Poly-Orogenic Melting of Metasedimentary Crust From a Granite Geochemistry and Inherited Zircon Perspective (Southern Calabria-Peloritani Orogen, Italy)

Inherited zircon ages and geochemical features of late Cadomian and late Variscan granitoids from the north-eastern Peloritani Mountains (NE Sicily) and the western Aspromonte Massif (SW Calabria) shed new light on the sources and processes involved in poly-orogenic granitoid magmatism. The two groups of strongly peraluminous granitoids have similarities in trace element abundance patterns, and Sr and Nd isotopic compositions consistent with both being derived from crustal sources, possibly with a minor contribution from mantle-related components. Comparison of the granite compositions with those of experimental melts derived from various metaigneous and metasedimentary sources indicates that both groups of granitoids originated exclusively from different degrees of melting of similar greywacke-dominated turbidite. Abundant inherited zircon cores from representative samples of metamorphosed late Cadomian (545 ± 5 Ma) granite and late Variscan (300 ± 4 Ma) leucogranodiorite have the same range of U–Pb ages, from Early Paleoproterozoic to latest Neoproterozoic, with main age clusters at ∼0.55 and ∼0.63 Ga, and minor age clusters at ∼0.95 and ∼2.5 Ga. The pattern of detrital zircon ages from a paragneiss, host rock to the late Cadomian granite, is the same, indicating, in conjunction with the geochemistry, that both granites originated by partial melting of deeper crustal equivalents of those paragneisses. The same crustal sequence melted during successive orogenies under different thermal regimes and in different post-collisional tectonic settings, giving rise to granitoid associations with different ages and geochemical features largely reflecting the melting conditions. On the other hand, the zircon inheritance patterns and specific chemical features of S-type granitoids reflect the nature of their crustal magma sources, independently from the effects of the thermal regime or tectonic setting at the time of magmatism

Study of alteration and degradation products of a Roman marble sarcophagus located in the medieval cloister of the old st Cosimato’s Convent, now the new "Regina Margherita Hospital” (Rome)

Optical and SEM-EDS microscopy, FT-IR and mFT-IR spectroscopy investigations have been applied to the study of alteration and degradation products of a Roman sarcophagus located in the medieval cloister of St Cosimato’s Convent, now the new “Regina Margherita Hospital” (Rome) before restoration work. This scientific analysis was performed in order to compare it with a diagnosis report based on the restorer’s expertise. The sarcophagus is small and consists of a single block of fine-grained marble covered by a thick pink patina. The results obtained from this diagnostic investigation, allow us to draw important conclusions about the state of conservation of this archaeological artefact. The main components found in the samples analyzed are: black crust, calcium oxalate, organic matter due to recent conservation treatment, calcite, iron-oxides and coloured earths. In particular, the combined used of petrographical and mFT-IR analysis provided useful insights into the polishing and consolidation processes of archaeological artefacts

Crustal Contributions to Late Hercynian Peraluminous Magmatism in the Southern Calabria-Peloritani Orogen, Southern Italy: Petrogenetic Inferences and the Gondwana Connection

Sensitive high-resolution ion microprobe (SHRIMP) analyses of zircon from granites of the medium-high grade Aspromonte-Peloritani Unit, Calabria-Peloritani Orogen (CPO), southern Italy, show that one of the minor trondhjemites (313·7 ± 3·5 Ma) represe

Peri-Gondwanan origin and early geodynamic history of NE Sicily: A zircon tale from the basement of the Peloritani Mountains

The ages of detrital zircon grains from one paragneiss and inherited zircon cores from two augen gneisses from the amphibolite facies basement of the Peloritani Mountains (southern Italy) measured by SHRIMP U-Pb constrain the previously unknown deposition age of the original sediments and help to elaborate a model for their provenance and subsequent evolution. The deposition age is latest Neoproterozoic to Cambrian (~ 545. Ma), bracketed by the combined ages of the youngest detrital/inherited zircon populations and of zircon from virtually coeval granitoids that intrude the metasediments. This is consistent with the subgreenschist facies Palaeozoic volcano-sedimentary sequences exposed in the southern Peloritani Mountains being the original cover rocks of the northern Peloritani late Neoproterozoic to early Cambrian basement. The age spectra of the detrital/inherited zircon grains show that the Neoproterozoic/Cambrian sediments were derived from the erosion of sources dominated by Neoproterozoic rocks with ages in the range of 0.85-0.54. Ga, with other main components aged 1.1-0.9 and ~. 2.7-2.4. Ga, and a minor one aged ~. 1.6. Ga, as typically found in peri-Gondwanan terranes. The presence of a large amount of Grenvillian-aged zircon contradicts previous models that propose a West African affinity for the Calabria-Peloritani Terrane, and the absence of 2.2-1.9. Ga Trans Amazonian/Tapajós-Parima/Eburnean zircon rules out an Amazonian provenance. The age spectra are more consistent with the basement sediments having an East African origin, similar to that of the early Palaeozoic sandstones in southern Israel and Jordan, part of a "provenance regionality" shared with other terranes currently located in the eastern Mediterranean area

