Compositional variations in ferrotapiolite + tantalite pairs from the beryl-columbite pegmatite at Moravanynad Váhom, Slovakia

Summary ?Three texturally and compositionally distinct pairs of ferrotapiolite + tantalite, all spatially related to a cleavelandite unit, were distinguished in the zoned beryl-columbite pegmatite at Moravany nad Váhom, Považsky Inovec Mts., Slovakia. (1) Inclusions of ferrotapiolite I (∼200 μm) in zoned ferrotantalite I exhibit crosscutting tielines of coexisting compositions in the columbite-tantalite quadrilateral. (2) Large ferrotapiolite II grains and adjacent, compositionaly variable grains of ferro- to manganotantalite II (∼100 μm) display remarkably diverse tielines, not yet observed in a single sample or locality. (3) Sn-depleted and slightly Mn,Ta-enriched narrow rims (∼20 μm) of ferrotapiolite III with small inclusions of manganotantalite III (≤ 5 μm) are located along a late, hydrothermal, fracture-filling microlite vein cross-cutting ferrotapiolite II. Changes in fO₂ derived from calculated Fe₂O₃ as well as variations in Ti, Sn, W concentrations through the ferrotapiolite + tantalite pairs I to III are negligible. Consequently, it seems plausible to explain the broadening of the two-phase field and the enrichment of ferrotapiolite and tantalite in Mn and Ta particularly by decreasing temperature. A disequilibrium crystallization from highly evolved residual melt and/or fluids is suggested for all textural types.

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Zusammenfassung ?Zusammensetzung von Ferrotapiolit-Tantalit-Paaren im Beryll-Columbit Pegmatit von Moravany nad Váhom (Považsky Inovec Mts., Slowakei) Drei Ferrotapiolit-Tantalit-Paare k?nnen in dem zonierten Beryll-Columbit-Pagmatit von Moravany nad Váhom, Povazsky Inovec Mts., Slowakei, auf der Basis detaillierter textureller und chemischer Untersuchungen unterschieden werden. Sie wurden in verschiedenen Stadien der Pegmatit-Kristallisation gebildet und sind r?mlich in Beziehung zu der Cleavelandit-Einheit (1). Einschlüsse von Ferrotapiolit I (∼200 μm) in zoniertem Ferrotantalit I zeigen sich kreuzende Konoden im Columbit-Tantalit Quadrilateral, die koexistierende K?rner beider Minerale miteinander verbinden. Dies legt nahe, dass Ferrotapiolit ein Produkt prim?rer (magmatischer) Disequilibrium-Kristallisation ist, und gleichzeitig mit den assoziierten Mineralen der Columbit-Gruppe gebildet wurde (2). Gro?e Ferrotapiolit II K?rner und K?rner von angrenzenden Ferro- bis Manganotantalit II (∼100 μm) zeigen Konoden mit bemerkenswerter Verschiedenheit, die bisher nicht in einer einzigen Probe beobachtet wurden. Eine sehr betonte Disequilibrium-Kristallisation aus stark fraktionierter Restschmelze dürfte hierfür verantwortlich sein (3). An Zinn verarmte und etwas an Mn, Ta angereicherter Ferrotapiolit III bildet dünne R?nder (∼20 μm) mit schmalen Einschlüssen von Manganotantalit III (≤5 μm) l?ngs einer Mikrolit-Ader. Erhat sich w?hrend hydrothermaler Subsolidus Verdr?ngung von Ferrotapiolit II durch Sprünge füllenden Microlit gebildet. Schwankungen in fO₂, berechnet aus Fe₂O₃ und die Gehalten an Ti, Sn und W k?nnen in den Ferrotapiolit-Tantalit-Paaren (1) bis (3) vernachl?ssigt werden. Dementsprechend erscheint es naheliegend, die Erweiterung des Zweiphasenfeldes und die Anreicherung von Ferrotapiolit und Tantalit an Mn und Ta durch Temperaturabnahme zu erkl?ren.

