U-Pb geochronology on zircon and columbite-group minerals of the Cap de Creus pegmatites,NE Spain     

Van Lichtervelde  Marieke  Grand’Homme  Alexis  de Saint-Blanquat  Michel  Olivier  Philippe  Gerdes  Axel  Paquette  Jean-Louis  Melgarejo  Joan Carles  Druguet  Elena  Alfonso  Pura 《Mineralogy and Petrology》2017,111(1):1-21

Mineralogy and Petrology - The Cap de Creus granitic pegmatites in the eastern Catalan Pyrenees were dated using in situ U-Pb geochronology by laser ablation ICP-MS on zircon and columbite-group...  相似文献   

The Iberian Pyrite Belt: a mineralized system dismembered by voluminous high-level sills     

Clive A. Boulter  Carles Soriano  & Pascale Zimman 《地学学报》2001,13(2):99-103

The Iberian Pyrite Belt is a world-ranking massive sulphide province in which a reassessment of the palaeovolcanology has dramatically changed understanding of the source of metals and mechanism of ore formation. In the northern sector, the deposits are hosted by a sill–sediment complex in which more than 90% of the sills post-date the sulphide sheets. Because of a very high sill/sediment ratio, these late intrusions dominate the host succession and have severely disrupted the post-mineralization configuration thus obscuring the true genetic relationships. For example, some oxide deposits have been separated by hectometric sills from sulphide deposits they originally capped, creating seemingly totally independent mineralizing systems. In addition, stratiform sulphide sheets without underlying stockworks are not necessarily allochthonous. An early timing for the mineralization with respect to volcanism means that metals had to be predominantly sourced from the sedimentary basin and the continental crust below the volcanogenic sequence.  相似文献   

Non integrability of theJ 2 problem     

Maylis Irigoyen  Carles Simó 《Celestial Mechanics and Dynamical Astronomy》1993,55(3):281-287

We consider the motion of a massless particle around an oblate planet, keeping only in the expression of the perturbing potential the second degree zonal harmonic. We prove the analytical non integrability of this problem, by using Ziglin's theorem and the Yoshida criterion for homogeneous potentials.  相似文献   

Acid drainage at the inactive Santa Lucia mine,western Cuba: Natural attenuation of arsenic,barium and lead,and geochemical behavior of rare earth elements     

Francisco Martín Romero  Rosa María Prol-Ledesma  Carles Canet  Laura Núñez Alvares  Ramón Pérez-Vázquez 《Applied Geochemistry》2010

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Co-evolution of coarse grain structuring and bed roughness in response to episodic sediment supply in an experimental aggrading channel     

Marwan A. Hassan  Matteo Saletti  Chendi Zhang  Carles Ferrer-Boix  Joel P.L. Johnson  Tobias Müller  Claudia von Flotow 《地球表面变化过程与地形》2020,45(4):948-961

We use flume experiments to better understand how gravel-bed channels maintain bed surface stability in response to pulses of sediment supply. Bed elevations and surface imagery at high spatial resolutions were used to quantify the co-evolution of surface grain-size distribution (GSD), bed roughness statistics, and bed surface structures (clusters, cells and transverse features). Using a new semi-automated method, we identified individual stone structures over a 2 m × 1 m area throughout the experiments. After an initial coarsening, surface GSD and armouring ratio remained nearly stable as sediment pulses caused net bed aggradation. In contrast, individual grain structures continued to form, increase or decrease in size, and disappear throughout the experiments. The response of the bed to sediment pulses depended on the history of surface roughness evolution and bed surface structure development, as these factors changed much more in response to supply perturbations earlier in the experiments compared to later, even as the bed continued to aggrade. We interpret that the dynamic production and destruction of bed surface structures can act as a ‘buffer’ to sediment supply pulses, maintaining a stable bed surface during aggradation with minimal change in grain size or armouring. © 2019 John Wiley & Sons, Ltd.  相似文献   

Dependence of sediment sorting on bedload transport phase in a river meander          下载免费PDF全文

Albert Rovira  Francisco Núñez‐González  Carles Ibañez 《地球表面变化过程与地形》2018,43(10):2077-2088

It is widely recognized nowadays that there are at least two different phases of bedload sediment transport in gravel‐bed rivers. However, the transition between these phases is still poorly or subjectively defined, especially at bends in rivers, where cross‐stream sediment transport can strongly influence changes in the texture of the transported sediment. In this paper, we use piecewise models to identify objectively, at two points in the cross‐section of a river bend, the discharge at which the transition between bedload transport phases occurs. Piecewise models were applied to a new bedload data set collected during a wide range of discharges while analysing the associated changes in sediment texture. Results allowed the identification of two well‐differentiated phases of sediment transport (phase I and phase II), with a breakpoint located around bankfull discharge. Associated with each phase there was a change in bedload texture. In phase I there was non‐dominance in the transport of fine or coarse fractions at a particular sampling point; but in phase II bedload texture was strongly linked to the position of the sampling point across the channel. In this phase, fine particles tended to be transported to the inner bank, while coarse sizes were transferred throughout the middle parts of the channel. Moreover, bedload texture at the inner sampling point became bimodal while the transport of pebble‐sized particles was increasing in the central parts of the river channel. It is suggested that this general pattern may be related both to secondary currents, which transfer finer particles from the outer to the inner bank, and to the progressive dismantling of the riverbed surface layer. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

Variable hillslope-channel coupling and channel characteristics of forested mountain streams in glaciated landscapes     

