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The central Apennines are a Cenozoic fold-and-thrust belt that has been affected by post-orogenic extension in its axial region since the end of the early Pliocene (ca. 4 Ma). Post-orogenic extension generated several intermontane basins bounded by high-angle normal faults, striking NW-SE, subparallel to the backbone of the chain. The Monte Pettino and the Monte Marine seismogenic faults (MPF, MMF) are the boundary faults of the western portion of the late Pliocene-Quaternary L’Aquila intermontane basin. Their long-term activity is typified by exhumed fault cores that coexist with active fault strands localised at the fault hanging walls, providing evidence of a polyphase tectonic activity. The fault cores are decorated by diffuse dolomitization, which indicates structurally controlled fluid-flow and metasomatism. To constrain the long-term (space-time) evolution of the MPF-MMF faults, we integrated fieldwork, stable isotope systematics (δ18O, δ13C and Δ47), carbonate thermoluminescence and U-Th dating. Our results highlight two main tectonic phases, with different structural evolution and fluid-rock interaction. The first phase corresponds to the development of a major cataclastic zone, defined by meter-thick, SW-dipping (65-70°), fault cores exposed at the piedmont of the MPF-MMF ridges. The C-O systematics of the cataclasite and of the associated calcite slickenfibers, which are in the range of the carbonate bedrock, indicate a "closed" system behaviour during fault nucleation and development. Preliminary results from Δ47 thermometry of syn-kinematic carbonate structures indicate temperatures of 34 ± 2 °C. Thermoluminescence dating of dolomite clasts in the fault zone indicates age in the range of 3.0 – 3.4 Ma, whilst the cataclastic fault core is younger (< 800 ka). The second phase is mainly recorded in upper Pleistocene sedimentary Breccias (ca. 350 ka) which unconformably cover the bedrock and the exhumed fault cores at the SE termination of the MPF. It consists of anastomosed, high-angle WNW-ESE striking fault strands, spaced meters apart and with cm-m displacements, associated with carbonate veining and travertines. Stable isotopes measured from the fault slickenfibers, carbonate veins and travertines show negative δ13C and δ18O values, suggesting a depositional system dominated by meteoric fluid ("open" system) with an important contribution of organic carbon. Travertines and veins precipitated at colder temperatures (12 ± 4 °C), in the range of the average local air temperatures, thus excluding precipitation from a hydrothermal circuit. Moreover, their U-Th ages range between 182 and 331 ka, compatible with the temporal constraints from stratigraphic data. Structural and isotopic results do not support tectonic reactivation of the cataclastic core of the MPF during the middle-late Pleistocene, confirming the stratigraphic evidence. Our results provide the first absolute age constraint on the post-orogenic extensional faulting in the L’Aquila basin, demonstrating a two-stage fault activity, characterised by a change from localised (from ca. 3 to ca. 0.8 Ma) to delocalised faulting (200-300 ka to present). We infer that this change in the style of extensional faulting was consequence of the evolving rheological structure of the fault zones, primarily regulated by the feedback and interactions involving structurally-controlled fluid flow, rock metasomatism and cataclastic processes in space and time.

The geodynamic evolution of Iran during Mesozoic-Cenozoic time is the story of formation and destruction of a convergent plate margin. This evolution has been controlled by the transition from ocea...

The Alpine orogenic edifice of Corsica (northern Tyrrhenian Sea) offers the possibility to investigate the mode through which continental crust responds to the propagation of regional shortening at convergent plate margins. The geology of Corsica has been traditionally described as separating domains affected by the Alpine tectonism (Alpine Corsica) from those that did not experience the Alpine tectono-metamorphic overprint (Hercynian Corsica), but recent studies show that most of Hercynian Corsica was thermally reset in post-Eocene times, questioning this paradigm. The continental units formed at the expenses of the stretched continental margin of the European plate and consist of Hercynian granitoid basement rocks and cover sequences (Permian volcaniclastics and Mesozoic sedimentary successions). By integrating meso- and microstructural investigations with metamorphic thermobarometry and 40Ar-39Ar geochronology along three E-W trending structural transects running across the basement section exposed below the Alpine orogenic wedge, we document middle-late Eocene (c. 50-33 Ma) westward-verging syn-metamorphic (low-grade blueschist facies) thick-skinned, basement-involved thrusting. Significantly, crustal shortening in the continental basement predated of c. 15-10 Ma the subduction zone metamorphism in the oceanic-derived Schistes Lustres Complex. When the P-T-t-deformation history as reconstructed from the Corsica basement is integrated with the regional scenario of the Alpine-Apennine orogeny, a tectonic reconstruction is proposed, which frames the Alpine orogeny in Corsica within the Apennine-Maghrebian subduction system in the retroside (retrowedge) of the Apennine orogenic wedge.

The hinterland of the Cenozoic Northern Apennines fold-and-thrust belt exposes the metamorphic roots of the chain, vestiges of the subduction-related tectono-metamorphic evolution that led to the buildup of the Alpine orogeny in the Mediterranean region. Like in other peri-Mediterranean belts, the tectono-metamorphic evolution of the Paleozoic continental basement in the Apennines is still poorly constrained, hampering the full understanding of their Alpine orogenic evolution. We report the first comprehensive tectono-metamorphic study of the low-grade metasedimentary (metapsammite/metapelite) succession of the Monti Romani Complex (MRC) that formed after Paleozoic protoliths and constitutes the southernmost exposure of the metamorphic domain of the Northern Apennines. By integrating fieldwork with microstructural studies, Raman spectroscopy on carbonaceous material and thermodynamic modelling, we show that the MRC preserves a D1/M1 Alpine tectono-metamorphic evolution developed under HP-LT conditions (~ 1.0-1.1 GPa at T ~400 °C) during a non-coaxial, top-to-the-NE, crustal shortening regime. Evidence for HP-LT metamorphism is generally cryptic within the MRC, dominated by graphite-bearing assemblages with the infrequent blastesis of muscovite ± chlorite ± chloritoid ± paragonite parageneses, equilibrated under cold paleo-geothermal conditions (~ 10 °C/km). Results of this study allow extending to the MRC the signature of subduction zone metamorphism already documented in the hinterland of the Apennine orogen, providing further evidence of the syn-orogenic ductile exhumation of the HP units in the Apennine belt. Finally, we discuss the possible role of fluid-mediated changes in the reactive bulk rock composition on mineral blastesis during progress of regional deformation and metamorphism at low-grade conditions.

