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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).