Arenas Martín, Ricardo

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First Name
Last Name
Arenas Martín
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Mineralogía y Petrología
Petrología y Geoquímica
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Now showing 1 - 10 of 115
  • Publication
    The metahyaloclastitic matrix of a unique metavolcanic block reveals subduction in the Somozas Mélange (Cabo Ortegal Complex, NW Iberia): tectonic implications for the assembly of Pangea
    (Wiley Online Library, 2016) Novo Fernández, Irene; Garcia Casco, Antonio; Arenas Martín, Ricardo; Díez Fernández, Rubén
    The allochthonous Cabo Ortegal Complex (NW Iberian Massif) contains a ~ 500 m thick serpentinite-matrix mélange located in the lowest structural position, the Sómozas Mélange. The mélange occurs at the leading edge of a thick nappe pile constituted by a variety of terranes transported to the East (present-day coordinates; NW Iberian allochthonous complexes), with continental and oceanic affinities, and represents a Variscan suture. Among other types of metaigneous (calc-alkaline suite dated at 527-499 Ma) and metasedimentary blocks, it contains close-packed pillow lavas and broken pillow-breccias with a metahyaloclastitic matrix formed by muscovite – paragonite – margarite – garnet – chlorite – kyanite – hematite – epidote – quartz - rutile. Pseudosection modelling in the MnCNTKFMASHO system indicates metamorphic peak conditions of ~ 17.5-18 kbar and ~ 550 °C followed by near-isothermal decompression. This P-T evolution indicates subduction/accretion of an arc-derived section of peri-Gondwanan transitional crust. Subduction below the Variscan orogenic wedge evolved to continental collision with important dextral component. Closure of the remaining oceanic peri-Gondwanan domain and associated release of fluid led to hydration of the overlying mantle wedge and the formation of a low-viscosity subduction channel, where return flow formed the mélange. The submarine metavolcanic rocks were deformed and detached from the subducting transitional crust and eventually incorporated into the subduction channel, where they experienced fast exhumation. Due to the cryptic nature of the high-P metamorphism preserved in its tectonic blocks, the significance of the Somozas Mélange had remained elusive, but it is made clear here for the first time as an important tectonic boundary within the Variscan Orogen formed during the late stages of the continental convergence leading to the assembly of Pangea.convergence leading to the assembly of Pangea.
  • Publication
    Tectonic evolution of the upper allochthon of the Órdenes complex (northwestern Iberian Massif): Structural constraints to a polyorogenic peri-Gondwanan terrane
    (Geological Society of America, 2007-01-01) Gómez Barreiro, Juan; Martínez Catalán, José Ramón; Arenas Martín, Ricardo; Castiñeiras García, Pedro; Abati Gómez, Jacobo; Díaz García, Florentino; Wijbrans, Jan R.; Linnemann, Ulf; Nance, R. Damian; Kraft, Petr; Zulaud, Gernold
    The upper allochthon of northwest Iberia represents the most exotic terrane of this part of the European Variscan belt. Recent advances in the metamorphic petrology, structural geology, and geochronology of the upper allochthon in the Órdenes complex are integrated into a synthesis of its tectonic evolution, constraining the main tectonothermal events. Important aspects of this synthesis are (1) the interpretation of Cambro-Ordovician magmatism and earliest metamorphic event, as the result of drifting of a peri-Gondwanan terrane; (2) the subsequent shortening and crustal thickening of the terrane related to its subduction and accretion to Laurussia; (3) a younger cycle of shortening and extension resulting from convergence between Laurussia and Gondwana; and (4) the emplacement of this exotic terrane as the upper allochthon, together with underlying ophiolitic and basal allochthons, during the Laurussia-Gondwana collision. Implications derived from the well-established tectonothermal sequence are discussed in the context of Paleozoic paleogeography and geodynamics. The evolution of this part of the belt is related first to the closure of the Tornquist Ocean, and later to that of the eastern branch of the Rheic Ocean. Furthermore, the relative paleopositions of the upper allochthon and the Iberian autochthon in northern Gondwana are discussed.
