Diagenetic K-feldspar pseudomorphs in the Triassic Buntsandstein sandstones of the Iberian Range, Spain

Early diagenetic K-feldspar in the Triassic Buntsandstein of the Iberian Range (Spain) occurs as pseudomorphs after detrital K-feldspar (Or<93) and plagioclase (Ab<96). These pseudomorphs are chemically pure (Or>99), untwinned, commonly heavily clouded by vacuoles and tiny inclusions, dark-luminescing and are composed of numerous fine euhedral crystals of K-feldspar. The latter property suggests that the pseudomorphs form via dissolution of detrital K-feldspar and plagioclase and precipitation of authigenic K-feldspar. X-ray diffraction analysis shows that the authigenic K-feldspar is intermediate microcline.     

On the origin of bleaching phenomena in red bed sediments of Triassic Buntsandstein deposits in Central Germany

The Lower Triassic Buntsandstein in Central Germany comprises one of the major clastic, lithified hydrocarbon reservoirs, it is a major groundwater aquifer and it is considered as a potential underground gas storage lithology. Thus, sandstones of the Buntsandstein from Thuringia and NE Hesse were used to analyse their geochemical composition combined with mineralogical data in order to investigate the origin of several bleaching phenomena in primary red beds, since these give a hint for mineral alteration, mineral formation and mineral reactivity in the course of fluid-rock-interactions. This is relevant for e.g. recent Carbon Capture and Storage (CCS) efforts. The origin of the observed bleaching phenomena is diverse and it is linked to certain stages of diagenesis and different episodes of fluid flow: (1) eodiagenetic bleaching coupled with palaeosoil formation and iron mobilisation, (2) mesodiagenetic bleaching as a result of hydrocarbon migration, (3) Tertiary bleaching due to CO₂ degassing from Miocene volcanism, (4) Tertiary telodiagenetic bleaching due to weathering under humid climate conditions, and (5) weathering processes related to recent telodiagenesis/pedogenesis. This study emphasizes the multiple nature of fluids, which can induce iron mobilisation and bleaching of red beds.     

The fluvial architecture of the upper Buntsandstein in the Iberian Basin, central Spain

The Cercadillo Sandstone and Siltstone (CSS) Formation forms the upper part of the Buntsandstein fluvial facies in the western margin of the Iberian Basin. Sedimentation was controlled by two major pre-Triassic tectonic systems: the Iberian Ranges System (NW-SE) and the Central System (NE-SW). Fluvial sedimentation during this period took place in coexisting braided and meandering channels, together with associated ephemeral episodes. This unusual association was due to a combination of structural control by the main normal faults coupled with large discharge fluctuations. The CSS Formation consists of two major fluvial sequences with very similar vertical patterns comprising low sinuosity stream deposits that pass upwards into high sinuosity deposits associated with extensive floodplain sediments. A widespread calcrete horizon is developed at the top of the lower sequence and a surface with pedogenic features is present at the top of the upper sequence. These horizons are interpreted to be the result of subaerial exposure during a period of no subsidence and equilibrium in the erosion-sedimentation processes in the area, probably due to quiescent periods on the master faults that delineate the basin. Minor changes within the sequences are probably due to discharge fluctuations of a climatic origin whereas the general vertical trend of the sequences is suggested to be tectonically controlled. Palaeocurrent data show a general flux of sediments to the south-east, parallel to the axis of the Iberian Basin, but the final part of the upper sequence palaeocurrents to the north-east are interpreted to indicate a local reactivation of secondary, transverse faults in the south-east part of the study area.     

Contrasting palaeosol development in two different tectonic settings: the Upper Buntsandstein of the Western Iberian Ranges, Central Spain

Palaeosols may offer excellent evidence for the development of sedimentary basins but few studies have used diagenetically altered material: here we show that material of this sort can also reflect the sedimentary environment. The Lower to Middle Triassic red beds of the western Iberian Ranges were deposited in a tectonically active half-graben in which subsidence rates varied along the basin as a response to differential fault movements. During this period the basin was filled by a set of fluvial units with interbedded palaeosols. The palaeosols show typical pedogenic calcrete profiles, although extensive dolomitization has deleted part of their microstructure; however, macrostructure and morphology are preserved. Differences in the maturity stages of the palaeosols are related to the changes in subsidence and sedimentation rates along the basin. Thus, two different scenarios are recognized at: (i) the hanging wall, Riba de Santiuste area, where palaeosols reach stage III as the episodic tilting of the floodplain inhibited the development of more mature soils and (ii) the footwall, Cercadillo area, where palaeosols attain stage V maturity, favoured by prolonged periods of tectonic stability resulting in lower sedimentation rates over the floodplain areas.     

