Abstract The small Plio-Quaternary volcanic centre of Cabezo Negro de Tallante in SE Spain includ... more Abstract The small Plio-Quaternary volcanic centre of Cabezo Negro de Tallante in SE Spain includes a thick deposit of polymictic pyroclastic tuff-breccia, whose fragments are agglutinated by a carbonate-rich component. This feature is also observed in other monogenetic volcanic centres cropping out in the Tallante-Cartagena volcanic district. The carbonate fraction has been recently interpreted in literature as representing a mantle component, therefore pointing to the existence of a diffuse carbonatitic activity in the area. Based on detailed sedimentological (presence of pisoids and root remnants), petrographic (presence of plagioclase and absence of euhedral silicate minerals in the calcite plagues), mineral chemistry (Ba-Sr-poor calcite composition), whole-rock chemistry (overall low incompatible element content in the pure carbonate fraction and a monotonous trace element negative correlation with CaO) as well as isotopic constraints (perfect correlation between Sr-Nd-Pb isotopic ratios with CaO in the basaltic and carbonate fraction, as well as heavy δ18O and light δ13C isotopic composition of the carbonate fraction), we propose a secondary origin for the carbonate component, excluding any contribution of mantle carbonatite melts. The presence of carbonates infiltrating the abundant mantle and crustal xenolith fragments found in the pyroclastic breccia is not related to the presence of carbonatitic melts at mantle to lower crustal depths, but to in-situ fragmentation of the Strombolian tuff-breccia deposit, followed by secondary carbonate infiltration. The pyroclastic breccia was indeed affected by an alternation of carbonate precipitation and dissolution in a vadose zone, where the activity of bacteria, fungi, roots and meteoric water led to the formation of a calcrete (caliche)-type deposits. Basaltic rocks (hawaiites and basanites) occur in the area as scoria and lava fragments in the pyroclastic breccia as well as small lava flows. They have been modelled with a low-degree partial melting of an amphibole-bearing peridotitic mantle close to the lithosphere-asthenosphere boundary. The origin of the mildly alkaline sodic basaltic activity in SE Spain post-dates the abundant and long-lasting subduction-related volcanic phase in the Betic Chain. Its origin is explained without requiring the presence of any thermal anomaly, but simply as consequence of the difference of lithospheric depths and edge-driven-type small-scale convection.
<div> <p>The northernmost sector of the western branch of the East Af... more <div> <p>The northernmost sector of the western branch of the East African Rift (EAR) includes the young (~40-50 ka [1]) volcanic province of Toro Ankole, characterized by the presence of exotic volcanic products such as carbonatites, melilitites, kamafugites and foidites [2]. Among these, the occurrence of kamafugites (kalsilite-bearing volcanic rocks [3]) is noteworthy, as Toro Ankole represents the type locality for these compositions, found in only two other localities worldwide. The Toro Ankole volcanic province developed along the margin of the Archean Tanzanian craton, and its magmatic products show the influence of metasomatic processes and phases developed in the thick continental lithosphere. Indeed, MARID-like metasomatism is proposed in literature, with the formation of a veined mantle [4].</p> <p>A multidisciplinary approach, based on a detailed petrographic, mineral chemical, geochemical and isotopic (Sr, Nd, Pb and B) study, has been carried out on 53 samples, which include not only lavas and tuffs, but also holocrystalline and wall rock xenoliths. Two types of lava may be identified: the first is represented by carbonatites and silico-carbonatites, characterized by low SiO<sub>2</sub> (4.89-21.78 wt%) and low alkali (0.44-2.03 wt%) and high CaO (25.17-47.57 wt%), while the second most peculiar lithotypes is represented by kamafugites; katungites (melilite-rich kalsilite-olivine-bearing volcanic rocks), mafurites (kalsilite-rich melilite-olivine-bearing) and ugandites (olivine-rich kalsilite-melilite-bearing). The kamafugites are strongly SiO<sub>2</sub>-undersaturated and moderately ultrabasic, potassic to ultrapotassic volcanic rocks, with high MgO (6.08-22.20 wt%) and CaO (up to 15.46 wt%). They consist of phenocrysts of clinopyroxene and olivine set in a hypo-holocrystalline fine-grained groundmass made up of microliths of clinopyroxene, olivine, perovskite, kalsilite, nepheline, leucite, melilite, phlogopite, carbonates and opaques.