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Received May 4, 1999;/revised version accepted January 5, 2000     

Ice caps existed throughout the Lateglacial Interstadial in northern Scotland

We constrain, in detail, fluctuations of two former ice caps in NW Scotland with multibeam seabed surveys, geomorphological mapping and cosmogenic ¹⁰Be isotope analyses. We map a continuous sequence of 40 recessional moraines stretching from ～10 km offshore to the Wester Ross mountains. Surface‐exposure ages from boulders on moraine ridges in Assynt and the Summer Isles region show that substantial, dynamic, ice caps existed in NW Scotland between 13 and 14 ka BP. We interpret this as strong evidence that large active glaciers probably survived throughout the Lateglacial Interstadial, and that during the Older Dryas period (ca. 14 ka BP) ice caps in NW Scotland were thicker and considerably more extensive than in the subsequent Younger Dryas Stadial. By inference, we suggest that Lateglacial ice‐cap oscillations in Scotland reflect the complex interplay between changing temperature and precipitation regimes during this climatically unstable period (ca. 15–11 ka BP). © Natural Environment Research Council (NERC) copyright 2008. Reproduced with the permission of NERC. Published by John Wiley & Sons, Ltd.     

Groundwater geochemistry of the Chihuahua City region in the Rio Conchos Basin (northern Mexico) and implications for water resources management

The Chihuahua City region, located in the semiarid-arid northern highlands of Mexico, has experienced intensive groundwater abstraction during the last 40 years to meet water demands in the region. A geochemical survey was carried out to investigate the evolution from baseline to modern conditions of a 130-km flow path including the El Sauz–Chihuahua–Aldama–San Diego de Alcalá regions. The research approach included the use of major chemical elements, chlorofluorocarbons and environmental isotope (¹⁸O, ²H, ¹³C and ¹⁴C) tracers. Stable isotopes indicate that groundwater evolves from the evaporation of local rainfall and surface water. Groundwater located at the lower end of the flow section is up to 6000 years old and older groundwater in the order of 9000 years BP was found in a deep well located in the upper part of the flow system, implying contribution from a neighbour basin. The background groundwater chemistry upstream of Chihuahua City results from feldspar weathering. Beyond Chihuahua City the chemical conditions are strongly modified owing to disposal of sewage from public and industrial water supplies into the Rio Chuviscar, subsequent allocation of this water to agricultural irrigation areas and direct infiltration under the river bed. As a consequence, anions like chloride and sulphate are mainly related to surface sources. Nitrate is controlled in part by sewage from public supply and industry and in part by agricultural practices. Arsenic and fluoride are related to weathering of rock formations of local mineralized ranges and subsequent enrichment of the basin-fill by magmatic processes. The results of this study have implications for groundwater management in an arid region that depends entirely on groundwater for domestic, industrial and agricultural water consumption. Copyright © 2008 John Wiley & Sons, Ltd.     

A generalized additive model for the spatial distribution of snowpack in the Spanish Pyrenees

A generalized additive model (GAM) was used to model the spatial distribution of snow depth in the central Spanish Pyrenees. Statistically significant non‐linear relationships were found between distinct location and topographical variables and the average depth of the April snowpack at 76 snow poles from 1985 to 2000. The joint effect of the predictor variables explained more than 73% of the variance of the dependent variable. The performance of the model was assessed by applying a number of quantitative approaches to the residuals from a cross‐validation test. The relatively low estimated errors and the possibility of understanding the processes that control snow accumulation, through the response curves of each independent variable, indicate that GAMs may be a useful tool for interpolating local snow depth or other climate parameters. Copyright © 2005 John Wiley & Sons, Ltd.     

Floodplain hydrology of the Mekong Delta,Vietnam

The Mekong Delta is one of the largest and most intensively used estuaries in the world. Each year it witnesses widespread flooding which is both the basis of the livelihood for more than 17 million people but also the major hazard. Therefore, a thorough understanding of the hydrologic and hydraulic features is urgently required for various planning purposes. While the general causes and characteristics of the annual floods are understood, the inundation dynamics in the floodplains in Vietnam which are highly controlled by dikes and other control structures have not been investigated in depth. Especially, quantitative analyses are lacking, mainly due to scarce data about the inundation processes in the floodplains. Therefore, a comprehensive monitoring scheme for channel and floodplain inundation was established in a study area in the Plain of Reeds in the northeastern part of the Vietnamese Delta. This in situ data collection was complemented by a series of high‐resolution inundation maps derived from the TerraSAR‐X satellite for the flood seasons 2008 and 2009. Hence, the inundation dynamics in the channels and floodplains, and the interaction between channels and floodplains, could be quantified for the first time. The study identifies the strong human interference which is governed by flood protection levels, cropping patterns and communal water management. In addition, we examine the tidal influence on the inundation in various parts of the Delta, since it is expected that climate change‐induced sea level rise will increase the tidal contribution to floodplain inundation. Copyright © 2011 John Wiley & Sons, Ltd.     