This study integrates field, geochronological and geochemical data to constrain fluid circulation in the damage and core zone of the seismogenic Monte Morrone Fault System (MMFS), central Apennines (Italy). Faulting along the MMFS evolved from a diffuse deformation at the damage zone towards progressive localisation of a narrower fault core and, finally, to (re)activation of discrete slip surfaces at shallower crustal conditions. Multiple generations of carbonate mineralisations, including veins and slickfibers, occur along the main fault surfaces. Carbonate mineralisations are locally fractured and incorporated in the surrounding cataclasites, documenting repetitive structurally-controlled fluid infiltration during transient episodes of permeability creation and destruction. Stable carbon and oxygen isotopes of the carbonate mineralisations document a dominant meteoric water source probably mixed with deeper circulating waters having longer residence time. Clumped-isotope yield formation temperatures of vein and slickenfibers in the range between 23 and 40 °C. UTh dating of carbonate mineralisations yield Middle Pleistocene ages (from 268 to 189 ka BP), with a 10–15-ka cyclicity that we link to the coseismic rejuvenation of the structural permeability in the fault zone. We propose that fault-related mineralisations recorded the interactions among tectonic deformation and climate during the Quaternary. Our study is the first documentation of fault-controlled recurrence intervals in fluid infiltration in a seismically active fault of central Apennines. Keywords: Normal faulting; Mineralising fluid; Seismic cycle; U-Th carbonate dating; Monte Morrone Fault; Central Apennines

International audience; As part of the Variscan orogen, the Pyrenean realm has undergone several rifting episodes, starting from the Permian-Carboniferous post-orogenic collapse and culminating with mid-Cretaceous lithospheric mantle exhumation. We present the Pressure-Temperature-time-deformation (P-T-t-d) evolution of the tonalite bodies (here described for the first time) intruded in the late Carboniferous high pressure (HP) granulites of the Saleix Complex, forming the inner envelope of the Lherz peridotites (Aulus Basin, Ariège, France), that is used as a proxy to reconstruct the post-Hercynian evolution of the Pyrenean continental crust. By integrating textural investigations with metamorphic thermobarometry, and zircon and titanite Usingle bondPb geochronology, we (i) constrain timing and thermo-baric conditions related to the transition from magma emplacement to solid-state syn-tectonic deformation in tonalite(s); and (ii) discuss implications on the polyphase exhumation history of the granulite host rocks. Emplacement of the Saleix tonalite(s) took place in the early Permian (ca. 281 Ma), in a thermo-baric environment (P = 0.5 ± 0.1 GPa and T = 750–880 ± 20 °C) attesting for an important thinning of the Pyrenean crust at the end of the Variscan cycle. Solid-state deformation occurred during the mid-Cretaceous (ca. 96 Ma), at shallow crustal depths (≤10 km) and under amphibolite facies metamorphic conditions. These results document that rifting events had already thinned the Pyrenean crust prior to the Cretaceous mantle exhumation and that the lower crust was affected by ductile deformation during the Cretaceous rifting. Our study demonstrates that in the Pyrenean realm the Permian crustal thinning played a very important role and that mantle exhumation resulted from polyphase post-Variscan, Permian-to-Cretaceous crustal thinning episodes.

In this contribution, we investigate the space and time distribution of the Cenozoic magmatism and the asso-ciated porphyry Cu-Mo +/- Au and other hydrothermal (mostly epithermal) ore deposits along the south Caucasus -west Iranian tectono-magmatic belt. We use a comprehensive georeferenced database containing whole-rock and geochronological analyses of 3150 samples from the igneous rocks distributed in the study area. Overall, the timing of the ore deposits overlaps with the timing of the Eocene to Miocene diachronous collision between the Arabia and Eurasia plates. This is associated with a change in the geochemical fingerprints of the magmas during and after collisional thickening, with a marked increase in Sr/Y values associated with a general transition to-wards adakitic signatures. This is interpreted with a change towards an amphibole-(+/- garnet) rich residue at the arc roots. Clusters of ore mineralization are observed within areas of long-lived magmatism (lasting >10 Myr), usually located at the intersections of basement fault zones, parallel and orthogonal to the collisional boundaries and likely formed along inherited zones of crustal/lithospheric weakness. The isotopic data of the ore-forming magmas show a pronounced correlation with young (

The variety of temporal and structural constraints on the Alpine tectonometamorphic signature of the metamorphic core of the Betic-Rif orogen (Alboran Domain) has supported a long-lasting debate regarding the Alpine tectonic and geodynamic evolution of the Western Mediterranean region. Uncertainty still exists on the timing and tectonic significance of (a) the Alpine orogenic construction; (b) exhumation of the deep roots of the orogen; and (c) transition from orogenic shortening to crustal extension. In this study, we address these major geological issues by focusing on the lower-grade units of the Alboran Domain (Upper Sebtides and Ghomarides) exposed in the Rif belt of northern Morocco. Through a multidisciplinary approach that integrates mesostructural and microstructural investigations with X-ray diffraction, quantitative mineral chemistry, and 40Ar/39Ar geochronology, a 20Ma long tectonic history is reconstructed, which involves burial of the tectonic units at depth (late Eocene) and postorogenic exhumation under brittle conditions in the upper crust (early Miocene). We document a Priabonian (∼37-34Ma) D1/M1 progressive compressional deformation, during the formation of a SW-verging orogenic wedge (present coordinates), accreted toward the Africa plate. Brittle extensional detachment tectonics operated during the Burdigalian (∼18-17Ma), controlling the thinning of the previously structured Alboran Domain nappe stack and the final exhumation of the Alpine orogenic units. We propose that transition from orogenic build-up to collapse in the hinterland of the Betic-Rif orogen occurred when the retreat of the Apennine-Maghrebian subduction was efficient to drive transition from shortening to extension in the back-arc domain of the western termination of the Apennine-Maghrebian subduction zone.

