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The Triassic/Jurassic boundary section cropping out at Mt Sparagio in north-western Sicily (Italy) consists of a thick and continuous peritidal succession typical of a Tethyan carbonate platform. The combined chemostratigraphic and biostratigraphic study of this section allowed us to parallel the environmental variations inferred by the isotopic records and the extinction trends recorded by the benthic organisms. In the studied section, the isotope data of C, O, and S are indicative of serious environmental perturbations related to the Central Atlantic Magmatic Province (CAMP) activity, as recorded worldwide. Two negative excursions in the C-curve (Initial-CIE and Main-CIE) confirm the acidification processes that affected the benthic community. Moreover, the oxygen isotopes curve indicates a strong warming-trend that corresponds to the reduction in biodiversity and size of the megalodontoids in the upper part of the Rhaetian beds, probably due to the deterioration of the photosymbiotic relationships of these pelecypods. We here present some novel isotope data (Zn, Pb, Sr) from the Mt Sparagio section that offer additional clues on a tight control of CAMP volcanism on the End-Triassic Extinction.

National audience; Understanding how magmatic arcs develop is crucial for the comprehension ofsubduction systems and the processes leading to continental growth and lithosphericrecycling. Chronologic and provenance from U-Pb single grain dating by LA-ICP-MS ofdetrital zircons obtained from the forearc basin paired with Hf and O isotopic data andtrace elements have provided indicators of the Late Cretaceous-Cenozoic evolution ofthe Ecuadorian magmatic arc. A major Late Cretaceous accretionary event (75-65 Ma)is marked by large isotopic variations (Hf>20 and 18O>8) attesting for intensemagmatism resulting from melting of lower and upper crust materials. Highlyfractionated signatures in trace elements and Eu/Eu* paired with 18O mantle-like andHf juvenile values prevailed up to 45 Ma, suggesting that the arc was most likelyemplaced in an over thickened crust. Subsequently, negative isotopic incursions from45 to 30 Ma are defined by mantle sources as well as drops in the U/Yb, Eu/Eu* andTh/U ratios laying rough indicators of a broad extensional magmatic arc. From 30 to10 Ma the arc evolved towards a bi-modal arc, with highly juvenile isotopical values inthe North and slightly juvenile values in the south. Temporal trends from detritalanalysis are further compared with: 1) in-situ zircon geochemical and isotopic data and2) geophysical data sets, mostly gravimetric, magnetometric and seismic reflectionrecords. The geophysical analysis provide a good template on the first-ordersegmentation of this part of the Andes, including deep anomalies related to ancientaccreted arcs and/or serpentinized mantle and sub-surface extensional tectonics. Theseresults give fresh perspectives on the long-term evolution of magmatic arcs in accretedoceanic terranes.

