Differentiation, crustal contamination and emplacement of magmas in the formation of the Nantianwan mafic intrusion of the ~260?Ma Emeishan large igneous province, SW China

The Nantianwan mafic intrusion in the Panxi region, SW China, part of the ~260?Ma Emeishan large igneous province, consists of the olivine gabbro and gabbronorite units, separated by a transitional zone. Olivine gabbros contain olivine with Fo values ranging from 83 to 87, indicating crystallization from a moderately evolved magma. They have 0.2 to 0.9?wt?% sulfide with highly variable PGE (17?C151?ppb) and variable Cu/Pd ratios (1,500?C32,500). Modeling results indicate that they were derived from picritic magmas with high initial PGE concentrations. Olivine gabbros have negative ??Nd(t) values (?1.3 to ?0.1) and positive ??Os(t) values (5?C15), consistent with low degrees of crustal contamination. Gabbronorites include sulfide-bearing and sulfide-poor varieties, and both have olivine with Fo values ranging from 74 to 79, indicating crystallization from a more evolved magma than that for olivine gabbros. Sulfide-bearing gabbronorites contain 1.9?C4.1?wt?% sulfide and 37?C160?ppb PGE and high Cu/Pd ratios (54,000?C624,000). Sulfide-poor gabbronorites have 0.1?C0.6?wt?% sulfide and 0.2?C15?ppb PGE and very high Cu/Pd ratios (16,900?C2,370,000). Both sulfide-bearing and sulfide-poor gabbronorites have ??Nd(t) values (?0.9 to ?2.1) similar to those for olivine gabbros, but their ??Os(t) values (17?C262) are much higher and more variable than those of the olivine gabbros. Selective assimilation of crustal sulfides from the country rocks is thus considered to have resulted in more radiogenic ¹⁸⁷Os of the gabbronorites. Processes such as magma differentiation, crustal contamination and sulfide saturation at different stages in magma chambers may have intervened during formation of the intrusion. Parental magmas were derived from picritic magmas that had fractionated olivine under S-undersaturated conditions before entering a deep-seated staging magma chamber, where the parental magmas crystallized olivine, assimilated minor crustal rocks and reached sulfide saturation, forming an olivine- and sulfide-laden crystal mush in the lower part and evolved magmas in the upper part of the chamber. The evolved magmas were forced out of the staging chamber and became S-undersaturated due to a pressure drop during ascent to a shallow magma chamber. The magmas re-attained sulfide saturation by assimilating external S from S-rich country rocks. They may have entered the shallow magma chamber as several pulses so that several gabbronorite layers each with sulfide segregated to the base and a sulfide-poor upper part. The olivine gabbro unit formed from a new and more primitive magma that entrained olivine crystals and sulfide droplets from the lower part of the staging chamber. A transitional zone formed along the boundary with the gabbronorite unit due to chemical interaction between the two rock units.     

http://www.sciencedirect.com/science/article/pii/S1674987111001290

The Three Gorges Dam(TGD) of the Yangtze River.China,is one of the largest irrigation and hydroelectric engineering projects in the world.The effects of huge man-made projects like TGD on fauna and macrophyte are obvious,mainly through changes of water dynamics and flow pattern;however, it is less clear how microorganisms respond to such changes.This research was aimed to examine differences in microbial diversity at different seasons and locations(in front of and behind the TGD).In addition, differences between particle-attached and free-living communities were also examined.The community structures of total and potentially active microorganisms in the water columns behind and in front of the TGD were analyzed with the DNA- and RNA-based 16S rRNA gene phylogenetic approaches over three different seasons.Clone libraries of 16S rRNA genes were prepared after amplification from extracted DNA and.for some samples,after preparing cDNA from extracted rRNA.Differences were observed between sites at different seasons and between free-living and particle-attached communities.Both bacterial and archaeal communities were more diverse in summer than in winter, due to higher nutrient levels and warmer temperature in summer than in winter.Particle-attached microorganisms were more diverse than free-living communities,possibly because of higher nutrient levels and heterogeneous geochemical micro-environments in particles.Spatial variations in bacterial community structure were observed,i.e..the water reservoir behind the TGD(upstream) hosted more diverse bacterial populations than in front of the dam(downstream),because of diverse sources of sediments and waters from upstream to the reservoir.These results have important implications for our understanding of responses of microbial communities to environmental changes in river ecosystems affected by dam construction.     