The inner Apennines (Italy) are characterized by scattered outcrops of continent‐derived orogenic metamorphic units exposed along the Tyrrhenian coast from northern to southern Apennines. At least since the 1970s, some peculiar rocks exposed on Zannone Island (central Italy) have been described as the only Paleozoic‐Triassic metamorphic complex linking those exposed in the northern—with those in the southern Apennines. Assessing the protolith nature, thermobaric conditions, and structural features of what is accepted to be the metamorphic unit of Zannone is, therefore, crucial to elucidate the early paleotectonic evolution of the Apennines‐Tyrrhenian orogenic system. To that end, we interpreted seismic reflection profiles offshore Zannone, we carried out mesoscale and microscale structural investigations of representative outcrops on the island, performed X‐ray diffraction analysis, and K‐Ar and U‐Pb geochronology of representative clay gouge and syntectonic carbonate veins. Results show that the metamorphic rocks of Zannone can actually be reinterpreted as belonging to nonmetamorphic siliciclastic turbidites, likely deposited in foredeep settings, and coeval to the Oligocene‐Miocene Macigno Fm. of the northern Apennines. The turbiditic sequence was overthrust by Triassic dolostone in the early Miocene (~22 Ma), weakly deformed at

Structural studies in active caldera systems are widely used in geothermal exploration to reconstruct volcanological conceptual models. Active calderas are difficult settings to perform such studies mostly because of the highly dynamic environment, dominated by fast accumulation of primary and secondary volcanic deposits, the variable and transient rheology of the shallow volcanic pile, and the continuous feedback between faulting and geothermal fluid circulation/alteration that tend to obliterate the tectonic deformation structures. In addition, deformation structures can be also caused by near- and far-field stress regimes, which include magmatic intrusions at various depths (volumes and rates), the evolving topography and regional tectonics. A lack of consideration of all these factors may severely underpin the reliability of structural studies. By rebutting and providing a detailed discussion of all the points raised by the comment of Norini and Groppelli (2020) to the Urbani et al. (2020) paper, we take the opportunity to specify the scientific rationale of our structural fieldwork and strengthen its relevance for geothermal exploration/exploitation in active caldera geothermal systems in general, and, particularly, for the Holocene history of deformation and geothermal circulation in the Los Humeros caldera. At the same time, we identify several major flaws in the approach and results presented in Norini and Groppelli (2020).

Back-arc regions are usually punctuated by pulses of tectonic deformation, lasting for few tens of millions of years. Yet, the origin of those short-lived deformation episodes is disputed. Here, we compile structural, stratigraphic, geochemical, and geochronological data from Iran and we combine them with a kinematic reconstruction to show that the back-arc region of the Central Neotethys subduction zone was affected by alternating pulses of extension and compression, linked to episodes of trench retreat and advance, respectively. To back-up these observations and investigate the causes of such a trench behavior, we run 2D numerical models exploring (i) the dynamics of subduction into a viscously stratified mantle, and (ii) the deep slab deformation induced by mineral phase changes at the mantle transition zone. Our results indicate that episodes of trench retreat and trench advance, like those observed in the Central Neotethys domain, emerge spontaneously by slab folding, and penetration into the mantle transition zone. We propose a coupled mantle-surface tectonic evolution model of the Central Neotethys slab that reconciles back-arc deformation and short-lived pulses of upper-plate vertical motion in a unique, dynamically self-consistent model of deep mantle subduction.

International audience; The structural and thermal relaxation overprint associated with the Neogene Alboran rifting have obscured the early Alpine tectono‐metamorphic evolution of the Alboran Domain, representing the metamorphic core of the Betic–Rif orogen of the western Mediterranean region. This study focuses on the Beni Mzala unit, forming the lower and deeper structural level of the Alpine metamorphic nappe stack (Upper Sebtides) in the Moroccan Rif. Meso‐ and micro‐scale structural investigations are carried out on high‐P aluminum silicate (Ky‐bearing)‐quartz segregations that occur as boudins within the main retrogressive syn‐greenschist foliation (S2/D2) and assumed to preserve the early M1 HP metamorphism associated with the Alpine orogenic construction in the Alboran Domain. These boudins host an early crenulated high‐P foliation (S1, D1/M1) made of quartz–kyanite–white mica–rutile. A large spread in white mica composition is documented, with the highest Si content per formula unit (up to 3.18 apfu) preserved along the S1 foliation and the lower Si content observed in the white mica marking the S2 retrogressive foliation (D2/M2) and the rim of S1 mica. Microtextural evidence documents post‐tectonic andalusite growth and static recrystallization of the quartz microlithons. Inverse (Zr‐in‐Rt thermometry) and forward modelling thermobarometry are integrated with Ar–Ar white mica geochronology to define the peak and exhumation pressure–temperature–time (P–T–t) path of the Beni Mzala unit. Minimum thermo‐baric estimates for the M1 event are ~1.4 GPa and 600°C, corresponding to a metamorphic gradient of ~11°/km, consistent with subduction zone metamorphism. Exhumation is constrained by re‐equilibration of the white mica composition (from high to low celadonite) between c. 29 and 22 Ma, during a nearly isothermal retrogressive path, with final equilibration at high‐T/low‐P conditions within the andalusite stability field (~0.2–0.3 GPa and 500°C). A minimum late Oligocene age is proposed for the Alpine D1 tectono‐metamorphic stage in the Rif, suggesting as feasible the previously proposed Eocene timing for the subduction‐zone metamorphism of the Alboran Domain. Conclusive evidence is provided to link the early Miocene tectono‐metamorphic event to a late thermal perturbation that affected the Alboran Domain at shallow crustal conditions, post‐dating the almost complete exhumation of the deep roots of the Alpine belt in the western Mediterranean.