The upper Oligocene San Rafael intrusive complex (SRIC), located at the southwest margin of the Eastern Cordillera of southeast Peru, is an exceptional case study to investigate the petrogenesis of a large composite granitic pluton associated with the largest known high-grade Sn deposit (>1 Mt. Sn). The granitic rocks are quasi-continuously exposed over more than 1.4 km vertically, from the cupola at surface to deeper levels in the underground mine workings, thus providing access to the upper part of a large pluton. We describe new field relationships and petrographic observations of the main granite varieties of the SRIC, and we report quantitative mineral analyses, whole rock geochemistry (major and trace elements, radiogenic Sr, Nd, and Pb isotopes), and in situ U–Pb dating and trace element analysis of zircons. The SRIC is dominantly composed of a biotite-cordierite -bearing K-feldspar megacrystic granite, which contains comagmatic enclaves and dismembered dikes of fine-grained and medium-grained granites, and subordinate lamprophyres. While the granitic rocks are widely affected by variable degrees of pervasive hydrothermal alteration, the least altered samples are characterized by moderately fractionated peraluminous S-type compositions, with similar enrichments in incompatible elements (Li, B, Ga, Rb, Sn, Cs, Th, and U), relatively high Zr/Hf and Nb/Ta ratios, and strongly crustal Sr, Nd, and Pb isotopic signatures. In situ U–Pb dating and trace element analysis of zircons indicate that the granitic magmas crystallized contemporaneously within age uncertainty at 24.02 ± 0.25 Ma (megacrystic granite), 24.17 ± 0.28 Ma (fine-grained granite), and 24.26 ± 0.26 Ma (medium-grained granite) at Ti-in-zircon temperatures from 638° to 840 °C (avg = 759 ± 49 °C). The lamprophyres have high contents of lithophile elements (Li, Rb, Cs, Sn, W) while showing more primitive Sr–Nd isotopic compositions, indicating a metasomatized subcontinental lithospheric mantle source contaminated by crustal assimilation and/or mixing with granitic magmas. Tin contents of the main San Rafael granites are moderate (3–40 ppm; avg. = 13 ppm Sn) and fall in the same range of values as reported for “tin granites” from the Central Andean tin belt. Based on our petrological and geochemical data, we conclude that the SRIC results from multiple injection and mingling/mixing of several types of coexisting felsic and mafic magmas in a shallow-crustal reservoir. The granitic magmas were largely derived from partial melting of metasedimentary protoliths and hybridization with mantle-derived mafic melts, in a regional geodynamic setting dominated by anomalous asthenospheric heat flow beneath the southern Peruvian Altiplano during the Oligocene to Miocene. Based on the moderately fractionated peraluminous character of the SRIC, we conclude that the granitic pluton was a passive host for Sn mineralization and only provided the structural focusing for metal-rich magmatic fluids derived from a deeper part of the granitic magma reservoir. We propose a model in which the injection of high-temperature mafic melts into a more reduced, fractionated granitic magma reservoir triggered late-magmatic oxidation, crystal mush reactivation, and exsolution (second boiling) of metal-rich magmatic fluids. The latter ascended toward the upper part of the crystallized granitic pluton and were focused along subvertical dilational structures, where they cooled down and mixed with downwelling meteoric waters, thus generating the world-class San Rafael Sn (–Cu) deposit., Lithos, 400-401, ISSN:0024-4937

Post-Variscan Early Permian magmatism is widespread from Corsica to the Eastern Alps. After the formation of the Variscan orogenic belt between Laurussia and Gondwana, felsic and mafic bodies were emplaced during an extensional tectonic phase. This study focuses on a mafic dyke swarm that intruded in the region of Ajaccio (Corsica, France) and on a gabbroic intrusive complex outcropping in the Eastern Alps (Bressanone/Brixen, South Tyrol, Italy) both of which were emplaced during this extensional event. New U-Pb data from zircon show that both of these intrusions were emplaced at ca. 282 Ma. Most Ajaccio dykes display a calc-alkaline affinity and are characterized by enrichment of LILE (Large Ion Lithophile Elements) and LREE over HREE (Light and Heavy Rare Earth Elements) and HFSE (Nb, Ta, Hf, Zr; High Field Strength Elements). Two dykes show tholeiitic affinity and are characterized by marked LREE and Th-U depletion and by minor negative Nb-Ta anomalies on multi-element diagrams, which is typical for within-plate basalts. Bressanone/Brixen gabbros display similar geochemical features to the Ajaccio calc-alkaline samples with LREE enrichment over MREE (Medium Rare Earth Elements) and HREE, and HFSE depletion. Such characteristics are also confirmed by trace element data obtained by LA-ICP-MS on clinopyroxene and plagioclase crystals. The calc-alkaline to tholeiitic dykes are characterized by enriched to depleted Sr-Nd-Pb isotopic compositions, respectively. Some Ajaccio dykes and the Bressanone/Brixen gabbros are clearly affected by crustal contamination. However, the combination of trace element and isotopic variations suggests that mantle source heterogeneities were also involved. Isotopic compositions of the Ajaccio dykes reveal the presence of two distinct mantle source signatures: an enriched mantle (EM) component, which dominates the composition of the calc-alkaline-like suite, while a DMM (Depleted MORB Mantle) component dominates the source of the tholeiitic suite. The EM mantle source likely formed during Variscan subduction, however the composition of the tholeiitic suite requires a source composed dominantly of depleted mantle, with a minor contribution from both the subducting slab and supra-subduction mantle wedge. The mantle source of the tholeiitic magmas possibly originated from greater depths (compared to the calc-alkaline-like suite) during the post-orogenic extensional phase potentially due to break-off and/or roll-back of the Variscan slab or mantle flow from the front or margins of the subducted slab. Notably, coeval Permian mafic intrusive bodies from throughout Corsica (Bocca di Tenda, Porto, Pila Canale) and from the Australpine and Southalpine Alps intruded at a similar time and have geochemical features that are very similar to the Ajaccio dyke swarm and Brixen gabbro. This indicates that a widespread Permian magmatic province developed in a post-orogenic extensional tectonic setting at the margin of the former Variscan belt. During the Middle-Late Triassic magmatism with similar enriched geochemical signatures occurred in the Southern Alps, Dinarides, Australpoine domains and at the end of the Triassic over central Pangea (Central Atlantic Magmatic Province). This would highlight the importance that the Variscan orogeny had in the development of a more fertile mantle.

