Timing of magmatic-hydrothermal activity in the Variscan Orogenic Belt: LA-ICP-MS U–Pb geochronology of skarn-related garnet from the Schwarzenberg District, Erzgebirge

[EN] Here, we present in situ U-Pb laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) ages of andradite-grossular garnet from four magmatic-hydrothermal polymetallic skarn prospects in the Schwarzenberg District, Erzgebirge (Germany), located in the internal zone of the Variscan Orogenic Belt. Within the geochronological framework of igneous rocks and hydrothermal mineralization in the Erzgebirge, the obtained garnet ages define three distinct episodes of Variscan skarn formation: (I) early late-collisional mineralization (338-331 Ma) recording the onset of magmatic-hydrothermal fluid flow shortly after the peak metamorphic event, (II) late-collisional mineralization (similar to 327-310 Ma) related to the emplacement of large peraluminous granites following large-scale extension caused by orogenic collapse and (III) post-collisional mineralization (similar to 310-295 Ma) contemporaneous with widespread volcanism associated with Permian crustal reorganization. Our results demonstrate that the formation of skarns in the Schwarzenberg District occurred episodically in all sub-stages of the Variscan orogenic cycle over a time range of at least 40 Ma. This observation is consistent with the age range of available geochronological data related to magmatic-hydrothermal ore deposits from other internal zones of the Variscan Orogenic Belt in central and western Europe. In analogy to the time-space relationship of major porphyry-Cu belts in South America, the congruent magmatic-hydrothermal evolution in the internal zones and the distinctly later (by similar to 30 Ma) occurrence of magmatic-hydrothermal ore deposits in the external zones of the Variscan Orogenic Belt may be interpreted as a function of their tectonic position relative to the Variscan collisional front.Open Access funding enabled and organized by Projekt DEAL. This study was funded by the Federal State of Saxony and the European Social Fund (Grant no. 100339454 received by M. Burisch

Masa-espektrometria bidezko prozedura analitiko berrien garapena Geokimika Isotopikoan eta haien aplikazioa presio altuko arroka metamorfikoen azterketan

Geokimika Isotopikoak/Geokronologiak azken hamarkadetan izan duen bilakaerak hainbat teknika analitikoren hobekuntza eragin du, gerriko metamorfikoen tektonikaren gaineko informazioan iraultza eraginez. Euskal Herriko Unibertsitatea (UPV/EHU) berariazko tresneria analitikoaren jabe da, munduan gehien erabiltzen di-ren metodo geokronologikoen inplementazioa eta hobekuntza ahalbidetuz. Lan hone-tan, Rb-Sr eta Lu-Hf sistemak MC-ICP-MS bidez analizatzeko metodologia garatu da alde batetik, eta Hf-Hf eta U-Pb sistemak LA-ICP-MS bidez neurtzeko teknikak beste-tik. Teknika horiek Iberiar mendigunearen ipar-mendebaldeko Malpica-Tui eta Cabo Ortegal Konplexu Aloktonoetako presio altuko arroka metamorfikoen dataziorako eta trazaketarako erabili dira.; The development of Isotope Geochemistry/Geochronology has triggered many technical improvements in the past decades and has revolutionised the potential information available on the tectonics of metamorphic belts. The University of the Basque Country (UPV/EHU) has acquired the specific analytical equipment, which has allowed the implementation and improvement of several of the worldwide most used geochronological methods. In the present work, techniques for Rb-Sr and Lu-Hf analy-sis by MC-ICP-MS, and Hf-Hf and U-Pb analysis by LA-ICP-MS have been devel-oped. These techniques have been employed to date and trace the origin of high-pres-sure rocks from the Malpica-Tui and Cabo Ortegal Allochthonous Complexes of the NW Iberian Massif

