Geochemistry of basalts from the Caribbean Large Igneous Province

Oceanic flood basalts are poorly understood, short-term expressions of highly increased heat flux and mass flow within the convecting mantle. The uniqueness of the Caribbean Large Igneous Province (CLIP, 92-74 Ma) with respect to other Cretaceous oceanic plateaus is its extensive sub-aerial exposures, providing an excellent basis to investigate the temporal and compositional relationships within a starting plume head. We present major element, trace element and initial Sr-Nd-Pb isotope composition of 40 extrusive rocks from the Caribbean Plateau, including onland sections in Costa Rica, Colombia and Curaçao as well as DSDP Sites in the Central Caribbean. Even though the lavas were erupted over an area of ~3*10**6 km**2, the majority have strikingly uniform incompatible element patterns (La/Yb=0.96+/-0.16, n=64 out of 79 samples, 2sigma) and initial Nd-Pb isotopic compositions (e.g. 143Nd/144Ndin=0.51291+/-3, epsilon-Nd i=7.3+/-0.6, 206Pb/204Pbin=18.86+/-0.12, n=54 out of 66, 2sigma). Lavas with endmember compositions have only been sampled at the DSDP Sites, Gorgona Island (Colombia) and the 65-60 Ma accreted Quepos and Osa igneous complexes (Costa Rica) of the subsequent hotspot track. Despite the relatively uniform composition of most lavas, linear correlations exist between isotope ratios and between isotope and highly incompatible trace element ratios. The Sr-Nd-Pb isotope and trace element signatures of the chemically enriched lavas are compatible with derivation from recycled oceanic crust, while the depleted lavas are derived from a highly residual source. This source could represent either oceanic lithospheric mantle left after ocean crust formation or gabbros with interlayered ultramafic cumulates of the lower oceanic crust. High 3He/4He in olivines of enriched picrites at Quepos are ~12 times higher than the atmospheric ratio suggesting that the enriched component may have once resided in the lower mantle. Evaluation of the Sm-Nd and U-Pb isotope systematics on isochron diagrams suggests that the age of separation of enriched and depleted components from the depleted MORB source mantle could have been <=500 Ma before CLIP formation and interpreted to reflect the recycling time of the CLIP source. Mantle plume heads may provide a mechanism for transporting large volumes of possibly young recycled oceanic lithosphere residing in the lower mantle back into the shallow MORB source mantle.

Modelos de modernización para el desarrollismo: el influjo de las propuestas estadounidenses en el Servicio de Extensión Agraria (1955-1975)

Con este trabajo nos proponemos estudiar las políticas agrarias del franquismo y particularmente la creación y actuación del Servicio de Extensión Agraria (1955) en el contexto de la difusión de la Teoría de la Modernización. Comenzaremos con una contextualización de las relaciones culturales entre España y los EE.UU. y su potencial proyección sobre el ámbito rural. A continuación, prestaremos atención a la impronta del modelo extensionista norteamericano en la organización y metodología del Servicio de Extensión Agraria. Sin perder de vista la importancia de la escala estatal para la implementación y adaptación de las distintas políticas agrarias, atenderemos al contexto político e ideológico internacional como elemento que permite ampliar la comprensión y estudio de dichas políticas. En ese sentido, propondremos finalmente una primera aproximación comparativa al estudio del SEA en relación con diferentes experiencias de extensionismo agrario en Latinoamérica.

Azerbaijan-a growing problem for the West. OSW Commentary No. 146, 15.09.2014

Azerbaijan’s cooperation with the West, launched two decades ago, has helped it become a relatively strong and ambitious actor on the international stage. It has become a key country in the region from the Western (USA and the EU) and Turkish points of view, as well as an important partner in the energy sector. The strategic EU concept of the Southern Gas Corridor, also supported by the United States, is among the initiatives based on cooperation with Azerbaijan. Surprisingly, however, Azerbaijan’s increased ambition and importance have caused its policy to diverge ever farther from the expectations and plans formulated by the West. The changes in the balance of power in the South Caucasus, occurring in the context of the conflict in Ukraine, have forced Azerbaijan to revise its assessment of its position in the region. The main impetus for Azerbaijan’s actions is fear of Russia, as well as the weakness of the West which has become particularly apparent in the recent stages of the Ukrainian crisis. Azerbaijan’s actions so far have displayed its tendency to deepen its self-isolation in foreign affairs and consolidate its authoritarian system. This comes as a challenge to the West, whose ability to shape its relations with Azerbaijan has weakened considerably. This state of affairs poses the threat that in the current situation, the Southern Gas Corridor concept, which Azerbaijan amended in 2012 in its own favour, might become totally blocked.

