Multistage crystallization of tonalitic enclaves in granitoid rocks (Hercynian belt,Spain): implications for magma mixing

The crystallization sequence, nucleation density and crystal index (n = nucleation density/mode) of tonalitic enclaves from different granitoids of the Hercynian orogeny indicate that they are pieces of magma partially crystallized in the interior of synplutonic bodies of basic magma, which was injected into a silicic magma chamber. A rapid cooling stage can be identified from the high nucleation density and high n-values of minerals. A final stage of slow cooling, is identified by a low nucleation density and low n-values. At this stage a residual melt crystallized in thermal equilibrium to the cooling rate of the whole magma chamber. Thermal equilibrium and convection are necessary conditions for mixing. Enclaves can be interpreted as the remaining, non-disaggregated portions of an early injected mafic magma, which in turn underwent hybridization during injection. Their presence indicates the existence of magma mixing processes and the possibility that the host granitoid was a hybrid rock.

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Zusammenfassung Die Kristallisationsabfolge, Keimdichte und der Kristallindex (n = Keimdichte/Modus) von tonalitischen Einschlüssen verschiedener Granitoide des variszischen Orogens zeigen, daß sie Teile eines Magmas sind, das teilweise im Inneren von basischen synplutonischen Magmenkörpern auskristallisierte und in eine silikatische Magmenkammer injiziert wurde. Eine Zeit schnellen Abkühlens kann an Hand der hohen Keimdichte und der niedrigen n-Werte festgestellt werden. Zu diesem Zeitpunkt kristallisierte eine Restschmelze unter thermischen Gleichgewichtsbedingungen und der Abkühlungsgeschwindigkeit der ganzen Magmenkammer aus. Thermisches Gleichgewicht und Konvektion sind für das Mischen notwendig. Einschlüsse können als nichtzerfallene Reste eines früh injizierten mafischen Magmas angesehen werden, welches während der Injizierung eine Hybridisierung erfuhr. Ihre Gegenwart zeigen das Vorhandensein von Magmenmischungsvorgängen und die Möglichkeit, daß der Muttergranitoid ein Hybridgestein war, an.

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Resumen La secuencia de cristalización, densidad de nucleación e índice cristalino (n = densidad de nucleación/moda) de enclaves tonalíticos de diferentes granitoides hercínicos, indican que dichos enclaves representan fragmentas de magma parcialmente cristalizados en el interior de cuerpos simplutónicos de magma básico, que originalmente fue inyectado en una cámara magmática félsica. Se puede identificar una etapa de enfriamiento rápido a partir de los altos valores de n y alta densidad de nucleación de los minerales. Una etapa final de enfriamiento lento es detectada por una baja densidad de nucleación y bajos valores de n de determinados minerales. Un líquido residual cristalizó en esta etapa lenta en equilibrio térmico y a la misma tasa de enfriamiento que toda la cámara magmática en conjunto. Equilibrio térmico y convección son condiciones necesarias para que se produzca mezcla. Los enclaves pueden ser interpretados como porciones no hibridadas de magma que han sido homogéneamente distribuidos dentro del granitoide encajante. Su presencia indicaría la existencia de procesos de mezcla de magmas y la posibilidad de que el granitoide encajante sea una roca híbrida.

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Caii H and K spectroscopic observations in active binary systems

We have performed high resolution spectroscopic observations of five active binary systems in the Caii H and K lines at La Palma Observatory. We present the absolute fluxes calculated at the surface of the stars and we discuss the spectral characteristics observed, presence of double emissions and phase variations.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

Suspended-sediment response to pulses in river flow and semidiurnal and fortnightly tidal variations in a mesotidal estuary

The effects of the tidal regime and high river flows on the suspended sediment concentration field have been separated and the retention time of fluvial sediment has been determined. The study was carried out in the upper Sado estuary, Portugal, and included surveys at high and low tide in different semidiurnal tide ranges every month for 1 year, including contrasting freshwater discharge. DDT and its metabolites (DDD and DDE) were determined in the suspended sediment and in the whole soft tissues of oysters, and they have been used as tracers of the derived flood material in the upper estuary. The tide is responsible for the relatively slow relaxation time following a winter runoff event.     

