Petrología y geoquímica de rocas granitoides y enclaves asociados del batolito de los Pedroches (Macizo Ibérico)

El batolito de Los Pedroches está formado por importantes conjuntos plutónicos epizonales. Los litotipos plutónicos dominantes en cada uno de estos conjuntos son una granodiorita biotítica ±anfibol y un monzogranito biotítico ±cordierita porfídico de grano grueso a medio. Los datos petrográficos y geoquímicos presentados en este trabajo sugieren que los enclaves microgranitoides incluidos en granodioritas y monzogranitos no están relacionados con procesos de hibridación magmática, sino con la evolución tardía, en la corteza, de los magmas granitoides generados. Los diagramas de Harker ponen de manifiesto un notable paralelismo en el comportamiento de los elementos mayores de cada asociación enclave microgranitoide-roca huésped que sugiere una similitud de lo procesos petrogéneticos que originaron ambos grupos de enclaves. Además, la similitud mineralógica, química e isotópica de estos enclaves con sus respectivas rocas huéspedes sugiere interpretarlos, al menos en su mayoría, como autolitos.-----------------------------------------------------The los Pedroches batholith consists of two main epizonal plutonic units. The dominant plutonic lithotypes prevailing in each of these units are a biotite ± amphibole granodiorite and a coarse-grained, biotite ± cordierite monzogranite with alkali feldspar megacrysts. Petrographic and geochemical data of this work suggest that microgranitoid enclaves hosted by granodiorites and monzogranites are not related to first-order magmatic hybridization processes, but to the late, crustal evolution of the granitoid magmas. Chemical data show a clear parallelism between the behaviour of each of the enclave-host rock associations, suggesting that, in each of the rock groups, enclaves were generated by similar processes and from melts very similar to those originating their respective hosts. This chemical, mineralogical and isotopic evenness of hosts and enclaves suggests that most of these latter are to be interpreted as autoliths

The Cabo de Gata-Níjar UNESCO Global Geopark (Almería, Spain). A Volcanism between Land and Sea

Cabo de Gata-Níjar geopark is an exceptional volcanic zone in the western Mediterranean because of the submarine effusive volcanism and the large volume of subaerial pyroclastic deposits; volcanism developed between land and sea. Its extensive outcrops attract students and researchers from all over Europe to have a better and more precise understanding of the processes behind this volcanism. The compositional range of the outcrops and climatic conditions have generated amazingly well exposed areas, where a wide range of volcanic deposits can be observed and studied. Its current position makes the whole complex an outstanding area for research and education in geology and volcanology. All this led to the designation of the area as a UNESCO Global Geopark in 2015 and the development of a strategy to highlight the value of the geological heritage of the area, developing diverse tools in the form of brochures, maps, a geosite inventory and a legal framework to make conservation and research main objectives of the management team

Geochemical and Volcanological Criteria in Assessing the Links between Volcanism and VMS Deposits: A Case on the Iberian Pyrite Belt, Spain

VMS deposits in the Iberian Pyrite Belt (IPB), Spain and Portugal, constitute the largest accumulation of these deposits on Earth. Although several factors account for their genetic interpretation, a link between volcanism and mineralization is generally accepted. In many VMS districts, research is focused on the geochemical discrimination between barren and fertile volcanic rocks, these latter being a proxy of VMS mineralization. Additionally, the volcanological study of igneous successions sheds light on the environment at which volcanic rocks were emplaced, showing an emplacement depth consistent with that required for VMS formation. We describe a case on the El Almendro–Villanueva de los Castillejos (EAVC) succession, Spanish IPB, where abundant felsic volcanic rocks occur. According to the available evidence, their geochemical features, εNd signature and U–Pb dates suggest a possible link to VMS deposits. However, (paleo)volcanological evidence here indicates pyroclastic emplacement in a shallow water environment. We infer that such a shallow environment precluded VMS generation, a conclusion that is consistent with the absence of massive deposits all along this area. We also show that this interpretation lends additional support to previous models of the whole IPB, suggesting that compartmentalization of the belt had a major role in determining the sites of VMS depositionThis research is supported by the research project “Caracterización y datación isotópicas de rocas ígneas y sistemas hidrotermales en la Faja Pirítica Ibérica Española” (BTE2003-04354, Plan Nacional I+D) Careful revisions by anonymous reviewers have importantly contributed to improve this work and are acknowledged with than

Choosing the site, getting the stones, building the dolmens: local sourcing of andesites at the El Pozuelo megalithic complex (Huelva, Spain)

The geoarchaeological study focuses on the lithological characterization and provenance determination of the rocks of the El Pozuelo dolmens. The difficulty of identifying volcanic rocks in the intensely altered and deformed environment of the Iberian Pyrite Belt has required the implementation of a research methodology combining the archaeological and geological analysis of the megaliths and the area surrounding the Los Llanetes group. A total of 29 thin sections and 14 geochemical analyses (ICP-AES, ICP-MS and REE) have been carried out on samples from the dolmens and potential source areas, focusing on the chemical elements considered immobile during alteration processes. The petrological analyses confirm the identification of different andesite lithotypes and enable us to correlate the rocks used in the construction of the megaliths with source areas and quarries located within a 50–350 m radius. Several patterns are observed in the selection of the rocks, based on the material, visual and symbolic properties of the different lithologies. Foliated andesite is the most common stone used in the monuments, due to its excellent physical properties and technological suitability for extraction and transformation into megalithic supports. Other types of andesite (sheared, massive and amphibole-phyric), white quartz, ferruginous agglomerate and gabbro were also used for different architectural purposes. The results confirm the importance of locally available suitable rocks in determining site location, raw material procurement and monument construction during the Late Neolithic.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This study was funded by the ERDF Operational Programme and the Consejería de Economía y Conocimiento de la Junta de Andalucía (2014-2020), and has been developed within the R+D+i Project "MEGA-LITHOS. Geo-archaeological study methods for the investigation of the Huelva megalithisms" (UHU-1263153), University of Huelva. The funding of the Open Access charge has been assumed by the Complutense University of Madrid, thanks to the agreement established by CRUE-CSIC with Springer Nature