Diagenetic paths in the margin of a Triassic Basin: NW zone of the Iberian Chain, Spain

Buntsandstein deposits generated in a slowly subsiding basin on the western margin of the Iberian Chain are represented by a stratigraphic succession of fluvial deposits less than 100 m thick (conglomerates, sandstones, and shales). Diagenetic processes in sandstones can be grouped as eodiagenetic, mesodiagenetic, and telodiagenetic. Eodiagenesis can be associated with Muschelkalk, Keuper, and probably early Jurassic times. Mesodiagenesis is probably related to Jurassic times. Diagenetic chemical reactions suggest a maximum burial less than 1.5 km and low temperatures (<120°C). Patterns of porosity reduction by compaction and cementation suggest four diagenetic stages: (1) Loss of primary porosity by early mechanical compaction; (2) early cementation (K-feldspar and dolomite); (3) dissolution of cements; and (4) framework collapse by re-compaction. These stages are manifested by the presence of two types of sandstone. Type I sandstones present high intergranular volume (mean, 30%). Type II sandstones are characterized by high compactional porosity loss and exhibit low values of intergranular volume (mean, 16.9%). Type II sandstones are associated with the dissolution of cement and later re-compaction of type I sandstones. An intermediate telodiagenetic phase is deduced and related to the sharp unconformity between Lower Cretaceous sediments and the underlying sediments. This suggests that a mechanically unstable framework collapsed during the Cretaceous, generating type II sandstones. The analyzed diagenetic paths have a wide applicability on similar marginal areas of rift basins.     

Early kaolinization of detrital Weald facies in the Galve Sub-basin (Central Iberian Chain,north-east Spain) and its relationship to palaeoclimate

A set of samples from the Camarillas Formation (Barremian, Weald facies) in the Galve Sub-basin (Central Iberian Chain, north-east Spain) was studied to determine the origin of the abundant kaolinitic clays and their relationship to the sedimentary environment, palaeoclimate and diagenetic processes. The samples were examined by X-ray diffraction and scanning and transmission electron microscopy, with special emphasis on clay-mineral characterization. The analysed materials are a mixture of detrital (quartz, micas, and K-feldspars) and authigenic phases (kaolinite, Fe-oxides, gibbsite, dickite, and calcite). Therefore, the mineralogy of the rocks reflects the source area, the sedimentary conditions, and the diagenetic evolution. The most abundant authigenic phases are kaolinites. The combination of XRD and electron microscopy shows that the kaolinites are well crystallized and have as high a degree of ordering as those formed by weathering in palaeosols; this clay formed the rock matrix, intergrowths with muscovite, and vermicular booklets that replaced detrital silicates as a consequence of intense dissolution processes. The diagenetic processes have recrystallized kaolinites in the sandstones, producing larger crystallinity indices and dickite. In contrast, kaolinites from the claystones and siltstones probably reflect formation by weathering. The kaolinitization process described, associated with the crystallization of gibbsite and iron oxides, is in agreement with the relatively warm and humid conditions described for the Iberian Range basin in the early Barremian.     

Chemical variations and significance of phosphates from the Fregeneda-Almendra pegmatite field, Central Iberian Zone (Spain and Portugal)

Granitic pegmatites are widespread within a schist-metagreywacke complex in the Fregeneda-Almendra area (Central Iberian Zone). They intrude pre-Ordovician metasedimentary rocks and show a zonal distribution relative to the Meda-Penedono-Lumbrales granitic complex, from barren bodies to those enriched in Li, F, Sn, Nb>Ta, P and Be. Based on mineralogical criteria, these pegmatites are classified into three main categories: barren, intermediate and rare-element pegmatites, with each type including various subtypes. Phosphates are present in many pegmatites that usually occur as fine-grained accessory minerals. The most complex association of such minerals includes numerous Fe–Mn phosphates that occur in intermediate pegmatites. Al-phosphates are characteristic of Li-rich pegmatites. Electron microprobe analyses of representative phosphates reflect compositional differences depending on the pegmatite type. The Fe/(Fe+Mn) ratio of phosphates tends to decrease as the evolution degree of the pegmatites increases.     