Zannone is a very important island, located in the Neogene-Quaternary extensional domain of the Tyrrhenian back-arc basin, as it is the unique spot where the Paleozoic (?) crystalline basement is hypotesized to be exposed in central Apennines. The exposure of such hypothetical basement in the Zannone Island is very problematic as it implies very large normal displacements (> 3 km) along surrounding faults. No such displacements are known along faults close to Zannone Island.In this work, we study the hypothetical Paleozoic crystalline basement exposed in the Zannone Island with the main aim of understanding its geological nature and relationships with the surrounding rocks. We use a multidisciplinary approach including 1) interpretation of seismic reflection profile; 2) field survey; 3) petro-textural observations; 4) microthermometry on fluid inclusions; 5) geochemical analyses of stable and clumped isotopes; 6) Illite crystallinity and mineralogical analyses of clays and host rocks; 7) analyses of minor gaseous species (He, Ne, and Ar concentrations and isotope ratios) in fluid inclusions; 8) U-Pb geochronology of syn-tectonic calcite, and 9) K-Ar dating of syn-kinematic clay minerals.Our results show that the hypothetical Paleozoic (?) crystalline basement exposed on the Zannone Island is, instead, represented by siliciclastic rocks of very low metamorphic grade. This is testified by the quartzarenites nature of the rocks, the presence of chloritoid and by the observed incipient foliation marked by fine-grained white micas and disposed parallel to the bedding. The contact between such siliciclastic rocks and the overlapping Triassic Dolostone is represented by a low-angle thrust cut by sets of high-angle normal faults with associated calcite mineralizations. K-Ar dating on clay minerals in fault gouge reveals that at least one event of authigenesis (i.e. fluid-assisted tectonic activity) occurred in Zannone Island

To unravel the Neotethys subduction history and the evolution of the slab morphology at depth since the mid-Cretaceous, we produced a synthesis of the main events affecting the Persian domain. This synthesis is focused on the upper and lower plates (i.e. the Persian and the Neotethys ocean, respectively) of the subduction system and is based on the compilation of available structural, geochemical and geochronological data. Overall, this compilation allows exploring the structural evolution of the Persian domain and the Neotethys oceanic lithosphere on map view and along selected cross-sections. Furthermore, we performed a 2D single-sided numerical model where we explored the slab behavior at depth and its influence on upper plate deformation. The model suggests that episodic deformation is driven by the folding slab behavior at the mantle transition zone. We combine our data and numerical model into a conceptual scenario to overcome the complexity of the kinematics of the Neotethys slab since the Early Cretaceous. Our modeling approach shows that back-arcs opening and associated extensional deformation are driven by the roll-back of the folded slab into the mantle transition zone. In contrast, back-arc closure and upper plate shortening are triggered by the roll-over of the folding slab. Finally, we associate the widespread, upper plate, Early Miocene marine flooding event to the Neotethys slab avalanche into the lower mantle.

Active faults are characterized by creation/destruction of secondary (tectonic) permeability in response to a continuous interplay between deformation and fluid pressure fluctuations during the seismic cycle. The study of the paleofluid circulation in fault rocks can thus provide insights into the hydraulic and mechanical behavior of the seismogenic crust.This work integrates data from field geology with geochemical and geochronological constraints to understand the spatio-temporal evolution of the paleofluid circulation in the Mount Morrone Fault System (MMFS), a ~25 km-long tectonic structure activated during the extensional Quaternary phase of the central Apennines (Italy). The MMFS cuts through a Mesozoic-Cenozoic multilayer carbonate succession for a cumulative stratigraphic offset of about 2 km. Fluvio-lacustrine and slope deposits (Middle-Late Pleistocene) occur at its hanging wall and are variably involved by faulting. The MMFS is currently classified as a silent seismic fault, with an estimated Mw= 6.5-7.0 potential magnitude and recurrence time at 2.4 ka for an expected earthquake.The structural survey focused on the western strand of the MMFS cutting through a succession of Sinemurian dolomitized limestones. A composite network of NW-SE-striking, SW-dipping fault surfaces defines the structural architecture of the MMFS in the study outcrops, with high angle (dip > 55°) faults that systematically cut and displace medium-to-low angle (dip in the order of 30°-50°) faults. Both fault systems are characterized by dominant dip-slip movement and normal kinematics. Lenses of cm-thick cataclasites often occur along the slip surfaces. Cataclasites are made by sub-angular to sub-rounded carbonate clasts (up to 1 cm-wide) dispersed in a very fine-grained matrix. Layers of cm-thick carbonate concretions occur associated with the cataclasites, testifying for pulses of fluid discharge along the fault surface during the tectonic activity of the MMFS. Microstructural investigations document that: (i) carbonate concretions show an internal texture of fibrous vein having fiber growth direction roughly perpendicular to the vein wall, and (ii) the basal portions of the carbonate concretions are fractured and incorporated within the underlying cataclasites through the deposition of a new calcite cement. The geochemical (δ13C and δ18O stable isotope) analyses on selected samples attest for a progressive chemical shift of the mineralizing fluid from marine (in host rock and in cataclasites) to meteoric waters (in carbonate concretions). The U-Th dating of carbonate concretions and calcite slickenfibers constrains the fault-controlled fluid circulation to the Middle Pleistocene, with ages spanning from 270 to 180 ka. Significantly, the dating of carbonate concretions documents a 12-kyr cyclicity of the fluid infiltration in the fault zone.The development of the secondary permeability in the MMFS thus corresponds to a combination of faulting and tensile fracturing, in response to a cyclic increasing of the shear stress and the pore pressure during the seismic cycle. The polyphasic deformation system of the MMFS constitutes a record of fault activation and reactivation episodes that could contribute to define the recurrence model of seismic events on regional-scale faults.

