No abstract

The Mount Avic massif consists of serpentinized peridotite exposed in the southern Aosta valley (Northwestern Alps), covering an area of ca. 180 km 2 . The 1:10,000 scale geological map is located in the southern portion of the massif, where serpentinite is in contact with ophiolitic rocks pertaining to the Piemonte Zone, which represents the fossil Mesozoic Tethyan ocean. Southwards, ophiolites are overthrusted by the continental-derived Austroalpine Mont Glacier unit. Serpentinite consists of antigorite, magnetite, and coarse grained Ti-clinohumite, olivine, and diopside, which are reminiscent of the original mantle texture. Rodingitic mafic dykes are intruded within serpentinite; other mafic rocks, consisting of (not rodingitized) metagabbro and metabasalt with relict eclogitic minerals, occur as tectonic slices associated with serpentinite, calcschist and sulphide-rich epidosite. The map gives detailed and updated information on the structure and lithostratigraphy of the Mount Avic ophiolites, providing an insight to the mantle-crust transition of the Tethyan oceanic lithosphere.Keywords: geological map; Mount Avic; Western Alps; ophiolite; Aosta Valley; serpentinite IntroductionThe Main Map shows ophiolites cropping out at the Mount Avic massif in the southern Aosta Valley (Western Italian Alps, Figure 1). The petrology and geochemistry of the ophiolites of the Western Alps have been widely investigated (e.g. Angiboust & Agard, 2010;Baldelli, Dal Piaz, & Lombardo, 1985;Ballevre & Merle, 1993;Bearth, 1967;Benciolini, Lombardo, & Martin, 1988;Bucher, Fazis, Capitani, & Grapes, 2005;Castelli, 1985;Dal Piaz, 1999;Baldelli, Dal Piaz, & Lombardo, 1985;Dal Piaz, Martinotti, & Hunziker, 1972;Frezzotti, Selverstone, Sharp, & Compagnoni, 2011;Groppo, Beltrando, & Compagnoni, 2009;Lapen et al., 2003;Martin & Kienast, 1987;Martin & Tartarotti, 1989;Martin, Rebay, Kienast, & Mével, 2008;Michard, Goffé, Chopin, & Henry, 1996;Rebay & Powell, 2012;Reinecke, 1998;Tartarotti, Martin, & Polino, 1986;Tartarotti & Caucia, 1993;Tumiati et al., 2005;Tumiati, Martin, & Godard, 2010;Zanoni, Rebay, Bernardoni, & Spalla, 2012), but an integrated structural and petrological analysis of this area was needed to improve the reconstruction of the evolution of the Mesozoic Tethyan oceanic realm and to better understand the relationships between crustal-and mantle-related rocks. The purpose of this work is

The ocean crust is formed by the rising of magma from mid-ocean ridges and voluminous (1-30 km 3 ) flows of lava away from ridge axes. However, our understanding of the emplacement kinematics of submarine lava is often limited to plan view geometries of near-axis lava. Drilled cores provide in situ access to the intact internal structure of submarine lavas. We used neutron diffraction to study off-axis lava flows drilled into the uppermost crust of ODP/IODP-Site 1256 (Cocos Plate). We provide quantitative insights into submarine lava microstructures and strong evidence for a secondary lava injection into the interior of a solidifying flow of lava along the NW-SE direction parallel to the paleo-ridge axis of the East Pacific Rise. The dynamics of lava inflow are controlled by crystal abundance and the temperature of the lava-crystal mixture rather than by local seafloor topography. We provide a description of an in situ shear within submarine lavas revealed by composite shape and lattice preferred orientations, accounting for a dominant laminar nonuniform-type flow.