  • Publication
    Geochemistry and Sm–Nd isotopic sources of Late Ediacaran siliciclastic series in the Ossa–Morena Complex: Iberian–Bohemian correlations
    (Springer, 2021) Rojo-Pérez, Esther; Fuenlabrada Pérez, José Manuel; Linnemann, Ulf; Arenas Martín, Ricardo; Sánchez Martínez, Sonia; Díez Fernández, Rubén; Martín Parra, Luis Miguel; Matas, Jerónimo; Andonaegui Moreno, Pilar; Fernández Suárez, Javier
    The Cadomian basement in central and southern Europe is composed by Ediacaran–Early Cambrian sequences that appear dismembered along the Variscan Orogen. These ancient series contain geochemical and isotopic keys related to their deposition in different basins located along the paleo margin of Gondwana. The southwest of Iberian Massif (Ossa–Morena Complex) contains an excellent representation of Cadomian basement. The oldest sedimentary succession of this region, the Serie Negra Group (c. 600–541 Ma), is composed by the Montemolín Formation which consists of metapelites, metagreywackes and abundant amphibolites; and the Tentudía Formation which consists of metagreywackes, black quartzites and metapelites. The whole-rock and Nd isotopic geochemistry of the Montemolín and Tentudía formations, are consistent with a deposition in a back-arc or fore-arc setting. Their Nd isotopic composition shows highly negative εNd(t) values in a range between − 6.9 and − 11.5, resulting in old Paleoproterozoic Nd model ages between 1.9 and 1.7 Ga. The Nd isotopic signatures obtained for the Cadomian basement in the Iberian Massif are almost identical to those obtained for equivalent sedimentary series in the Saxo-Thuringian Zone (Bohemian Massif), where Nd model ages range between 2 and 1.6 Ga. The limited variability of these Nd-TDM ages suggests that the southwestern Iberian and North Bohemian series shared a common source during Ediacaran times, which would be located close to the periphery of the West African Craton. The Nd isotopic data considered herein provide solid evidence about the peri-Gondwanan location and correlation between the Cadomian basement of southwestern Iberia and North Bohemia.
  • Publication
    The Bazar Ophiolite of NW Iberia: a relic of the Iapetus–Tornquist Ocean in the Variscan suture
    (Blackwell Publishing Ltd, 2012) Sánchez Martínez, Sonia; Gerdex, Axel; Arenas Martín, Ricardo; Abati Gómez, Jacobo
    The Bazar Ophiolite, one of the ophiolitic units involved in the Variscan suture of NW Iberia, is mainly formed by metagabbroic high T amphibolites with N-MORB affinity. The ophiolite appears accreted under an arc-derived upper terrane affected by intermediate-P granulite facies metamorphism dated at 496– 484 Ma. U-Th-Pb geochronology and Lu-Yb-Hf isotope geochemistry of zircons allow recognizing two growth stages. The first occurred during crystallization of the gabbroic protolith and has been dated at 495 ± 2 Ma, whereas the second one, interpreted as dating the high T metamorphism, yielded an age of 475 ± 2 Ma. The chronology of the Bazar Ophiolite and its accretionary history suggest that this unit is a relic of the Cambrian ocean located to the North of Gondwana, the Iapetus–Tornquist Ocean, accreted to a dissected arc during or before the early stages in the opening of the Rheic Ocean.
  • Publication
    Paleogeografía geoquímica de las series metasedimentarias del Macizo Ibérico
    (Sociedad Geológica de España., 2016) Fuenlabrada Pérez, José Manuel; Arenas Martín, Ricardo; Sánchez Martínez, Sonia; Díez Fernández, Rubén; Pieren Pidal, Agustín Pedro
    Las características geoquímicas e isotópicas de las series turbidíticas del Macizo Ibérico reflejan distintos escenarios tectónicos en la periferia de Gondwana. Estos cambios se observan en el registro sedimentario de la transición Ediacarense-Cámbrico, que tuvo lugar en el contexto general de un margen continental activo. TDM jóvenes y ɛNd menos negativos resultan característicos de cuencas sedimentarias más exteriores, con una importante contribución de material juvenil derivado del sector más activo del arco volcánico (metagrauvacas culminantes de las Unidades Superiores del Complejo de Órdenes). Las cuencas sedimentarias más próximas al continente se caracterizan por mayores aportes desde dominios alejados del arco activo que dan lugar a valores de TDM más antiguos y ɛNd muy negativos (metagrauvacas de las Unidades Basales del Complejo de Malpica-Tui). Una evolución desde contextos activos hasta otros más propios de márgenes pasivos se detecta con claridad en la transición Ediacarense-Cámbrico, y debe relacionarse con una disminución de la actividad del arco volcánico y la transición hacia un margen pasivo. El diagrama de fSm/Nd vs ɛNd confirma esta variación de los escenarios tectónicos asociados al margen de Gondwana, perfectamente registrados en los metasedimentos de diferentes sectores y unidades del Macizo Ibérico.