</p> <p>The xenolith cargo shows wide range of compositions, varying from clinopyroxenite to glimmerite, with low modal abundance of opaques and perovskite in agreement with the literature data that generally report a lack of olivine and orthopyroxene in the mineral assemblage [5]. The common presence of phlogopite, abundant clinopyroxene and carbonate-rich veins indicate the presence of veined lithosphere [6]. This is consistent with the isotopic data for lavas and xenoliths (<sup>87</sup>Sr/<sup>86</sup>Sr = 0.70480-0.70563 and <sup>143</sup>Nd/<sup>144</sup>Nd = 0.512515-0.512575), which outlines an enriched and complex mantle source. <sup>206</sup>Pb/<sup>204</sup>Pb is extremely variable, with values from the holocrystalline xenolith (19.99-19.27) being slightly higher than lava samples (19.28-19.63). The d<sup>11</sup>B values for lavas and xenoliths, show a wide range, varying from DMM-like values (-6 and -8‰) to more variable OIB-like values (down to -12 and up to -3‰; [7]), through to positive values (up to +6.6‰ in the lavas). These latter also exhibit the highest Sr isotopic ratios of the dataset, pointing to the possible occurrence of old and altered oceanic crust and/or serpentinite in the mantle source.</p> <p><strong>Bibliography </strong></p> </div><p>[1] Boven et al., 1998, <em>J. Afr. Earth Sci.</em>, 26, 463-476.</p><p>[2] Holmes and Harwood, 1932, <em>Quarterly J. Geol. Soc.</em>, 88, 370-442.</p><p>[3] Le Maitre, 2002, Cambridge University Press.</p><p>[4] Rosenthal et al., 2009, <em>Earth Planet. Sci. Lett.</em>, 284, 236-248.</p><p>[5] Link et al., 2008, 9<sup>th</sup> Int. Kimb. Conf., 1-3.</p><p>[6] Foley, 1992, Lithos, 28, 435-453.</p><p>[7] Agostini et al., 2021, Sci. Rep., https://doi.org/10.1038/s41598-021-90275-7.</p>
ABSTRACT The present-day northern Apennines represent an area where two different orogenic cycles... more ABSTRACT The present-day northern Apennines represent an area where two different orogenic cycles took place. The most ancient is the Alpine Orogeny, initiated with a south- to south-eastward subduction of oceanic lithosphere (Early Cretaceous to Late Eocene phase), followed by continental collision. The younger is referred to the Apennines Orogeny, characterized by a west- to north-westward oceanic lithosphere subduction started from Late Eocene and still active in the southernmost sectors of Italy (Calabrian Arc). In this framework, during the Early Oligocene, an ~ 800 m thick conglomeratic succession extremely rich in volcanic material (up to ~ 90% in volume) was deposited in the Northern Apennines, forming the Aveto-Petrignacola Formation (APF). The volcanic fraction of this succession is made up of basaltic andesites, andesites and dacites, with minor rhyolites, basalts and gabbros found as pebbles ~ 0.001-0.5 m3 in size. Petrographic, mineral chemical, major and trace element analyses, as well as Sr-Nd-Pb isotopic ratios are compatible with calc-alkaline magmatism generated as a consequence of metasomatic modifications related to the subduction of oceanic lithosphere. The large spectrum of lithologies is compatible with processes of fractional crystallization of the main phases observed in thin sections. However, the large range of isotopic ratios (87Sr/86Sr = 0.7044-0.71013; 143Nd/144Nd = 0.51278-0.51223; 206Pb/204Pb = 18.44-18.83; 207Pb/204Pb = 15.55-15.67; 208Pb/204Pb = 38.05-38.85) suggests the presence of heterogeneous mantle sources, possibly coupled with interaction of melts with crustal rocks at shallow depth.On the basis of field geology constraints, we propose that the subduction-related geochemical and mineralogical characteristics of the APF volcanic rocks reflect ancient modifications of their mantle sources, lacking any evidence for a genetic link with the Apennine subduction system. Subduction-related metasomatism of APF mantle sources likely occurred during the older south-east dipping subduction of the Alpine Tethys under Northern Adria (present day Northern Italy).
