基于势流理论和OpenFOAM的耦合模型对多向不规则波浪的模拟

基于势流理论的数值水池可以快速计算波浪的传播及其对建筑物的作用,但是势流理论是基于波浪的无黏性假设的,而在工程中,通常需要在固体边界及波浪破碎的区域考虑黏性效应。针对基于求解Navier-Stokes方程的黏性水池计算量较大、速度较慢的缺点,采用耦合的方法模拟多向不规则波浪的传播,即在外域通过基于势流理论的数值水池产生多向不规则波浪,内域采用求解Navier-Stokes方程和流体体积法(VOF方法)对自由表面进行追踪,通过外域所提供的边界波浪,内域计算可以在较小区域进行计算,从而达到减少计算量、提高计算效率的目的。     

Is maturity index an efficient tool to assess the effects of the physical disturbance on the marine nematode assemblages?—A critical interpretation of disturbance-induced maturity successions in some study cases in Maldives

Maturity index(MI), based on nematode life strategies, has been proposed in 1990 to assess the possible variations of the terrestrial and freshwater nematode assemblages induced by anthropogenic activities. It was subsequently applied also to marine ecosystems and, even if comparatively not yet very popular, it offers a good method to assess the ecological quality in relation to a wide range of anthropogenic drivers. However, few data are available on its response to physical stress, a key factor especially in the coastal areas. In this study, marine nematode genera from two study cases carried out in Maldives are used to test both MI and life strategy traits(i.e., c-p classes) for detecting the effects of physical disturbance. The results confirm that nematodes are well adapted to physical stress showing a general high rate of recovery. C-p scaling and MI did not seem to be appropriate for revealing this disturbance type probably because there are no empirical evidences on the life strategy of several genera, and a possible differential response to various disturbance types may be hypothesized.     

Effects of heavy metal (Pb) concentration on some growth parameters of plants grown in lead polluted soil under organic fertilizer amendment

This study investigated morphological variation and biomass accumulation that occurred in Sida acuta and Chromolaena odorata plants grown in lead polluted soil under organic fertilizer amendment. The study was carried out in the screen house at the Biological Gardens of the Obafemi Awolowo University, Ile-Ife, Osun State. The experiment was a factorial combination of one heavy metal (Pb) at five levels of concentration (0, 200, 400, 800 and 1,000 mg/kg) in a completely randomized design, and were replicated three times for each of the two plants and two levels (0 g/kg and 9.4 g/kg) of organic fertilizer (OBD-Plus). Each pot was filled with 5 kg of air-dried and sieved soil and placed on a plastic tray for the collection of excess water. Two weeks after planting, seedlings of uniform height were transplanted from the nursery to experimental pots at the rate of one seedling per pot and grown for 10 weeks. The growth parameters of the plants were biomonitored for 7 weeks. After 10 weeks of treatment, the plants were harvested and dried to calculate the biomass accumulation. The two plant species performed better under fertilizer application than without it. For each of the plant species the growth parameters decreased as the levels of Pb concentration increased. Furthermore, the plants' biomass decreased significantly (p<0.05) as the levels of Pb concentration increased. The organic fertilizer helped to improve the plants' performance in lead-polluted soil.     

