高压相的流变行为

在过去十五年里,最初在日本,为了合成高压相矿物使压力达到25GPa,已研制许多大体积新类型复式压砧的高压设备。然而在同一段时期,为了变形实验没有研制出任何设备在压力上超过3Gpa。因此,我们几乎没有或根本没有关于高压相流变行为任何一点信息,如具有β或尖晶石结构的Mg_2SiO_4和具有石榴石、钛铁矿或钙钛型结构的MgSiO_3,这些结构直接涉及到地球深部内的流动。我们根本不了解在地幔内所出现     

Impacts of aggregate dredging on sediment composition and associated benthic fauna at an offshore dredge site in the southern North Sea

Dredging and associated screening at a dredge site in the southern North Sea (Area 408) is associated with areas of well-sorted fine sand that extend for up to 3 km to the south-east of the dredged area and overlay sediments with a more variable particle size composition. This well-sorted fine sand may reflect deposition and transport of material mobilised by the dredging and screening processes at the dredge site. Multivariate analysis of the benthic community structure suggests that marine aggregate dredging, at the level of intensity employed in the study area prior to sample collection, has had a limited impact on benthic community composition compared with that reported from studies elsewhere. This is ascribed to the likely rapid rates of recolonisation by the mobile opportunistic polychaetes and crustaceans that dominate the macrofauna of the sandy gravel deposits at this particular dredge site. Analysis of variance showed, however, that significant differences existed between the sample treatments in terms of species evenness (Pielou's J). Dredged samples were found to have the lowest mean species evenness (0.71) when compared to controls (0.77). The present study highlights the inherent difficulties in the application of general impact/recovery predictions to dredged sites with varying environmental characteristics.