International audience; The Admiralty Mountains region forms the northern termination of the northern Victoria Land, Antarctica. Few quantitative data are available to reconstruct the Cenozoic morpho-tectonic evolution of this sector of the Antarctic plate, where the Admiralty Mountains region forms the northern termination of the western shoulder of the Mesozoic-Cenozoic West Antarctica Rift System. In this study we combine new low-temperature thermochronological data (apatite fission-track and (U-Th-Sm)/He analyses) with structural and topography analysis. The regional pattern of the fission-track ages shows a general tendency to older ages (80–60 Ma) associated with shortened mean track-lengths in the interior, and younger fission-track ages clustering at 38–26 Ma with long mean track-lengths in the coastal region. Differently from other regions of Victoria Land, the younger ages are found as far as 50–70 km inland. Single grain apatite (U-Th-Sm)/He ages cluster at 50–30 Ma with younger ages in the coastal domain. Topography analysis reveals that the Admiralty Mountains has high local relief, with an area close to the coast, 180 km long and 70 km large, having the highest local relief of >2500 m. This coincides with the location of the youngest fission-track ages. The shape of the area with highest local relief matches the shape of a recently detected low velocity zone beneath the northern TAM, indicating that high topography of the Admiralty Mountains region is likely sustained by a mantle thermal anomaly. We used the obtained constraints on the amount of removed crustal section to reconstruct back-eroded profiles and calculate the erosional load in order to test flexural uplift models. We found that our back-eroded profiles are better reproduced by a constant elastic thickness of intermediate values (Te = 20–30 km). This suggests that, beneath the Admiralty Mountains, the elastic properties of the lithosphere are different with respect to other TAM sectors, likely due to a stationary Cenozoic upper mantle thermal anomaly in the region.

This work aims to numerically simulate experimental pull-out tests in masonry wall anchors. Advanced Finite Element (FE) 3D models were built to fully reproduce the loadbearing capacity, the failure mode, the stresses and the force-displacement curve and, in general, all the phenomena involved for both brick and stone specimens. Three different modelling approaches were considered. First, a macro-model was adopted, where both brick and stone masonry were assumed as a homogeneous isotropic material. The steel bar and the grouted mortar of the anchor system were considered linear elastic and the system was placed in the specimen using interfaces. The second approach was a unit model, developed with the aim to reproduce the influence of the unit where the anchoring fastening is located. The last approach studied was a micro-model, where both the units and the mortar are considered. The challenge in modelling these systems is highlighted from the different modelling strategies used and compared.

The metamorphic core of the Betic-Rif orogenic chain (Alboran Domain) is made up of lower crustal rocks forming the envelope of the Ronda (Spain) and Beni Bousera (Morocco) peridotites. The deepest sections of the crustal envelopes are made of migmatitic granulites associated with diffuse acidic magmatic products, making these exposure and ideal site to investigate the textural and petrological connection between crustal anatexis and granite magmatism in the contintental crust. However, still debated is the timing of intracrustal emplacement of the peridotite bodies, with models proposing either Alpine (early Miocene) or Hercynian ages, and still uncertain is the linkage between peridotite emplacement and crustal anatexis. In this study, by combining rock textures with whole-rock geochemistry, metamorphic thermobarometry, the U-Pb zircon geochronology and the analysis of the garnet and zircon REE chemistry, we document the P-T-t evolution of the granulite fades migmatites that form the immediate envelope of the Beni Bousera peridotites of the Rif belt. A main episode of Permo-Carboniferous (ca. 300-290 Ma) deep crustal anatexis, melt extraction and migration is documented that we link to the crustal emplacement of the Beni Bousera peridotites during collapse of the Hercynian orogen. Correlation at a regional scale suggests that the Beni-Bousera section can be tentatively correlated with the pre-Alpine (Permo-Carboniferous) basement units tectonically interleaved within the orogenic structure of the Alpine chain. The results of this study provide ultimate constraints to reconstruct the tectono-metamorphic evolution of the Alboran Domain in the Western Mediterranean and impose re-assessment of the modes and rates through which Alpine orogenic construction and collapse occurred and operated in the region. (C) 2020 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Numerous studies exist on exhumed tectonic melanges along subduction channels whereas, in accretionary wedge interiors, deformation mechanisms and related fluid circulation in tectonic melanges are still underexplored. We combine structural and microstructural observations with geochemical (stable and clumped isotopes and isotope composition of noble gases in fluid inclusions of calcite veins) and U-Pb geochronological data to define deformation mechanisms and syn-tectonic fluid circulation within the Mt. Massico intra-wedge tectonic melange, located in the inner part of the central-southern Apennines accretionary wedge, Italy. This melange developed by shear deformation at the base of a clastic succession. Deformation was characterized by disruption of the primary bedding, mixing, and deformation of relicts of competent olistoliths and strata within a weak matrix of deformed clayey and marly interbeds. Recurrent cycles of mutually overprinting fracturing/veining and pressure-solution processes generated a block-in-matrix texture. The geochemical signatures of syntectonic calcite veins suggest calcite precipitation in a closed system from warm (108°-147 °C) paleofluids, with δ18O vlaues between +9‰ and 14‰, such as trapped pore waters after extensive 18O exchange with the local limestone host rock and/or derived by clay dehydration processes at T > 120 °C. The 3He/4He ratios in fluid inclusions are lower than 0.1 Ra, indicating that He was exclusively sourced from the crust. We conclude that: (1) intraformational rheological contrasts, inherited trapped fluids, and low-permeability barriers such as marly-shaly matrix, can promote the generation of intra-wedge tectonic melanges and the development of transient fluid overpressure; (2) clay-rich tectonic melanges, developed along intra-wedge decollement layers, may generate low-permeability barriers hindering the fluid redistribution within accretionary wedges.

The nucleation and concentration of asbestos in rocks are mostly associated with mechanisms of fibre formation, combined with the water-dependent mineralogical alteration produced during the serpentinization of ultramafic masses. Very little is known about the structural settings and tectonic histories that influence and control the occurrence of asbestos in non-serpentinized rocks diffusely embedded within tectonized ophiolitic suites. Focusing on a case history provided by a tectonized metagabbro from the Ligurian Alps (northern Italy), a multiscale structural–petrographic approach is used to investigate the relationships between rock fabric and fibrous amphibole growth within the metagabbro. Meso- to microstructural observations are used to document the role of structurally controlled fluid–rock interactions in localizing the growth of fibrous amphibole during ductile-to-brittle shearing (mylonitic foliation to shear veins). A qualitative structural scenario is provided to illustrate the growth of asbestos amphiboles in shear veins during the progression of shear deformation towards semi-brittle rheological conditions. The mechanisms of the structurally controlled growth of fibrous amphibole in non-serpentinized rocks imply an examination of the tectonic boundary conditions that are at the origin of the concentration of asbestos in ophiolitic rocks involved in orogenic belt construction.

