Ofioliti https://metarock.it/ofioliti/web/index.php/ofioliti <p>Since 1976, <em>Ofioliti</em> provides an international forum for original contributions and reviews in the field of the geodynamics, petrology, geochemistry, biostratigraphy, stratigraphy, tectonics and paleogeography applied to ophiolitic terrains and modern oceanic lithosphere, including their sedimentary cover. Studies of topics such as geodynamics of the mantle, the evolution of orogens including ophiolites and paleoceanography are also welcome.</p><p>Ofioliti is a FREE ACCESS journal. To download the pdf files of our articles you can register <a href="/index.php/ofioliti/user/register" target="_blank">here</a>. </p><p><em>2018 Impact Factor: 0.86</em></p><p><em>5-year Impact Factor: 1.41</em></p> Edizioni ETS - Pisa en-US Ofioliti 0391-2612 SYN-EXHUMATION COUPLING OF OCEANIC AND CONTINENTAL UNITS ALONG THE WESTERN EDGE OF THE ALPINE CORSICA: A REVIEW https://metarock.it/ofioliti/web/index.php/ofioliti/article/view/563 The Alpine Corsica represents a segment of the Alpine collisional belt. In, its western edge, it is characterized by the close association of continental units deformed under high-pressure metamorphic conditions (Lower Units) and oceanic units showing a metamorphism ranging from high-pressure (Schistes Lustrés Complex) to very low-grade conditions (Upper Units). This paper provides a complete review of the relationships between the continental and oceanic units in selected five areas where the stratigraphic features, deformation history, metamorphic P-T path and tectonic setting are make available for each unit. The collected data indicate that the oceanic units occur not only at the top of the continental ones, as generally proposed in the literature, but also intercalated within them. These relationships were achieved during the late stage of exhumation of the continental units, when the development of top-to-the W shear zones allow their mechanical coupling, at shallow structural level, with the oceanic units already accreted to the orogenic wedge. During this coupling the continental units are able to drag slices from the orogenic wedge, i.e. the oceanic units, that are thus subsequently interposed among them. After the coupling, the stack of oceanic and continental units experienced a further exhumation-related deformation up to their exposure in the surface. A picture where the coupling between the continental and oceanic units occurred immediately before the transition from syn- to post-orogenic geodynamics regime that affected the whole Alpine-Apennine collisional system in the early Oligocene, is here proposed. Maria Di Rosa Chiara Frassi Alessandro Malasoma Michele Marroni Francesca Meneghini Luca Pandolfi Copyright (c) 2020 Ofioliti 2020-09-14 2020-09-14 45 2 71 102 10.4454/ofioliti.v45i2.533 Composition gradients in silicate inclusions in chromites from the dunitic mantle-crust transition (Oman ophiolite) reveal high temperature fluid-melt-rock interaction controlled by faulting https://metarock.it/ofioliti/web/index.php/ofioliti/article/view/562 <p>The transition between the mantle section and the oceanic crust in the Maqsad area (Oman ophiolite) is mainly made of variably impregnated dunites locally associated with chromitite ore bodies. There, the dunitic transition zone (DTZ) developed above a mantle diapir that fed with MORB the former oceanic spreading centre. However, orthopyroxene and amphibole impregnations in dunites from the DTZ are witnesses of a hydrated magmatism that looks restricted to this interface. The main other piece of evidence is the nature of silicate minerals included in chromite grains scattered in dunite (e.g. amphibole, orthopyroxene, mica), which are mostly issued from a hydrated and silica-rich melt or fluid. Here, we report on a study of such inclusions along a section sampled in detail in the Maqsad DTZ. It brings critical information on the processes involved in the fluid-melt-peridotite reaction below oceanic spreading centres, complementary to the one provided by the interstitial silicates forming the matrix of the dunite. We first show that both the nature and the composition of the inclusions are well-correlated to those of the impregnations in the host dunites, then that the chemical evolution along the cross-section for all materials correlate to the presence of faults that developed at an early, syn-magmatic stage. This confirms that the early tectonic in the deep oceanic lithosphere primarily controls the fluid-melt-rock reactions and can condition chemical cycling, including for halogens (Cl, F), in oceanic spreading centre setting.</p><p> </p><p><em>First published online: 30 April 2020</em></p> Mathieu Rospabé Georges Ceuleneer Mathieu Benoit Mary-Alix Kaczmarek Copyright (c) 2020 Ofioliti 2020-04-30 2020-04-30 45 2 103 114 10.4454/ofioliti.v45i2.534