The Albera zoned pegmatite field,Eastern Pyrenees,France

Summary Four types of pegmatites comprise the zoned pegmatite field in the eastern sector of the Albera Massif. Type I is represented by barren pegmatites with graphic textures; type II comprises transitional varieties with Li-Fe-Mn phosphates, Be (chrysoberyl) and scarce Nb-Ta and U oxide minerals; type III consists of pegmatites with significant zones of replacement containing Li-Fe-Mn phosphates, beryl and more abundant Nb-Ta oxide minerals; and type IV, muscovite-quartz-albite pegmatites are highly mineralized with Be, Nb-Ta and HREE. REE mineralization is strongly related to abundance of graphite in the late pegmatite units and in the host-rock. The individual pegmatite types are distributed within four subparallel zones concentric around anatectic muscovite-biotite leucogranites, with type I within the granites or close to the contact, and type IV pegmatites in the outermost areas. The zoning from type I to type IV could relate to fractionation processes which generated the pegmatites and is characterized by an enrichment of Mn, Ta, Na, Li, P, Be and REE. According to the pegmatite distribution and their fractionation trends, we propose an origin by differentiation of a granitic melt.

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Résumé On a établi quatre types de pegmatites dans le champ pegmatitique zoné du secteur est du Massif des Albères (Pyrénées Orientales, France). Celles de type I sont des pegmatites non minéralisées avec des textures graphiques, celles de type II sont des variétés intermediaires avec des phosphates à Li-Fe-Mn, Be (chrysobéryl) et des rares oxides à Nb-Ta et U; celles de type Ill sont des pegmatites avec des zones de réplacement bien dévéloppées et qui contiennent des phosphates à Li-Fe-Mn, du béryl et des oxides à Nb-Ta plus abondants; celles de type IV sont des pegmatites bien minéralisées à Be, Nb-Ta et des T.R. La minéralisation à T.R. est liée à des phénomènes de graphitisation répandus dans les unités tardives de la pegmatite et dans l'encaissant. La distribution de chaque type de pegmatite correspond à quatre zones à peu près parallèles et concentriques autour des granites anatectiques à muscovite-biotite, avec le type I dans les granites ou prochain au contact, et les pegmatites à type IV dans la bande plus externe. La zonation serait due à des processus de fractionnement qui auraient généré les pegmatites et qui sont caracterisés par un enrichissement en Mn, Ta, Na, Li, P, Be et T.R. dès les pegmatites de type I vers celles de type IV. On propose un origine par différentiation des granites en vue de la distribution des pegmatites.

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With 5 Figures     

Human Impact Since Medieval Times and Recent Ecological Restorationin a Mediterranean Lake: The Laguna Zoñar, Southern Spain

The multidisciplinary study of sediment cores from Laguna Zoñar (37°29′00′′ N, 4°41′22′′ W, 300 m a.s.l., Andalucía, Spain) provides a detailed record of environmental, climatic and anthropogenic changes in a Mediterranean watershed since Medieval times, and an opportunity to evaluate the lake restoration policies during the last decades. The paleohydrological reconstructions show fluctuating lake levels since the end of the Medieval Warm Period (ca. AD 1300) till the late 19th century and a more acute dry period during the late 19th century – early 20th century, after the end of the Little Ice Age. Human activities have played a significant role in Laguna Zoñar hydrological changes since the late 19th century, when the outlet was drained, and particularly in the mid-20th century (till 1982) when the spring waters feeding the lake were diverted for human use. Two main periods of increased human activities in the watershed are recorded in the sediments. The first started with the Christian conquest and colonization of the Guadalquivir River Valley (13th century) particularly after the fall of the Granada Kingdom (15th century). The second one corresponds to the late 19th century when more land was dedicated to olive cultivation. Intensification of soil erosion occurred in the mid-20th century, after the introduction of farm machinery. The lake was declared a protected area in the early 1980s, when some agricultural practices were restricted, and conservation measures implemented. As a consequence, the lake level increased, and some littoral zones were submerged. Pollen indicators reflect this limnological change during the last few decades. Geochemical indicators show a relative decrease in soil erosion, but not changes in the amount of chemical fertilizers reaching the lake. This study provides an opportunity to evaluate the relative significance of human vs. climatic factors in lake hydrology and watershed changes during historical times. Paleolimnological reconstructions should be taken into account by natural resources agencies to better define lake management policies, and to assess the results of restoration policies.     

Synoptic conditions and potential causes of the extreme heavy rainfall event of January 2009 over Mindanao Island,Philippines

Natural Hazards - This study investigates the synoptic conditions that led to the heavy rainfall/flood (HRF) event in Mindanao Island, Philippines (122??127°E;...     

First Telescope of the Russian–Cuban Observatory

Astronomy Reports - Beginning of operation of the first Russian–Cuban Observatory telescope, a wide-field 20-cm robotic telescope installed at the observational site optical station in...     

