Person:
Abati Gómez, Jacobo

First Name

Jacobo

Last Name

Abati Gómez

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Geológicas

Department

Mineralogía y Petrología

Area

Petrología y Geoquímica

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Now showing 1 - 10 of 53

Polycyclic metamorphic evolution of the Sierra Albarrana Schists (SW Iberian Massif): From low-pressure Ordovician rifting to medium-pressure Variscan overprint
(Elsevier Science B.V., Amsterdam, 2023-05) Solís Alulima, B.E.; López Carmona, Alicia; Abati Gómez, Jacobo; Rojas Agramonte, Yamirka; Bousquet, Romain; González del Tánago y del Río, José
This study presents new information on the polycyclic metamorphic evolution of the Sierra Albarrana Domain (SW Iberian Massif) obtained through a comprehensive assessment of mineral assemblages and petrological modelling (P–T–X pseudosection approach). The pelitic schists in this domain depict the uncommon paragenesis St-Grt-And together with And-Grt-Sil-bearing schists. The first assemblage has been accurately reproduced by pseudosection modelling using the whole rock composition directly analysed by XRF. In contrast, early attempts to model And-Grt-Sil-bearing schists were not as successful. Fe3+ can be a critical element influencing the phase relations in pelites. For this reason, we investigated the influence of the effective amounts of Fe3+ to estimate the oxidation estate during the metamorphism by computing a series of P/T–X pseudosections to explore whether somewhere in P–T–X space the matrix association can be reproduced. The Sierra Albarrana Domain recorded a regional low-pressure metamorphic event accompanied by a complex structural evolution, probably related with the Middle Cambrian-Lower Ordovician rifting developed in the NW Gondwanan margin. This episode has been constrained at ∼4 kbar and 580 °C in the St-Grt-And pelitic schists. Related granitic magma pulses contributed to a local thermal increase of the extending crust (preserved in the And-Grt-Sil-bearing schists), where temperature reaches up to 595 °C. This area shows the syntaxial replacement of coarse-grained andalusite porphyroblasts by sillimanite. This was followed by exhumation, characterised by decompression at ∼2 kbar and 510 °C. After the main pre-Variscan Buchan-type regional metamorphism, a localised medium-pressure metamorphic event, limited to granitic pegmatites and concordant ky-bearing quartz segregation veins was recorded, possibly due to the tectonic thickening corresponding to the Variscan cycle.
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.
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.
Detrital zircon ages and provenance of a Cambrian succession in the Sierra Albarrana Domain (SW Iberian Massif)
(Elsevier, 2022-01) Solís Alulima, B.E.; Abati Gómez, Jacobo; López Carmona, Alicia; Gutiérrez Alonso, Gabriel; Fernández Suárez, Javier; Stockli, Daniel F.
This study presents the first U-Pb geochronological data on detrital zircon grains from the metasedimentary successions of the Sierra Albarrana Domain (SW Iberian Massif) obtained by SHRIMP and LA-ICP-MS. We provide new information on the Maximum Depositional Ages (MDA) during the middle Cambrian through a systematic study, together with age comparisons of the successions, using Kernel Density Estimates (KDE) diagrams, Cumulative Age Distributions (CADs) and the Kolmogorov–Smirnov (K-S) test. On the other hand, the U-Pb zircon data presented in this study have been compared with all the existing data from detrital zircon grains in Neoproterozoic and Cambrian rocks of the Iberian Massif (20 samples, 2706 U–Pb zircon ages). For the comparison, in addition to the KDEs, CADs and K-S test, we apply 3D multidimensional scaling techniques (3D-MDS). The results, together with the geochemical and isotopic characterisation from previous studies, suggest that this domain is likely to be part of the autochthonous section of the Central Iberian Zone (CIZ). Zircon age patterns indicate a probable sedimentary provenance from the Saharan Metacraton with, or without, minor input from the Tuareg Shield. The most important local detrital source corresponds to Cadomian magmatism developed during a magmatic event (535–515 Ma) followed by back-arc extension and early Paleozoic rifting (535–460 Ma). The remaining Mesoproterozoic, Paleoproterozoic and Archean zircon grains would have been provided by the Paleoproterozoic basement and/or the older continental crust recycled in the western sections of the Gondwana margin.
Tectonic evolution of a continental subduction‐exhumation channel: Variscan structure of the basal allochthonous units in NW Spain
(European Geoscience Union, 2011) Díez Fernández, Rubén; Martínez Catalán, José Ramón; Arenas Martín, Ricardo; Abati Gómez, Jacobo