Geological Setting, Palaeoenvironment and Archaeology of the Red Sea, 2018
We present here 3D seismic reflection and gravity data obtained from an off-axis area of the NW R... more We present here 3D seismic reflection and gravity data obtained from an off-axis area of the NW Red Sea, as well as results of a study of gabbroic rocks recovered in the same area both from an oil well below a thick evaporitic-sedimentary sequence, and from a layered mafic complex exposed on the Brothers Islets. These new data provide constraints on the composition, depth of emplacement and age of early syn-rift magma intrusions into the deep crust. The Brothers are part of a series of sub-parallel NW-striking topographic highs associated with SW-dipping extensional fault blocks with significant footwall uplift during rifting that brought early syn-rift deep crustal rocks up to the seafloor. Assuming an important role played by magmatism in the evolution of narrow rifts helps to solve the controversy on the nature of the crust in the northern/central Red Sea (i.e., the crust outside the axial oceanic cells is either oceanic or it consists of melt-intruded extended continental crust). Gabbros show petrologic and geochemical signatures similar to those of MORB-type gabbroic cumulates and are compatible with their having been emplaced either in a continental or in an oceanic context. We explored the different hypotheses proposed to explain the lack of magnetic anomalies in the presence of oceanic crust in the northern Red Sea. Our results, combined with a review of all the geophysical and geological data in the area, suggest a stretched and thinned continental crust with few isolated sites of basaltic injections, in line with a model whereby asthenospheric melt intrusions contribute to weaken the lower crust enabling some decoupling between upper and lower crust, protracting upper crust extension and delaying crustal breakup. Our findings show that continental rupture in the northern Red Sea is preceded by intrusion of basaltic melts with MORB-type elemental and isotopic signature, that cooled forming gabbros at progressively shallower crustal depths as rifting progressed toward continental separation.
Abstract The small Plio-Quaternary volcanic centre of Cabezo Negro de Tallante in SE Spain includ... more Abstract The small Plio-Quaternary volcanic centre of Cabezo Negro de Tallante in SE Spain includes a thick deposit of polymictic pyroclastic tuff-breccia, whose fragments are agglutinated by a carbonate-rich component. This feature is also observed in other monogenetic volcanic centres cropping out in the Tallante-Cartagena volcanic district. The carbonate fraction has been recently interpreted in literature as representing a mantle component, therefore pointing to the existence of a diffuse carbonatitic activity in the area. Based on detailed sedimentological (presence of pisoids and root remnants), petrographic (presence of plagioclase and absence of euhedral silicate minerals in the calcite plagues), mineral chemistry (Ba-Sr-poor calcite composition), whole-rock chemistry (overall low incompatible element content in the pure carbonate fraction and a monotonous trace element negative correlation with CaO) as well as isotopic constraints (perfect correlation between Sr-Nd-Pb isotopic ratios with CaO in the basaltic and carbonate fraction, as well as heavy δ18O and light δ13C isotopic composition of the carbonate fraction), we propose a secondary origin for the carbonate component, excluding any contribution of mantle carbonatite melts. The presence of carbonates infiltrating the abundant mantle and crustal xenolith fragments found in the pyroclastic breccia is not related to the presence of carbonatitic melts at mantle to lower crustal depths, but to in-situ fragmentation of the Strombolian tuff-breccia deposit, followed by secondary carbonate infiltration. The pyroclastic breccia was indeed affected by an alternation of carbonate precipitation and dissolution in a vadose zone, where the activity of bacteria, fungi, roots and meteoric water led to the formation of a calcrete (caliche)-type deposits. Basaltic rocks (hawaiites and basanites) occur in the area as scoria and lava fragments in the pyroclastic breccia as well as small lava flows. They have been modelled with a low-degree partial melting of an amphibole-bearing peridotitic mantle close to the lithosphere-asthenosphere boundary. The origin of the mildly alkaline sodic basaltic activity in SE Spain post-dates the abundant and long-lasting subduction-related volcanic phase in the Betic Chain. Its origin is explained without requiring the presence of any thermal anomaly, but simply as consequence of the difference of lithospheric depths and edge-driven-type small-scale convection.