Calako skarn-a: ezaugarri geokimikoak eta U-Pb datazioak

Cala mine is located in the southwest of the Iberian Massif, in the Ossa-Morena Zone (OMZ). Due to the complexity of its mineralisation, there has been much debate in recent years but, according to recent studies, it is interpreted that part of the mineralisation is related to a calcic skarn that outcrops nearby. In this work, garnets from this skarn have been dated using the U-Pb geochronology by LA-ICP-MS, and the obtained age is 335 ± 1 Ma. Calcic garnets (Gros52-59Andr40-44) show homogeneous major elements distribution. A weak chemical zonation can be observed in trace elements and REE, more evident in trivalent elements. This chemical homogeneity has been related to a stable system, where P-T conditions have remained quite stable.; Cala meategia Ossa-Morena Zonaldean (OMZ) kokatzen da, Iberiar Mazizoaren hego-mendebaldean. Hango mineralizazioa nahiko konplexua denez, az- ken urteotan asko eztabaidatu da horren inguruan, baina berriki egin diren ikerketa- lanen arabera, mineralizazioaren zati bat bertan azaleratzen den skarn kaltziko bate- kin erlazionatuta dagoela interpretatu da. Lan honetan skarn-eko granateak datatu dira U-Pb sistema eta LA-ICP-MS metodoaren bidez. Mineral horiek primarioak direnez, metasomatismoa datatzea ere posible izan da skarna bera ere datatuz. Lortutako emai- tzen arabera skarna duela 335 ± 1 Ma sortu zela ondorioztatu da. Granate kaltzikoen (Gros52-59Andr40-44) konposizio kimikoa nahiko homogeneoa da, batez ere elementu nagusiak aztertzean, eta aztarna elementuen zein REE-en kontzentrazioak zonazio oso ahula erakusten dute, batik bat elementu tribalenteetan. Honenbestez, granate hauen so- rreran sistemako P-T baldintzak nahiko konstante mantendu zirela ondorioztatu da

Geochemical dataset of high-pressure acid migmatites from the Cabo Ortegal Complex (NW Spain)

This brief note presents geochemical data from rock samples from the Cabo Ortegal Complex (NW Spain). The samples belong to acid lithologies within the mainly basic to intermediate granulite unit that have been poorly investigated so far. For this communication, five samples of the migmatites and an amphibolitic enclave within them have been analysed. The whole-rock major and trace-element analyses were accomplished by means of Q-ICPMS. The dataset provides new and useful information relevant to the origin of the acid migmatites and can be used in addition to information from neighbouring lithologies to enhance understanding of the geological evolution of the Western Variscan Belt

U-Pb dating and geochemical dataset of fracture-filling calcite veins from the Boixols-Sant Corneli anticline (Southern Pyrenees)

U-Pb dating and geochemical analyzes ( 818 O, 813 C, A47 , 87 Sr/ 86 Sr and elemental composition) have been applied to fracture-filling calcite veins and host carbonates from the Boixols-Sant Corneli anticline, which developed along the front of the Boixols thrust sheet in the Southern Pyrenees. This robust dataset is used to determine: (i) the absolute timing of fracturing and mineralization from fluid flow; (ii) the age and duration of fold evolution; and (iii) the variations and implications of fluid behavior across the anticline, as has been described in the article "Spatio-temporal variation of fluid flow behavior along a fold: The Boixols-Sant Corneli anticline (Southern Pyrenees) from U-Pb dating and struc-tural, petrographic, and geochemical constraints - Marine and Petroleum Geology (2022) (Munoz-Lopez et al., 2022). In this new contribution, we present the raw data that have been analyzed and discussed in the related research article and, also, the whole elemental and REE composition of cal-cite veins and host carbonates that has not been published yet. These data may be used to unravel the age and origin of veins, to understand their sequential evolution in orogenic belts and to compare our results with those obtained in sim-ilar settings worldwide.This is a contribution to the DGICYT Spanish projects PGC2018-093903-B-C22 and PID2021-122467NB-C22 (Ministerio de Ciencia, Innovación y Universidades/Agencia Estatal de Investigación /10.13039/501100011033/ Fondo Europeo de Desarrollo Regional, Unión Europea), the Grup Consolidat de Recerca “Geologia Sedimentària” (2017-SGR-824) and the Grup Consolidat de Recerca “Modelització Geodinàmica de la Litosfera” (2017SGR-847). This work was also partially funded by ALORBE project (PIE–CSIC–202030E310). This is FIERCE contribution No. 107. We thank all comments provided by an anonymous reviewer, which helped improve the quality of the manuscript. Carbon and oxygen isotopic analyzes were carried out at the Centre Científics i Tecnològics of the Universitat de Barcelona. Strontium analyses were performed at the CAI de Geocronología y Geoquímica Isotópica of the Universidad Complutense de Madrid. The elemental composition was analyzed at the geochemistry facility lab-GEOTOP of Geosciences Barcelona (GEO3BCN–CSIC). U–Pb analyzes were performed at the Frankfurt Isotope and Element Research Center (FIERCE) from the Goethe-University Frankfurt (Germany)