Distribution of suspended sediment concentration in wide sediment‐laden streams: A novel power‐law theory

The diffusion equation of suspended sediment concentration in a wide sediment‐laden stream flow is dependent on the vertical gradient of streamwise velocity and the sediment diffusivity. This study aims at investigating the influence of the streamwise velocity laws on the suspended sediment concentration distributions, resulting from the solution of the diffusion equation. Firstly, the sediment concentration distributions are obtained numerically from the solution of the diffusion equation using different velocity laws and compared with the experimental data. It is found that the power‐law approximation produces good computational results for the concentration distributions. The accuracy of using a power‐law velocity model is comparable with the results obtained from other classical velocity laws, namely log‐law, log wake‐law and stratified log‐law. Secondly, a novel analytical solution is proposed for the determination of sediment concentration distribution, where a power‐law, wall‐concentration profile is coupled with a concentration wake function. The power‐law model (for velocity and concentration) is calibrated using the experimental data, and then a generalized wake function is obtained by choosing a suitable law. The developed power‐law model involving the wake function adjusted by an exponent predicts the sediment concentration distributions quite satisfactorily. Finally, a new explicit formula for the suspended‐load transport rate is derived from the proposed theory, where numerical computation of integrals, as needed in the Einstein theory, is avoided.     

Tectonic control of facies architecture, sequence stratigraphy and drowning of a Liassic carbonate platform (Betic Cordillera, Southern Spain)

This paper develops a tectono‐stratigraphic model for the evolution and drowning of Early Jurassic carbonate platforms. The model arises from outcrop analysis and Sr isotope dating of successions exposed in the Betic Cordillera in southeastern Spain. Here, an extensive Early Jurassic (Sinemurian) carbonate platform developed on the rifted Tethyan margin of the Iberian Plate. The platform was dissected by extensional faults in early jamesoni times (ca. 191 Ma) and again in late ibex times (ca.188 Ma) during the Pliensbachian stage. Extensional faults and fault block rotation are shown to control the formation of three sequence boundaries that divide the platform stratigraphy (the Gavilan Formation) into three depositional sequences. The last sequence boundary marks localised drowning of the platform and deposition of the deeper water Zegri Formation, whereas adjacent platforms remain exposed or continue as the site of shallow‐marine sediment accumulation. This study is based on mapping, facies analysis and dating of platform carbonates exposed in three tectonic units within the zone: Gabar, Ponce and Canteras. Facies analysis leads to the recognition of facies associations deposited in carbonate ramp environments and adjacent to synsedimentary, marine, fault scarps. Sr isotope dating enables us to correlate platform‐top carbonates from the different tectonic units at a precision equivalent to ammonite zones. A sequence stratigraphic analysis of sections from the three tectonic units is carried out using the facies models together with the Sr isotope dates. This analysis indicates a clear tectonic control on the development of the stratigraphy: depositional sequences vary in thickness, have wedge‐shaped geometries and vary in facies, internal geometries and systems tracts from one tectonic unit to another. Criteria characterising depositional sequences and sequence boundaries from the Gabar and Ponce units are used to establish a tectono‐stratigraphic model for carbonate platform depositional sequences and sequence boundaries in maritime rifts, which can be applied to other less well‐exposed or subsurface successions from other sedimentary basins. Onlapping transgressive and progradational highstand systems tracts are recognised on dip slope ramps. Falling stage and lowstand systems tracts are developed as thick breccia units in hangingwall areas adjacent to extensional faults. Sequence boundaries vary in character, amplitude and/or duration of sea‐level fall and persistence across the area. Some boundaries coalesce onto the Canteras unit, which remained as a relatively positive area throughout the early Pliensbachian (Carixian). The carbonate platform on the Ponce tectonic unit drowned in the latest Carixian (davoei biozone). However, the adjacent tectonic units remained emergent and developed a long‐lived sequence boundary, indicating tectonic subsidence as the major cause for platform drowning. The stratigraphic evolution of this area on the rifted southern Iberian margin indicates that a widespread restricted shallow‐water carbonate platform environment accumulating peritidal carbonates evolved with faulting to a more open‐marine setting. Sr dating indicates that this transition took place around the Sinemurian–Pliesbachian boundary and it was driven by local fault‐related subsidence together with likely post‐faulting regional subsidence.     

