Earthquakes normally occur as frictional stick-slip instabilities, resulting in catastrophic failure and seismic rupture. Tectonic faults also fail in slow earthquakes with rupture durations of months or more, yet their origin is poorly understood. Here, we present laboratory observations of repetitive, slow stick-slip in serpentinite fault zones and mechanical evidence for their origin. We doc...

ONE petrological approach to upper mant le studies is to determine which ultramafic rocks represent mantle material. Ultramafic rocks occur in a variety of field and petrographic associations : in recent reviews, Wyllie [1967b, 1968] outlined eleven petrographic associations, some with subdivisions. In this summary, it is convenient to consider these in four larger groups: (1) layered, stratifo...

A new method to determine fluid flux at high pressures and temperatures has been developed used study serpentinites subduction zone conditions. Drill cores of a natural antigorite-serpentinite with strong foliation were in multi-anvil experiments the range 2–5 GPa 450–800°C. Fluids released upon dehydration are fixed by formation brucite an adjacent sink. The amount distribution serves as proxy...

Mount St Helens is the most active volcano within the Cascade arc; however, its location is unusual because it lies 50 km west of the main axis of arc volcanism. Subduction zone thermal models indicate that the down-going slab is decoupled from the overriding mantle wedge beneath the forearc, resulting in a cold mantle wedge that is unlikely to generate melt. Consequently, the forearc location ...