This study focuses on the Elbeyli–Ordu Emeksen–Giresun Güzelyayla–Trabzon and Ulutas–Ispir porphyry typeprospects located in the Eastern Pontides Turkey. Our new LA ICP MS U–Pb zircon age data reveal that theElbeyli–Ordu Mo–Cu mineralization is hosted by a 77.0 ± 1.3 Ma old monzonite/monzodiorite with ashoshonitic character. The Emeksen Mo mineralization located 40 km southeast of the Elbeyli–Ordu prospectconsists of NW and NE striking quartz veins crosscutting a high K calc alkaline to shoshonitic granite dated at78.5±0.8Ma a granodiorite dated at 78.7±0.5Ma and porphyry granite dated at 77.7±0.5Ma. The Güzelyaylaporphyry Cu–Mo prospect consists of a stockwork type Cu–Mo mineralization crosscutting a calc alkaline 81.4 ± 1.1 Ma old dacite porphyry and Late Cretaceous calc alkaline andesite. The Ispir–Ulutas mineralizationis hosted within a highly sericitized 131.1 ± 0.9 Ma old quartz porphyry that intruded into a 132.9 ±0.6 Ma old calc alkaline granite porphyry. Our new U–Pb zircon ages lithogeochemical and radiogenic isotopicdata of the host rocks associated with the porphyry type prospects in the Eastern Pontides indicate that theyformed in an arc related environment during Cretaceous subduction of the Neotethys Ocean and the Ispir–Ulutas prospect is attributed to the main stage of the northward subduction of the Neotethys during the EarlyCretaceous. We conclude that the Güzelyayla and Emeksen hydrothermal systems were formed during a transitionalcompressional to extensional tectonic evolutionwhereas the Late Cretaceous Elbeyli hydrothermal systemwas emplaced during an extensional arc magmatic event. Highly oxidized high K calc alkaline to shoshoniticmagmas at Emeksen and Elbeyli were derived from a metasomatized heterogeneous and enriched lithosphericmantlewith variable degrees of partial melting of the mantle wedge and variable crustal contamination. Mixing/mingling processes between mafic magmas derived from the lower crust and acidic magmas at upper crustal levels played an important role in the formation of Cu–Moporphyry type mineralization in the Eastern Pontides.

Triassic igneous and sedimentary rocks exposed within the basement of the Andes were deposited in a series of rifts and may record the early disassembly of western Pangaea. These rocks are sporadically exposed along almost the entire length of western South America although reliable geochronological and isotopic data are sparse. We combine new geochronological (zircon U–Pb) isotopic (Hf Nd) and geochemical data with stratigraphic observations to constrain the age and tectonic setting of the Mitu Rift of southern Peru. The Peruvian Mitu Rift is compared with other Triassic rifts in Colombia and Ecuador (Palanda Rift; 240–225 Ma) Bolivia (Mitu Rift; Triassic) Bolivia Chile and Argentina (e.g. Cuyo Basin; 246–230 Ma) and conclusions are reached regarding the relationship between Triassic extension along the western margin of Pangaea and the eventual formation of the Proto Caribbean and Central Atlantic oceans. The Mitu Rift (Peru) was active during 245–240 to 220 Ma and was synchronous with rifting along the Pacific margin of Colombia and Ecuador along the Chilean margin and western Argentina and probably rifting within Bolivia. Rifting north of the Huancabamba Deflection was accompanied by subduction and led to seafloor spreading whereas rifting along the Peruvian and Chilean margins mainly occurred in the absence of subduction and terminated prior to the formation of extensive transitional crust. Extension within Peru and Chile probably occurred via a combination of transtension steepening and detachment of an arrested slab. Wepropose that plate tectonic forces initiated the early break up of Pangaea by attenuating its margins and enhancing mantle upwelling. Prolonged extension may have propagated along pre existing weak zones that extended into the continental interior captured melts derived from the upwelled mantle forming a LIP (e.g. Central Atlantic Magmatic Province) became hot and weak and eventually lead to the formation of a juvenile ocean (e.g. Central Atlantic).