Intensive agriculture, wetlands, quarries and water management. A case study (Campo de Dalias, SE Spain)

 The intensive agricultural activities that have developed over the last 50 years in the Campo de Dalias (Almeria region) have required large quantities of gravel and clay as the basic materials for the substrate over which crops are raised. With this motive, numerous gravel pits have been opened that have extracted several million cubic metres of material in recent years. Similar quantities of clay have been extracted from the distal sectors of the alluvial fans that descend from the Sierra de Gador, and from within a large endoreic basin. In the latter quarries, some wetlands have developed, probably because of the rise in the water-table level in the aquifer over which they lie. The gravel pits are situated in the apical sectors of the alluvial fans, overlying hydrogeological units that are widely overexploited. For this reason the gravel pits could be used for artificial recharge; in addition to increasing the availability of water in the aquifer, the risk of catastrophic flooding would also be reduced. Revision received: 19 November 1999 · Accepted: 28 December 1999     

Assess hydrological responses to a warming climate at the Lysina Critical Zone Observatory in Central Europe

Climate warming is having profound effects on the hydrological cycle by increasing atmospheric demand, changing water availability, and snow seasonality. Europe suffered three distinct heat waves in 2019, and 11 of the 12 hottest years ever recorded took place in the past two decades, which will potentially change seasonal streamflow patterns and long-term trends. Central Europe exhibited six dry years in a row since 2014. This study uses data from a well-documented headwater catchment in Central Europe (Lysina) to explore hydrological responses to a warming climate. We applied a lumped parameter hydrologic model Brook90 and a distributed model Penn State Integrated Hydrologic Model (PIHM) to simulate long-term hydrological change under future climate scenarios. Both models performed well on historic streamflow and in agreement with each other according to the catchment water budget. In addition, PIHM was able to simulate lateral groundwater redistribution within the catchment validated by the groundwater table dynamics. The long-term trends in runoff and low flow were captured by PIHM only. We applied different EURO-CORDEX models with two emission scenarios (Representative Concentration Pathways RCP 4.5, 8.5) and found significant impacts on runoff and evapotranspiration (ET) for the period of 2071–2100. Results from both models suggested reduced runoff and increased ET, while the monthly distribution of runoff was different. We used this catchment study to understand the importance of subsurface processes in projection of hydrologic response to a warming climate.     

Fire‐induced changes in soil water repellency increased fingered flow and runoff rates following the 2004 Huelva wildfire

Water repellency (WR) from fire‐affected soils can affect infiltration processes and increase runoff rates. We investigated the effects of fire‐induced changes in soil WR and the related soil hydrological response after one of the largest wildfires in Spain in recent years. The vertical distribution of WR in soil profiles was studied under oak and pine forests and the wetting pattern was analysed after rainfall simulations (85 mm h^?1 during 60 min). After burning, the persistence of WR in soils under oaks increased in the upper 0–5 cm of soil in comparison with pre‐fire WR, but no significant changes were observed under pines. After a fire, WR was stronger and the thickness of the water‐repellent layer increased in soils under pines in the upper 0–16 cm of soil. The hydrophobic layer was thinner under oaks, where no strong to extremely water‐repellent samples were observed below 12 (in burnt soils) and 8 cm (in unburnt soils). Uniform wetting was observed through soil depth in burnt and unburnt soils under oaks, as a consequence of the prevailing matrix flux infiltration. Water was mostly stored in the upper few centimetres and soil became rapidly saturated, favouring a continuous rise in the runoff rate during the experiments. Moisture profiles under pines showed a heterogeneous wetting pattern, with highly irregular wetting fronts, as a result of wettable and water‐repellent three‐dimensional soil patches. In this case, runoff rates on burnt plots increased in relation to unburnt plots, but runoff generation reached a steady state after 25–30 min of simulated rainfall at an intensity of 85 mm h^?1. Rainfall water infiltrated over a small part of the ponded area, where the vertical pressure of the water column overcame the WR. Copyright © 2010 John Wiley & Sons, Ltd.