Paleoseismological analysis of an intraplate extensional structure: the Concud fault (Iberian Chain,eastern Spain)

The Concud fault is a 13.5 km long, NW–SE striking normal fault at the eastern Iberian Chain. Its recent (Late Pleistocene) slip history is characterized from mapping and trench analysis and discussed in the context of the accretion/incision history of the Alfambra River. The fault has been active since Late Pliocene times, with slip rates ranging from 0.07 to 0.33 mm/year that are consistent with its present-day geomorphologic expression. The most likely empirical correlation suggests that the associated paleoseisms have potential magnitudes close to 6.8, coseismic displacements of 2.0 m, and recurrence intervals from 6.1 to 28.9 ka. At least six paleoseismic events have been identified between 113 and 32 ka. The first three events (U to W) involved displacement along the major fault plane. The last three events (X to Z) encompassed downthrow and hanging-wall synthetic bending prompting fissure opening. This change is accompanied by a decrease in slip rate (from 0.63 to 0.08–0.17 mm/year) and has been attributed to activation of a synthetic blind fault at the hanging wall. The average coseismic displacement (1.9–2.0 m) and recurrence period (6.7–7.9 ka) inferred from this paleoseismic succession are within the ranges predicted from empirical correlation. Such paleoseismic activity contrasts with the moderate present-day seismicity of the area (maximum instrumental Mb = 4.4), which can be explained by the long recurrence interval that characterizes intraplate regions.     

Influence of syntectonic sedimentation on thrust geometry. Field examples from the Iberian Chain (Spain) and analogue modelling

Steep thrusts are usually interpreted as oblique-slip thrusts or inverted normal faults. However, recent analogical and numerical models have emphasised the influence of surface mass-transfer phenomena on the structural evolution of compressive systems. This research points to sedimentation and erosion during deformation as an additional explanation for the origin of steeply dipping thrusts. The present study uses both field observations and analogue modelling to attempt to isolate critical parameters of syntectonic sedimentation that might control the geometry of the upper part of thrust systems.A field study of thrust systems bounding two compressive intermountain Tertiary basins of the Iberian Chain is first briefly presented. We describe the surface geometry of thrusts surrounding the Montalbán Basin and the Alto Tajo Syncline at the vicinity of deposits of Oligocene–Early Miocene alluvial fans at the footwall of faults. Field observations suggest that synthrusting sedimentation should influence the structure of thrusts. Indeed, the faults are steeper and splitted at the edge of the syntectonic deposits.Effects of sedimentation rate on footwall of thrusts, and of its change along fault strike are further investigated on two-layer brittle-ductile analogue models submitted to compression and syntectonic sediment supply. Two series of experiments were made corresponding to two end-members of depositional geometries. In the first series, the sedimentation was homogeneously distributed on both sides of the relief developed above the thrust front. In the second series, deposits were localised on a particular area of the footwall of thrust front. In all experiments, the sedimentation rate controls the number and the dip of faults. For low sedimentation rates, a single low-angle thrust develops; whereas for high sedimentation rates, a series of steeper dipping thrust is observed. In experiments with changing sedimentation rate along fault strike, the thrust geometry varies behind the areas with the thickest sediment pile.     

Tourmaline from the rare-element Pinilla pegmatite, (Central Iberian Zone, Zamora, Spain): chemical variation and implications for pegmatitic evolution

Summary Tourmaline is an ubiquitous constituent in the Pinilla de Fermoselle rare-element pegmatite (Zamora, Spain), as well as in barren pegmatitic and quartz–tourmaline veins inside the associated leucogranite. The rare-element pegmatite shows internal zoning, evolving from a barren facies, in the lower border zone, in contact with the leucogranite, to a Li-rich facies in the upper border zone, close to the host-rocks.Tourmalines from the veins within the leucogranite have highest Mg contents, and belong to the schorl–dravite series. The tourmalines from the rare-element pegmatite mostly belong to the schorl–elbaite series, with chemical compositions within the range of the end-members, whereas the tourmalines associated with the most evolved zone in the pegmatite belong to the elbaite–rossmanite series. The broad compositional range shown by the tourmalines correlates quite well with the pegmatite zoning. The most plausible substitution mechanism for the chemical evolution of tourmalines during crystallization seems to be Mg_–1Fe²⁺₁, [X]_–1^YAl_–1^XNa_–1^YFe²⁺₁, for the foitite–schorl series; ^YFe²⁺_–3^YAl_1.5^YLi_1.5, for the schorl–elbaite vector; ^XNa_–1^YLi_–0.5[X]₁^YAl_0.5, for the elbaite–rossmanite series; and, (OH)₁F₁ for all the tourmalines except the pink elbaites. This chemical variation in tourmaline is consistent with a crystal fractionation model for the evolution of the Pinilla pegmatite.     

