Slab

About: Slab is a research topic. Over the lifetime, 31617 publications have been published within this topic receiving 318693 citations.

Plate detachment, asthenosphere upwelling, and topography across subduction zones

Abstract: This study analyzes the topography across subduction zones, considering the separate contributions of the crust and the mantle lithosphere to the observed surface elevation. We have found a transition from a region where the overriding plate is coupled to the descending slab and pulled down along with it to a region where the overriding plate floats freely on the asthenosphere. When the subducting slab retreats oceanward rapidly this transition is abrupt, and the edge of the overriding plate is uplifted. We propose that at some point during rapid slab rollback the overriding plate detaches and rebounds like a boat released from its keel. This event is associated with suction of asthenospheric material into the gap that is opened between the plates up to the base of the crust. As a result, the forearc uplifts, and magmatism in the arc increases.

Separating mantle from slab signatures in arc lavas using B/Be and radiogenic isotope systematics

Abstract: AT convergent margins, tectonic processes juxtapose subducted slab, mantle wedge and the crust of the upper plate in a column beneath the overlying arc volcano. As each of these components is expected to be chemically heterogeneous, and as all may contribute to magma chemistry, identifying the different sources of arc magmas has been difficult. A working hypothesis has emerged, in which tholeiitic and calc-alkaline lavas in island arcs are partial melts of the mantle produced by fluxing of the wedge by hydrous fluids from the subducted slab1,2. Trace-element and radiogenic isotope ratios have been used to define the chemical characteristics of these sources but cannot be unequivocally identified with one source; by contrast, high B/Be and 10Be/9Be ratios in arc lavas uniquely identify the subduction component3,4, and thus separate chemical variability owing to recent subduction from that reflecting other causes. Here we combine B/Be with Sr, Nd and Pb isotope systematics of alkaline, calc-alkaline and tholeiitic lavas from Java and Flores, Indonesia, to constrain the isotopic composition of their mantle and subduction sources. The alkaline lavas always have low B/Be, from which we conclude that they are derived from mantle that has not been modified by recent subduction (in agreement with refs 5 and 6). We also show that the isotopic composition of the subducted component is relatively homogeneous along the length of the arc, suggesting that the subduction of Australian continental lithosphere in the east started too recently to have changed the nature of the subducted material at present beneath Flores.

Heat flow, gap formation and break-outs in the continuous casting of steel slabs

Abstract: A theoretical investigation of heat flow and gap formation in the mold of a continuous slab caster has been undertaken using a mathematical model, with the ultimate purpose of predicting the casting conditions which can lead to break-outs. The mathematical model that has been developed for this study is capable of treating the heat flow and air gap as coupled phenomena, and can accept operating variables such as slab size, casting speed, mold taper, and thermal conductivity of the mold powder, as input. Four different cases of slab casting have been investigated; and it has been found that hot spots can form on the surface of the slab within a few centimeters of the corners. Depending on their temperature, it is suggested that these hot spots may give rise to the formation of break-outs off the corners of the slab. From an examination of the behavior of the hot spots, the susceptibility of the cases studied to break-outs has been evaluated. The usefulness of the present analysis in qualitatively ascertaining the location and extent of mold wear under different casting conditions has also been examined.

Behavior of Extended End-Plate Moment Connections Subject to Cyclic Loading

Abstract: Extended end-plate moment connections are one alternative to fully welded connections that has been considered for use in seismic force resisting moment frames. As a part of the SAC Steel Project, a research program to investigate the behavior and design of extended end-plate moment connections under cyclic loading was conducted at Virginia Polytechnic Institute and State University. Six bare steel beam-to-column connection specimens and one composite slab beam-to-column connection specimen were tested. An overview of the design, fabrication, and testing of the specimens is presented. The test results show that extended end-plate moment connections can be designed to provide the strength, stiffness, and ductility required for use in seismic force resisting moment frames. The effects of the composite slab are discussed, and it is recommended that the effects of the slab be considered in the design of beam-to-column extended end-plate moment connections.