Figure 1. Schematic cross sections through (A) Galicia Margin west of Iberian Peninsula (Boillot et al., 1995) and (B) Jurassic margin of Apulian continent toward Alpine Tethys (Manatschal and Bernoulli, 1999). Inset in B displays present location of margin in Swiss Alps and paleoposition of section in Jurassic time. Abbreviations in A: lcc—lower continental crust; man— mantle; S—S-reflector; s...

Microbial life can leave various traces (or biosignatures) in rocks, including biotic alteration textures, biominerals, enrichments of certain elements, organic molecules, or remnants of DNA. In basalt glass from the ocean floor, microbial alteration textures as well as chemical and isotopic biosignatures have been used to trace microbial activity. However, little is known about the relationshi...

It is generally believed that an anomaly should be expected over the continent–ocean (C–O) boundary in the global magnetic anomaly maps. However, such maps prepared at satellite altitude do not show an anomaly over most of the C–O boundary. We address this issue by a forward modelling technique. We use a Geographic Information System (GIS) technique to integrate information of the various geolo...

the iranian plateau is characterized by diverse tectonic domains, including the continental collisions (e.g. the zagros and alborz mountains) and oceanic plate subduction (e.g. makransubduction zone). to derive a detailed image of the crust–mantle (moho) and lithosphere–asthenosphere (lab) boundaries in some tectonically units of the iranian plateau, we used a large number of s receiver functio...

[1] Seismic reflection profiles shot across the Cascadia forearc show that a 5–15 km thick band of reflections, previously interpreted as a lower crustal shear zone above the subducting Juan de Fuca plate, extends into the upper mantle of the North American plate, reaching depths of at least 50 km. In the extreme western corner of the mantle wedge, these reflectors occur in rocks with P wave ve...

Seamounts contribute to globally significant hydrothermal fluxes, but the dynamics and impacts of fluid flow through these features are poorly understood. Numerical models of coupled heat and fluid flow illustrate how seamounts induce local convection in the oceanic crust. We consider idealized axisymmetric seamounts and calculate mass and heat fluxes by using a coupled heatand fluid-flow model...

The deep biosphere is a major frontier to science. Recent studies have shown the presence and activity of cells in deep marine sediments and in the continental deep biosphere. Volcanic lavas in the deep ocean subsurface, through which substantial fluid flow occurs, present another potentially massive deep biosphere. We present results from the deployment of a novel in situ logging tool designed...

The basaltic ocean crust is the largest aquifer system on Earth, yet the rates of biological activity in this environment are unknown. Low-temperature (<100°C) fluid samples were investigated from two borehole observatories in the Juan de Fuca Ridge (JFR) flank, representing a range of upper oceanic basement thermal and geochemical properties. Microbial sulfate reduction rates (SRR) were measur...

Deep extensions of low seismic velocities in the mantle beneath volcanic centers are commonly attributed to high temperatures and have been used as a possible characteristic of hot plumes originating at the core-mantle boundary. To address this issue, we examine the effect of volatiles on melting to determine if regions of low seismic velocities may also be interpreted as regions of melting wit...