The dioritic-gabbroic intrusive complex of Susqueda (Montseny–Guilleries massif, Catalonia): lithological units and petrographic features

The intrusive complex of Susqueda constitutes the biggest association of plutonic mafic rocks of the Catalonian Coastal Ranges. It is located in the contact between the large calc-alkaline granitoid intrusions and the Paleozoic country rocks affected by Hercynian regional metamorphism. Intrusive relationships denote contemporaneity of basic magmas and, at least, an acid magma intrusion. A significant part of the outcrop consists of a heterogeneous mixing zone between the two magmas (mingling). The intrusion is made up of two oval-shaped outcrops about 3 km long, elongated in the N–S direction and separated by a NW–SE fault. In these units, the compositions of the plutonic rocks range from quartz diorites and tonalites (in the mixing zones) up to olivine hornblendites. Even though its distribution is quite heterogeneous, a preliminary cartography was made including the different petrographic types in three main groups: 1) hornblende gabbros and olivine hornblendites; 2) biotite-hornblende diorites; and 3) heterogeneous mixing zone between hornblende-biotite quartz diorite, granodiorite, and tonalite. The predominant mineral composition consists of plagioclase and amphibole, typical of dioritic rocks. Nevertheless, in a great part of the outcrop the plagioclase widely exceeds the 50% in An, typical of gabbroic rocksEl complejo intrusivo de Susqueda constituye la mayor asociación plutónica de rocas máficas del batolito de las Cordilleras Costeras Catalanas. Se halla situado en el contacto entre grandes intrusiones de granitoides calcoalcalinos y rocas encajantes paleozoicas afectadas por el metamorfismo regional herciniano. Las relaciones intrusivas indican una clara contemporaneidad entre los magmas básicos y, al menos, una intrusión ácida. Una parte significativa del afloramiento consiste en una zona de mezcla heterogénea entre los dos magmas (mingling). La intrusión está formada por dos afloramientos ovalados de unos 3 km de longitud, alargados en dirección N–S y separados por una falla NW–SE. En su interior se distinguen diversos tipos de rocas plutónicas con composiciones que varían desde cuarzodioritas y tonalitas (en las zonas de mezcla) hasta hornblenditas olivínicas. Aunque su distribución es bastante heterogénea se ha realizado una cartografía preliminar, incluyendo los distintos tipos petrográficos en tres grupos principales: 1) gabros hornbléndicos y hornblenditas olivínicas, 2) dioritas hornbléndico-biotíticas y 3) mezcla heterogénea entre cuarzodioritas biotítico-hornbléndicas, granodioritas y tonalitas. La mineralogía dominante consiste en plagioclasa y anfíbol que es típica de rocas dioríticas. No obstante, en gran parte del afloramiento la plagioclasa supera ampliamente el 50% de An, propia de rocas gabroica

Evolución de la deformación y los fluidos durante el tránsito dúctil-frágil del basamento cristalino Paleozoico de la Cadena Litoral Catalana.

El Turó de les Forques es un horst aislado de la Cadena Litoral Catalana, formado principalmente por filitas ordovícicas, caracterizado por una intensa fracturación que abarca desde el Hercínico al Neógeno. La deformación Hercínica está representada por una foliación muy penetrativa y por venas de quarzo-clorita sinesquistosas y tardiesquistosas de carácter dúctil. La extensión Mesozoica está definida por venas y brechas cementadas por las asociaciones albita-cuarzo-clorita±titanita-rutilo y dolomita-clorita-cuarzo y marca el cambio hacia condiciones de deformación frágiles. La compresión Paleógena genera cabalgamientos y fracturas cementadas por calcita-barita. Finalmente la extensión Neógena está representada por fallas normales que generan harinas de falla y fracturas cementadas por calcita. Tanto la deformación Hercínica como la Mesozoica están relacionadas con un flujo de fluidos local ligados al metamorfismo de bajo grado. En cambio, durante las dos siguientes fases deformativas, el flujo de fluidos se da a nivel de cuenca. La localización de este bloque a lo largo de la evolución de la Cadena Costero Catalana tuvo que jugar un control principal en la formación de las fracturas y paragénesis exclusivas del Turó de les Forques

Fluid composition changes in crystalline basement rocks from ductile to brittle regimes