Momentum and Turbulent Kinetic Energy Budgets Within the Park Avenue Street Canyon During the Joint Urban 2003 Field Campaign

Very few attempts have so far been made to quantify the momentum and turbulent kinetic energy (TKE) budgets within real urban canopies. In this study, sonic anemometer data obtained during the Joint Urban 2003 field campaign in Oklahoma City, U.S.A. were used for calculating the momentum and TKE budgets within a real-world urban street canyon. Sonic anemometers were deployed on multiple towers in the lower half of the canyon. Gradients in all three principal directions were included in the analyses. The storage and buoyancy terms were found to have negligible contributions to both the momentum and TKE budgets. The momentum budgets were generally found to be more complex than a simple balance of two physical processes. The horizontal terms were found to have significant and sometimes dominant contributions to the momentum and TKE budgets.     

Harmonization of land-use scenarios for the period 1500�C2100: 600?years of global gridded annual land-use transitions, wood harvest, and resulting secondary lands

In preparation for the fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC), the international community is developing new advanced Earth System Models (ESMs) to assess the combined effects of human activities (e.g. land use and fossil fuel emissions) on the carbon-climate system. In addition, four Representative Concentration Pathway (RCP) scenarios of the future (2005?C2100) are being provided by four Integrated Assessment Model (IAM) teams to be used as input to the ESMs for future carbon-climate projections (Moss et al. 2010). The diversity of approaches and requirements among IAMs and ESMs for tracking land-use change, along with the dependence of model projections on land-use history, presents a challenge for effectively passing data between these communities and for smoothly transitioning from the historical estimates to future projections. Here, a harmonized set of land-use scenarios are presented that smoothly connects historical reconstructions of land use with future projections, in the format required by ESMs. The land-use harmonization strategy estimates fractional land-use patterns and underlying land-use transitions annually for the time period 1500?C2100 at 0.5°?×?0.5° resolution. Inputs include new gridded historical maps of crop and pasture data from HYDE 3.1 for 1500?C2005, updated estimates of historical national wood harvest and of shifting cultivation, and future information on crop, pasture, and wood harvest from the IAM implementations of the RCPs for the period 2005?C2100. The computational method integrates these multiple data sources, while minimizing differences at the transition between the historical reconstruction ending conditions and IAM initial conditions, and working to preserve the future changes depicted by the IAMs at the grid cell level. This study for the first time harmonizes land-use history data together with future scenario information from multiple IAMs into a single consistent, spatially gridded, set of land-use change scenarios for studies of human impacts on the past, present, and future Earth system.     

Responding to change: Using scenarios to understand how socioeconomic factors may influence amplifying or dampening exploitation feedbacks among Tanzanian fishers

Environmental change often requires societies to adapt. In some instances, these adaptations can create feedbacks that amplify the change. Alternatively, other adaptations may dampen the change. We used semi-structured interviews with 240 fishers from nine Tanzanian coastal communities to explore responses to four hypothetical scenarios of increasingly severe declines in their average catch (10%, 20%, 30% and 50%). Overall, a higher proportion of fishers said they would respond to decline using amplifying adaptations (such as fishing harder) than dampening adaptations (such as reducing effort), particularly in the scenarios with lower levels of decline. We used a redundancy analysis to explore whether certain types of responses were related to the fishers’ socioeconomic characteristics. Fishers that would employ amplifying responses had greater economic wealth but lacked options. Fishers who would adopt dampening responses possessed characteristics associated with having livelihood options. Fishers who would adopt neither amplifying nor dampening responses were less likely to belong to community groups and sold the largest proportion of their catch. This study provides novel contributions by differentiating aspects of adaptive capacity that will amplify versus dampen environmental change and by highlighting what the resource users’ themselves say regarding responding to environmental change. Although direct policy application is limited by the study's hypothetical scenario nature, it provides a good beginning to incorporating resource users’ voices into such policy discussions.     