On the advantage of sharing a holdfast: effects of density and occurrence of kin aggregation in the kelp Lessonia berteroana

We investigated the density‐dependent and genetic relatedness that regulate the occurrence of inter‐individual (genet) fusion forming plurigenotypic organisms in the brown alga Lessonia berteroana. Recruitment generally occurs at high densities in the inter‐tidal, allowing contact of neighbouring holdfasts as they grow and expand on the substrate. Algal density, by contrast, is regulated by the effects of herbivory and wave impact, which often lead to low holdfast density. Herein, we investigated whether the occurrence of plurigenotypic organisms and their genotypic composition (number of genotypes per plurigenotypic organism) are density dependent and affected by kin selection in the inter‐tidal kelp L. berteroana. Four microsatellite loci were used to analyse DNA from 260 samples obtained from shared and non‐shared holdfasts, at two sites with high and two site with low holdfast density. Analyses showed that fusions forming plurigenotypic organisms are extremely common. Interestingly, the frequency of fusions was higher in low‐density sites, in which 100% of the plants had at least two genotypes and the average was 3.5. In high‐density sites, 62% of plants were plurigenotypic, with an average of 2.8 genotypes per plant. Additionally, we found that genotypes that shared a holdfast had a significantly higher genetic relatedness than the average in the population, compatible with a kin structure. Density dependence and kin structure suggest that the occurrence of plurigenotypic organisms is linked to environmental quality, and that kin or multilevel selection may be favouring the fusion of genetically related genets.     

A geological record of multiple Pleistocene tsunami inundations in an oceanic island: The case of Maio,Cape Verde

In the Central Atlantic archipelagos – the Canaries, Cape Verde, Madeira and the Azores – tsunami hazard is often regarded as low, when compared with other extreme wave events such as hurricanes and storms. The geological record of many of these islands, however, suggests that tsunami hazard may be underestimated, notwithstanding being lower than in areas adjacent to subduction zones, such as the margins of the Pacific and Indian oceans. Moreover, tsunamis in oceanic islands are generally triggered by local large-scale volcanic flank collapses, for which little is known about their frequency, making it difficult to estimate the probability of a new occurrence. Part of the problem lies in the fact that tsunami deposits are usually difficult to date, and few islands in the world exhibit evidence for repeated tsunami inundation on a protracted timescale. This study reports on the presence of abundant tsunami deposits (conglomerates and sandstones) on Maio Island (Cape Verde) and discusses their stratigraphy, sedimentological characteristics, probable age and tsunamigenic source. Observations indicate that four distinct inundation events of variable magnitude took place during the Pleistocene. One of the tsunami deposits yielded a high-confidence U/Th age of 78·8 ± 0·9 ka, which overlaps within error with the 73 ± 7 ka age proposed for Fogo volcano's flank collapse, an event known to have had a significant tsunami impact on nearby Santiago Island. This shows that the Fogo tsunami also impacted Maio, resulting in runups in excess of 60 m above coeval sea-level at ca 120 km from the source. Two older deposits, possibly linked to recurrent flank collapses of the Tope de Coroa volcano in Santo Antão Island, yielded lower-confidence ages of 479 to 390 ka and 360 to 304 ka. A younger deposit (<78 ka) remains undated. In summary, the geological record of Maio exhibits well-preserved evidence of repeated tsunami inundation, reinforcing the notion that tsunami hazard is not so low at volcanic archipelagos featuring prominent and highly-active volcanoes such as in Cape Verde.     

Validation of the WAMC4 wave model for the Black Sea

The present paper describes the set-up and application of the third-generation wave model — WAM Cycle 4 to the Black Sea. The wind fields are calculated by a regional atmosphere model (REMO), which was driven with the conditions from the global NCEP re-analysis project. These atmospheric data are used to force the state-of-the-art WAM model. The validation is done by comparison of wave model output against directional buoy measurements registered at three deep-water locations and wave gauge data taken at a point in intermediate depth near the Black Sea coast. The results reveal that agreement between modeled and measured data is satisfactory and the quality of the simulations increases under more energetic and severer wind and wave conditions. Following the validation, a 41-year wave hindcast was implemented spanning the period 1958–1998.     

High-Ti amphibole as a petrogenetic indicator of magma chemistry: evidence for mildly alkalic-hybrid melts during evolution of Variscan basic–ultrabasic magmatism of Central Iberia

Central Iberian Variscan granite batholiths and anatectic complexes are punctuated by coeval stocks of hydrous, high-K calc-alkaline, ultrabasic to intermediate rock series. Despite their overall calc-alkaline affinity, the mafic–ultramafic members contain high-Ti amphibole oikocrysts rimmed by lower-Ti amphibole ± cummingtonite and high-Ti amphibole replacing early phlogopite. To understand the factors controlling the saturation of high-Ti amphibole in the parental magmas, clinopyroxene-melt, phlogopite-melt and amphibole-melt relationships are reviewed. This analysis reveals that for melts with intermediate compositions, the affinity of TiO₂ for amphibole rises in alkalic magmas. Accordingly, mildly alkalic trachytoid to subalkaline medium- to high-K andesite and dacite compositions are estimated for interstitial high-Ti amphibole-saturated melts. Amphibole Ce/Pb ratios reveal a mantle–crust hybrid nature for interstitial melts with subalkaline trachytoid compositions. The hydrous character of the Variscan basic magmas favoured an overall magmatic evolutionary trend with a low rate of variation of Na₂O with respect to silica during amphibole crystallization. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.