The Eocene-MioceneMianeh-Hashtroud igneous district in NW Iran is part of the Turkish-Caucasus-Iranian collision zone, a key region to decipher the assembly and differentiation of Gondwana-derived terranes along the Alpine-Himalayan convergence zone. Major inherited tectonic structures control in space and time the Mesozoic-Cenozoic transition from oceanic subduction to continental collision in the region. The geology of the study area is dominated by a polyphase, long-lived magmatic activity, spanning from similar to 45 to similar to 6 Ma. The igneous products are subalkaline to alkaline, with intermediate to acid compositions and a high-K calcalkaline to shoshonitic affinity. Evidence of crustal contamination is attested by inherited zircons in the oldest (Eocene-Oligocene) samples, with ages spanning from Neo-Archean to Paleocene. The Sr-Nd isotopic compositions of the Eocene-Oligocene samples plot close to the Bulk Silicate Earth estimate, whereas the Miocene samples document stronger crustal contamination. The lack of correlation between Nd-Sr isotopes and SiO2 supports a scenario of magma differentiation of different magma batches rather than crustal contamination. Major oxide and Sr-Nd isotopic variation lead us to suggest that magmatism is the consequence of re-melting of earlier underplated (Mesozoic-Tertiary) magmatic products, controlled by amphibole-dominated fractionation processes. Regional scale correlations show long-lived Cenozoic magmatism in NW Iran and Caucasus region, where the main porphyry and epithermal deposits occur. We propose that the Cenozoic collisional magmatism and the associated mineralisation at the junction between NW-Iran and Caucasus was controlled by the activity of a major, lithosphere-scale inherited boundary, transverse to the convergence zone. In such a geodynamic setting, the along-strike segmentation of the lithosphere slab generated asthenospheric melts, their upwelling into the metasomatised supra-subduction mantle wedge and the potential activation of different mantle and crustal sources, with consequent mineral endowment in the region. (C) 2020 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

The Siah-Kamar Mo deposit (SKMD) is located at the northwestern termination of the Urumieh-Dokhtar magmatic zone and it is the only porphyry Mo ore reserve in Iran. The exploration program documented 39.2 Mt proved reserves @ 539 ppm Mo and 66.4 Mt probable reserves @ 266 ppm Mo. In this study, field and petrographic investigations, integrated with geochemical (fluid inclusion and quartz chemistry) and geochronological (U-Pb zircon, Re-Os molybdenite, and Rb-Sr multimineral isochron) studies are used to propose a metallogenic model for the Mo mineralisation in the SKMD. The geology of the SKMD is characterized by the emplacement of a multiphase Oligocene basic/intermediate (at ca. 33–30 Ma) to acidic (29–28 Ma) magmatic suite, which intruded the Eocene volcanic country rocks. The alteration zone, about 4 × 3 km in size and with a general NW-SE trend, is centered within the main basic porphyry stock, grading from an inner potassic-sodic zone to peripheral phyllic/propylitic halos. The late acidic magmatic products (stocks and dykes) intruded and post-dated the main alteration zone. Two-stage Mo mineralisation is recognised, including: (i) stage-1, disseminated molybdenite, coeval with the formation of potassic-sodic alteration and minor, microscale Fsp, Bt, Qz + Po veinlets; and (ii) stage-2, high-grade molybdenite + carbonate (±sericite), structurally-controlled stockwork veining. Fluid inclusion systematics combined with TitaniQ thermometry documents a mineralising fluid system compatible with a transition from high-temperature (up to ca. 600 °C) magmatic to epithermal (250 °C) conditions during progressive cooling, exhumation and mixing with meteoric sources at shallow crustal conditions (ca. 7–3 km). The Re-Os molybdenite dating constrains the high-grade Mo ore formation at ca. 29–28 Ma, attesting for the intimate linkage between the main Mo mineralisation and the acidic magmatic phase in the area. The Rb-Sr geochronology of the potassic-sodic alteration zones confirms the two-stage magmatic/mineralisation scenarios, overlapping within errors with the results obtained from the U-Pb zircon geochronology and constraining the formation of the potassic-sodic and phyllic alteration at ca. 33 and 28 Ma, respectively. Our results document an uncommon scenario of two-stage porphyry Mo mineralisation associated with intensive late stage carbonate precipitation and achieved during a long-lasting and multiphase magmatic pulses of Oligocene age. We highlight the dominant role of acidic fluid neutralisation for further ore enrichment during polyphase magma intrusion as the dominant factor controlling the Mo mineralisation in the SKMD. Comparison at a regional-scale indicates that parameters such as longevity of magma supply, progressive magma crystallization/differentiation, and the presence of a possible pre-enriched crustal material should be considered responsible for the Mo endowment in the UDMZ.

A better understanding of intraplate deformation requires the knowledge of the space–time scales involved in its development and to decipher possible links with the dynamic evolution of the plate boundaries. Central Iran provides an ideal test site to approach this scientific issue, since it is characterised by a prolonged history of Mesozoic–Cenozoic intraplate deformation that has been interfering with the spatio-temporal re-organization of the Zagros convergence zone along the Eurasia plate boundary. This study focus on the Doruneh Fault (DF) region that is considered as the northern mechanical boundary of the Central East Iranian Microcontinent. By combining field investigations with apatite low-temperature thermochronology, we present a revised tectono-stratigraphic scenario for the DF region, typified by a punctuated history of fault-related exhumation, burial and cooling history back to the Upper Cretaceous. When framed at regional scale, these results attest that the Zagros convergence zone, and its hinterland domain were fully mechanically coupled since ca. 40–35 Ma, a time lapse that is here referred as to the onset of continental collision along the Arabia–Eurasia plate boundary. In this scenario, the DF region operated throughout the Cenozoic as a major zone of residual stress accommodation and transfer in the hinterland domain of the Zagros convergence zone. Results of this study also suggest that the tectonic evolution along the Arabia–Eurasia plate boundary was modulated by the plate-boundary dynamics and by the modes of tectonic reactivation of the intracontinental weak zones of Central Iran and at its tectonic boundaries.

