Measure of the color of beach nourishment sands: A case study from the Belgium coast

La percepción estética de una playa como lugar de recreo está estrechamente ligada al color de la arena. Esta es una de las características más perceptibles de una playa. El color de la arena puede ser alterado después de un trabajo de reposición. Este tipo de obras son cada vez más populares ya que representan una buena herramienta para preservar las playas de la erosión. Sin embargo, se ha prestado poca (o ninguna) atención al color de la arena durante los trabajos de reposición. Los colores de las arenas de la costa belga fueron determinados en el espacio Cielab, junto con su granulometría y composición. Las coordenadas de color varían entre 50 y 60 para L*, 0,5 a 4,0 para a* y 10,5 a 16,5 para b*. La composición muestra una fracción de cuarzo dominante, seguida de fragmentos de conchas y finalmente fragmentos de roca. La granulometría es bastante homogénea, siendo la distribución de grano más estrecha para la parte este de la costa que para la costa oeste. Este trabajo describe la metodología para realizar el análisis colorimétrico en playas de arena antes de un trabajo de reposición, junto con los principales criterios de aceptación al escoger la arena adecuada para el reemplazo.The aesthetical perception of a beach as a recreational place is closely linked to the sand color. This is one of the most perceptible characteristics of a beach. Sand color can be altered after a nourishment work. This type of works is becoming more and more popular since they represent a good tool for preserving beaches from erosion. However, only little (or none) attention has been paid to sand color during nourishment works. Colors of the sands from the Belgian coast were determined in the Cielab space, together with their granulometry and composition. Color coordinates range between 50 and 60 for L*, 0.5 to 4.0 for a*, and 10.5 to 16.5 for b*. The composition shows a dominant quartz fraction, followed by shell fragments and finally rock fragments. Granulometry is rather homogeneous, being the grain distribution for the east part of the coast narrower than for the west coast. This work describes the methodology for performing colorimetric analysis in sand beaches before a nourishment work, together with the main acceptance criteria when choosing the appropriate sand for replacement

In Search of Human Remains in the Layers of a Passage Tomb: The Combination of ICP-MS, Fluorescence (XRF) and SEM Methods at the Cobertoria Dolmen (Salas, Asturias, Spain)

Este artículo resume los resultados de la primera investigación dentro del megalitismo asturiano sobre composiciones químicas de los horizontes funerarios. La combinación de tres técnicas analíticas permitió una caracterización detallada de los niveles del dolmen de la Cobertoria (Salas, Asturias), monumento datado sobre el 3500 a.C. En el texto se describen las técnicas utilizadas para analizar estos niveles, así como los resultados obtenidos y su relación con el contexto arqueológico. La presencia de algunos componentes corresponde a la naturaleza geológica del sitio mientras que otros, como el fósforo, deben ser explicados por otros motivos. El uso de FRX y de ICP-MS mostró cifras elevadas de este componente que no pueden ser entendidas sin tener en cuenta el uso funerario que tuvo esta entrada. La descomposición de cadáveres, o de elementos orgánicos asociados a estos, es aquí la razón más probable para explicar estos altos índices de fósforo

Zircon morphology as a petrogenetic indicators in the tonalite-leucogranite association; Zarza la Mayor pluton case (Cáceres, Spain)

Zarza la Mayor pluton is a good example of the tonalite-leucogranite association. A new survey has been carried out and some additional study of zircon morphologies has been performed. Detailed survey shows the true intrusive character of the leucogranite pinpointing to a ring-dyke emplacement mechanism. Zircon morphologies show different characteristics for the tonalite (anatectic, with zircon typologies S1- Q1-L1) and leucogranite (calc-alkaline, with zircon typologies S6-Q2). This apparent paradox is explained taking care of the strong assimilation of CXG metasediments (Neoproterozoic - Lower Cambrian) by a dioritic-tonalitic magma through piecemeal-stopping processe

Polyorogenic structure of the San Rafael Block, Mendoza, Argentina: New data for the interpretation of the Chanic Orogen