Turtles from the Lower Cretaceous of the Cameros Basin (Iberian Range, Spain)

Knowledge of the turtle fauna from the Lower Cretaceous of the Iberian Peninsula has been very limited until now. There are several fossil sites where Lower Cretaceous associations of continental vertebrates have been found. Although turtles have been identified in some of them, most of these specimens have not been studied, so the diversity is unknown. Among all these findings, the turtles from the Cameros Basin are considered particularly relevant, both in their abundance and diversity. Their study has allowed the identification of several taxa. At least one representative of Solemydidae and three taxa of Eucryptodira are recognized. This study establishes kinship and biogeographic relationships between the taxa in Cameros with those found in other Spanish fossil sites and with those of other European regions.     

Role of extensional structures on the location of folds and thrusts during tectonic inversion (northern Iberian Chain,Spain)

The Aguilón Subbasin (NE Spain) was originated daring the Late Jurassic-Early Cretaceous rifting due to the action of large normal faults, probably inherited from Late Variscan fracturing. WNW-ESE normal faults limit two major troughs filled by continental deposits (Valanginian to Early Barremian). NE-SW faults control the location of subsidiary depocenters within these troughs. These basins were weakly inverted during the Tertiary with folds and thrusts striking E-W to WNW-ESE involving the Mesozoic-Tertiary cover with a maximum estimated shortening of about 12 %. Tertiary compression did not produce the total inversion of the Mesozoic basin but extensional structures are responsible for the location of major Tertiary folds. Shortening of the cover during the Tertiary involved both reactivation of some normal faults and development of folds and thrusts nucleated on basement extensional steps. The inversion style depends mainly on the occurrence and geometry of normal faults limiting the basin. Steep normal faults were not reactivated but acted as buttresses to the cover translation. Around these faults, affecting both basement and cover, folds and thrusts were nucleated due to the stress rise in front of major faults. Within the cover, the buttressing against normal faults consists of folding and faulting implying little shortening without development of ceavage or other evidence of internal deformation.     

Geological and Palaeontological context of three new Barremian (Lower Cretaceous) vertebrate sites in the Iberian Peninsula (Cuenca Province,Central Spain)

Three new Lower Cretaceous vertebrate sites (Vadillos-1, Vadillos-2, El Tobar) have been recently discovered and studied in the Cuenca Province (Central Spain). They are located in deposits of “Wealden” facies belonging to the El Collado Sandstone and Clay Formation. In these outcrops, micro and macroremains corresponding to plants, invertebrates and vertebrates have been collected and subsequently assigned to macrophytes, charophytes (e.g., Atopochara trivolvis triquetra, Globator maillardii trochiliscoides, Clavator harrisii harrisii), ostracods (e.g., Cypridea gr. modesta, Cypridea cf. C. isasae, Cypridea sp. aff. C. moneta, Cypridea sp. 1, Cypridea sp. 2), molluscs (Unionoida, Viviparus sp.), fishes, amphibians, turtles (cf. Eucryptodira), crocodyliforms (Neosuchia) and dinosaurs (ankylosaurs, ornithopods, theropods). Among the vertebrate remains, scales, teeth, plates, osteoderms, phalanges, ribs, vertebrae and other incomplete bones, as well as eggshell fragments have been identified. This rich and diverse assemblage was deposited in an upper Barremian alluvial-palustrine muddy floodplain crossed by braided sandy channels.     

