Sopesar el río a vasos de agua : (Reseña sobre) Dubin, Mariano (2011): Bardo. La Plata, PIXEL Editora, pp. 56

Fil: Tomassoni, Paula. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Sopesar el río a vasos de agua : (Reseña sobre) Dubin, Mariano (2011): Bardo. La Plata, PIXEL Editora, pp. 56

Fil: Tomassoni, Paula. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Sopesar el río a vasos de agua : (Reseña sobre) Dubin, Mariano (2011): Bardo. La Plata, PIXEL Editora, pp. 56

Fil: Tomassoni, Paula. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Geochemical history at DSDP Leg 56 Holes

A geological model of subduction postulated by Karig, Ingle, et al. (1975) and Karig and Sharman (1975) proposes that the sedimentary prism at the foot of the landward wall is being actively built as sediment is scraped off the subducting oceanic and plastered onto the base of the wedge, forming an accretionary wedge containing overthrust sedimentary layers or intense sedimentary folding. Because overlying layers must continually be uplifted and compressed to accommodate new matter at the base, the accreting wedge will provide a geochemical record of this process at or near the Japan Trench. Several recent papers have discussed the metalliferous sediments on the active oceanic ridges. The geochemistry of such sediments is now reasonably well known: generally these deposits are considered products of volcanic processes (Boström and Peterson, 1969; Böstrom et al., 1969; Horowitz, 1970, 1974; Cronan et al., 1972; Cronan and Garrett, 1973). The geochemistry of subduction zone sediments, however, is less well known, and the need for studies of these sediments is particularly urgent if such sediments provide a record of the effects of subduction of oceanic plates under continental crust. Because the Japan Trench contains welldeveloped subduction zone deposits, Leg 56 sampling was of utmost importance to the discovery of how they originate.

Concentrations of major-element oxides and minor and trace elements at DSDP Legs 87, 57, 56 and 31

Sediments from Sites 582 (11 samples), 583 (19 samples), 584 (31 samples), 294 (1 sample), 296 (9 samples), 297 (3 samples), 436 (11 samples), and 439 (3 samples) were analyzed by X-ray fluorescence and/or instrumental neutron activation analysis. Ten major elements and 24 minor and trace elements (including 7 rare earth elements) were determined with these methods. Geochemistry varies systematically with both the site location and sediment age. Such variations are explained in terms of changes in sedimentation processes caused by plate motion and changes in ocean currents.