Quaternary deformation and uplift of coral reef terraces produced by oblique subduction and underthrusting of the Bahama Platform below the northern Hispaniola forearc

[EN] Active tectonics linked to the rise of the Hispaniola forearc explain the morphological characteristics, spatial distribution and U-Th geochronological ages of the uplifted coral reef terraces of the La Isabela Formation in both the eastern Cordillera Septentrional and the Saman ́a Peninsula of northeastern Dominican Republic. Depositional coral reef terraces of MIS 5e (TII), 7e (TIII) and 9 (TIV) stages occur respectively at maximum heights of about 25 m, 80 m and 120 m above the current sea level. The development of heterogeneous brittle deformation structures in the coral limestone at all scales document active tectonics and include small faults, shear fractures, extensional joints and calcite veins. Their geometric and kinematic characteristics, as well as the stress tensors calculated from fault-slip and fracture orientation data, are all compatible with ENE to NE-trending regional shortening, and indicate that a left-lateral transpressive regime is deforming the forearc during the Quaternary. Along the northern Hispaniola coastline, the tectonic uplift mimics the distribution of the bathymetric features on the subducting Bahamas Platform, outboard the Hispaniola-Puerto Rico Trench. The highest calculated uplift rates in the eastern Cordillera Septentrional and Saman ́a Peninsula correspond to the collision zone of the Silver Spur and Navidad Bank (≥0.4 m/ka), respectively. Uplift rates decrease towards the west (≤0.2 m/ka), where the oblique collision of carbonate ridges and related forearc deformation would not have been recorded since at least the Early Pleistocene. Oblique subduction and underthrusting of the Bahamas Platform followed by basal erosion at the subduction channel explain the observed time-transgressive pattern of uplift and subsidence in the northern Hispaniola forearc and the change from accretionary to erosive processes in the convergent margin.The research has been funded by Spanish CGL2012-33669/BTE project, as well as through the PRX12/00152 grant to the first author. The second author acknowledge a postdoctoral grant of the Basque Country Government.Peer reviewe

Upper Ordovician magmatism in the Central Pyrenees: First U-Pb zircon age from the Pallaresa Massif

Ordovician geodynamics: The Sardic Phase in the Pyrenees, Mouthoumet and Montagne Noire massifs International Meeting (2017. Figueras, España)The Late Ordovician magmatism is well represented in all massifs of the Eastern Pyrenees and the Catalan Coastal Ranges, which contain Upper Ordovician rocks. Nevertheless, data about this magmatic episode in the Central Pyrenees are scarce. This work shows the first geochronological data for Upper Ordovician magmatism in the Pallaresa massif. This massif is a large E-W trend antiformal structure included in the metamorphic structural units of the Pyrenean Axial Zone, where Cambro-Ordovician and Upper Ordovician rocks crop out. The Cambro-Ordovician rocks consist of a low-grade monotonous alternation of quartzites and slates with some limestone and conglomerate intercalations, which show evidence of a pre-Variscan penetrative deformation. The Upper Ordovician succession lies unconformably on the older Cambro-Ordovician beds and is represented by a siliciclastic succession with an intermediate limestone level. Volcanic rock levels have been observed interbedded within what was considered a Cambro-Ordovician succession close to outcrops of Upper Ordovician rocks in the eastern part of Pallaresa massif. Both metasedimentary and volcanic rocks were deformed and metamorphosed during the Variscan Orogeny.The volcanic rocks are rhyodacitic to dacitic crystal-rich meta-tuffs with a pervasive foliation. Their mineralogical composition is mainly volcanic quartz, feldspar and biotite. The matrix consists of fine grained of biotite, muscovite, quartz and clinozoisite, the latter mainly developed in highly deformed bands. In addition to these mineral phases, idiomorphic crystals of zircon are recognized.Instituto Geológico y Minero de España, EspañaDepartamento de Geología, Universidad de Oviedo, EspañaPeer reviewe