<div> <p>The Pleistocene Intra-Apennine Province (IAP... more <div> <p>The Pleistocene Intra-Apennine Province (IAP) in central Italy contains several small volume eruptive centres, characterized by basic-ultrabasic lithologies, often characterized also by ultracalcic and ultrapotassic compositions. They are emplaced above the thick carbonate and evaporite sedimentary sequence of the Apennine Chain. The small monogenetic volcano of Cupaello (~640 ka) offers the chance to investigate exotic volcanic rocks such as ultracalcic kamafugites, known in literature as coppaelite. This volcano also offers the opportunity to study the interaction of ultrabasic melts with sedimentary carbonates (Maiolica Formation). Indeed, assimilation of local carbonate-rich sediments has been already documented as a likely process at least in the neighbouring IAP volcanoes of San Venanzo [1] and Polino [2] volcanoes. On the other hand, alternative views considers the CaO-rich (CaO up to 38.8 wt%) and SiO<sub>2</sub>-poor (SiO<sub>2 </sub>down to 14.2 wt%) composition of some Cupaello pyroclastic rocks a reflection of a carbonatitic component in their mantle source [3].</p> <p> Cupaello lavas are ultrabasic (silica = 42.6-44.1 wt%) and ultrapotassic (K<sub>2</sub>O = 5.2-7.6 wt%; K<sub>2</sub>O/Na<sub>2</sub>O = 18.0-33.9) rocks, characterized by euhedral to subhedral phenocrysts of clinopyroxene and phlogopite set in a hypohyaline-hypocrystalline groundmass made of melilite, kalsilite, phlogopite, olivine, calcite and glass. Perovskite, opaques, wollastonite, monticellite and apatite represent the accessory phases.</p> <p>The trace element signatures of Cupaello kamafugites, such as high LILE (e.g., Rb = 482-673 ppm), high LILE/HFSE ratios (Ba/Nb = 71-82), negative Eu anomalies (Eu/Eu* = 0.68-0.72), as well as the presence of negative anomalies for Nb, Ta, P and Ti coupled with peaks for Pb in primitive mantle-normalized diagrams are compatible with the derivation from a subduction-modified source [4]. Isotopic ratios confirm this hypothesis, with the presence of strongly radiogenic <sup>87</sup>Sr/<sup>86</sup>Sr (0.71123-0.71125), unradiogenic <sup>143</sup>Nd/<sup>144</sup>Nd (0.51200-0.51207) and <sup>206</sup>Pb/<sup>204</sup>Pb isotopic ratios buffered to 18.76.</p> <p>The negative correlation of major oxides and trace elements with CaO, pointing toward an end-member represented by the Apennines limestone lithologies, offers an alternative hypothesis to the widely accepted presence of a carbonatitic component. The very small volume of emplaced magma, as well as the thick carbonate succession to be pierced to reach the surface renders unavoidable strong crustal assimilation by the original magma. The high Fo (89.5-90.2) in Cupaello olivine, as well as the thin border of monticellite around the rare olivine could be explained by assimilation of limestone wall rock, as demonstrated experimentally [5]. The CaO-richest (CaO up to 38.8 wt%) and SiO<sub>2</sub>-poorest (SiO<sub>2</sub> down to 14.2 wt%) compositions are found in pyroclastic/epiclastic deposits (no longer available for sampling). We believe that these whole-rock compositions reflect the presence of abundant, almost completely sterile, secondary calcite.</p> <p><strong>Bibliography </strong></p> </div><p> </p><div> <p>[1] Lustrino et al., 2020, Earth-Sci. Rev., 208, 103256.</p> <p>[2] Lustrino et al., 2019, Sci. Rep., 9, 1-14.</p> <p>[3] Stoppa and Cundari, 1995, Contrib. Mineral. Petrol., 122, 275-288.</p> <p>[4] Carminati et al., 2012, Tectonophysics., 579, 173-192.</p> <p>[5] Lustrino et al., 2022, Geology, https://doi.org/10.1130/G49621.1</p> </div>
Good conservation and restoration practices of cultural heritage assets rely on the knowledge of ... more Good conservation and restoration practices of cultural heritage assets rely on the knowledge of original materials. In the framework of the HERACLES Project (HERACLES—HEritage Resilience Against CLimate Events on Site, H2020 Grant Agreement 700395), dealing with the effects of climatic actions and natural hazards on built heritage, a set of important heritage sites are currently under study to improve their resilience against climate events. Among these are the medieval Gubbio Town Walls in Italy. The present work focuses on the mortars and binders of this monument and collected samples related to different parts of the Walls, corresponding to various historical periods of construction and interventions. They were characterized to determine their minerochemical composition, thermal behavior, and morphology. For that purpose, ex-situ laboratory techniques, such as X-ray diffraction (XRD), wavelength dispersive X-ray fluorescence (WDXRF), optical microscopy (OM), polarized light micr...