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Indonesia is periodically affected by severe volcanic eruptions and earthquakes, which are geologically coupled to the convergence of the Australian tectonic plate beneath the Sunda Plate. This work is aimed at performing an analysis of ground displacements over Indonesian sites through Multi-temporal SAR interferometry (MTI). Two test sites, in Sumatra and Java, have been selected according to the following requirements: presence of ground instabilities, possibly related to onshore active faults or volcanoes; good expected interferometric coherence, availability of reliable archived interferometric SAR datasets, availability of ancillary geophysical data. Displacement maps have been obtained by processing COSMO-SkyMed and Sentinel-1 datasets available on the area, through SPINUA algorithm, which performs Persistent Scattering (PS) analysis. The use of datasets coming from two datasets, allows cross-validating final results. The processing of Sentinel-1 data has been more complex w.r.t. that of COSMO-SkyMed data, as standard MTI displacement maps showed strong artifacts, likely due to residual atmospheric contributions and orbital errors. In order to overcome this problem, an alternative processing scheme has been experimented. The tectonic analysis in Indonesia is difficult because the vegetation cover in the area causes lack of PS along and across the faults. Our MTI results provided useful information about the ground stability/instability within the selected test sites. In particular, concerning the tectonic activity in Sumatra, the MTI displacement analysis seems to confirm the inactivity of the Aceh fault segment, as foreseen by geodetic studies. Also, in the Java test site no displacement signal was detected related to possible activity of the faults present in the area. Besides the tectonic activity, ground displacements were also identified basically reflecting local effects. The causes of these displacements were investigated by using ancillary geological data, and in situ inspections. The subsidence phenomena are mainly related to the presence of unconsolidated coastal/alluvial sediments and groundwater pumping. An interesting example concerns a coastal area in Banda Aceh, which was overrun and completely destroyed by the 2004 tsunami. Most subsiding PS targets are positioned on port facilities structures and embankments. Extensive rebuilding and new constructions in the area add weight to the unconsolidated sediments. There is also an extensive presence of seasonally flooded crops and salt production flats. This suggests that the subsidence occurring in the area is probably related to compaction of sediments and/or recent artificial fill. A subsidence has been also revealed in Java over the Yogyakarta urban area. This local displacement is induced by groundwater exploitation and soft sediment compaction, a result of major urban expansion and human activity during the last years. The high resolution of COSMO-SkyMed data allows catching interesting details over urban structures. Finally, interesting localised subsidence rates are observed upon recent (2010) volcanic deposits at the flanks of Mt Merapi in Java, a result of compaction of the soft explosive products (pyroclastic density currents and pumice).