  • Publication
    Evolución tectónica del Macizo Ibérico durante la orogenia Varisca: colisión Gondwana - Laurrusia
    (Sociedad Geológica de España., 2016) Díez Fernández, Rubén; Arenas Martín, Ricardo; Pereira, M. Francisco; Sánchez Martínez, Sonia; Albert Roper, Richard; Martín Parra, Luis Miguel; Rubio Pascual, Francisco J.; Matas, J.
    La revisión de la evolución tectonometamórfica y magmática del Macizo Ibérico revela periodos de extensión y convergencia alternantes dentro de un proceso global de convergencia entre Gondwana y Laurrusia durante la formación de Pangea en el Paleozoico Superior. Fases dominadas por compresión a escala litosférica se caracterizan por el desarrollo de subducción oceánica y continental, generación de arcos magmáticos, cabalgamientos y procesos de acreción de litosfera continental y plegamiento. Eventualmente, la convergencia Varisca durante el Carbonífero produjo la transferencia de un conjunto de terrenos alóctonos peri-Gondwánicos, el denominado Alóctono Ibérico, sobre Gondwana. El Alóctono Ibérico muestra una impronta tectonometamórfica previa a ese proceso de transferencia fruto de la yuxtaposición temprana de Gondwana y Laurrusia tras el cierre del océano Reico en el Devónico Inferior. Las fases dominadas por fenómenos extensionales están representadas por la apertura de dos cuencas oceánicas efímeras a expensas de la corteza orogénica formada hasta el momento, primero en el Devónico Inferior-Medio, tras el cierre del Reico, y luego durante el Carbonífero Inferior, tras el emplazamiento del alóctono peri-Gondwánico. Seguidamente, un evento de extensión intra-orogénica durante el Carbonífero Inferior-Medio desmembró al Alóctono Ibérico en apilamientos individuales de unidades exóticas separados por fallas extensionales y domos. La tectónica transcurrente jugó un papel fundamental durante toda la orogenia Varisca, especialmente durante la creación de nuevos bloques tectónicos separados por zonas de cizalla transcurrentes intra-continentales en las últimas etapas de convergencia continental.
  • Publication
    A complex accretionary assembly of Pangea developed in the range c. 400–340 Ma: the four successive events of high-P/ultra-high-P metamorphism of the Variscan Orogen
    (Taylor & Francis, 2022-10-09) Novo Fernández, Irene; Arenas Martín, Ricardo; Díez Fernández, Rubén; Garcia Casco, Antonio
    In the most internal zone of the Variscan Orogen, a stack of ophiolites and (ultra)high-P belts hold evidence for c. 60 Myr (c. 400–340 Ma) of almost continuous metamorphism and accretion onto the continental margin of Gondwana. Subduction of the peri-Gondwanan lithosphere led to three successive (ultra)high-P metamorphic episodes prior to the continental collision between Gondwana and Laurussia that shaped Pangea. A first high-P, high-T metamorphic belt developed during subduction of a peri-Gondwanan magmatic arc in the Early Devonian. Related to this event is the ensuing opening of intra-Gondwana Middle Devonian oceanic basins, which rapidly closed leading to ophiolite accretion. The second high-P metamorphic episode is related to the formation of a serpentinitic mélange after the sequential subduction of oceanic and transitional crust during Middle Devonian time. Tectonic blocks of subducted crustal material recording high-P, low-T metamorphism were detached from the slab and incorporated into a low-viscosity channel developed between the downgoing slab and the mantle wedge. As convergence progressed, a Late Devonian high-P, low- to intermediate-T metamorphic belt developed due to subduction of the most external margin of Gondwana. Subsequently, the scenario switched to continental collision. In this context, Early Carboniferous intracontinental subduction of the Gondwanan foreland below the accretionary wedge triggered ultra-high-P metamorphism and ensuing exhumation via trans-lithospheric diapirism and doming up to the base of the accretionary wedge.