Emplacement, hydrothermal alteration and metamorphism sequence in the Jörn Granitoid Complex, Skellefte mining district, northern Sweden

The Skellefte district is one of the most important mining districts in Sweden, located in an early Proterozoic (1.90-1.87Ga) volcanic arc province in the Baltic Shield, northern Sweden. The district consists of a complex volcanosedimentary succession formed by submarine, mainly felsic, volcanic rocks named Skellefte Group, overlain by a subaerial, felsic volcanic succession named Arvidsjaur Group and shallow- to deep-marine sedimentary rocks known as Vargfors Group (Allen et al., 1996). The Jörn Granitoid Complex (JGC) crops out at the northern boundary of the Skellefte district, and is constituted by several intrusions ranging in composition from gabbro to granite. Some features of the JGC suggest that it is comagmatic with the volcanic rocks of the Skellefte and Arvidsjaur Group. Our recent study has revealed that earlier intrusives in the complex (GI) have significant geochemical differences with the rest of plutonic rocks in the complex (GII to GIV). Crystallization of GI was followed by intense hydrothermal alteration and late, regional contact metamorphism that do not affect the later GII to GIV facies. This sequence in time, together with the chemical contrasts between the successive Jörn facies, suggests that a significant time gap lasted between the emplacement of GI and the later plutonic rocks in the Jörn complex. This is probably relevant to the geological history and ore research in the district, in that a major change occurred between GI and the rest of the JGC facies, involving changes in the geochemical character of magmatism and coeval thermal activit

Succession of felsic volcanic sequences in the Volcano-Sedimentary Complex in the Iberian Pyrite Belt: discrimination between volcanic and subvolcanic models

A field study is presented on two selected areas in the Volcano-Sedimentary Complex (VSC) of the Iberian Pyrite Belt (IPB), the Odiel River section and the Paymogo Volcanic lineament. Field evidence has allowed to distinguish two major groups of felsic rocks, which successively appear in the stratigraphic column. Probably, this conclusion can be extended to other areas in the IPB. In addition, field, petrographic and geochemical evidence shows that at least the felsic rhyolitic succession in the Odiel River (and probably also in Paymogo) formed in a volcanic, environment, favouring a volcanic-pile model in the VS

El sitio megalítico de La Torre-La Janera (Huelva): monumentalidades prehistóricas del Bajo Guadiana

Research on the megalithic site of La Torre-La Janera, located in the Lower Guadiana (Huelva), has integrated several non-invasive techniques of sampling, analysis and documentation: prospections, geoarchaeology, geographic information technologies and photogrammetry. The most important results have been: a) the discovery of a large number of various types of megaliths (standing-stones, dolmens, mounds, cists and enclosures) from different chrono-cultural periods built in greywacke, some of which are new to the area; b) the presence of monuments integrating outcrops as architectural and symbolic elements; c) the probable synchrony between standing-stones and funerary structures. This research contributes to the advancement of the knowledge of the megalithism in the Iberian Peninsula, opening up future lines of study, new problems and other ways of interpreting the genesis and complexity of prehistoric monumentality.Este trabajo tiene por objeto presentar el sitio megalítico de La Torre-La Janera, ubicado en el Bajo Guadiana (Huelva). Su investigación ha integrado varias técnicas de muestreo, análisis y documentación: prospecciones, geoarqueología, tecnologías de información geográfica y fotogrametría. Los resultados más destacados han sido: a) la constatación de una gran cantidad y variedad de megalitos (menhires, dólmenes, túmulos, cistas y recintos) de diferentes periodos crono-culturales construidos en grauvaca, parte de ellos novedosos en la zona; b) la presencia de monumentos que integran afloramientos como elementos arquitectónicos y simbólicos; c) la probable sincronía entre los menhires y las estructuras funerarias. Su investigación contribuye al avance del conocimiento del megalitismo en la península ibérica, abriendo futuras líneas de estudio, nuevas problemáticas y otras vías de interpretación sobre la génesis y complejidad de la monumentalidad prehistórica

Sucesión de secuencias volcánicas félsicas en el Complejo Vulcanosedimentario de la Faja Pirítica Ibérica: discriminación entre modelos volcánicos y subvolcánicos

A field study is presented on two selected areas in the Volcano-Sedimentary Complex (VSC) of the Iberian Pyrite Belt (IPB), the Odiel River section and the Paymogo Volcanic lineament. Field evidence has allowed to distinguish two major groups of felsic rocks, which successively appear in the stratigraphic column. Probably, this conclusion can be extended to other areas in the IPB. In addition, field, petrographic and geochemical evidence shows that at least the felsic rhyolitic succession in the Odiel River (and probably also in Paymogo) formed in a volcanic, environment, favouring a volcanic-pile model in the VSC