Tectonically driven fluid flow and associated low-grade metamorphism during the Alpine compression in the eastern Iberian Chain (Spain)

Fluid inclusions and clay mineralogy of the Permo-Triassic rocks from the Espina and Espadà Ranges (SE Iberian Chain, Spain) have been investigated to establish their relationship with hydrothermal fluid circulation during the Alpine Orogeny. Primary fluid inclusions in quartz-filled tension gashes in Permo-Triassic sandstones reveal maximum temperatures around 230 °C and very constant salinities of 8.5% wt. eq. NaCl. Secondary fluid inclusions found in quartz from the Santonian Ba–Cu–Hg deposits show similar compositional and thermodynamic characteristics, denoting an Alpine recrystallization. Clay mineral composition of Permo-Triassic mudrocks is characterized by pyrophyillite, indicating low-grade metamorphic conditions. Field observations and experimental data suggest that the crystallization of quartz in tension gashes, the formation of secondary fluid inclusions and the development of the metamorphism are contemporaneous and related to fluid circulation during the Alpine compression. Fluid flow took place along the Hercynian fault system that was reactivated during the Mesozoic rift stage and inverted during the Alpine deformation.     

Low-light and nutrient-rich coral assemblages in an Upper Aptian carbonate platform of the southern Maestrat Basin (Iberian Chain, eastern Spain)

A Lower Cretaceous (Aptian) succession of carbonate rocks in the southern Maestrat Basin (Iberian Chain, Spain) was analysed in terms of sedimentological and palaeontological criteria. The shallow marine sequence was deposited upon a homoclinal carbonate ramp. Five main facies types were distinguished: (A) peloidal and bioclastic grainstones and rudstones of the inner ramp shoals; (B) orbitolinid wackestones-packstones of the distal outer ramp; (C) peloid and Ostrea wackestones-packstones of the middle outer ramp; (D) coral-algal sheetstones of the proximal outer ramp; and (E) coral-algal platestones-domestones of the middle ramp. Coral-bearing facies types (D) and (E) showed similar major environmental factors: low energy hydrodynamism, low light intensity and apparently nutrient-rich water. Slight differences in these conditions are reflected in the different growth forms and coral assemblages. Coral-algal sheetstones are characterized by sheet-like and lamellar forms with a low coral diversity not clearly dominated by any taxon. Coral-algal platestones-domestones develop platy, tabular and irregular massive forms with a slightly higher coral diversity characterized by a Microsolenina-Faviina association. The coral fauna is revised taxonomically and yielded a total of 22 species in 18 genera (21 Scleractinia species, one Octocorallia species). Genera of the suborders Microsolenina and Faviina predominate, those of the suborders Stylinina, Fungiina, Rhipidogyrina and the order Coenothecalia are subordinate.     

Mineralogy and environmental relevance of AMD-precipitates from the Tharsis mines,Iberian Pyrite Belt (SW,Spain)

This paper documents the solid phases associated to acid mine drainage (AMD) at the Tharsis mines (SW Spain). It provides an inventory of the AMD-precipitates, describing their main modes of occurrence and mineral assemblages. Results indicate that iron, aluminum and magnesium sulfates predominate in the assemblages. They occur as efflorescences composed of complex mixtures of metallic salts, and as ochres (jarosite combined with goethite). Also, their distributions illustrate two hydrochemical environments: the open pits, which reflect a proximal secondary paragenesis; and the downstream river banks (Meca River), which represent a more evolved paragenesis, resulting from the evolution of AMD produced throughout the system. These environments can be differentiated by composition and variety of minerals, which is considerably lower along the Meca River.The newly-formed minerals have monitoring significance and proved capable of participating in cycles of retention–liberation of hydrogen ions, sulfate, and metals. In a semi-arid climate, the importance of the AMD-precipitates as environmental indicators is stressed. They may help to understand the response of the system to the episodic rainfall events that occur after prolonged dry periods.     

Sequence stratigraphy and architecture of a late Early–Middle Aptian carbonate platform succession from the western Maestrat Basin (Iberian Chain, Spain)