The ophiolitic rocks of the Attic-Cycladic crystalline belt are considered of key importance for understanding the Mesozoic tectonic evolution of the Aegean region. Unresolved questions concern their tectono-stratigraphic relationships across the region. The mode of occurrence of the Cycladic ophiolites varies, as they appear as: (a) dismembered blocks (olistoliths) within the supra-detachment units of Paros and Naxos; (b) mélange formations in the upper structural unit of western Samos and Skyros; and (c) meta-ophiolitic mélange in the Cycladic Blueschist Unit (CBU) from central Samos. The trace element geochemistry and Pb-Sr-Nd isotopes of the mafic ophiolitic rocks indicate four geochemical groups: (a) the upper unit metabasites from Paros and western Samos (Kallithea) display an evolved basaltic composition (Mg# 40.2-59.6), with low Zr/Nb values (5-16) and high Ce/Y values (1.3 to 2.6) compared to MORB, indicating island-arc tholeiite affinities; (b) Naxos upper unit metabasalts show spider diagrams patterns indicating ocean island basalt (OIB-type) affinities; (c) Central Samos metagabbros (CBU) are primitive rocks with Back-Arc Basin basalt affinities; (d) the Skyros metadolerites and Tinos (Mt Tsiknias) and S. Evia (CBU) metagabbros, cluster as a separate geochemical group; they exhibit high MgO values (>10 wt %), very low TiO2 values (0.1-0.2 wt %), Y and Yb, and depleted trace element N-MORB normalized patterns, similar to volcanic rocks formed in modern oceanic fore-arc settings, such as boninites. A combination of the Pb- and Sr-isotopic compositions of Cycladic metabasites indicate that the Pb and Sr incorporated in the Cycladic ophiolites correspond to mixtures of magmatic fluids with seawater (206Pb/204Pb = 18.51-18.80; 207Pb/204Pb = 15.59-15.7; 208Pb/204Pb = 39.03-39.80 and initial 87Sr/86Sr80 = 0.705-0.707). Furthermore, peridotite relicts from Samos, Paros, and Naxos-irrespective of the structural unit-display chemical affinities of ocean floor peridotites formed in a supra-subduction zone. The characteristics of harzburgite relicts in Cycladic serpentinites and Skyros indicate a highly residual nature of the mantle source. Geochemical data from this study shed further light on the complex structure of the oceanic lithosphere from which the Cycladic ophiolites originated. © 2017 by the authors. Licensee MDPI, Basel, Switzerland.

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International audience

International audience

International audience

International audience

Cool-water carbonates are the dominant limestones in the Mediterranean Basin since the Early Pliocene. Their deposition typically resulted in ramp morphologies due to high rates of resedimentation. Several such fossil carbonate ramps are characterised by a bimodal facies stacking pattern, where background deposition of subaqueous dune and/or tempestite deposits is repeatedly interrupted by anomalously thick sedimentary units, dominated by backset-stratification formed by supercritical flows. A multitude of exceptional triggers (e.g. storms, floods, tsunamis) have been invoked to explain the origin of these supercritical flows, which, in the absence of a quantitative analysis, remains speculative as yet. Here, for the first time, the catastrophic evolution of one such Mediterranean carbonate ramp, on Favignana Island (Italy), is quantified by combining 87Sr/86Sr dating, outcrop-based palaeoflow reconstructions and hydraulic calculations. We demonstrate that rare tsunami-induced flows, occurring on average once every 14 to 35 kyr, lasting a few hours only, deposited the anomalously thick backset-bedded units that form half of the sedimentary record. In between such events, cumulative two years of storm-induced flows deposited the remaining half of the succession by the stacking of subaqueous dunes. The two to four orders of magnitude difference in average recurrence period between the two flow types, and their associated sedimentation rates, emphasises the genetic differences between the two styles of deposition. In terms of sediment transport, the studied carbonate ramp was inactive for at least 99% of the time with gradual progradation during decennial to centennial storm activity. Carbonate ramp evolution attained a catastrophic signature by the contribution of rare tsunamis, producing short-lived, high-energy sediment gravity flows.

Advanced multi-temporal interferometry (MTI) techniques are being increasingly used in landslide assessment, as they can provide precise (mm-cm resolution) measurements of very slow ground surface displacements for huge areas with limited vegetation cover. We illustrate the potential of high resolution MTI for wide-area and local-scale detection of slope and associated infrastructure instability hazards in the peri-Adriatic region. This is done by presenting MTI applications to two landslide-prone mountainous areas characterized by different geomorphic, climatic and vegetation conditions, and hence by variable density and distribution of potential radar targets: the eastern-most part of the Southern Apennines and the mountains in central Albania. The results demonstrate that even in such scarcely urbanized areas MTI can provide valuable information on the presence of slope movements that locally affect small human settlements and road network. The gaps in satellite-derived information, especially evident in the more forested Albanian mountains, suggest that MTI could be most profitably exploited in the reconnaissance stage of a slope hazard assessment, to be followed by more detailed investigation and monitoring of sites at risk.

