Slab

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

Anatomy of the Andean subduction zone: three-dimensional density model upgraded and compared against global-scale models

Abstract: SUMMARY We present an upgraded version of a previously published 3-D density model of the Andean subduction zone between 18°S and 45°S. This model consists of 3-D bodies of constant density, which geometry is constrained by independent seismic data and is triangulated from vertical cross-sections. These bodies define the first-order morphology and internal structure of the subducted Nazca slab and South American Plate. The new version of the density model results after forward modelling the Bouguer anomaly as computed from the most recent version of the Earth Gravitational Model (EGM2008). The 3-D density model incorporates new seismic information to better constrain the geometry of the subducted slab and continental Moho (CMH) and has a trench-parallel resolution doubling the resolution of the previous model. As an example of the potential utility of our model, we compare the geometry of the subducted slab and CMH against the corresponding global models Slab1.0 and Crust2.0, respectively. This exercise demonstrates that, although global models provide a good first-order representation of the slab and upper-plate crustal geometries, they show large discrepancies (up to ±40 km) with our upgraded model for some well-constrained areas. The geometries of the slab, lithosphere–asthenosphere boundary below the continent, CMH and intracrustal density discontinuity that we present here as Supporting Information can be used to study Andean geodynamic processes from a wide range of quantitative approaches.

Tectonic and magmatic transitions in the Western Great Basin, USA

Abstract: The isotope and trace-element geochemistry of late Cenozoic basalts from the Western Great Basin of California and Nevada demonstrates contributions from two distinct mantle source regions. High concentrations of large-ion lithophile relative to high-field strength elements (50 < Ba/Nb < 250) are often taken to reflect a contribution from contemporaneous subduction processes. But in this area they are associated with a marked change in 87Sr/86Sr and 143Nd/144Nd across a major lithospheric boundary, which is normal to the orientation of the palaeo-subduction zone and implies that these samples derived their isotope and trace element signatures from the mantle lithosphere. The second component is similar to that seen in ocean island basalts, and is attributed to asthenospheric source regions within the convecting upper mantle. Significantly, the onset of asthenosphere dominated magmatism migrated northwards during the Plio-Pleistocene about 2–3 Myr behind the trailing edge of the subducted slab. During this period it is proposed that asthenospheric diapirs rose from the level of the subducted slab into the zone of melt generation, implying ascent rates of between 5 and 8 cm per annum.