The relationships between deformation and fluid flow have been investigated in the Paleozoic basement of an isolated horst of the Catalan Coastal Ranges. A structural, petrological and geochemical study has been performed in a complex fracture network that resulted from a long-lived tectonic history (from Carboniferous to Miocene). Nine fracture types, developed from a ductile regime in the greenschist facies to a shallow brittle regime, have been characterized in order to establish P, T and fluid compositions during the evolution of the horst. Syncleavage and late-cleavage quartz veins (qtz1-chl1 ± mu and late qtz2-chl2-dol1) formed during the Hercynian ductile deformation. These minerals precipitated from metamorphic fluids, possibly evolved from seawater, at temperatures between 240 and 340 °C. En-echelon albite vein arrays (ab-qtz3-chl3 ± ti-an) and NE-SW normal faults generating breccias mark the change from ductile to brittle, from compression to extension and from a closed to an open hydrologic regime. This paragenesis precipitated from the mixing of metamorphic and magmatic fluids at temperatures between 180 and 290 °C during the early Permian extension. Dolomite veins (dol2-chl4-qtz4), precipitated at 210-280 °C from the mixing of previous fluids with hypersaline oxidizing external brines, possibly during the late stage of the early Permian extension. Reverse faults and calcite veins (Cc1-ba) formed either during the Paleogene compression or during the Langhian to early Serravallian minor compression. Calcite and barite precipitated from meteoric or marine waters in an open hydrological system at temperatures below 50 °C. The Miocene extension is represented by NE-SW normal faults with fault gouges and NNW-SSE normal faults cemented by calcite 2 that precipitated at temperatures below 50 °C from meteoric fluids in an open basin-scale hydrological system. The studied horst was part of a relay zone between two segments of the NNW-SE Llobregat fault during the early Permian, explaining the high fracture density and the fast upflowing of hydrothermal fluids at that time, thus controlling the development of albite veins exclusively in this area

Influence of basement rocks on fluid evolution during multiphase deformation: the example of the Estamariu thrust in the Pyrenean Axial Zone

Calcite veins precipitated in the Estamariu thrust during two tectonic events decipher the temporal and spatial relationships between deformation and fluid migration in a long-lived thrust and determine the influence of basement rocks on the fluid chemistry during deformation. Structural and petrological observations constrain the timing of fluid migration and vein formation, whilst geochemical analyses (δ13C, δ18O, 87Sr/86Sr, clumped isotope thermometry and elemental composition) 15 of the related calcite cements and host rocks indicate the fluid origin, pathways and extent of fluid-rock interaction. The first tectonic event, recorded by calcite cements Cc1a and Cc2, is related to the Alpine reactivation of the Estamariu thrust, and is characterized by the migration of meteoric fluids, heated at depth (temperatures between 56 and 98 ºC) and interacted with crystalline basement rocks before upflowing through the thrust zone. During the Neogene extension, the Estamariu thrust was reactivated and normal faults and shear fractures with calcite cements Cc3, Cc4 and Cc5 developed. Cc3 and Cc4 precipitated 20 from hydrothermal fluids (temperatures between 127 and 208 ºC and between 102 and 167 ºC, respectively) derived from crystalline basement rocks and expelled through fault zones during deformation. Cc5 precipitated from low temperature meteoric waters percolating from the surface through small shear fractures. The comparison between our results and already published data in other structures from the Pyrenees suggests that regardless of the origin of the fluids and the tectonic context, basement rocks have a significant influence on the fluid chemistry, particularly on the 87Sr/86Sr ratio. Accordingly, the cements 25 precipitated from fluids interacted with crystalline basement rocks have significantly higher 87Sr/86Sr ratios (> 0.710) with respect to those precipitated from fluids that have interacted with the sedimentary cover (< 0.710)

Integració dels sistemes de classificació de les roques: eina d'aprenentatge transversal per al foment d'equips docents en l'àmbit de la Geologia.

As a response to the need to implement a comprehensive tool for the classification of rocks, an interdisciplinary and interuniversity teaching team formed by teachers and students has been constituted. The team develops teaching actions to improve the university learning on petrology and mineralogy. Such actions will have positive repercussions to undergraduates and postgraduates students as well as to secondary and baccalaureate teachers, and to other professional not directly related to teaching. Moreover, with the implementation of such tool will clearly promote the self-learning of students by means of a uniform and common system of classification of rocks aimed to all types of public

Archaeopetrological approximation to the lithic procurement of the neolithic axes and adzes from Can Sadurní’s cave (Begues, NE Iberian Peninsula)

Can Sadurní’s cave, located in Begues (NE Iberian Peninsula), in the Baix Llobregat region, is an archaeological site with a wide stratigraphic sequence covering from the Epipaleolithic hunter-gatherers societies at the beginning of the Holocene to Roman times. During the excavations of the last years a large number of different raw materials used for the manufacture of axes have been recovered.The present study is focused on the Neolithic sequence. 31 axes and adzes have been characterised petrographically with the aid of a binocular microscope and transmission microscope. A great variety of rocks constitute the raw materials of these stone tools, ranging from contact and regional metamorphic rocks to plutonic and porphyric igneous rocks. The formers are the most abundant (up to 78%) and include hornfels, spotted phyllites, marbles, quartzites, slates and phyllites. The igneous rocks consist of granodiorite, porphyry and aplites. Such a great assemblage of rocks matches in a geological context representative of a plutonic intrusion and its metamorphic contact aureole. Following that scenario we suggest that the most likely source area for all these materials occur at the Collserola hills, at 27 km far to the east from the cave, at the other side of the Llobregat River, where an Hercynian granodiorite and related igneous rocks intruding Ordovician metasedimentary materials are presented.