Eclogite inclusions from subducted metaigneous continental crust (Malpica-Tui Allochthonous Complex, NW Spain): Petrofabric, geochronology, and calculated seismic properties

This study describes the strain geometry, crystal‐plastic deformational features, isotopic age of metamorphism, and calculated seismic properties of two medium‐temperature eclogite types from the Malpica‐Tui Allochthonous Complex of Variscan NW Iberia. The eclogite types are eclogites with coronitic garnets and eclogites with a planolinear fabric. Both of them were buried, deformed and recrystallized under maximum pressure and temperature of 2.6 GPa and 610–640°C, and subsequently exhumed in a late Devonian subduction channel. The metamorphic peak of the subduction‐exhumation cycle occurred ~375 Ma ago. Omphacite petrofabric ties eclogites with coronitic garnet to noncoaxial constrictional strain and eclogites with planolinear fabrics to noncoaxial flattening strain and stretching along the lineation. We also used omphacite crystallographic preferred orientations to calculate and constrain the seismic properties of the eclogites. The slight variations in petrophysical properties observed are interpreted to result from variations in the strain regime recorded by pristine eclogites, or from variations in the modal proportions of the constituent high‐pressure minerals. We foresee that eclogite in subduction metamorphic complexes might be either seismically undetectable or detected as planar features with high impedance contrasts relative to their host rocks.Departamento de Geodinámica, Universidad del País Vasco, EspañaÁrea de Laboratorios, Instituto Geológico y Minero de España, EspañaDepartamento de Mineralogía y Petrología, Universidad del País Vasco, EspañaServicio General de Geocronología y Geoquímica Isotópica, Universidad del País Vasco, EspañaServicio General de Microscopía y Microanálisis de Materiales, Universidad del País Vasco, Españ

Lower Ordovician unconformities and the Ollo de Sapo magmatic event: coeval 478 Ma pyroclastic base-surge deposits and subvolcanic granite intrusion in the Hiendelaencina Antiform

Ordovician geodynamics: The Sardic Phase in the Pyrenees, Mouthoumet and Montagne Noire massifs International Meeting (2017. Figueras, España)The Cambro-Ordovician Ollo de Sapo volcanic event in the Central Iberian Zone has different stratigraphic unconformities associated with it. In the Ollo de Sapo antiform of northwest Iberia and its continuation in the Hiendelaencina antiform of Central Spain, there is not clear evidence of an angular unconformity at its base. However, an erosive unconformity is mentioned in the literature separating the coarse Ollo de Sapo from the overlying Ordovician sequence in the Hiendelaencina Antiform. The Bornova conglomerate of Soers (1972) was interpreted as a product of the erosion of the underlaying felsic tuffs and ignimbrites of the Hiendelaencina gneiss of Schäfer (1969). Closer examination of this unit, along new clean road cuts near the village of La Bodera indicates that these “microconglomerates” are part of metric-scale pyroclastic base surge deposits. These base surge deposits are approximately 1 m thick with a felsic volcanic breccia at the base, a coarse unit with well-developed cross bedding and abundant rounded volcanic quartz and thin 1-2 cm thick siltstone at the top. The deposits are locally truncated by successive surges and intercalated with quartzite beds, suggesting that they might be the product of phreatomagmatic eruptions in a near-shore environment.Instituto Geológico y Minero de España, EspañaGeological Survey of Canada, CanadáPeer reviewe