International audience; Unravelling the evolution of supradetachment basins developed in the hanging wall of low‐angle detachment faults may be an invaluable tool in reconstructing the tectonic evolution of highly extended terrains. These basins may record major regional tectonic events related to the exhumation of metamorphic core complexes, and the reconstruction of their evolution helps to quantify the amount of extension accommodated by such processes. Here we present stratigraphic and structural field evidence and micropaleontological constraints to the Neogene‐to‐Quaternary evolution of the supradetachment Gediz Graben that developed on top of the exhuming Central Menderes Massif (SW Turkey). This basin displays three different structural styles during its evolution: (i) it initiated as a ramp basin following the activation of the Gediz Detachment in the Middle Miocene; (ii) evolved as a half graben during the Late Miocene following the activation of high‐angle brittle faults at its southern margin; and (iii) reached its final symmetric graben configuration in Late Pliocene (?) – Quaternary times following the activation of its northern margin. New micropaleontological data document a short‐lived upper Tortonian marine episode in the basin, and major along‐strike variations in exhumation are documented on its southern margin. Our reconstruction shows how sedimentary basins originally formed in the hanging‐wall of detachment faults may eventually end up in tectonic contact with the mylonitic footwall. Finally, we highlight the importance of magmatism in localizing the deformation in highly extended terrains and in controlling the evolution of supradetachment systems.

The Miocene “Corte Blanco Tuff” rhyolite deposit is the product of a large volume and high intensity Plinian eruption from the solitary and monogenetic Ramadas Volcanic Centre (Central Andes, Province of Salta, NW Argentina). The “Corte Blanco Tuff” consists of vitreous tube pumices with rare euhedral sub-millimetric Mn-garnet phenocrysts, typically hosting inclusions of U-phases as zircon and monazite. Here, we present new textural, major and trace elemental analyses of garnet, zircon and glass that, combined with in situ U-(Th)-Pb zircon and monazite dating, are used to reconstruct the thermobaric environment of formation, age and longevity of the magmatic plumbing system of the Ramadas magma. The results indicate to a crystallization path of a peraluminous rhyolitic melt at shallow crustal levels (≤6 km), as sequentially tracked by the initial nucleation of zircon (780 °C at 9.16 Ma) and garnet (above or at ca. 700 °C), to the final monazite growth (660–670 °C, at 8.70 Ma) in a water-saturated (H2O = 3–5 wt%) environment, shortly before the eruption started. These data (1) define for the first time the primary magmatic origin of Mn-garnet in a rhyolitic volcanic setting; (2) provide new partition coefficients of rare earth elements (REE) between natural garnet, zircon and rhyolitic melts; and (3) permit reconstruction of the magmatic processes that resulted in the Ramadas eruption. On a wider scale, our results document the spatio-temporal (P-T conditions, timing and longevity) time scales involved in the petrogenesis of a shallow peraluminous water-saturated rhyolitic magmatic plumbing system that is able to generate the conditions for extremely explosive Plinian eruptions. Fil: Lucci, Federico. Università Degli Studi Roma Tre; Italia Fil: Rossetti, Federico. Università Degli Studi Roma Tre; Italia Fil: Becchio, Raul Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentina Fil: Theye, Thomas. Universität Stuttgart; Alemania Fil: Gerdes, Axel. Goethe Universitat Frankfurt; Alemania Fil: Opitz, Joachim. Universität Stuttgart; Alemania Fil: Baez, Walter Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Instituto Geonorte; Argentina Fil: Bardelli, Lorenzo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Instituto Geonorte; Argentina Fil: De Astis, Gianfilippo. Istituto Nazionale di Geofisica e Vulcanologia; Italia Fil: Viramonte, Jose German. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energía no Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energía no Convencional; Argentina. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Instituto Geonorte; Argentina Fil: Giordano, Guido. Università Degli Studi Roma Tre; Italia

The Iranian ophiolites are part of the vast orogenic suture zones that mark the Alpine-Himalayan convergence zone. Few petrological and geochronological data are available from these ophiolitic domains, hampering a full assessment of the timing and regimes of subduction zone metamorphism and orogenic construction in the region. This paper describes texture, geochemistry, and the pressure-temperature path of the Early Cretaceous mafic granulites that occur within the Tertiary Sabzevar ophiolitic suture zone of NE Iran. Whole rock geochemistry indicates that the Sabzevar granulites are likely derived from a MORB-type precursor. They are thus considered as remnants of a dismembered dynamo-thermal sole formed during subduction of a back-arc basin (proto-Sabzevar Ocean) formed in the upper-plate of the Neotethyan slab. The metamorphic history of the granulites suggests an anticlockwise pressure-temperature loop compatible with burial in a hot subduction zone, followed by cooling during exhumation. Transition from a nascent to a mature stage of oceanic subduction is the geodynamic scenario proposed to accomplish for the reconstructed thermobaric evolution. When framed with the regional scenario, results of this study point to diachronous and independent tectonic evolutions of the different ophiolitic domains of central Iran, for which a growing disparity in the timing of metamorphic equilibration and of pressure-temperature paths can be expected to emerge with further investigations.

Recent works documented Neogene to Quaternary dextral strike-slip tectonics along the Kuh-e-Sarhangi and Kuh-e-Faghan intraplate strike-slip faults at the northern edge of the Lut Block of Central Iran, previously thought to be dominated by sinistral strike-slip deformation. This work focuses on the evidence of Quaternary activity of one of these fault systems, in order to provide new spatiotemporal constraints on their role in the active regional kinematic scenario. Through geomorphological and structural investigation, integrated with optically stimulated luminescence dating of three generations of alluvial fans and fluvial terraces (at ~53, ~25, and ~6 ka), this study documents (i) the topographic inheritance of the long-term (Myr) punctuated history of fault nucleation, propagation, and exhumation along the northern edge of Lut Block; (ii) the tectonic control on drainage network evolution, pediment formation, fluvial terraces, and alluvial fan architecture; (iii) the minimum Holocene age of Quaternary dextral strike-slip faulting; and (iv) the evidence of Late Quaternary fault-related uplift localized along the different fault strands. The documented spatial and temporal constraints on the active dextral strike-slip tectonics at the northern edge of Lut Block provide new insights on the kinematic model for active faulting in Central Iran, which has been reinterpreted in an escape tectonic scenario.