The Paleozoic pre-Carboniferous rocks of the San Rafael Block, located to the east of the Los Reyunos Gondwanan Thrust, show Chanic structures (Late Devonian–early Carboniferous) with east vergence, which were generated in the absence of metamorphism. This Paleozoic succession is unconformably located on the basement of Cuyania. The rocks, located to the west of the Los Reyunos Thrust, were deformed by two fold episodes, the first and main (D1) west verging, developed under low to very low-grade metamorphic conditions, and the second (D2) east verging and mainly developed near Los Reyunos Reservoir. Therefore, the Los Reyunos Thrust must be considered a reactivation of a Chanic structure during the Gondwanan Orogeny (late Carboniferous–early Permian). The ancient Chanic thrust could be responsible for the overlay of the hinterland of the western branch of the Chanic Orogen on the foreland of its eastern branch, at the end of the collision between the Cuyania and Chilenia subplates. The results of this work have been related to those of nearby areas located to the north and west, which has allowed the elaboration of a model that explains the characteristics of the Chanic Orogen in this area. During the Carboniferous, the Los Reyunos Thrust was reactivated as a normal fault, facilitating the sedimentation of carboniferous rocks thousands of meters thick in its hanging wall and later, during the Gondwanan deformation, it underwent a tectonic inversion. During the Andean cycle, the Permian–Triassic beds of the Choiyoi Group were deposited in relation to NW–SE trending normal faults, giving rise to rollover structures. Finally, during the Cenozoic, Andean compression gave rise to the formation of an open antiform, in whose core is the Mesoproterozoic–Paleozoic basement of the San Rafael Block.Facultad de Ciencias Naturales y Muse

Reconstructing the Crustal Section of the Intra-Oceanic Caribbean Island Arc: Constraints From the Cumulate Layered Gabbronorites and Pyroxenites of the Rio Boba Plutonic Sequence, Northern Dominican Republic

Located in northern Dominican Republic, the Early Cretaceous Rio Boba mafic-ultramafic plutonic sequence constitutes a lower crust section of the Caribbean island arc, made up by gabbroic rocks and subordinate pyroxenite. Modal compositions, mineral chemistry, whole-rock compositions and thermobarometric calculations indicate that pyroxenites and gabbronorites represent a cumulate sequence formed by fractionation of tholeiitic magmas with initially very low H2O content in the lower crust of the arc (0.6–0.8 GPa). Melts evolved along a simplified crystallization sequence of olivine → pyroxenes → plagioclase → Fe-Ti oxides. The magmatic evolution of the Rio Boba sequence and associated supra-crustal Puerca Gorda metavolcanic rocks is multi-stage and involves the generation of magmas from melting of different sources in a supra-subduction zone setting. The first stage included the formation of a highly depleted substrate as result of decompressional melting of a refractory mantle source, represented by a cumulate sequence of LREE-depleted island arc tholeiitic (IAT) and boninitic gabbronorites and pyroxenites. The second stage involved volumetrically subordinate cumulate troctolites and gabbros, which are not penetratively deformed. The mantle source was refractory and enriched by a LILE-rich hydrous fluid derived from a subducting slab and/or overlying sediments, and possibly by a LREE-rich melt. The third stage is recorded in the upper crust of the arc by the Puerca Gorda “normal” IAT protoliths, which are derived from an N-MORB mantle source enriched with a strong subduction component. This magmatic evolution has implications for unraveling the processes responsible for subduction initiation and subsequent building of the Caribbean island arc.This research was funded through CGL2012-33669/BTE and PID2019-105625RB-C22 of the MCIN/AEI/10.13039/501100011033 projects and PRX18/00055 stay grant to the J. Escuder-Viruete of the Ministerio de Ciencia e Innovación of the Spanish Government

Geochemistry of the orthoamphibolites and metabasic rocks from Zarza la Mayor-Ceclavín (Cáceres, Spain)