Abstract The small Plio-Quaternary volcanic centre of Cabezo Negro de Tallante in SE Spain includ... more Abstract The small Plio-Quaternary volcanic centre of Cabezo Negro de Tallante in SE Spain includes a thick deposit of polymictic pyroclastic tuff-breccia, whose fragments are agglutinated by a carbonate-rich component. This feature is also observed in other monogenetic volcanic centres cropping out in the Tallante-Cartagena volcanic district. The carbonate fraction has been recently interpreted in literature as representing a mantle component, therefore pointing to the existence of a diffuse carbonatitic activity in the area. Based on detailed sedimentological (presence of pisoids and root remnants), petrographic (presence of plagioclase and absence of euhedral silicate minerals in the calcite plagues), mineral chemistry (Ba-Sr-poor calcite composition), whole-rock chemistry (overall low incompatible element content in the pure carbonate fraction and a monotonous trace element negative correlation with CaO) as well as isotopic constraints (perfect correlation between Sr-Nd-Pb isotopic ratios with CaO in the basaltic and carbonate fraction, as well as heavy δ18O and light δ13C isotopic composition of the carbonate fraction), we propose a secondary origin for the carbonate component, excluding any contribution of mantle carbonatite melts. The presence of carbonates infiltrating the abundant mantle and crustal xenolith fragments found in the pyroclastic breccia is not related to the presence of carbonatitic melts at mantle to lower crustal depths, but to in-situ fragmentation of the Strombolian tuff-breccia deposit, followed by secondary carbonate infiltration. The pyroclastic breccia was indeed affected by an alternation of carbonate precipitation and dissolution in a vadose zone, where the activity of bacteria, fungi, roots and meteoric water led to the formation of a calcrete (caliche)-type deposits. Basaltic rocks (hawaiites and basanites) occur in the area as scoria and lava fragments in the pyroclastic breccia as well as small lava flows. They have been modelled with a low-degree partial melting of an amphibole-bearing peridotitic mantle close to the lithosphere-asthenosphere boundary. The origin of the mildly alkaline sodic basaltic activity in SE Spain post-dates the abundant and long-lasting subduction-related volcanic phase in the Betic Chain. Its origin is explained without requiring the presence of any thermal anomaly, but simply as consequence of the difference of lithospheric depths and edge-driven-type small-scale convection.
<div> <p>The northernmost sector of the western branch of the East Af... more <div> <p>The northernmost sector of the western branch of the East African Rift (EAR) includes the young (~40-50 ka [1]) volcanic province of Toro Ankole, characterized by the presence of exotic volcanic products such as carbonatites, melilitites, kamafugites and foidites [2]. Among these, the occurrence of kamafugites (kalsilite-bearing volcanic rocks [3]) is noteworthy, as Toro Ankole represents the type locality for these compositions, found in only two other localities worldwide. The Toro Ankole volcanic province developed along the margin of the Archean Tanzanian craton, and its magmatic products show the influence of metasomatic processes and phases developed in the thick continental lithosphere. Indeed, MARID-like metasomatism is proposed in literature, with the formation of a veined mantle [4].</p> <p>A multidisciplinary approach, based on a detailed petrographic, mineral chemical, geochemical and isotopic (Sr, Nd, Pb and B) study, has been carried out on 53 samples, which include not only lavas and tuffs, but also holocrystalline and wall rock xenoliths. Two types of lava may be identified: the first is represented by carbonatites and silico-carbonatites, characterized by low SiO<sub>2</sub> (4.89-21.78 wt%) and low alkali (0.44-2.03 wt%) and high CaO (25.17-47.57 wt%), while the second most peculiar lithotypes is represented by kamafugites; katungites (melilite-rich kalsilite-olivine-bearing volcanic rocks), mafurites (kalsilite-rich melilite-olivine-bearing) and ugandites (olivine-rich kalsilite-melilite-bearing). The kamafugites are strongly SiO<sub>2</sub>-undersaturated and moderately ultrabasic, potassic to ultrapotassic volcanic rocks, with high MgO (6.08-22.20 wt%) and CaO (up to 15.46 wt%). They consist of phenocrysts of clinopyroxene and olivine set in a hypo-holocrystalline fine-grained groundmass made up of microliths of clinopyroxene, olivine, perovskite, kalsilite, nepheline, leucite, melilite, phlogopite, carbonates and opaques.