http://www.sciencedirect.com/science/article/pii/S167498711600030X

Proterozoic(pre-Ediacaran) glaciations occurred under strongly seasonal climates near sea level in low palaeolatitudes.Metre-scale primary sand wedges in Cryogenian periglacial deposits are identical to those actively forming,through the infilling of seasonal(winter) thermal contraction-cracks in permafrost by windblown sand,in present-day polar regions with a mean monthly air temperature range of40 ℃ and mean annual air temperatures of-20 ℃ or lower.Varve-like rhythmites with dropstones in Proterozoic glacial successions are consistent with an active seasonal freeze-thaw cycle.The seasonal(annual) oscillation of sea level recorded by tidal rhythmites in Cryogenian glacial successions indicates a significant seasonal cycle and extensive open seas.Palaeomagnetic data determined directly for Proterozoic glacial deposits and closely associated rocks indicate low palaeolatitudes:Cryogenian deposits in South Australia accumulated at 10°,most other Cryogenian deposits at 20° and Palaeoproterozoic deposits at 15° palaeolatitude.Palaeomagnetic data imply that the Proterozoic geomagnetic field approximated a geocentric axial dipole,hence palaeolatitudes represent geographic latitudes.The Cryogenian glacial environment included glacier-free,continental permafrost regions with ground frozen on a kyr time-scale,aeolian sand-sheets,extensive and long-lived open seas,and an active hydrological cycle.This palaeoenvironment conflicts with the 'snowball Earth' and 'slushball Earth' hypotheses,which cannot accommodate large seasonal changes of temperature near the equator.Consequently,their proponents have attempted to refute the evidence for strong seasonality by introducing Popperian'auxiliary assumptions'.However,non-actualistic arguments that the Cryogenian sand wedges indicate diurnal or weakly seasonal temperature changes are based on misunderstandings of periglacial processes.Modelling of a strongly seasonal climate for a frozen-over Earth is invalidated by the evidence for persistent open seas and glacier-free continental regions during Cryogenian glaciations,and gives a mean monthly air temperature range of only 10 ℃ for 10° latitude.By contrast,a strongly seasonal climate in low palaeolatitudes,based on the actualistic interpretation of cryogenic sand wedges and other structures,is consistent with a high obliquity of the ecliptic(54°) during Proterozoic low-latitude glaciations,whereby the equator would be cooler than the poles,on average,and global seasonality would be greatly amplified.     

The Mesoproterozoic to early Neoproterozoic passive margin Lajeado Group and Apiaí Gabbro,Southeastern Brazil

The Lajeado Group in the Ribeira Belt,southeastern Brazil,corresponds to an open-sea carbonate platform,comprised of seven overlapping siliciclastic and carbonatic formations,intruded in its upper portion by the Apiai Gabbro.These rocks have a Neoproterozoic tectonometamorphic overprint related to arc magmatism and the Brasiliano collisional orogeny.Geochronological constraints are given by new UPb SHRIMP and LA-ICP-MS data for Lajeado Group detrital zircons and for magmatic zircons from the Apiai Gabbro.The youngest detrital zircons in the Lajeado Group are 1400-1200 Ma,and constrain its maximum age of deposition to be 1200 Ma,whereas the 877 ± 8 Ma age for magmatic zircons in the Apiai Gabbro give the minimum age.Detritus source areas are mainly Paleoproterozoic(2200-1800 Ma)with some Archean and Mesoproterozoic contribution(1500-1200 Ma),with distal or tectonic stable cratonic character.The Lajeado Group should be a Stenian-Tonian carbonate platform passive margin of a continent at this time,namely the Columbia/Nuna or the Rodinia.The Apiai Gabbro displays similar age to other intrusive basic rocks in the Lajeado and Itaiacoca groups and represents tholeiitic MORB-like magmatism that we relate to the initial break-up of a Mesoproterozoic continent and the formation of the Brasiliano oceans.     

http://www.sciencedirect.com/science/article/pii/S1674987115000882

A detailed vibrational Raman-IR spectroscopic and diffractional analyses have been performed on basalts from two locations from Tenerife Island:(1) the Arenas Negras volcano which belongs to the historical eruption not showing visible alteration and(2) Pillow Lavas zone from Anaga Massif which shows a clearly fluid-rock interaction caused by submarine alteration.These places have been extensively studied due to its similarity with the surface of Mars.The analysis is based on the mineral detection of selected samples by a Micro-Raman study of the materials.The complementary techniques have confirmed the mineralogy detected by the Raman measurement.The results show a volcanic environment behavior with primary phases like olivine,pyroxene,and feldspar/plagioclase.Moreover,the presence of accessory minerals or secondary mineralization like phosphate,iron oxides,zeolite or carbonates shows the alteration processes on each outcrop.The variation in the crystallinity and amorphous phases is related to fluid-rock interaction caused by hydrothermal episodes and external weathering processes,which shows several analogies with the ancient volcanic activity from Mars.     

