El origen geológico, galaico, del ejemplar de Marabiu (Teverga, Asturias) y consideraciones culturales sobre los útiles-arma, calificados de "hachas nórdicas", del Noroeste ibérico

The physical analysis of a perforated item from Asturias shows that its only presence in the Cantabric region is due to an import from Galicia (cianites of Touro, near Santiago de Compostela). The concentration of these tool-weapons in barrows of the III millenium in Galicia is a unique focus in the Iberian peninsula of a very well known phenomenon in Europe. In this article, geographic, economic and cultural arguments are offered, justifiyng the peculiar presence of these sceptres or status symbols and of their local character, although they remind us of types in the continental NW, so that the Galician perforated tools are classified as ''northern battle-axes".El análisis físico de un ejemplar perforado del centro de Asturias (Marabiu) prueba que su solitaria presencia en la Región Cantábrica se debe a una importación desde Galicia (cianitas deTouro, al E de Santiago de Compostela). La concentración de estos útiles-arma en túmulos del III milenio en Galicia (Coruña y O de Lugo) dibuja el foco único en la Península Ibérica de un fenómeno bien conocido en Europa. En el artículo se ofrecen argumentos geográficos, económicos y culturales justificativos de la presencia singular de estos "cetros" o símbolos de estatus, de su carácter local aunque se aprecien resonancias de tipos de NO continental, lo que hizo que se calificara a los perforados gallegos de "hachas de combate nórdicas"

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

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

Phase relations in the Cabeza de Araya cordierite monzogranite, Iberian Massif : implications for the formation of cordierite in a crystal mush

Experimental investigations and thermodynamic calculations of the phase relations of a cordierite-rich monzogranite from the Cabeza de Araya batholith (Cáceres, Spain) have been performed to understand the formation of cordierite. The experiments failed to crystallize cordierite in the pressure range 200-600MPa, in the temperature range 700-975ºC and for different water activities (melt water contents between 2 and 6 wt.%). In contrast, clinopyroxene and orthopyroxene (absent in the natural mineral rock assemblage), together with biotite, were observed as ferromagnesian assemblage in a wide range of experimental conditions. Thermodynamic calculations, using the software PERPLE_X, describe the formation of cordierite only at 200 and 400MPa and very low water contents, and the amount of cordierite formed in the models is always below 3.5 vol.%. The results indicate that cordierite is not in equilibrium with the bulk rock compositions. The most probable explanation was that cordierite nucleated and crystallized from a melt that is not in equilibrium with part of the mineral assemblage present in the magma. This "non-reactive" mineral assemblage was mainly composed of plagioclase. The silicate melts from which cordierite crystallized was more Al-rich and K-rich than the silicate melt composition in equilibrium with the bulk composition. One possible process for the high Al content of the silicate melt is related to assimilation and partial melting of Al-rich metasediments. An exo-perictetic reaction is assumed to account for both textural and geochemical observations. On the other hand, hybridization processes typical for calc-alkaline series can also explain the high proportions of "non-reactive" minerals observed in relatively high temperature magmas. This study clearly demonstrates that silicate melts in a crystal mush can depart significantly from the composition of melt that should be in equilibrium with the bulk solid assemblage

Petrographic and geochemical differentiation of the igneous rocks from Arroyo Farandón (Asturias)

This paper deals with the Arroyo Farandón (Asturias) igneous sills, which intruded within the sedimentary rocks of Oville Formation. They have alkaline composition and are classified as trachytes. As a consequence of a new detailed survey, continuous zonation has been distinguished along the main sill, which show outstanding developing of vesicular-amigdalar zones at the top and bottom of the body, suggesting vesiculation processes controlled by temperature gradients. Slight geochemical variations across the sills have been recorde

Las tierras raras en el Plutón de Caldas de Reyes: influencia de la mineralogía en su evolución

This paper deals with the role of the mineral phases in the evolution and behaviour of the REE elements in the Caldas de Reyes Zoned Pluton (Galicia-Spain). The study of normative and chemical relationships reveals the preponderant influence of the accesory minerals over REE spectra of the PlutonEste artículo trata sobre el papel de las fases del mineral en la evolución y comportamiento de los elementos de tierras raras (REE) en la zona de Plutón de Caldas de Reyes (Galicia, España). El estudio de las relaciones normativas y químicas demuestra la influencia dominante de los minerales accesorios sobre los espectros de REE de Plutón

Enclaves in peraluminous allochthonous granites: The case study of Cabeza de Araya Batolith (Cáceres, Spain)

This paper deals with the preliminar study of the petrography and geochemistry of the scarce enclaves of the peraluminous granites of Cabeza de Araya. Three types of enclaves have been distinguished: xenolidc enclaves, leucocratic igneous enclaves and tonalitic igneous enclaves. From geochemical diagrams and mass balance procedures, the different hypothesis have been tested. The main conclusion is that in absence of water-saturated melting processes of crustal rocks (pelites and graywackes metasediments CXC) the most plausible model is the reaction zone in which a contribution of some 25% ofgabbroic rocks should be necessary to account the composition of the most mafic tonalitic enclave