</p> <p>The xenolith cargo shows wide range of compositions, varying from clinopyroxenite to glimmerite, with low modal abundance of opaques and perovskite in agreement with the literature data that generally report a lack of olivine and orthopyroxene in the mineral assemblage [5]. The common presence of phlogopite, abundant clinopyroxene and carbonate-rich veins indicate the presence of veined lithosphere [6]. This is consistent with the isotopic data for lavas and xenoliths (<sup>87</sup>Sr/<sup>86</sup>Sr = 0.70480-0.70563 and <sup>143</sup>Nd/<sup>144</sup>Nd = 0.512515-0.512575), which outlines an enriched and complex mantle source. <sup>206</sup>Pb/<sup>204</sup>Pb is extremely variable, with values from the holocrystalline xenolith (19.99-19.27) being slightly higher than lava samples (19.28-19.63). The d<sup>11</sup>B values for lavas and xenoliths, show a wide range, varying from DMM-like values (-6 and -8‰) to more variable OIB-like values (down to -12 and up to -3‰; [7]), through to positive values (up to +6.6‰ in the lavas). These latter also exhibit the highest Sr isotopic ratios of the dataset, pointing to the possible occurrence of old and altered oceanic crust and/or serpentinite in the mantle source.</p> <p><strong>Bibliography </strong></p> </div><p>[1] Boven et al., 1998, <em>J. Afr. Earth Sci.</em>, 26, 463-476.</p><p>[2] Holmes and Harwood, 1932, <em>Quarterly J. Geol. Soc.</em>, 88, 370-442.</p><p>[3] Le Maitre, 2002, Cambridge University Press.</p><p>[4] Rosenthal et al., 2009, <em>Earth Planet. Sci. Lett.</em>, 284, 236-248.</p><p>[5] Link et al., 2008, 9<sup>th</sup> Int. Kimb. Conf., 1-3.</p><p>[6] Foley, 1992, Lithos, 28, 435-453.</p><p>[7] Agostini et al., 2021, Sci. Rep., https://doi.org/10.1038/s41598-021-90275-7.</p>
ABSTRACT The present-day northern Apennines represent an area where two different orogenic cycles... more ABSTRACT The present-day northern Apennines represent an area where two different orogenic cycles took place. The most ancient is the Alpine Orogeny, initiated with a south- to south-eastward subduction of oceanic lithosphere (Early Cretaceous to Late Eocene phase), followed by continental collision. The younger is referred to the Apennines Orogeny, characterized by a west- to north-westward oceanic lithosphere subduction started from Late Eocene and still active in the southernmost sectors of Italy (Calabrian Arc). In this framework, during the Early Oligocene, an ~ 800 m thick conglomeratic succession extremely rich in volcanic material (up to ~ 90% in volume) was deposited in the Northern Apennines, forming the Aveto-Petrignacola Formation (APF). The volcanic fraction of this succession is made up of basaltic andesites, andesites and dacites, with minor rhyolites, basalts and gabbros found as pebbles ~ 0.001-0.5 m3 in size. Petrographic, mineral chemical, major and trace element analyses, as well as Sr-Nd-Pb isotopic ratios are compatible with calc-alkaline magmatism generated as a consequence of metasomatic modifications related to the subduction of oceanic lithosphere. The large spectrum of lithologies is compatible with processes of fractional crystallization of the main phases observed in thin sections. However, the large range of isotopic ratios (87Sr/86Sr = 0.7044-0.71013; 143Nd/144Nd = 0.51278-0.51223; 206Pb/204Pb = 18.44-18.83; 207Pb/204Pb = 15.55-15.67; 208Pb/204Pb = 38.05-38.85) suggests the presence of heterogeneous mantle sources, possibly coupled with interaction of melts with crustal rocks at shallow depth.On the basis of field geology constraints, we propose that the subduction-related geochemical and mineralogical characteristics of the APF volcanic rocks reflect ancient modifications of their mantle sources, lacking any evidence for a genetic link with the Apennine subduction system. Subduction-related metasomatism of APF mantle sources likely occurred during the older south-east dipping subduction of the Alpine Tethys under Northern Adria (present day Northern Italy).