Comparative performance of convolutional neural network,weighted and conventional support vector machine and random forest for classifying tree species using hyperspectral and photogrammetric data

ABSTRACT

The classification of tree species can significantly benefit from high spatial and spectral information acquired by unmanned aerial vehicles (UAVs) associated with advanced classification methods. This study investigated the following topics concerning the classification of 16 tree species in two subtropical forest fragments of Southern Brazil: i) the potential integration of UAV-borne hyperspectral images with 3D information derived from their photogrammetric point cloud (PPC); ii) the performance of two machine learning methods (support vector machine – SVM and random forest – RF) when employing different datasets at a pixel and individual tree crown (ITC) levels; iii) the potential of two methods for dealing with the imbalanced sample set problem: a new weighted SVM (wSVM) approach, which attributes different weights to each sample and class, and a deep learning classifier (convolutional neural network – CNN), associated with a previous step to balance the sample set; and finally, iv) the potential of this last classifier for tree species classification as compared to the above mentioned machine learning methods. Results showed that the inclusion of the PPC features to the hyperspectral data provided a great accuracy increase in tree species classification results when conventional machine learning methods were applied, between 13 and 17% depending on the classifier and the study area characteristics. When using the PPC features and the canopy height model (CHM), associated with the majority vote (MV) rule, the SVM, wSVM and RF classifiers reached accuracies similar to the CNN, which outperformed these classifiers for both areas when considering the pixel-based classifications (overall accuracy of 84.4% in Area 1, and 74.95% in Area 2). The CNN was between 22% and 26% more accurate than the SVM and RF when only the hyperspectral bands were employed. The wSVM provided a slight increase in accuracy not only for some lesser represented classes, but also some major classes in Area 2. While conventional machine learning methods are faster, they demonstrated to be less stable to changes in datasets, depending on prior segmentation and hand-engineered features to reach similar accuracies to those attained by the CNN. To date, CNNs have been barely explored for the classification of tree species, and CNN-based classifications in the literature have not dealt with hyperspectral data specifically focusing on tropical environments. This paper thus presents innovative strategies for classifying tree species in subtropical forest areas at a refined legend level, integrating UAV-borne 2D hyperspectral and 3D photogrammetric data and relying on both deep and conventional machine learning approaches.     

Continuous metal biosorption applied to industrial effluents: a comparative study using an agricultural by-product and a marine alga

Fixed-bed column experiments have been conducted to evaluate the removal of metals from real industrial wastewaters. The effluents tested were provided by two different metallurgical companies: Industrial Goñabe, a galvanizing plant, and Sao Domingos mine, an abandoned sulfide mine. Sugar-beet pulp, a by-product of the sugar industry, and brown alga Fucus vesiculosus were used as biosorbents. The influence of pH on the sorption process was insignificant for the tests using Industrial Goñabe wastewater. On the contrary, an increase of pH improved metal sorption uptake and yield and saturation rate in the case of the Sao Domingos wastewater. A lower metal concentration in Sao Domingos wastewater resulted in a higher availability of metal-binding sites on the biomass. Better sorption parameters for both real wastewaters were obtained using brown alga Fucus vesiculosus. At pH 5, Zn sorption in continuous mode increased from 36 to 48% for Industrial Goñabe wastewater and from 34 to 37% for Sao Domingos wastewater. In the latter case, copper sorption increased from 73 to 88%. Breakthrough points that determine the service time of columns were reached later using alga as biosorbent. For Zn, column adsorption performance improved substantially with alga and its service time by 5 times. In the case of Cu, the breakthrough point of the second column was not reached during 1750 min of experimentation. The results obtained reaffirm the industrial applicability of these techniques.     

Age constraints to the relationships between magmatism, metamorphism and tectonism in the Aracena metamorphic belt, southern Spain

 The Aracena metamorphic belt (AMB), southwest Iberian peninsula, is characterized by the following geological elements: (a) a high-temperature/low-pressure (HT/LP) metamorphic belt a few kilometres wide and more than 200 km long; (b) a linear belt of oceanic amphibolites with a low-pressure inverted metamorphic gradient; (c) crustal-scale ductile shear zones; and (d) mafic, noritic intrusions of high-Mg andesite (boninite) composition. The relationships between these elements led to the proposal of a model of ridge subduction for this sector of the Hercynian belt of Europe. This interpretation is supported by the age relationships displayed between the main rock units considered representative of the main tectonic and petrological processes responsible for the geological elements mentioned previously. The results of a geochronological study (Ar–Ar, Rb–Sr and Sm–Nd) clearly support a Late Paleozoic tectonic evolution at an active continental margin. The time evolution of the metamorphism in the oceanic domain, ranging from 342.6±0.6 Ma in the west to 328.4±1.2 Ma in the east, over a distance of 70 km along the metamorphic belt, support a tectonic model of triple-junction migration responsible for the creation at depth of a slab-free window with decisive consequences for the thermal evolution of the region. The origin of the linear metamorphic belt of HT/LP regime may be explained by the migration along a continental margin of a punctual thermal anomaly induced by the creation of a triple-junction at the continental margin. Received: 9 March 1998 / Accepted: 9 December 1998