A regional study starting from detailed geological mapping has been carried out in the Malpica‐Tui Complex of Galicia in NW Spain. The complex is formed by two units representing pieces of the external edge of Gondwana, subducted and exhumed during the Variscan collision. The study shows that synsubduction and early synexhumation structures in continental subduction channels tends to be obscured and even erased once exhumation is complete. Detailed structural analysis, matched with the knowledge of the history, and available data for other Galician basal units have elucidated the major structures developed during the subduction‐exhumation process. The results include evidence of the plate convergence causing early Variscan continental subduction of the Gondwana margin. Subduction was followed by exhumation driven by ductile thrusting within the subduction channel, which, in turn, provoked crustal duplication in the subducted slab and modified the initial tectonometamorphic architecture of the subduction wedge. The next step was accretion to the adjacent continental domains, placing the subduction wedge on top of unsubducted parts of the Gondwana margin via ductile thrusting. Thrusting was preceded by progressive propagation of a train of recumbent folds toward the foreland that affected the previous structural stack. Subsequent transference of oceanic (Rheic) and peri‐Gondwanan terranes to the Gondwana margin took place by out‐of‐sequence thrusting followed by crustal extensional collapse and strike‐slip tectonics
Análisis de la evolución en la adquisición de competencias específicas y transversales en los Grados de Geología e Ingeniería Geológica
(2019-06-28) García Lorenzo, Mari Luz; Abati Gómez, Jacobo; Orejana García, David; Castiñeiras García, Pedro; Crespo Feo, María Elena; Piña García, Rubén; García Romero, Emilia; Granja Bruña, José Luis; López García, José Ángel; Fernández Barrenechea, José María; Arribas Mocoroa, María Eugenia; Ortega Menor, Lorena; Pérez Moreno, Elisa María; Benito Moreno, María Isabel
Metamorphic evolution of anthophyllite/cummingtonite-cordierite rocks from the upper unit of the Ordenes Complex (Galicia, NW Spain)
(Geoscienceworld, 2005) Abati Gómez, Jacobo; Arenas Martín, Ricardo
Two types of low-Ca amphibolites are described for the first time in the Ordenes Complex (Galicia, NW Spain). The first type exhibits an initial mineral assemblage containing sillimanite, staurolite and anthophyllite, which are found as microinclusions in cordierite crystals. This association indicates medium pressure and temperatures above 600ºC, and is replaced in the matrix by a medium to low-pressure assemblage of anthophyllite, cordierite and garnet. The second type is represented by lowpressure amphibolitic gneisses formed mainly of cummingtonite, cordierite, andalusite and garnet. The first type of amphibolite would appear to give rise to the second type as a result of metamorphic evolution to lower pressures . A fragment of the decompressive P-T path was obtained by a detailed study of the mineral assemblage succession and the textural relationships of these rocks. The P-T path begins with an almost isothermal decompression from ca. 6-7 kbar and 650ºC. This kind of P-T path (isothermal) is usually interpreted, according to thermal models, as originating during exhumation favoured by some tectonic process. Hence, the exhumation of the uppermost unit of the Ordenes Complex, in which the anthophyllite-cummingtonite rocks are located, appears to have been facilitated by some kind of extensional tectonic process.
Magmatism and early-Variscan continental subduction in the northern Gondwana margin recorded in zircons from the basal units of Galicia, NW Spain
(Geological Society of America, 2010) Abati Gómez, Jacobo; Fernández Suárez, Javier; Arenas Martín, Ricardo; Whitehouse, Martín J.; Díez Fernández, Rubén
In situ uranium-lead dating (LA-SF-ICPMS and SIMS) and Lu-Hf isotope analyses (LA-MC-ICP-MS) of zircon from eclogite facies rocks from the basal units of the Variscan Belt in Galicia constrain their magmatic and metamorphic evolution and give some clues about the nature and origin of the involved basement. The samples studied are two felsic gneisses, two eclogites, and one eclogitic gneiss of intermediate composition (metatonalite). Oscillatory-zoned zircon cores from the felsic samples gave a main clustering of U-Pb ages at 493 ± 2 and 494 ± 2 Ma, and some older ages that represent inherited cores. Zircon grains from the intermediate and one of the mafic rocks show no inherited cores and yielded ages of 494 ± 3 and 498 ± 6 Ma, respectively, interpreted as time of protolith crystallization. Variably developed homogeneous