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The middle Miocene is an important time to understand modern global climate evolution and its consequences on marine systems. The Mid-Miocene Climatic Optimum (between 17·0Ma and 13·5Ma) was the warmest time interval of the past 35 million years during which atmospheric CO2concentrations were lower than today. In the Mid-Miocene Climatic Optimum, a significant carbon cycle perturbation occurred, expressed as a last long-term positive carbon isotope shift, known in literature as the Monterey Carbon Isotope Excursion and recorded in open-ocean settings. In this work, the lower to middle Miocene carbon isotope records from three different domains of the Central Mediterranean are analysed with the aim of identifying the local carbonate platform response to the major global carbon cycle perturbation of the Monterey Event. Carbon and oxygen isotope ratios have been measured on samples belonging to three different stratigraphic sections, two of them are representative of shallow-water settings (Latium–Abruzzi and Apula platforms), and the latter of a hemipelagic setting (Umbria–Marche Basin). A well-defined Monterey Carbon Isotope Excursion is recorded also in these shallow-water sections. Despite their expected problematic stratigraphic constraints, a reliable age model is provided by calcareous nannofossil biostratigraphy and strontium isotope stratigraphy. In both of the carbonate platform successions examined, the Monterey Carbon Isotope Excursion coincides with a spread of bryozoans over other carbonate-producing biota. The high productivity of the bryozoan-dominated factory in the aphotic zone had an important control on the platform depositional profile. The high rates of sediment production in the deeper aphotic and oligophotic zones produced a depositional profile of a low-angle ramp.

Recent geochemical work shows that subduction-zone serpentinites are repositories for fluid-mobile elements absorbed during interaction with sediment-derived fluids. Unraveling the geochemical fingerprint of these rocks helps to define timing of tectonic accretion of sediments along the subduction interface and the role ofserpentinitein element recycling tovolcanic arcs. Here we present the trace element andisotopic composition(B–O–H, Sr, Pb) of high-pressure serpentinites from the Voltri Massif (Ligurian Western Alps, Italy), to discuss their role as incompatible element carriers and their contribution to recycling of sediment-derived components in subduction zones. The serpentinites presented here record metamorphic olivine growth during eclogite-faciesmetamorphismand show undeformed and mylonitic textures. Field relations show that undeformed rocks are enclosed in deformed ones and that nometasedimentary rocksare present nearby. Undeformed serpentinite has very high δ11BSRM951(from +26‰ to +30‰), low Sr and Pbisotope ratios(87Sr/86Sr=0.7053–0.7069;206Pb/204Pb=18.131–18.205) and low As and Sb contents (0.1 and 0.01μg/g, respectively). Oxygen and hydrogen isotope compositions are +4.5‰ and −67‰, respectively. In contrast, mylonitic serpentinite shows lower δ11B (from +22‰ to +17‰), significant enrichment in radiogenic Sr and Pb isotopes (87Sr/86Sr up to 0.7105;206Pb/204Pb up to 18.725), and enrichment in As and Sb (1.3 and 0.39μg/g, respectively). δ18O of the mylonitic serpentinites reaches values of +5.9‰, whereas δD is comparable with that of undeformed rocks (approximately −70‰). In mylonitic serpentinites, the B and Sr isotopic values and the fluid-mobile element (FME) concentrations are near those for the Voltri metasedimentary rocks (calc- and mica-schists). Pb systematics also reveal influx of a crust-derived component. Our dataset shows that undeformed serpentinite still preserves an oceanic geochemical fingerprint, whereas mylonitic serpentinite is reset in its concentrations of FME and its B, Sr and Pb isotope compositions, due to interaction with sediment- and crust-derived fluids. The environment of this interaction is either compatible with (i) an outer-rise zone setting, withpercolationof seawater-derived fluids enriched in sedimentary components into bending-related fault structures, or with (ii) subduction channel domains, where ascending sediment-derived slab fluids infiltrate slices of former oceanic serpentinite accreted to the plate interface domain. Influx of sediment-derived subduction fluids along major deformation zones in serpentinite modifies the element budget of the rocks, with important implications for element recycling and the tectonic history of serpentinite. The B, Sr and Pb isotopic systematics, coupled with FME concentration in serpentinites are particularly helpful geochemical tracers of interaction between different reservoirs in subduction-interface environments, and are more sensitive than the traditionally applied stable oxygen and hydrogen isotope compositions.

The Western Anatolia Miocene-to-Present Day magmatism evolved from calc-alkaline and shoshonitic rocks (21-16 Ma) to lamproites (16-14 Ma), and eventually into OIB-type magmas (2-0 Ma) represented by the Kula volcanics. In the calc-alkaline and shoshonitic association, Sr and Nd isotopic ratios and trace element variations suggest that the interaction with the crust was moderate, so that the geochemistry of these rocks is considered to reflect the heterogeneous chemical nature of their mantle source. The ultrapotassic and lamproitic rocks are characterised by a high Sr and low Nd isotopic composition and are strongly enriched in K and Rb with respect to Ba, indicating a phlogopite-bearing lithospheric source. Low Sr and high Nd isotopic compositions, together with low LILE/HFSE ratios, reveal the OIB-type nature of the Kula volcanics. Therefore, the products switch from supra-subduction orogenic suites to volcanics coming from sub-slab astenospheric mantle. The evolution is interpreted as being due to a 'horizontal' stretching of the slab (no slab pull break-off) generated by different velocities in the subduction hangingwall lithosphere. This triggered the extensional movement between Greece and Turkey and the stretching into two slabs of the NE-directed African subduction, due to the faster southwestward slab rollback of Africa underneath Greece relative to the slab segment below Cyprus and Anatolia. (c) 2005 Elsevier B.V. All rights reserved.

The Pali Aike Volcanic Field (PAVF) represents the southernmost occurrence of the Cenozoic back-arc Patagonian Plateau Lavas. Its activity (Pliocene–Recent) started forming tabular lavas followed by the growth of about 470 essentially monogenetic volcanic centers (tuff-rings, maars, spatter and scoria cones). Azimuths of cone alignment, cone elongation and morphologic lineations show prevailing ENE–WSW and NW–SE trends. Erupted products consist mainly of alkaline basalt and basanite, with minor olivine basalt. PAVF rocks are quite primitive in composition (average Mg#=66, Ni=220ppm and Cr=313ppm) with relatively high TiO2(average 3.0wt.%). Ultramafic garnet- and/or spinel-bearing xenoliths are found within PAVF volcanics. Chondrite-normalized REE patterns are significantly LREE-enriched and almost rectilinear [(La/Yb)N=10.9–21.0]. Primordial mantle-normalized distributions of incompatible trace elements, as well as Sr and Nd isotope ratios (87Sr/86Sr=0.70317–0.70339,143Nd/144Nd=0.51290–0.51294), show values typical of intra-plate basalts, despite the fact that these rocks occur only 200km east of the Andean Cordillera. Primary magmas were generated from a fertile garnet-bearing asthenospheric source atP=1.9–2.9GPa andT=1420–1470°C. The data suggest a geodynamic model that implies sub-slab asthenosphere flow through a slab window, which started opening below this sector of South America 14m.y. ago as a consequence of the collision of the Chile Ridge with the Chile Trench. The trailing edge of the Nazca Plate crossed below the Pali Aike area at 9–10Ma, that is 6–5m.y. before the onset of the volcanic activity. We hypothesize that this time delay resulted from changes in the kinematics of the South America–Scotia transform plate boundary which only allowed the Pali Aike magmas to rise after about 4m.y.