Marwan A. Hassan  Stephen Bird  David Reid  Carles Ferrer-Boix  Dan Hogan  Francesco Brardinoni  Shawn Chartrand 《地球表面变化过程与地形》2019,44(3):736-751

Channel morphology of forested, mountain streams in glaciated landscapes is regulated by a complex suite of processes, and remains difficult to predict. Here, we analyze models of channel geometry against a comprehensive field dataset collected in two previously glaciated basins in Haida Gwaii, B.C., to explore the influence of variable hillslope–channel coupling imposed by the glacial legacy on channel form. Our objective is to better understand the relation between hillslope–channel coupling and stream character within glaciated basins. We find that the glacial legacy on landscape structure is characterized by relatively large spatial variation in hillslope–channel coupling. Spatial differences in coupling influence the frequency and magnitude of coarse sediment and woody material delivery to the channel network. Analyses using a model for channel gradient and multiple models for width and depth show that hillslope–channel coupling and high wood loading induce deviations from standard downstream predictions for all three variables in the study basins. Examination of model residuals using Boosted Regression Trees and nine additional channel variables indicates that ~10 to ~40% of residual variance can be explained by logjam variables, ~15–40% by the degree of hillslope–channel coupling, and 10–20% by proximity to slope failures. These results indicate that channel classification systems incorporating hillslope–channel coupling, and, indirectly, the catchment glacial legacy, may present a more complete understanding of mountain channels. From these results, we propose a conceptual framework which describes the linkages between landscape history, hillslope–channel coupling, and channel form. © 2018 John Wiley & Sons, Ltd.  相似文献   

What controls the disequilibrium state of gravel-bed rivers?     

Shawn M. Chartrand  A. Mark Jellinek  Marwan A. Hassan  Carles Ferrer-Boix 《地球表面变化过程与地形》2019,44(15):3020-3041

A river at equilibrium is described by a statistically-stationary mean bed elevation profile that arises in response to steady supplies of relief, water and sediment. Outside of the profile shape, how is the equilibrium state of a river most reliably identified and rigorously defined? Motivated by a proposed link between equilibrium and physical processes, we use scaling theory to develop the dimensionless channel response number ξ=KU_b/U_p. ξ is a metric for the local disequilibrium state of gravel-bed mountain streams, which reflects a balance between the rate of topographic adjustment U_b, and the rate of bed sediment texture adjustment U_p. The coefficient K can take one of two forms depending on choice of length scale for topographic adjustment. We hypothesize that equilibrium occurs where and when ξ≈O(1), and consequently, disequilibrium is the more general state captured by conditions of ξ≉O(1). The rates U_b and U_p are controlled by the mechanics of sediment deposition and entrainment at the local scale of the channel width. The extent to which either process regulates disequilibrium depends on the bed strength, which is set by the time-varying grain size distribution and packing. We use flume experiments to understand ξ and find that in the limit ξ>>1, the time-varying response of an experimental channel depends sensitively on the spatially-averaged bed shear stress ratio τ/τ_ref. When τ/τ_ref≈1.5, U_b was the dominant control on disequilibrium. However, when τ/τ_ref≈2.0, U_p contributed more significantly to disequilibrium. These results suggest that after an upstream supply perturbation, the equilibrium timescale is governed by U_p, which we show is consistent with expectations from linear damping theory. Our experimental test of ξ is promising, but inconclusive with respect to our hypothesis. This uncertainty can be readily addressed with numerical or additional physical experiments. © 2019 John Wiley & Sons, Ltd.  相似文献   

Hydrogeological origin of the CO2-rich mineral water of Vilajuïga in the Eastern Pyrenees (NE Catalonia,Spain)     

Mas-Pla  Josep  Brusi  David  Roqué  Carles  Soler  David  Menció  Anna  Costa  Josep M  Zamorano  Manuel  Meredith  Warren 《Hydrogeology Journal》2023,31(3):661-684

The mineral water of Vilajuïga village in Alt Empordà (NE Catalonia, Spain) owes its uniqueness to an emanation of geogenic CO₂ that modifies groundwater hydrochemistry to produce a differentiated HCO₃–Na- and CO₂-rich groundwater among the usual Ca–HCO₃ type found in this region. A hydrogeological conceptual model attributes its occurrence to the intersection of two faults: La Valleta and Garriguella-Roses. The former provides a thrust of metamorphic over igneous rocks, formed during the Paleozoic, over a layer of ampelitic shale that, from a hydrogeological perspective, acts as a confining layer. The Garriguella-Roses normal fault, which originated during the Neogene, permits the degassing of geogenic CO₂ that is attributed to volcanic activity occurring in the Neogene. Groundwater mixing from the metamorphic and igneous rock units plus the local occurrence of CO₂ creates a HCO₃–Na water that still holds free-CO₂ in solution. Interaction with the gas phase is restricted at the intersection of the two faults. Radiocarbon dating, after correcting for geogenic dead carbon, estimates an age of 8,000 years BP. The low tritium content (0.7 TU) indicates that Vilajuïga water is a mix of “older” groundwater recharged in the metamorphic rocks of the Albera range and “younger” groundwater from the igneous rocks of the Rodes range, over a recharge area of 45 km² and a maximum elevation of 600 m. Given its origin as rare groundwater in the southern slope of the Eastern Pyrenees, purposeful monitoring is necessary to evaluate the groundwater vulnerability and anticipate impacts from nearby wells and climate-change effects.

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