Perthite microstructure in magmatic alkali feldspar with oscillatory zoning; Weinsberg Granite, Upper Austria

Feldspar megacrysts from the Weinsberg granite (Moldanubian Zone) show oscillatory zoning with respect to the albite- and orthoclase components. All growth zones show perthitic exsolutions which take the form of bleb- and lens shaped albite-rich precipitates in an orthoclase-rich host. The average sizes and shapes of the precipitates show systematic variation with the integrated bulk compositions of the respective growth zones. The precipitates are abundant and relatively small in growth zones with intermediate bulk composition (Or50Ab41An09 - Or80Ab18An02), and they are less abundant and larger in more orthoclase-rich zones (Or88Ab11An01). Small precipitates have a relatively high aspect ratio, whereas the large precipitates in the potassium-rich zones are more spherical. The relation between microstructure and integrated bulk composition suggests that exsolution and subsequent growth and coarsening occurred by different mechanisms in the respective growth zones. Numerical modeling shows that rapid growth of precipitates over extended periods of time and attainment of relatively large final size is favored, if only few nuclei are formed in an oversaturated host. In contrast, precipitates can grow rapidly only over limited time intervals and remain relatively small, if abundant nuclei are present. During cooling of the oscillatorily zoned alkali-feldspar, exsolution started at relatively high temperatures in growth zones of intermediate integrated bulk composition as compared to exsolution in the more orthoclase-rich growth zones. Irrespective of whether exsolution occurred by spinodal decomposition or by nucleation at relatively high temperatures in the growth zones of intermediate integrated bulk composition, it produced abundant nuclei and resulted in relatively small precipitates. In contrast, comparatively few nuclei were formed in the orthoclase-rich growth zones resulting in large precipitates. The Na/K partitioning between precipitates and the host is independent of the integrated bulk composition of the respective growth zone reflecting re-equilibration during cooling down to relatively low temperatures (<?400°C). The shape of the precipitates probably has evolved from an initially lamellar or spindle-like geometry with high aspect ratio to more isometric, spheroidal shapes during precipitate growth and coarsening. Host/precipitate interfaces served as fluid pathways during late stage deuteric alteration.     

GhostNet marine debris survey in the Gulf of Alaska--satellite guidance and aircraft observations

Marine debris, particularly debris that is composed of lost or abandoned fishing gear, is recognized as a serious threat to marine life, vessels, and coral reefs. The goal of the GhostNet project is the detection of derelict nets at sea through the use of weather and ocean models, drifting buoys and satellite imagery to locate convergent areas where nets are likely to collect, followed by airborne surveys with trained observers and remote sensing instruments to spot individual derelict nets. These components of GhostNet were first tested together in the field during a 14-day marine debris survey of the Gulf of Alaska in July and August 2003. Model, buoy, and satellite data were used in flight planning. A manned aircraft survey with visible and IR cameras and a LIDAR instrument located debris in the targeted locations, including 102 individual pieces of debris of anthropogenic or terrestrial origin.     

Soil acidity adaptive control problem

Problem of soil acidity regularization is modeled as stochastic adaptive control problem with a linear difference equation of the dynamics of a field pH level. Stochastic component in the equation represents an individual time variability of soil acidity of an elementary section. We use Bayesian approach to determine a posteriori probability density function of the unknown parameters of the stochastic transition process. The Kullback–Leibler information divergence is used as a measure of difference between true distribution and its estimation. Algorithm for the construction of an adaptive stabilizing control in such a linear control system is proposed in the paper. Numerical realization of the algorithm is represented for a problem of a field soil acidity control.     

Petrological and experimental evidence for differentiation of water-rich magmas beneath St. Kitts,Lesser Antilles