The Gondwana Orogeny in northern North Patagonian Massif:Evidences from the Caita Có granite,La Se?a and Pangaré mylonites,Argentina

Structural analyses in the northern part of the North Patagonia Massif,in the foliated Caita Co granite and in La Sena and Pangare mylonites,indicate that the pluton was intruded as a sheet-like body into an opening pull-apart structure during the Gondwana Orogeny.Geochronological studies in the massif indicate a first,lower to middle Permian stage of regional deformation,related to movements during indentation tectonics,with emplacement of foliated granites in the western and central areas of the North Patagonian Massif.Between the upper Permian and lower Triassic,evidence indicates emplacement of undeformed granitic bodies in the central part of the North Patagonian Massif.A second pulse of deformation between the middle and upper Triassic is related to the emplacement of the Caita Co granite,the development of mylonitic belts,and the opening of the Los Menucos Basin.During this pulse of deformation,compression direction was from the eastern quadrant.     

http://www.sciencedirect.com/science/article/pii/S1674987115001516

The Semail ophiolite of Oman and the United Arab Emirates(UAE) provides the best preserved large slice of oceanic lithosphere exposed on the continental crust,and offers unique opportunities to study processes of ocean crust formation,subduction initiation and obduction.Metamorphic rocks exposed in the eastern UAE have traditionally been interpreted as a metamorphic sole to the Semail ophiolite.However,there has been some debate over the possibility that the exposures contain components of older Arabian continental crust.To help answer this question,presented here are new zircon and rutile U-Pb geochronological data from various units of the metamorphic rocks.Zircon was absent in most samples.Those that yielded zircon and rutile provide dominant single age populations that are 95-93 Ma,partially overlapping with the known age of oceanic crust formation(96.5-94.5 Ma),and partially overlapping with cooling ages of the metamorphic rocks(95-90 Ma).The data are interpreted as dating high-grade metamorphism during subduction burial of the sediments into hot mantle lithosphere,and rapid cooling during their subsequent exhumation.A few discordant zircon ages,interpreted as late Neoproterozoic and younger,represent minor detrital input from the continent.No evidence is found in favour of the existence of older Arabian continental crust within the metamorphic rocks of the UAE.     

Palaeoenvironmental Reconstruction of the Early to Middle Miocene Sequence in West Central Sinai,Egypt, as Revealed from Fossil Diatoms

A detailed analysis of the diatoms from the sedimentary sequence exposed in Abu Qada basin, west central Sinai, was used to determine the palaeoenvironmental changes during the Lower to Middle Miocene. A total of 85 diatom species and varieties belonging to 37 genera were identified from 154 samples collected throughout the stratigraphic succession. The lithological characters of the studied samples varied between sandstone, silty interbeds, sandy shales, shales, and terminated with anhydrite and limestones. These rock units are included in two lithostratigraphic formations (Rudies and Kareem), which are separated by a marked unconformity. The distribution and preservation of fossil diatoms in the sedimentary record are examined with the aim of outlining the temporal and spatial variation in the composition of the diatom assemblages, in order to estimate the changes in depositional environments during the Lower to Middle Miocene. The distributional pattern of the recorded diatom taxa distinguished four diatom eco-zones. The environment of each eco-zone is deduced and a proposed paleobathymetric change and depositional history of the Miocene sediments in the studied area are given.     

Geochemistry and Petrogenesis of Intracontinental Basaltic Volcanism on the Northwest Arabian Plate,Gaziantep Basin,Southeast Anatolia,Turkey

Volcanism along the northwest boundary of the Arabian Plate found in the Gaziantep Basin, southeast Turkey, is of Miocene age and is of alkaline and calc-alkaline basic composition. The rare earth element data for both compositional series indicates spinel–peridotite source areas. The rare earth and trace elements of the alkaline lavas originate from a highly primitive and slightly contaminated asthenospheric mantle; those of the calc-alkaline lavas originate from a highly heterogeneous, asthenospheric, and lithospheric mantle source. Partial melting and magmatic differentiation processes played a role in the formation of the petrological features of these volcanics. These rocks form two groups on the basis of their ~(87) Sr/~(86) Sr and ~(143) Nd/~(144) Nd isotopic compositions in addition to their classifications based on their chemical compositions(alkaline and calc-alkaline). These isotopic differences indicate a dissimilar parental magma. Therefore, high Nd isotope samples imply a previously formed and highly primitive mantle whereas low Nd isotope samples may indicate comparable partial melting of an enriched heterogeneous shallow mantle. Other isotopic changes that do not conform to the chemical features of these lavas are partly related to the various tectonic events of the region, such as the Dead Sea Fault System and the Bitlis Suture Zone.