Among a number of advanced satellite-based remote sensing techniques, synthetic aperture radar (SAR), multi-temporal interferometry (MTI) appears the most promising for fostering new research opportunities in landslide and subsidence hazards detection and assessment. MTI is attractive to those concerned with terrain instability hazards because it can provide very precise quantitative information on slow displacements of the ground surface over huge areas with limited vegetation cover. Although MTI is a mature technique, we are only beginning to realize the benefits of the high-resolution imagery that is currently acquired by the new generation radar satellites (e.g. COSMO-SkyMed, TerraSAR-X). In this work we demonstrate the great potential of high resolution MTI for regular, wide-area detection of ground instability hazards by presenting results from two regions characterized by different geomorphic, climatic and vegetation conditions: densely populated metropolitan area of Port-au-Prince (Haiti), with the coastal areas and local slopes destabilized by the 2010 Mw 7.0 earthquake, and the remote high mountain region of Southern Gansu Province (China) prone to large slope failures. The interpretation and widespread exploitation of high spatio-temporal resolution MTI data can be facilitated by web-based applications (e.g. Google EarthTM tools with the associated high resolution optical imagery).

The petrogenesis of the Kerforne dyke tholeiitic basalts (Brittany, France), the northernmost outcrop of the 200 Ma Central Atlantic magmatic province (CAMP), is constrained by its zoned augite and plagioclase crystals. Augite cores with high Mg/Fe and Cr suggest crystallization from near-primary magmas, with slightly enriched Rare Earth element (REE) patterns. Plagioclase crystals with high-An (An85) rounded cores are MgO- and K-rich, REE-poor, and display 87Sr/86Sr200Ma (0.7058) significantly higher than those of the surrounding ground-mass (0.7052–0.7053) suggesting open-system evolution processes. We propose a differentiation process involving mixing of different mafic magmas which occurred in less than a few hundred years judging from the lack of diffusive re-equilibration of major and trace elements in augite and of 87Sr/86Sr200Ma in plagioclase cores. The relatively large range of incompatible element contents and ratios of observed and calculated magmas are possibly due to fractional crystallization and to moderate amounts of crustal contamination which affected the more primitive magmas in particular. The calculated magmas reach near-primitive compositions and suggest that they originated from melting of a spinel peridotite slightly enriched in LREE vs. HREE.

Gabbros and dolerite dikes of the Eldivan ophiolite and basaltic volcanic rocks of the ophiolitic mélange in the central part of the ?zmir-Ankara-Erzincan (IAE) suture zone were investigated for their 40Ar/39Ar age and whole-rock-major-trace element and Sr-Nd-Pb isotope compositions. Based on geological and geochemical characteristics basaltic volcanic rocks in the ophiolitic mélange are subdivided into two groups (Groups I and II) with ocean island basalts or enriched mid-ocean ridge basalt characteristics, respectively. Gabbros and dolerite dikes of the Eldivan ophiolite (Groups III and IV) have instead geochemical compositions indicative of a subduction-related environment. The volcanic rocks of Group I have 87Sr/86Sr(i) between 0.7037 and 0.7044, ?Nd(i)-DM of - 4.5 to - 5.6, and 206Pb/204Pb(i) ranging between 18.35 and 18.75. Group II volcanic rocks have higher 87Sr/86Sr(i) values (0.7049-0.7055), ?Nd(i)-DM ranging between - 5.4 and - 6.0, and 206Pb/204Pb(i) between 18.14 and 18.62. The Nd isotopic signatures and 207Pb/204Pb(i) values of the volcanic rocks of both groups point to a different source with respect to those of the Eldivan ophiolite. The low 206Pb/204Pb(i) values relative to the ophiolitic rocks seem to exclude a significant contribution from a HIMU reservoir, whereas the 207Pb/204Pb(i) values slightly above the NHRL might indicate some contribution from an EM2-type reservoir. Gabbros (Group III) of the Eldivan ophiolite and dolerite dikes (Group IV) cross-cutting the ultramafic part of the ophiolite show 87Sr/86Sr(i) between 0.7038 and 0.7053, ?Nd(i)-DM from - 2 to - 3.6 and 206Pb/204Pb(i) between 18.10 and 18.80. The gabbros yield ca. 150 Ma 40Ar/39Ar amphibole-plateau ages, which, together with the geochemical data, indicate that they were produced above subducted oceanic lithosphere in the IAE ocean domain in Late Jurassic times. Therefore, the Eldivan ophiolite in the IAE suture zone constitutes a link between the Hellenide-Dinaride ophiolite belts to the west and the Armenian-Iranian ophiolites to the east.