St. Kitts lies in the northern Lesser Antilles, a subduction-related intraoceanic volcanic arc known for its magmatic diversity and unusually abundant cognate xenoliths. We combine the geochemistry of xenoliths, melt inclusions and lavas with high pressure–temperature experiments to explore magma differentiation processes beneath St. Kitts. Lavas range from basalt to rhyolite, with predominant andesites and basaltic andesites. Xenoliths, dominated by calcic plagioclase and amphibole, typically in reaction relationship with pyroxenes and olivine, can be divided into plutonic and cumulate varieties based on mineral textures and compositions. Cumulate varieties, formed primarily by the accumulation of liquidus phases, comprise ensembles that represent instantaneous solid compositions from one or more magma batches; plutonic varieties have mineralogy and textures consistent with protracted solidification of magmatic mush. Mineral chemistry in lavas and xenoliths is subtly different. For example, plagioclase with unusually high anorthite content (An_≤100) occurs in some plutonic xenoliths, whereas the most calcic plagioclase in cumulate xenoliths and lavas are An₉₇ and An₉₅, respectively. Fluid-saturated, equilibrium crystallisation experiments were performed on a St. Kitts basaltic andesite, with three different fluid compositions (XH₂O = 1.0, 0.66 and 0.33) at 2.4 kbar, 950–1025 °C, and fO₂ = NNO ? 0.6 to NNO + 1.2 log units. Experiments reproduce lava liquid lines of descent and many xenolith assemblages, but fail to match xenolith and lava phenocryst mineral compositions, notably the very An-rich plagioclase. The strong positive correlation between experimentally determined plagioclase-melt Kd_Ca–Na and dissolved H₂O in the melt, together with the occurrence of Al-rich mafic lavas, suggests that parental magmas were water-rich (> 9 wt% H₂O) basaltic andesites that crystallised over a wide pressure range (1.5–6 kbar). Comparison of experimental and natural (lava, xenolith) mafic mineral composition reveals that whereas olivine in lavas is predominantly primocrysts precipitated at low-pressure, pyroxenes and spinel are predominantly xenocrysts formed by disaggregation of plutonic mushes. Overall, St. Kitts xenoliths and lavas testify to mid-crustal differentiation of low-MgO basalt and basaltic andesite magmas within a trans-crustal, magmatic mush system. Lower crustal ultramafic cumulates that relate parental low-MgO basalts to primary, mantle -derived melts are absent on St. Kitts.     

Batisite,Na2BaTi2(Si4O12)O2, from Inagli massif,Aldan, Russia: crystal-structure refinement and high-temperature X-ray diffraction study

Mineralogy and Petrology - The crystal structure of batisite, Na2BaTi2 (Si4O12)O2, from the Inagli massif (Aldan, Yakutia, Russia) was refined to R 1&nbsp;=&nbsp;0.032 for 1449 unique...     

Dynamic of Sea Water Interface using Hydrochemical Facies Evolution Diagram

This paper analyzes the results of a theoretical simulation of sea water intrusion and its dynamics. The assignment of hydrochemical facies identifies whether the aquifer is in the phase of sea water intrusion or freshening, indicating the status of the aquifer in terms of the advance or regression of the saline front. A new multi-rectangular diagram is proposed that aids interpretation of these important processes through the representation and evolution of hydrochemical facies (hydrochemical facies evolution diagram, HFE-D). As an example, the HEF-D is applied to an alluvial aquifer in the Vinaroz-Peñíscola Plain (Spain), where Ca-Cl facies characterize the sea water intrusion phase, while Na-MixHCO₃/MixSO₄ facies characterize a freshening stage.     

Numerical reconstruction of trajectory of small-size surface drifter in the Mediterranean sea

In this study, we addressed the effects of wind-induced drift on Lagrangian trajectories of surface sea objects using high-resolution ocean forecast and atmospheric data. Application of stochastic Leeway model for prediction of trajectories drift was considered for the numerical reconstruction of the Elba accident that occurred during the period 21.06.2009–22.06.2009: a person on an inflatable raft was lost in the vicinity of the Elba Island coast; from the initial position, the person on a raft drifted southwards in the open sea and later he was found on a partially deflated raft during rescue operation. For geophysical forcing, we used high-resolution currents from the Mediterranean Forecasting System and atmospheric wind from the European Centre for Medium-Range Weather Forecasts. To investigate the effect of wind on trajectory behavior, numerical simulations were performed using different categories of drifter-like particles similar to a person on an inflatable raft. An algorithm of spatial clustering was used to differentiate the most probable search areas with a high density of particles. Our results showed that the simulation scenarios using particles with characteristics of draft-limited sea drifters provided better prediction of an observed trajectory in terms of the probability density of particles.     

Land Cover Change Characteristics of North-South Transect in Northeast Asia from 2001 to 2012

Northeast Asia is an area with relative concentrations of resources, a complex ecological environment pattern, and a marked human-land contrast relationship. This area has significance for analyzing land cover patterns and variations for regional sustainable development among the trans-boundary areas of China, Russia, and Mongolia. In this paper, the transect analysis research tool and transfer matrix method are used to capture the regional land cover change characteristics by using Moderate Resolution Imaging Spectroradiometer(MODIS) datasets recorded from 2001 to 2012.The spatial distribution results show that forests have increased dramatically, cropland increased marginally, and grassland and shrubs decreased totally. The inter-annual variation, results show a steady and slowly increasing trend for grassland and shrubs, dramatic fluctuation features with an increasing trend for forest land, and zigzag wave changing characteristic for cropland. The total land use dynamic degree (TLUDD)was steady, with an overall slightly increasing trend.