El stock granodiorítico-tonalítico de Zarza la Mayor (noroeste de Cáceres, España) está bordeado por afloramientos pequeños y discontinuos de rocas metabásicas de afinidades gabroicas a dioríticas, con texturas entre grano fino-medio y porfídicas. El presente estudio geoquímico muestra que estas rocas son composicionalmente equivalentes a basaltos subalcalinos de características toleíticas, mientras que los diagramas de discriminación tectonomagmática las sitúan en un contexto tectónico intraplacaThe granodioritic-tonalitic stock of Zarza la Mayor (western central Spain) is bordered by small, discontinuous outcrops of low grade metabasic rocks with gabbroic to dioritic affinities, ranging from fine-medium grained to porphyritic in texture. The present geochemical study demonstrates that these rocks are equivalent in composition to subalcalic tholeiitic basalt while tectono-magmatic discrimination diagrams place them in a within-plate tectonic environmen

Polyorogenic structure of the San Rafael Block, Mendoza, Argentina: New data for the interpretation of the Chanic Orogen

The Paleozoic pre-Carboniferous rocks of the San Rafael Block, located to the east of the Los Reyunos Gondwanan Thrust, show Chanic structures (Late Devonian–early Carboniferous) with east vergence, which were generated in the absence of metamorphism. This Paleozoic succession is unconformably located on the basement of Cuyania. The rocks, located to the west of the Los Reyunos Thrust, were deformed by two fold episodes, the first and main (D1) west verging, developed under low to very low-grade metamorphic conditions, and the second (D2) east verging and mainly developed near Los Reyunos Reservoir. Therefore, the Los Reyunos Thrust must be considered a reactivation of a Chanic structure during the Gondwanan Orogeny (late Carboniferous–early Permian). The ancient Chanic thrust could be responsible for the overlay of the hinterland of the western branch of the Chanic Orogen on the foreland of its eastern branch, at the end of the collision between the Cuyania and Chilenia subplates. The results of this work have been related to those of nearby areas located to the north and west, which has allowed the elaboration of a model that explains the characteristics of the Chanic Orogen in this area. During the Carboniferous, the Los Reyunos Thrust was reactivated as a normal fault, facilitating the sedimentation of carboniferous rocks thousands of meters thick in its hanging wall and later, during the Gondwanan deformation, it underwent a tectonic inversion. During the Andean cycle, the Permian–Triassic beds of the Choiyoi Group were deposited in relation to NW–SE trending normal faults, giving rise to rollover structures. Finally, during the Cenozoic, Andean compression gave rise to the formation of an open antiform, in whose core is the Mesoproterozoic–Paleozoic basement of the San Rafael Block.Facultad de Ciencias Naturales y Muse

Structural petrology and mantle mineralogy of the Loma Caribe Peridotite, Cordillera Central, Dominican Republic

Las diferencias texturales, químico-mineralógicas y en la orientación de la fábrica en la peridotita de Loma Caribe (PLC) permiten distinguir peridotitas granulares (PG) y porfiroclásticas (PPC). Las PG presentan foliaciones dúctiles de alta-T desarrolladas durante el ascenso de manto bajo una zona de dorsal y el posterior cizallamiento corteza-manto producido al alejarse la litosfera de la dorsal. Sin embargo, las foliaciones porfiroclásticas a miloníticas presentes en las PPC, así como la presente en las serpentinitas foliadas suprayacentes, se relacionan con la exhumación tectónica y denudación del manto. El manto de la PLC está compuesto principalmente por harzburgitas empobrecidas que gradualmente pasan a harzburgitas ricas en Cpx y lherzolitas, con composiciones minerales similares a peridotitas de ante-arco. En comparación con datos experimentales, las variaciones en las proporciones modales y la química mineral son consistentes con 26-38% de fusión parcial para las PG y 12-44% para las PPCThe Loma Caribe Peridotite (LCP) consists of granular and porphyroclastic peridotites, (GP and PCP, respectively). GP developed high-T ductile foliations during the mantle upwelling beneath the spreading ridge and the subsequent crust-mantle shear as the lithosphere migrated away from the ridge. However, the porphyroclastic to mylonitic foliations present in the PCP, as well as those present in the overlying foliated serpentinites, are related to tectonic exhumation and denudation of the mantle. The LCP mantle is composed mainly of depleted harzburgites grading to Cpx-rich harzburgites and lherzolites, with mineral compositions similar to those of fore-arc peridotites. By comparation with experimental data, variations in modal proportions and mineral chemistry are consistent with 26-38% and 12-44% partial melting for PG and PPC, respectivel