Since the first discovery of ultrahigh pressure (UHP) rocks 30 years ago in the Western Alps, the mechanisms for exhumation of (U)HP terranes worldwide are still debated. In the western Mediterranean, the presently accepted model of synconvergent exhumation (e.g., the channel-flow model) is in conflict with parts of the geologic record. We synthesize regional geologic data and present alternative exhumation mechanisms that consider the role of divergence within subduction zones. These mechanisms, i.e., (i) the motion of the upper plate away from the trench and (ii) the rollback of the lower plate, are discussed in detail with particular reference to the Cenozoic Adria-Europe plate boundary, and along three different transects (Western Alps, Calabria-Sardinia, and Corsica-Northern Apennines). In the Western Alps, (U)HP rocks were exhumed from the greatest depth at the rear of the accretionary wedge during motion of the upper plate away from the trench. Exhumation was extremely fast, and associated with very low geothermal gradients. In Calabria, HP rocks were exhumed from shallower depths and at lower rates during rollback of the Adriatic plate, with repeated exhumation pulses progressively younging toward the foreland. Both mechanisms were active to create boundary divergence along the Corsica-Northern Apennines transect, where European southeastward subduction was progressively replaced along strike by Adriatic northwestward subduction. The tectonic scenario depicted for the Western Alps trench during Eocene exhumation of (U)HP rocks correlates well with present-day eastern Papua New Guinea, which is presented as a modern analog of the Paleogene Adria-Europe plate boundary.

The Kuh-e-Faghan strike-slip fault system (KFF), located to the northern edge of the Lut Block in central Iran, developed through a Neogene-Quaternary pulsed history of eastward fault propagation and fault-related exhumation. This system is a consequence of the residual stresses transmitted from the Arabia-Eurasia convergent plate boundary. Here we integrate structural and textural analysis with new and previously published apatite fission-track (AFT) and apatite (U-Th)/He (apatite He) results, chlorite thermomentry, and hematite (U-Th)/He data from hematite-coated brittle fault surfaces to constrain the timing of tectonic activity and refine patterns of late Miocene-Pliocene burial and exhumation associated with the propagation of the KFF. Twenty-nine hematite (U-Th)/He (hematite He) dates from three striated hematite coated slip surfaces from the KFF fault core and damage zone yield individual dates from ~12–2 Ma. Petrographic analysis and chlorite thermometry of a polyphase, fossil fluid system in the KFF fault core document that fluid circulation and mineralization transitioned from a closed system characterized by pressure solution and calcite growth to an open system characterized by hot hydrothermal (T = 239 ± 10 °C) fluids and hematite formation. Hematite microtextures and grain size analysis reveal primary and secondary syntectonic hematite fabrics, no evidence of hematite comminution and similar hematite He closure temperatures (~60–85 °C) in each sample. Integration of these results with thermal history modeling of AFT and apatite He data shows that KFF activity in the late Miocene is characterized by an early stage of fault nucleation, fluid circulation, hematite mineralization, and eastward propagation not associated with vertical movement that lasted from ~12 to 7 Ma. Hematite He, AFT, and apatite He data track a second phase of fault system activity involving fault-related exhumation initiating at ~7 Ma and continuing until present time. Our new data constrain the onset of the recognized Late Miocene-Pliocene tectonic reorganization in north-central Iran.

A polyphase history of oceanic construction and consumption is documented by the distribution of the Tethyan ophiolitic suture zones in Iran. Despite the geodynamic significance of these suture zones, few modern petrological and geochronological data are available from these ophiolitic domains, hampering a full assessment of the timing, thermobaric regimes and palaeotectonic scenarios leading to oceanic suturing and continental assembly in Iran and, more in general, along the southern margin of Eurasia. In this paper, we describe a newly discovered HP ophiolite melange within the Rasht ophiolites, at the NW termination of the Palaeo-Tethyan suture in Iran. Petrological investigations on the metamorphic units embedded within the ophiolite melange are integrated with whole-rock geochemistry and Ar–Ar phengite geochronology to constrain the geotectonic setting of formation and to define the associated P – T – t paths. We provide evidence that the Rasht ophiolite domain corresponds to an exhumed subduction complex formed during Early Carboniferous ( c. 350 Ma) subduction of a branch of the Palaeo-Tethyan oceanic realm, with peak metamorphism equilibrated under blueschist- to eclogite-facies metamorphic conditions. Implications of these data for the palaeotectonic reconstruction during closure of the Palaeo-Tethyan ocean and the terminal collisional assembly along the southern margin of the Eurasia plate are also discussed. Supplementary material: Analytical methods and protocols are available at https://doi.org/10.6084/m9.figshare.c.3706852

The Mediterranean offers a unique opportunity to study the driving forces of tectonic deformation within a complex mobile belt. Lithospheric dynamics are affected by slab rollback and collision of two large, slowly moving plates, forcing fragments of continental and oceanic lithosphere to interact. This paper reviews the rich and growing set of constraints from geological reconstructions, geodetic data, and crustal and upper mantle heterogeneity imaged by structural seismology. We proceed to discuss a conceptual and quantitative framework for the causes of surface deformation. Exploring existing and newly developed tectonic and numerical geodynamic models, we illustrate the role of mantle convection on surface geology. A coherent picture emerges which can be outlined by two, almost symmetric, upper mantle convection cells. The downwellings are found in the center of the Mediterranean and are associated with the descent of the Tyrrhenian and the Hellenic slabs. During plate convergence, these slabs migrated backward with respect to the Eurasian upper plate, inducing a return flow of the asthenosphere from the backarc regions towards the subduction zones. This flow can be found at large distance from the subduction zones, and is at present expressed in two upwellings beneath Anatolia and eastern Iberia. This convection system provides an explanation for the general pattern of seismic anisotropy in the Mediterranean, first-order Anatolia and Adria microplate kinematics, and may contribute to the high elevation of scarcely deformed areas such as Anatolia and Eastern Iberia. More generally, the Mediterranean is an illustration of how upper mantle, small-scale convection leads to intraplate deformation and complex plate boundary reconfiguration at the westernmost terminus of the Tethyan collision.