  • Publication
    Evolución tectonotermal asociada con extensión a escala cortical: el ejemplo hercínico del domo gneísico del Tormes (NO Salamanca, Macizo Ibérico)
    (Seminario de Estudos Galegos. Area de Xeoloxía e Minería ; Instituto Universitario de Xeoloxía "Isidro Parga Pondal", 1994) Escuder Viruete, J.; Arenas Martín, Ricardo; Martínez Catalán, J.R.
  • Publication
    Thickening vs. extension in the Variscan belt: P–T modelling in the Central Iberian autochthon
    (Elsevier, 2016-06) Rubio Pascual, Francisco J.; López-Carmona, Alicia; Arenas Martín, Ricardo
    The Variscan tectonothermal structure of the NW and Central Iberian Massif shows an important thickening during the Early Carboniferous, prior to its thermal weakening and gravitational collapse in the Middle Carboniferous, triggering the uplift of its orogenic roots. Pseudosections modelling of selected samples from Somosierra, in the Barrovian metamorphic area of Central Iberia, yield P–T conditions of at least 6 kbar and 500–540 °C for a micaschist of the garnet zone, 5.0–9.7 kbar and 580–620 °C for a psammitic schist of the staurolite zone, above 9.0 kbar and 680 °C for a kyanite micaschist of the sillimanite zone, and 4.0–9.0 kbar and 750–800 °C for a migmatitic paragneiss structurally beneath the Barrovian sequence. These data, together with previous metamorphic and structural data, imply the near-parallel emplacement of a > 9 km-thick allochthonous nappe over the Central Iberian foreland during the Early Carboniferous. Emplacement was probably related to the lateral extension of a mid-European orogenic plateau in the form of a channel between opposite-verging collisional wedges. This orogen-parallel extension flow can be traced from the Bohemian Massif through the French Massif Central, South Domain of the Armorican Massif and NW of the Iberian Massif, to the Central Iberian area. The highly oblique emplacement of the thick allochthonous nappe explains the orogen-parallel stretching lineations, the development of Barrovian and subsequent Low-Pressure metamorphisms, and it could also explain the massive granitic magmatism located in the NW and central areas of the Central Iberian Zone.
  • Publication
    Large extensional structures developed during emplacement of a crystalline thrust sheet: the Mondoñedo nappe (NW Spain)
    (Elsevier Ltd., 2003) Martínez Catalán, José Ramón; Arenas Martín, Ricardo; Díez Balda, M.A.
    The Mondoñedo nappe is a crystalline thrust sheet characterized by large recumbent folds, regional intermediate-pressure metamorphism, synkinematic intrusion of granitoids during nappe emplacement, and an extensional ductile shear zone developed within the nappe during thrusting. A large tectonic window permits the study of the footwall unit, revealing another extensional shear zone contemporaneous with thrusting and a low-pressure metamorphic evolution, in contrast to that of the hanging wall unit. The two main extensional shear zones produced E–W extension parallel to the direction of orogenic shortening and normal to the orogenic structural trend. Furthermore, subordinate N–S longitudinal extension was accommodated by normal faults in the footwall, and some of these faults were used as lateral ramps in late stages of thrusting. The role of the extensional shear zones and faults described is discussed in the context of an evolving orogenic wedge dominated by plate convergence but characterized by large-scale rheological heterogeneities within it. Deep-seated viscous flow, triggered by heat accumulation, seems to account for the horizontal stretching and probable tapering of the orogenic wedge, which was induced by gravitational instabilities due to partial melting and underplating by buoyant continental crust.