Petrography, geochemistry and physical properties of a continuous extrusive section from the Sarami Massif, Semail Ophiolite

As opposed to ocean crustal drilling that often yields a discontinuous core , ophiolites provide a unique opportunity to study continuous sections of o ceanic basalts. In order to provide high frequency constraints on the const ruction of the upper oceanic crust, a continuous 280 m thick volcanic trans ect was sampled in the Semail ophiolite in Oman. The analyzed section is lo cated in the Sarami Massif, in the central part of the ophiolite, and expos ed along Wadi Shaffan. A multidisciplinary study was carried out after samp ling in the field. Core measurements including porosity, grain density, com pressional velocity, magnetic susceptibility and electrical resistivity for over 100 samples from this transect have been made. Geochemical analyses i ncluding major, trace and Rare Earth Elements were also performed on 23 sel ected samples from this transect. The Wadi Shaffan transect appears as comp osed of two main petrological and geochemical members providing the main li thostratigraphic signal. The boundary between the two sequences is marked b y the presence of a massive flow unit equating to the most primitive lava a nd across which significant changes in mineralogy and texture are observed. The physical properties equally record significant changes. In all, the se ction is characterized by chemical compositions coherent with that of V1-Ge otime volcanism and appears as built through two main sequences of volcanic activity. The magnetic susceptibility profile correlated to geochemical va riations present the most detailed evolution allowing to individualize a su ccession of at least 4 volcanic phases. These phases are interpreted as mag matic cycles characterized by differentiation processes, allowing one to pl ace high frequency constraints on the volcanic behavior of fast spreading r idges. Some of the physical properties also reflect this series of differen tiation trends, as noticed in the past from downhole measurements recorded in the context of deep ocean drilling into the crust.