zircon rims in one felsic gneiss yielded an age of 372 ± 3 Ma, and very tiny zircons of one eclogite gave 350 ± 2 Ma, both of which we interpret as metamorphic ages. The new age data demonstrate that the calc-alkaline magmatic suite described in the basal unit is ca. 20 Ma older than the alkaline to peralkaline plutonic suite of the same unit (dated at 472 ± 2 Ma; Rodríguez et al., 2007), and thus probably represents a distinct geologic event. Overgrowth rims are interpreted as metamorphic on the basis of their Lu/Hf and Th/U ratios. The 372 ± 3 age is considered as dating the high-pressure (high-P) metamorphism, and is essentially in agreement with previous Ar-Ar and Rb-Sr data. This high-P metamorphism marks the initial early-Variscan subduction of the Gondwana margin. The inherited zircon ages and Hf isotopic composition of zircons point to a considerable input of crustal material with West African Craton provenance to the felsic magma.
Insights on the crustal evolution of the West African Craton from Hf isotopes in detrital zircons from the Anti-Atlas belt
(Elsevier Science B.V., Amsterdam, 2012) Abati Gómez, Jacobo; Aghzer, Abdel Mouhsine; Gerdes, Axel; Ennih, Nasser
The Lu-Hf isotopic composition of detrital zircons has been used to investigate the crustal evolution of the northern part of the West African Craton (WAC). The zircons were separated from six samples of siliciclastic sedimentary rocks from the main Neoproterozic stratigraphic units of the Anti-Atlas belt, from the Sirwa and Zenaga inliers. The data suggest that the north part of the WAC formed during three cycles of juvenile crust formation with variable amount of reworking of older crust. The younger group of zircons, with a main population clustering around 610 Ma, has a predominant juvenile character and evidences of moderate mixing with Paleoproterozoic and Neoarchean crust, which supports that most igneous and metamorphic rocks where zircons originally crystallized were formed in an ensialic magmatic arc environment. The group of zircons in the age range 1.79–2.3 Ga corresponds to the major crust forming event in the WAC: the Eburnian orogeny. The isotopic data indicate that the provenance area should represent a crustal domain that was separated from a mantle reservoir at ∼2050–2300 Ma, and further evolved with a time-integrated 176Lu/177Hf of ∼0.01, characteristic of continental crust. The evolution of the Eburnian orogeny is, consequently, compatible with new crust formation in an island arc environment, the transition to a continental arc setting and a final continent–continent collision. The Lower Paleoproterozoic and Neoarchean evolution (2.3–2.75 Ga) includes a group of detrital zircon ages that has not been identified up to now in the igneous or metamorphic rocks of the north WAC basement. Their Hf isotopic signature points to reworking of mainly juvenile Neoarchean crust with some Meso- to Palaearchean contributions. The significance of these ages is uncertain: they can represent a tectonothermal event not discovered yet in the Reguibat Shield or the zircons can be far traveled from an unknown source.
Early Paleozoic rifting in the Ossa Morena Complex (SW Iberian Massif): geochemistry and geochronology of a pre-Variscan event in the Sierra Albarrana Domain and La Cardenchosa Pluton
(Sociedad Geológica de España., 2021) Solís Alulima, B.E.; López Carmona, Alicia; Abati Gómez, Jacobo
Recognition of preorogenic geological features in the internal zones of polyorogenic areas, like the Sierra Albarrana Domain and La Cardenchosa Pluton, is difficult. New SHRIMP ages indicate that the main tectonomagmatic event recorded in these areas occurred between Late Cambrian (granite emplacement; 481±2 Ma) and Lower Ordovician (migmatization; 478±2 Ma). These ages also suggest that the intrusion of the igneous body is closely related with the low-pressure partial melting and the deformation of the structurally lower detrital formations. Geochemical data show that the granite from La Cardenchosa Pluton is peraluminous with a slight tendency towards an alkaline geochemical character, and a within-plate setting for the magmatism. Sr-Nd isotope data indicate an igneous origin with a strong upper crustal component, compatible with an extensional environment in the middle-upper crustal levels that marked the early stages of a continental rift development. These data are in agreement with the magmatism reported in other zones from the Iberian Peninsula, and are compatible with the latest magmatic event of the Early Paleozoic rifting. Our results, together with the main regional fabrics, suggest that the granitic magmatism and the migmatization are part of a single event, only slightly modified by Variscan reworking.