Barcelona Rocks, A mobile App to learn Geology in your city.

Barcelona Rocks is an application for personal mobile devices suitable for secondary and high school students as well as the general public without a solid background in Earth Sciences

BCN Rocks: aprendiendo geología urbana a través de una aplicación App interactiva.

Barcelona Rocks (BCN Rocks) es una aplicación (App) para dispositivos móviles personales (con versiones para Android y iOS) apta para ser utilizada por estudiantes de Enseñanza Secundaria Obligatoria (ESO) y Bachillerato, y para el público en general, con el objetivo de aprender geología a partir de recursos didácticos proporcionados por las rocas de las fachadas y pavimentos de dos zonas emblemáticas y céntricas de la ciudad de Barcelona como son el Passeig de Gràcia y el Barri Gòtic. La aplicación presenta tres grandes apartados "ELEMENTOS", "EXPLORA" y "LABORATORIO" que pretenden satisfacer diversas facetas del usuario. En el apartado Elementos, el usuario encontrará el conjunto de edificios que contiene la aplicación, toda la información sobre las rocas que los forman, así como una breve explicación sobre la historia y arquitectura de cada uno de ellos. Con el apartado Explora, se pretende despertar la curiosidad o la parte más expedicionaria del usuario. Para ello se proponen una serie de rutas que pueden realizarse siguiendo, bien el criterio de posición geográfica de los edificios incluidos en la App, bien teniendo en cuenta la antigüedad de las construcciones (desde la Barcino romana hasta la Barcelona actual). Finalmente, el partado Laboratorio, permite al usuario investigar distintos aspectos geológicos mediante experimentos interactivos

Metamorphic evolution of granulite facies kinzigites from Agly massif

In the Agly massif outcrops one of the deepest parts of the Hercynian crust. Its basement is constituted by a monotonous pile of paragneisses and anatectic migmatites which presents numerous intercalations of kinzigites, marbles, calcsilicates and basic rocks. This work describes the main structural and metamorphic features of the kinzigites in order to define the P-T evolution of a granulite facies crustal segment. The main mineral metamorphic association is in equilibrium at the univariant prograde reaction biotite + sillimanite + quartz = cordierite + garnet + K-feldspar + H2O and it is formed synchronously with the development of the regional foliation (S2). Following this association and close to the climax, there is a slight pressure drop recorded in the formation of cordierite coronas around garnet porphyroblasts; finally there is a retrograde stage linked to a high grade extensional event (D3). Petrographic observations in conjunction with Schreinemakers analysis and thermobarometric calculations have enable the construction of a nearlyisobaric P-T path and determine that the metamorphic peak is reached at 790 ºC and 5,5 kbar by the deepest rocks. Assuming a linear gradient it is concluded that the climax is achieved at different times and at different crustal levels and that, af ter the climax, there is an important shor tening of the lithological column consistent with an extensional unroofin

Evolución metamórfica de las kinzigitas en facies granulita del macizo del Aglí

In the Agly massif outcrops one of the deepest parts of the Hercynian crust. Its basement is constituted by a monotonous pile of paragneisses and anatectic migmatites which presents numerous intercalations of kinzigites, marbles, calcsilicates and basic rocks. This work describes the main structural and metamorphic features of the kinzigites in order to define the P-T evolution of a granulite facies crustal segment. The main mineral metamorphic association is in equilibrium at the univariant prograde reaction biotite + sillimanite + quartz = cordierite + garnet + K-feldspar + H2O and it is formed synchronously with the development of the regional foliation (S2). Following this association and close to the climax, there is a slight pressure drop recorded in the formation of cordierite coronas around garnet porphyroblasts; finally there is a retrograde stage linked to a high grade extensional event (D3). Petrographic observations in conjunction with Schreinemakers analysis and thermobarometric calculations have enable the construction of a nearlyisobaric P-T path and determine that the metamorphic peak is reached at 790 ºC and 5,5 kbar by the deepest rocks. Assuming a linear gradient it is concluded that the climax is achieved at different times and at different crustal levels and that, af ter the climax, there is an important shor tening of the lithological column consistent with an extensional unroofing