There is growing evidence that the top part of the oceanic mantle is pervasively serpentinized prior to subduction. Because the interior of a subducting slab heats up slowly, the serpentinized layer can be preserved for tens of Myr, thereby forming a weak zone that allows for mechanical decoupling between the oceanic crust and underlying lithospheric mantle. Once the crust is eclogitized, a she...

We present a new crustal cross section through the east-west trending ultrahigh-pressure (UHP) Dabie Shan orogenic belt, east central China, based on a 400km-long seismic refraction profile. Data from our profile reveal that the cratonal blocks north and south of the orogen are composed of 35-km-thick crust consisting of three layers (upper, middle, and lower crust) with average seismic velocit...

[1] Analysis of Martian gravity and topography implies that crustal thickness variations created in the earliest evolution of planet have persisted to the present day. Relaxation of crustal thickness variations due to lower crustal flow by thermally activated creep is strongly temperature-dependent and so, for particular crustal rheology and thickness, provides a constraint on thermal evolution...

The dehydration of the lower crust and the assimilation of crustal materials into ascending magmas are two geologic phenomenon which lead to vertical mass transport and potentially, geochemical stratification of continental crust. LOWER CRUSTAL XENOLITHS, KILBOURNE HOLE This integrated Sr-Nd-Pb isotope study of paragneiss xenoliths from Kilbourne Hole maar, New Mexico, is the first of its kind ...

[1] We gathered seismic refraction and wide-angle reflection data from several active source experiments that occurred along the Mid-Atlantic Ridge near 35!N and constructed three-dimensional anisotropic tomographic images of the crust and upper mantle velocity structure and crustal thickness. The tomographic images reveal anomalously thick crust (8–9 km) and a low-velocity ‘‘bull’s-eye’’, from...

JULY 2005, GSA TODAY ABSTRACT The subduction factory processes raw materials such as oceanic sediments and oceanic crust and manufactures magmas and continental crust as products. Aqueous fluids, which are extracted from oceanic raw materials via dehydration reactions during subduction, dissolve particular elements and overprint such elements onto the mantle wedge to generate chemically distinc...

High-quality seismic data recorded during the 1999 Taiwan Chi-Chi earthquake (Mw=7.6) show that a smallscale orogenic process of both mountain-building and crust-thickening was simultaneously accomplished along one set of crustal-scale conjugated faults. Mountain-building near the surface was primarily produced by the main shock along an eastward low-angle thrust fault in the upper crust. In th...

The strong electric field at the surface of a strange star is discussed, and a self-consistent model is proposed to calculate its capability of supporting a “normal” nuclear material crust.We find that the electric field is already not able to support the crust even when the bottom density of the crust is still considerably lower than the neutron drip point, which means that it is not the neutr...

One of the fundamental geophysical observations made of the Earth is the stratified nature of the continental crust, in which the lower crust comprises denser, more mafic material and the upper crust comprises less dense, more felsic material. This chemically differentiated layered structure is developed and maintained by partial melting at depth and the ascent of magma to shallower crustal lev...