The attributes of a ‘four-systems-tract’ sequence are at times difficult to identify in outcrop-scale carbonate successions. Poor exposure conditions, variable rates of sediment production, erosion and/or superposition of surfaces that are intrinsic to the nature of carbonate systems frequently conceal or remove its physical features. The late Early–Middle Aptian platform carbonates of the western Maestrat Basin (Iberian Chain, Spain) display facies heterogeneity enabling platform, platform-margin and slope geometries to be identified, and provide a case study that shows all the characteristics of a quintessential four systems tract-based sequence. Five differentiated systems tracts belonging to two distinct depositional sequences can be recognized: the Highstand Systems Tract (HST) and Forced Regressive Wedge Systems Tract (FRWST) of Depositional Sequence A; and the Lowstand Prograding Wedge Systems Tract (LPWST), Transgressive Systems Tract (TST) and subsequent return to a highstand stage of sea-level (HST) of Depositional Sequence B. An extensive carbonate platform of rudists and corals stacked in a prograding pattern marks the first HST. The FRWST is constituted by a detached, slightly cross-bedded calcarenite situated at the toe of the slope in a basinal position. The LPWST is characterized by a small carbonate platform of rudists and corals downlapping over the FRWST and onlapping landwards. The TST exhibits platform backstepping and marly sedimentation. Resumed carbonate production in shelf and slope settings characterizes the second HST. A basal surface of forced regression, a subaerial unconformity, a correlative conformity, a transgressive surface and a maximum flooding surface bound these systems tracts, and are well documented and widely mappable across the platform-to-basin transition area analyzed. Moreover, the sedimentary succession studied is made up of four types of parasequence that constitute stratigraphic units deposited within a higher-frequency sea-level cyclicity. Ten lithofacies associations form these basic accretional units. Each facies assemblage can be ascribed to an inferred depositional environment in terms of bathymetry, hydrodynamic conditions and trophic level. The architecture of the carbonate platform systems reflects a flat-topped non-rimmed depositional profile. Furthermore, these carbonate shelves are interpreted as having been formed in low hydrodynamic conditions. The long-term relative fall in sea-level occurred during the uppermost Early Aptian, which subaerially exposed the carbonate platform established during the first HST and resulted in the deposition of the FRWST, is interpreted as one of global significance. Moreover, a possible relationship between this widespread sea-level drop and glacio-eustasy seems plausible, and could be linked to the cooling event proposed in the literature for the late Early Aptian. Because of the important implications in sequence stratigraphy of this study, the sedimentary succession analyzed herein could serve as an analogue for the application of the four-systems-tract sequence stratigraphic methodology to carbonate systems.     

Petrographic, Chemical and B-Isotopic Insights into the Origin of Tourmaline-Rich Rocks and Boron Recycling in the Martinamor Antiform (Central Iberian Zone, Salamanca, Spain)

Tourmaline in the Martinamor antiform occurs in tourmalinites(rocks with >15–20% tourmaline by volume), clasticmetasedimentary rocks of the Upper Proterozoic Monterrubio formation,quartz veins, pre-Variscan orthogneisses and Variscan graniticrocks. Petrographic observations, back-scattered electron (BSE)images, and microprobe data document a multistaged developmentof tourmaline. Overall, variations in the Mg/(Mg + Fe) ratiosdecrease from tourmalinites (0·36–0·75),through veins (0·38–0·66) to granitic rocks(0·23–0·46), whereas Al increases in thesame order from 5·84–6·65 to 6·22–6·88apfu. The incorporation of Al into tourmaline is consistentwith combinations of ^xAl(NaR)_–1 and AlO(R(OH))_–1exchange vectors, where ^x represents X-site vacancy and R is(Mg + Fe²⁺ + Mn). Variations in ^x/(^x + Na) ratios are similarin all the types of tourmaline occurrences, from 0·10to 0·53, with low Ca-contents (mostly <0·10apfu). Based on field and textural criteria, two groups of tourmaline-richrocks are distinguished: (1) pre-Variscan tourmalinites (probablyCadomian), affected by both deformation and regional metamorphismduring the Variscan orogeny; (2) tourmalinites related to thesynkinematic granitic complex of Martinamor. Textural and geochemicaldata are consistent with a psammopelitic parentage for the protolithof the tourmalinites. Boron isotope analyses of tourmaline havea total range of ¹¹B values from –15·6 to 6·8;the lowest corresponding to granitic tourmalines (–15·6to –11·7) and the highest to veins (1·9to 6·8). Tourmalines from tourmalinites have intermediate¹¹B values of –8·0 to +2·0. The observedvariations in ¹¹B support an important crustal recycling ofboron in the Martinamor area, in which pre-Variscan tourmaliniteswere remobilized by a combination of mechanical and chemicalprocesses during Variscan deformation, metamorphism and anatexis,leading to the formation of multiple tourmaline-bearing veinsand a new stage of boron metasomatism. KEY WORDS: tourmalinites; metamorphic and granitic rocks; mineral chemistry; whole-rock chemistry; boron isotopes