Feedback of Slab Distortion on Volcanic Arc Evolution: Geochemical Perspective From Late Cenozoic Volcanism in SW Japan

Southwest Japan is an island arc formed by subduction of the Philippine Sea (PHS) plate. The Quaternary magmatism in this region is characterized by eruptions of high-Sr andesites and dacites, considered to have been derived by melting of the PHS plate. The loci of these volcanoes spatially coincide with seismic discontinuities of the subducted PHS plate. Thus, the magmatism is interpreted as the result of slab melting at the plate tears. However, the processes that promote slab tearing remain unclear. In this study, we applied geochronological and geochemical analyses to late Cenozoic volcanic rocks in southwest Japan as tracers of slab morphology. Two different magma types, ocean-island basalt (OIB) and island-arc basalt (IAB), have occurred over 12 million years (Myr). These two magmas are attributed to different integrations of melts extracted from an originally fertile mantle; the OIBs from high temperature melt (1,300–1,400°C) were extracted at a depth of 40–80 km, whereas the IABs were extracted from a shallower, lower temperature region (30–60 km, 1,200–1,350°C). Secular change in Sr enrichment of IAB likely arose due to a transition of slab-derived fluids, incorporated into magmas as they formed, from water- to melt-dominant one. Progressive shallowing of the subducted PHS plate is responsible for secular change in the properties of slab-derived fluids as well as rollback of OIB volcanoes. Production of chemically variable magmas in the Chugoku district is the surface expression of distorting slab morphology by interaction between mantle and the subducting plate

Plastic deformation induced anisotropy in metallic glasses: A molecular dynamics study

The atomic structure of a Cu13Ni34Pd53 metallic glass was studied by molecular dynamics simulation at different temperatures along a shear deformation cycle. A simulation box of 1 million atoms was deformed in the x axis and then the original orthogonal shape was recovered. Directional pair distribution functions were computed in the coordinate planes and some significant directions along the shear deformation cycle. No anisotropy was found in the initial state, while post-deformation anisotropy was revealed by significant differences of the partial pair distribution functions. The analysis of atomic environments concluded that the remnant anisotropy remains constrained into the shear plane. Low temperature samples showed remnant anisotropy after the full shear sample, while close to the glass transition the anisotropy induced by the initial shear process is removed by the subsequent recovery process.Peer ReviewedPostprint (published version

Production of High‐Sr Andesite and Dacite Magmas by Melting of Subducting Oceanic Lithosphere at Propagating Slab Tears

We present K-Ar ages, major and trace element concentrations, and Sr-Nd-Pb isotope data for late Cenozoic volcanic rocks from the Chugoku district, southwest Japan arc. Andesite and dacite lavas in this region are enriched in Sr (mostly >800 μg g−1) and show geochemical characteristics of volcanic rocks commonly referred to as “adakite.” K-Ar dating of these lavas revealed that the eruption of high-Sr andesitic to dacitic magmas occurred during the last 2 Myr, following or concurrent with the eruption of basalt in adjacent regions. Trace-element characteristics of high-Sr andesites and dacites are consistent with the formation of their parent magmas by partial melting of the basaltic layer of the subducting Shikoku Basin Plate. Mass balance modeling of trace element concentrations and isotopic compositions suggests that the parental magmas of high-Sr andesites and dacites are best explained by mixing of partial melts from oceanic crust (F = 5–15%) and sediment (F = 30%) at 80:20 to 55:45 ratios. Spatial coincidence of the occurrences of high-Sr andesites and dacites and seismic gaps of the subducting slab demonstrates the causal link between slab melting and mantle upwelling at slab tears. We speculate that these tears could have been formed by subduction of ridges on the plate. A warm mantle upwelled through tears, preventing the solidification of the siliceous slab melts in the mantle and facilitating the transportation of these melts to the surface

Study of medium range reordering by plastic deformation in Cu46Zr46Al8

The influence of shear in the atomic structure of ternary Cu46Zr46Al8 metallic glass was studied at different temperatures by molecular dynamics (MD) simulation. At temperatures above and below the glass transition temperature the system was subjected to a shear deformation cycle; the shear deformation was carried in the [100] direction and then the original geometry was recovered. The system was analyzed in three states: initial state (before deformation), deformed state (sheared) and final state (recovery). The different states obtained by the atomistic simulations were examined by computing the directional pair distribution functions (dPDF) in the coordinate planes. The results showed by dPDFs of the planes perpendicular to the coordinate axis are apparently isotropic. However, the dPDF disengage when computed perpendicular to rotated axis. This reveals that the anisotropy introduced during the deformation cycles appears in directions [110] and [1?0], tilted 45° with respect to the direction of the applied shear. To analyze the subtle structural change we systematically computed the positions and widths of the dPDF peaks on the rotated directions, thence allowing us to describe in detail the different signatures of anisotropy induced by deformation in the metallic glasses.Peer ReviewedPostprint (published version

Lo estético en el diseño

La apreciación estética de la vivienda vernácula en México ha estado ligada a su “significación cultural” desde el siglo XX, o a su calidad de capital, en la posmodernidad neoliberal. Sin embargo, la aproximación estética como ejercicio del habitante ha sido repetidamente desdeñada. La contemporaneidad y su crisis de la razón, que nos permite considerar como válidas las posturas personales a partir de las consideraciones de “percepción” y “lectura” y la configuración de lo estético a través de la semiótica, permiten el acercamiento a la estética de la vivienda vernácula a partir de la valoración que el habitante hace se ella por ser el receptáculo de su vida y el generador de legítimos significados individuales. Ante la complejidad del contexto globalizante, parece ser que el testimonio de vida cotidiana que la vivienda vernácula representa tiene en lo utilitario un medio para defenderse.The aesthetic appreciation of vernacular housing in Mexico has been linked to its “cultural significance” since the twentieth century, or to its quality of capital, in the neo-liberal postmodernity. However, the aesthetic approach as an inhabitant exercise has been repeatedly neglected. Nowadays, in a crisis of reason, which allows us to consider as valid the personal positions from the considerations of “perception” and “reading” and the configuration of aesthetics through semiotics, allow the approach to the aesthetics of Vernacular housing, based on the valuation that the inhabitant makes. That because it is the receptacle of his life and the generator of legitimate individual meanings. Given the complexity of the globalizing context, it seems that the testimony of everyday life that vernacular housing represents has a means to defend itself in the utilitarian