The influence of hydrodynamic boundary conditions on characteristics,migration, and associated sand transport of sand dunes in a tidal environment

Large parts of the tidal estuary of river Elbe (Germany) are characterized by regular patterns of sand dunes. They evolve due to complex sand transport mechanisms and show multi-faceted migration patterns, which are influenced by hydrodynamic boundary conditions such as runoff and tidal forces. This study aims at increasing the understanding of the way hydrodynamic boundary conditions influence dune behavior. This is the basis of an effective sediment management as well as an important requirement for planning offshore structures. From a unique data set of up to six annual bathymetrical multibeam soundings between 1995 and 2010, bedform characteristics and migration rates were processed and analyzed with a set of automated methods. The influence of river runoff, water levels, current velocities, tidal range, and river depth on characteristics and migration were tested statistically. The results show that migration is mainly dominated by the incoming flood tide while rates and directions depend on the amount of runoff originating from the inland catchment.     

Dynamic morphology of small south‐eastern Mediterranean river mouths: a conceptual model

River mouths along the Israeli Mediterranean coast are characterized by a dynamic morphology as their channels migrate hundreds of meters along the coast. This study examines the dynamic morphology of seven such river mouths. It offers a conceptual model aimed at generalizing and describing their spatial and temporal morphological patterns, and the environmental factors influencing them. The study methodology comprised a detailed monitoring and mapping by GIS techniques, with quantitative data derived from historic aerial photographs, river discharge records, wave measurements, and a digital elevation model. These data were incorporated into a homogenous database and subsequently applied in the investigation of the morphological patterns of these mouths, and the analysis of their influencing factors. River mouths in this study occur in two distinctive topographic settings. In one setting (here termed barrier topography) the river mouth is deflected alongshore by a sandy barrier. In the second setting (termed funnel topography) the river mouth is confined to a funnel‐shaped topographic depression perpendicular to the coast. The behavior of river mouths in these two settings is quite distinctive. Barrier mouths usually migrate over larger distances, as they tend to deflect along a sand barrier and establish semi‐permanent channels along the dune toe. This enables the wide range migration of semi‐permanent channels over decades. Funnel topography mouths deflect over shorter distances and they rapidly migrate within the funnel boundaries. This study concludes that the topographic setting of the beach, a constant element in the temporal scale of this study, is the primary influencing factor on the morphology of the mouths studied. The influence of other factors on the morphology of these mouths differs in space and time and depends on the topographic settings.     

Kinetic analysis of cation exchange in birnessite using time-resolved synchrotron X-ray diffraction

In this study, we applied time-resolved synchrotron X-ray diffraction (TRXRD) to develop kinetic models that test a proposed two-stage reaction pathway for cation exchange in birnessite. These represent the first rate equations calculated for cation exchange in layered manganates. Our previous work has shown that the substitution of K, Cs, and Ba for interlayer Na in synthetic triclinic birnessite induces measurable changes in unit-cell parameters. New kinetic modeling of this crystallographic data supports our previously postulated two-stage reaction pathway for cation exchange, and we can correlate the kinetic steps with changes in crystal structure. In addition, the initial rates of cation exchange, R (ų min⁻¹), were determined from changes in unit-cell volume to follow these rate laws: R = 1.75[]^0.56, R = 41.1[]^1.10, R = 1.15[]^0.50. Thus, the exchange rates for Na in triclinic birnessite decreased in the order: Cs ? K > Ba. These results are likely a function of hydration energy differences of the cations and the preference of the solution phase for the more readily hydrated cation.     

<Emphasis Type="Italic">Scombroclupea occidentalis</Emphasis> sp. nov. (Clupeiformes,Teleostei) from the Cenomanian (Cretaceous) Plattenkalk deposits of NE Mexico

A new species of the clupeid genus Scombroclupea is described from the Upper Cretaceous (Cenomanian) Plattenkalk locality “Loma la Mula” in Coahuila, northeastern Mexico. The material provides new osteological data for the genus, which clarify its systematic position. The Mexican Scombroclupea points to an occurrence of the genus in the western Tethys and indicates a vicariant event between S. macrophthalma from Lebanon and Croatia and the new species described herein. The analysis of the functional morphology of Scombroclupea supports the reconstruction of an oscillatory locomotion mode in this genus.