Geological Setting, Palaeoenvironment and Archaeology of the Red Sea, 2018
We present here 3D seismic reflection and gravity data obtained from an off-axis area of the NW R... more We present here 3D seismic reflection and gravity data obtained from an off-axis area of the NW Red Sea, as well as results of a study of gabbroic rocks recovered in the same area both from an oil well below a thick evaporitic-sedimentary sequence, and from a layered mafic complex exposed on the Brothers Islets. These new data provide constraints on the composition, depth of emplacement and age of early syn-rift magma intrusions into the deep crust. The Brothers are part of a series of sub-parallel NW-striking topographic highs associated with SW-dipping extensional fault blocks with significant footwall uplift during rifting that brought early syn-rift deep crustal rocks up to the seafloor. Assuming an important role played by magmatism in the evolution of narrow rifts helps to solve the controversy on the nature of the crust in the northern/central Red Sea (i.e., the crust outside the axial oceanic cells is either oceanic or it consists of melt-intruded extended continental crust). Gabbros show petrologic and geochemical signatures similar to those of MORB-type gabbroic cumulates and are compatible with their having been emplaced either in a continental or in an oceanic context. We explored the different hypotheses proposed to explain the lack of magnetic anomalies in the presence of oceanic crust in the northern Red Sea. Our results, combined with a review of all the geophysical and geological data in the area, suggest a stretched and thinned continental crust with few isolated sites of basaltic injections, in line with a model whereby asthenospheric melt intrusions contribute to weaken the lower crust enabling some decoupling between upper and lower crust, protracting upper crust extension and delaying crustal breakup. Our findings show that continental rupture in the northern Red Sea is preceded by intrusion of basaltic melts with MORB-type elemental and isotopic signature, that cooled forming gabbros at progressively shallower crustal depths as rifting progressed toward continental separation.
Abstract The small Plio-Quaternary volcanic centre of Cabezo Negro de Tallante in SE Spain includ... more Abstract The small Plio-Quaternary volcanic centre of Cabezo Negro de Tallante in SE Spain includes a thick deposit of polymictic pyroclastic tuff-breccia, whose fragments are agglutinated by a carbonate-rich component. This feature is also observed in other monogenetic volcanic centres cropping out in the Tallante-Cartagena volcanic district. The carbonate fraction has been recently interpreted in literature as representing a mantle component, therefore pointing to the existence of a diffuse carbonatitic activity in the area. Based on detailed sedimentological (presence of pisoids and root remnants), petrographic (presence of plagioclase and absence of euhedral silicate minerals in the calcite plagues), mineral chemistry (Ba-Sr-poor calcite composition), whole-rock chemistry (overall low incompatible element content in the pure carbonate fraction and a monotonous trace element negative correlation with CaO) as well as isotopic constraints (perfect correlation between Sr-Nd-Pb isotopic ratios with CaO in the basaltic and carbonate fraction, as well as heavy δ18O and light δ13C isotopic composition of the carbonate fraction), we propose a secondary origin for the carbonate component, excluding any contribution of mantle carbonatite melts. The presence of carbonates infiltrating the abundant mantle and crustal xenolith fragments found in the pyroclastic breccia is not related to the presence of carbonatitic melts at mantle to lower crustal depths, but to in-situ fragmentation of the Strombolian tuff-breccia deposit, followed by secondary carbonate infiltration. The pyroclastic breccia was indeed affected by an alternation of carbonate precipitation and dissolution in a vadose zone, where the activity of bacteria, fungi, roots and meteoric water led to the formation of a calcrete (caliche)-type deposits. Basaltic rocks (hawaiites and basanites) occur in the area as scoria and lava fragments in the pyroclastic breccia as well as small lava flows. They have been modelled with a low-degree partial melting of an amphibole-bearing peridotitic mantle close to the lithosphere-asthenosphere boundary. The origin of the mildly alkaline sodic basaltic activity in SE Spain post-dates the abundant and long-lasting subduction-related volcanic phase in the Betic Chain. Its origin is explained without requiring the presence of any thermal anomaly, but simply as consequence of the difference of lithospheric depths and edge-driven-type small-scale convection.