The augen gneisses of the Peloritani Mountains (NE Sicily): Granitoid magma production during rapid evolution of the northern Gondwana margin at the end of the Precambrian

The medium- to high-grade polymetamorphic basement rocks of the Peloritani Mountains, northern Sicily, include large volumes of augen gneiss of controversial age and origin. By means of a geochemical and SHRIMP zircon study of representative samples, th

Premier bilan des recherches sur la pierre de construction à Mégara Hyblaea

International audienc

Premier bilan des recherches sur la pierre de construction à Mégara Hyblaea

Dans cet article, on propose un premier bilan des recherches préliminaires sur la pierre de construction à Mégara Hyblaea, fruits des travaux communs d’une équipe d’archéologues et de géologues. Les analyses pétrographiques d’échantillons représentatifs de l’architecture en pierre de Mégara ont d’abord montré que trois types de roche avaient été utilisés : il s’agit de calcarénites appartenant à des formations géologiques locales du Pléistocène et du Miocène. Dans le territoire de Mégara, on a ensuite identifié plusieurs anciennes carrières comme possibles sites d’extraction. Parmi celles-ci, trois possèdent des faciès géologiques parfaitement compatibles avec ceux des échantillons archéologiques : l’Intagliata, la Pirrera di Melilli et la côte Nord de la presqu’île de Thapsos.In this article, we offer a first assessment of the preliminary research on the construction stone in Megara Hyblaia, fruit of the joint works of a team of archaeologists and geologists. The petrographic analysis of representative samples of Megara’s stone architecture have first shown that three types of stone had been used: all three are calcarenites belonging to local Pleistocene and Miocene geological groups. In Megara’s territory, we have then identified several ancient stone quarries as potential extraction sites. Three of them bear geological features matching perfectly those of the archaeological samples: the Intagliata, the Pirrera di Melilli and the north coast of the Thapsos peninsula

Tectono-metamorphic map of the south-western flank of the Aspromonte Massif (southern Calabria -Italy)

<p>The structural-geological field survey (1:10,000 scale) of the south-western portions of the Aspromonte Massif (southern Calabria, Italy) clearly reveal a nappe-pile stack made of three main tectono-metamorphic units piled-up by means of tectonic contacts with associated cataclastic or mylonitic rocks developed at various crustal depth. These three units are from top to bottom: the Stilo Unit, the Aspromonte-Peloritani Unit (APU) and the Madonna di Polsi Unit. As part of an ongoing project, we have constructed a structural and metamorphic GIS database based on 285 sampling stations, which allows for metamorphic and structural maps to be obtained in the form of the metamorphic zoning of the SU.. This unit, made up of low greenschist- to low amphibolite-facies Palaeozoic metamorphic rocks, lies through a brittle tectonic contact over the APU, which is made up of amphibolite-facies metamorphic rocks intruded by late Hercynian peraluminous both locally overprinted by Alpine type metamorphism. The petrographic-derived metamorphic zonation chart here presented has been created after the detailed petrographic analysis of about 80 thin sections and the recognition of mineral assemblages of a thermal metamorphic aureole (biotite, muscovite and andalusite blastesis) produced by Late Hercynian magmatic bodies intruded into metapelites (Punta d'Atò granitoids, outcropping in the northern part of the mapped area).</p

THE BAROQUE MONUMENTS OF MODICA (EASTERN SICILY): ASSESSMENT OF CAUSES OF CHROMATIC ALTERATION OF STONE BUILDING MATERIALS

Published on line 08 april 201