct occurrences of wollastonite- and melilite-bearing rocks from Ricetto and Colle Fabbri, which are located in the central Italy Apennine Range, are referred to as “paralavas” generated by melting and recrystallization of marly sediments “likely due to coal fires” by Melluso et al. (2003). We submit data demonstrating that these conclusions are incorrect. Ricetto is clearly pyrometamorphic, as described by Capitanio et al. (2001, 2004). Colle Fabbri is clearly an igneous outcrop as described in Stoppa (1988). It is quite different in scale, field relationships, and chemistry, and thus Ricetto is irrelevant to its petrogenesis. The sediment mixing model of Melluso et al. (2003) does not relate to the Colle Fabbri field data. Furthermore, the Ricetto Miocene flysch country-rock and the Colle Fabbri enclosing Pliocene clays were not analyzed by Melluso et al. (2003). A limestone-shale mixing calculation using Sr and Nd isotopic data in Melluso et al. (2003, Tables 3.4) and a 143Nd/144Nd ratio of 0.51213 for Apennine shales (op.cit. p. 1297) fails to account for the Colle Fabbri samples, which remain well clear of the hypothetical mixing line. Rocks of mantle origin, including micaceous kimberlites and Western Australia lamproites, plot in the variation field of Colle Fabbri and regionally associated igneous rocks. Colle Fabbri is but one of a series of similar igneous melilite-bearing and carbonatite occurrences that constitute the Intramontane Ultra-alkaline Province of central Italy (IUP), although Colle Fabbri does have unique features, as do other of these occurrences (Stoppa et al. 2003).

Phthalates, heavy metals and PAHs in an overpopulated coastal region: Inferences from Abruzzo, central Italy

Phthalates are an emerging class of environmental pollutants whose distribution and effects in aquatic environments are not well characterized. We analyzed intertidal and emerged beach sediments from the Abruzzo coastline, along the Adriatic Sea, finding significant phthalate concentrations in marine sediments. Phthalate baseline levels in the intertidal environment, marked by substantial interplay of sediment, water and air, were determined. We used statistical rank methods to select representative phthalate compositions, for which we derived risk levels for ingestion, dermal absorption and inhalation. Our study shows that phthalates are a major cause of pollution along the Abruzzo coast, with river transport of sediments a continuous source of replenishment. Phthalate concentrations in two specific sites were determined to be of the same order of magnitude as the safety, remediation-warranting, threshold set by Italian law. Phthalates, heavy metals, PAHs appear to be correlated. We discuss possible intervention and mitigation strategies.

CommentonReported data and interpretation of some wollastonite- and melilite-bearing rocks from the Central Apennines of Italy

Abstract Two distinct occurrences of wollastonite- and melilite-bearing rocks from Ricetto and Colle Fabbri, which are located in the central Italy Apennine Range, are referred to as “paralavas” generated by melting and recrystallization of marly sediments “likely due to coal fires” by Melluso et al. (2003). We submit data demonstrating that these conclusions are incorrect. Ricetto is clearly pyrometamorphic, as described by Capitanio et al. (2001, 2004). Colle Fabbri is clearly an igneous outcrop as described in Stoppa (1988). It is quite different in scale, field relationships, and chemistry, and thus Ricetto is irrelevant to its petrogenesis. The sediment mixing model of Melluso et al. (2003) does not relate to the Colle Fabbri field data. Furthermore, the Ricetto Miocene flysch country-rock and the Colle Fabbri enclosing Pliocene clays were not analyzed by Melluso et al. (2003). A limestone-shale mixing calculation using Sr and Nd isotopic data in Melluso et al. (2003, Tables 3.4) and a 143Nd/144Nd ratio of 0.51213 for Apennine shales (op.cit. p. 1297) fails to account for the Colle Fabbri samples, which remain well clear of the hypothetical mixing line. Rocks of mantle origin, including micaceous kimberlites and Western Australia lamproites, plot in the variation field of Colle Fabbri and regionally associated igneous rocks. Colle Fabbri is but one of a series of similar igneous melilite-bearing and carbonatite occurrences that constitute the Intramontane Ultra-alkaline Province of central Italy (IUP), although Colle Fabbri does have unique features, as do other of these occurrences (Stoppa et al. 2003).

Comment on Mellusoetal. (2003)

Abstract Two distinct occurrences of wollastonite- and melilite-bearing rocks from Ricetto and Colle Fabbri, which are located in the central Italy Apennine Range, are referred to as “paralavas” generated by melting and recrystallization of marly sediments “likely due to coal fires” by Melluso et al. (2003). We submit data demonstrating that these conclusions are incorrect. Ricetto is clearly pyrometamorphic, as described by Capitanio et al. (2001, 2004). Colle Fabbri is clearly an igneous outcrop as described in Stoppa (1988). It is quite different in scale, field relationships, and chemistry, and thus Ricetto is irrelevant to its petrogenesis. The sediment mixing model of Melluso et al. (2003) does not relate to the Colle Fabbri field data. Furthermore, the Ricetto Miocene flysch country-rock and the Colle Fabbri enclosing Pliocene clays were not analyzed by Melluso et al. (2003). A limestone-shale mixing calculation using Sr and Nd isotopic data in Melluso et al. (2003, Tables 3.4) and a 143Nd/144Nd ratio of 0.51213 for Apennine shales (op.cit. p. 1297) fails to account for the Colle Fabbri samples, which remain well clear of the hypothetical mixing line. Rocks of mantle origin, including micaceous kimberlites and Western Australia lamproites, plot in the variation field of Colle Fabbri and regionally associated igneous rocks. Colle Fabbri is but one of a series of similar igneous melilite-bearing and carbonatite occurrences that constitute the Intramontane Ultra-alkaline Province of central Italy (IUP), although Colle Fabbri does have unique features, as do other of these occurrences (Stoppa et al. 2003).