~(146)Tb的能级结构研究

利用能量为161—175MeV的~(32)S束流,通过反应~(118)Sn(~(32)S,1p3n)~(146)Tb研究了双奇核~(146)Tb的高自旋态能级结构。实验进行了γ射线的激发函数、γ射线的各向异性度、X-γ和γ-γ-t符合测量。基于这些测量结果,建立了激发能达8390kev的~(146)Tb核的能级纲图,其中包括新发现的41条γ射线和新建立的27个能级,并指定了~(146)Tb新发现能级的自旋值。用一个h_(11/2)价质子和一个h_(11/2)~(-1)价中子空穴耦合、πh_(11/2)υh_(11/2)~(-1)与~(146)Gd核实激发态的耦合对~(146)Tb的能级结构进行了定性地讨论。

Optical and infrared photometry of the Type IInSN1998S: days 11-146

We present contemporaneous optical and infrared (IR) photometric observations of the Type IIn SN 1998S covering the period between 11 and 146 d after discovery. The IR data constitute the first ever IR light curves of a Type IIn supernova. We use blackbody and spline fits to the photometry to examine the luminosity evolution. During the first 2-3 months, the luminosity is dominated by the release of shock-deposited energy in the ejecta. After similar to 100 d the luminosity is powered mostly by the deposition of radioactive decay energy from 0.15 +/-0.05 M-. of Ni-56 which was produced in the explosion. We also report the discovery of an astonishingly high IR excess, K-L'=2.5, that was present at day 130. We interpret this as being due to thermal emission from dust grains in the vicinity of the supernova. We argue that to produce such a high IR luminosity so soon after the explosion, the dust must be pre-existing and so is located in the circumstellar medium of the progenitor. The dust could be heated either by the UV/optical flash (IR echo) or by the X-rays from the interaction of the ejecta with the circumstellar material.

Glacial to paraglacial history and forest recovery in the Oglio glacier system (Italian Alps) between 26 and 15 ka cal BP

The integrated stratigraphic, radiocarbon and palynological record from an end-moraine system of the Oglio valley glacier (Italian Alps), propagating a lobe upstream in a lateral reach, provided evidence for a complete cycle of glacial advance, culmination and withdrawal during the Last Glacial Maximum and early Lateglacial. The glacier culminated in the end moraine shortly after 25.8 +/- 0.8 ka cal BP, and cleared the valley floor 18.3-17.2 +/- 0.3 ka cal BP. A primary paraglacial phase is then recorded by fast progradation of the valley floor.

As early as 16.7 +/- 0.3 ka cal BP, early stabilization of alluvial fans and lake filling promoted expansion of cembran pine. This is an unprecedented evidence of direct tree response to depletion of paraglacial activity during the early Lateglacial, and also documents the cembran pine survival in the mountain belt of the Italian Alps during the last glaciation. Between 16.1 and 14.6 +/- 0.5 ka cal BP, debris cones emplacement points to a moisture increase favouring tree Betula and Pinus sylvestris-mugo. A climate perturbation renewed paraglacial activity. According to cosmogenic ages on glacial deposits and AMS radiocarbon ages from lake records in South-Eastern Alps such phase compares favourably with the Gschnitz stadial and with the oscillations recorded at lakes Ragogna. Langsee and Jeserzersee, most probably forced by the latest freshening phases of the Heinrich Event 1.

A further sharp pine rise marks the subsequent onset of Bolling interstadial. The chronology of the Oglio glacier compares closely with major piedmont glaciers on the Central and Eastern Alpine forelands. On the other hand, the results of the present study imply a chronostratigraphic re-assessment of the recent geological mapping of the Central Italian Alps. (C) 2012 Elsevier Ltd. All rights reserved.