<div> <p>The Pleistocene Intra-Apennine Province (IAP... more <div> <p>The Pleistocene Intra-Apennine Province (IAP) in central Italy contains several small volume eruptive centres, characterized by basic-ultrabasic lithologies, often characterized also by ultracalcic and ultrapotassic compositions. They are emplaced above the thick carbonate and evaporite sedimentary sequence of the Apennine Chain. The small monogenetic volcano of Cupaello (~640 ka) offers the chance to investigate exotic volcanic rocks such as ultracalcic kamafugites, known in literature as coppaelite. This volcano also offers the opportunity to study the interaction of ultrabasic melts with sedimentary carbonates (Maiolica Formation). Indeed, assimilation of local carbonate-rich sediments has been already documented as a likely process at least in the neighbouring IAP volcanoes of San Venanzo [1] and Polino [2] volcanoes. On the other hand, alternative views considers the CaO-rich (CaO up to 38.8 wt%) and SiO<sub>2</sub>-poor (SiO<sub>2 </sub>down to 14.2 wt%) composition of some Cupaello pyroclastic rocks a reflection of a carbonatitic component in their mantle source [3].</p> <p> Cupaello lavas are ultrabasic (silica = 42.6-44.1 wt%) and ultrapotassic (K<sub>2</sub>O = 5.2-7.6 wt%; K<sub>2</sub>O/Na<sub>2</sub>O = 18.0-33.9) rocks, characterized by euhedral to subhedral phenocrysts of clinopyroxene and phlogopite set in a hypohyaline-hypocrystalline groundmass made of melilite, kalsilite, phlogopite, olivine, calcite and glass. Perovskite, opaques, wollastonite, monticellite and apatite represent the accessory phases.</p> <p>The trace element signatures of Cupaello kamafugites, such as high LILE (e.g., Rb = 482-673 ppm), high LILE/HFSE ratios (Ba/Nb = 71-82), negative Eu anomalies (Eu/Eu* = 0.68-0.72), as well as the presence of negative anomalies for Nb, Ta, P and Ti coupled with peaks for Pb in primitive mantle-normalized diagrams are compatible with the derivation from a subduction-modified source [4]. Isotopic ratios confirm this hypothesis, with the presence of strongly radiogenic <sup>87</sup>Sr/<sup>86</sup>Sr (0.71123-0.71125), unradiogenic <sup>143</sup>Nd/<sup>144</sup>Nd (0.51200-0.51207) and <sup>206</sup>Pb/<sup>204</sup>Pb isotopic ratios buffered to 18.76.</p> <p>The negative correlation of major oxides and trace elements with CaO, pointing toward an end-member represented by the Apennines limestone lithologies, offers an alternative hypothesis to the widely accepted presence of a carbonatitic component. The very small volume of emplaced magma, as well as the thick carbonate succession to be pierced to reach the surface renders unavoidable strong crustal assimilation by the original magma. The high Fo (89.5-90.2) in Cupaello olivine, as well as the thin border of monticellite around the rare olivine could be explained by assimilation of limestone wall rock, as demonstrated experimentally [5]. The CaO-richest (CaO up to 38.8 wt%) and SiO<sub>2</sub>-poorest (SiO<sub>2</sub> down to 14.2 wt%) compositions are found in pyroclastic/epiclastic deposits (no longer available for sampling). We believe that these whole-rock compositions reflect the presence of abundant, almost completely sterile, secondary calcite.</p> <p><strong>Bibliography </strong></p> </div><p> </p><div> <p>[1] Lustrino et al., 2020, Earth-Sci. Rev., 208, 103256.</p> <p>[2] Lustrino et al., 2019, Sci. Rep., 9, 1-14.</p> <p>[3] Stoppa and Cundari, 1995, Contrib. Mineral. Petrol., 122, 275-288.</p> <p>[4] Carminati et al., 2012, Tectonophysics., 579, 173-192.</p> <p>[5] Lustrino et al., 2022, Geology, https://doi.org/10.1130/G49621.1</p> </div>
Good conservation and restoration practices of cultural heritage assets rely on the knowledge of ... more Good conservation and restoration practices of cultural heritage assets rely on the knowledge of original materials. In the framework of the HERACLES Project (HERACLES—HEritage Resilience Against CLimate Events on Site, H2020 Grant Agreement 700395), dealing with the effects of climatic actions and natural hazards on built heritage, a set of important heritage sites are currently under study to improve their resilience against climate events. Among these are the medieval Gubbio Town Walls in Italy. The present work focuses on the mortars and binders of this monument and collected samples related to different parts of the Walls, corresponding to various historical periods of construction and interventions. They were characterized to determine their minerochemical composition, thermal behavior, and morphology. For that purpose, ex-situ laboratory techniques, such as X-ray diffraction (XRD), wavelength dispersive X-ray fluorescence (WDXRF), optical microscopy (OM), polarized light micr...
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Papers by Sara Ronca