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In the Variscan Bohemian Massif, (ultra-)potassic plutons are conspicuously associated with the high-grade, lower crustal/upper mantle Gfohl Unit (Moldanubian Zone). They can be subdivided into two contrasting groups: (1) coarse amphibole–biotite melagranite to quartz syenite with conspicuous K-feldspar phenocrysts (the ‘durbachite suite’), and (2) essentially equigranular biotite–two-pyroxene quartz syenites to melagranites (the ‘syenitoid suite’). The latter suite, represented by the Tabor and Jihlava plutons, is characterized by an originally ‘drier’ mineral assemblage orthopyroxene + clinopyroxene + Mg-biotite + plagioclase + K-feldspar + quartz, with accessory zircon, apatite, ilmenite, monazite and/or rutile + chromite. The rich assemblage of both rock-forming and accessory minerals allows testing of numerous geothermobarometers. The resulting P–T data are mutually consistent; they document emplacement of the parental magmas at mid-crustal levels (~5 kbar/19 km for Tabor and 7–8 kbar/26–30 km for Jihlava) and record near-isobaric crystallization from at least 1170 °C to the solidus. New Isotope-Dilution Thermal Ionization Mass-Spectrometry (ID-TIMS) U–Pb ages for zircon (336.9 + 0.6 Ma) and rutile (336.8 + 0.8 Ma) from the Tabor Pluton, together with previously published ages from the Jihlava Pluton, provide temporal constraints for the emplacement and rapid cooling of the syenitoids below c. 600 °C. This supports the hypothesis of post-tectonic emplacement of a hot and dry melt (>1200 °C?) into an essentially consolidated orogenic crust. The two syenitoid plutons have comparable, crust-like radiogenic isotope signatures (87Sr/86Sr337 = 0.7114–0.7133, e337Nd = −6.8 to −8.0). This, in context of whole-rock geochemical variation and K-feldspar Pb isotopic compositions, is consistent with generation from a strongly enriched lithospheric mantle source. Shortly before melting, the local orogenic mantle was most likely modified by deep subduction and relamination of felsic crustal material of the Saxothuringian provenance, transformed to the felsic high-pressure granulites common in the Moldanubian Zone. In the subsequent evolution of the two-pyroxene syenitoid plutons, crystal fractionation and accumulation played a key role, unlike in the durbachite suite itself, where magma mixing with leucogranitic melts was much more important. Structural relations inside and around the (ultra-)potassic plutons (~343–335 Ma) suggest that – besides different depths and specific processes of magma emplacement – these plutons track different kinematic histories and evolutions of regional strain fields in their high-grade country rocks in this crucial period of the Variscan Orogeny.

Garnet and zircon geochronology combined with trace element partitioning and petrological studies provide tight constraints on evolution of the UHT-(U)HP terrain of the Orlica-Śnieznik Dome (OSD) in the NE Bohemian massif. Lu-Hf dating of peritectic garnet from two mesocratic granulites constrained the time of its initial growth at 346.9 ± 1.2 and 348.3 ± 2.0 Ma recording peak 2.5 GPa pressure and 950 °C temperature. In situ, U-Pb SHRIMP dating of zircon from the same granulite gave a younger age of 341.9 ± 3.4 Ma. Ti-in-zircon thermometry indicates crystallization at 810–860 °C pointing to zircon formation on the retrograde path. Lu partitioning between garnet rim and zircon suggest equilibrium growth and thus U-Pb zircon age constrain the terminal phase of garnet crystallization which lasted about 6 Ma. All Sm-Nd garnet ages obtained for mesocratic and mafic granulites are identical and consistently younger than the corresponding Lu-Hf dates. They are interpreted as reflecting cooling of granulites through the Sm-Nd closure temperature at about 337 Ma. The estimated PTt path documents the ca. 10 Ma evolution cycle of the OSD characterized by two distinct periods: (1) 347 - > 342 Ma period corresponds to nearly isothermal decompression resulting from crustal scale folding and vertical extrusion of granulites, and (2) at > 342–337 Ma which corresponds to a fast, nearly isobaric cooling.

A new data set of ca. 500 LA–ICP-MS U–Pb detrital zircon ages for six metasedimentary units from the Tuscan basement (Apuan Alps, Monti Pisani, Monticiano-Roccastrada), along with a precise SHRIMP U–Pb crystallization age of a metavolcanic unit (Apuan Alps) have been collected to determine their depositional ages and provenance. These results have been integrated with the recently published ca. 900 U–Pb detrital zircon ages from Elba Island to draw a complete picture of the Paleozoic journey of the Tuscan basement. A major change in the sources supplying sediments to the Tuscan basins is shown to occur during this journey. Detrital zircon ages of early Cambrian to middle Ordovician metasediments mirror those of coeval northern Africa sediments: most samples were sourced in western Africa, while one sample is derived material from central northern Africa. The Tuscan block was therefore located at the peri-Gondwana margin, close to central northern Africa. The prominent mid-Ordovician magmatic arc activity (ca. 460 Ma) at the northern Gondwana margin and its detritus, characterise the zircon age distribution of Ordovician and Silurian volcano-sedimentary rocks, that were therefore generated at the northernmost Gondwana margin during subduction and subsequent initial Paleotethys rifting. The Carboniferous–Permian metasediments are dominated by populations of Ordovician and Variscan-age zircons, with a minor occurrence of Neoarchean and Paleoproterozoic zircons that is best explained by recycling of European Neoproterozoic–Cambrian metasediments. In summary, the main sources supplying the Tuscan basins were located in northern Africa throughout Cambrian–Ordovician times, shifting to the volcanic arc active at the northern Gondwana margin during the middle Ordovician. During Variscan and post-Variscan times, detrital zircon sources were mostly located in European terrains, witnessing the shift of Tuscany from Africa to Europe.

Elba Island, located midway between Corsica and mainland Italy, is a small but important fragment of the Adria Plate. It has a rich sedimentary record preserved in a stack of tectonic nappes of both continental margin and oceanic origin. Especially the detrital zircons in early Paleozoic to early Mesozoic metasedimentary rocks provide an archive of many important geological events in the island's history. Elba Island and Adria originated along the northern margin of Gondwana, but drifted north in Silurian times to become part of Europe. A large new dataset of LA-ICP-MS and SIMS U–Pb zircon ages allows us to trace this history. Three main stratigraphic units have been investigated. The oldest Porto Azzurro Unit was deposited in the early Cambrian and has zircon age distributions indicating a typical northern African provenance, most likely sourced from the Saharan Metacraton. The Ortano Unit has a simple, mostly unimodal Ordovician age distribution that is entirely dominated by metavolcanic rocks and their erosional products; a sample of the metavolcanic Ortano Porphyroids provided a SIMS U–Pb zircon age of 460 ± 3 Ma. This phase of intense volcanism is related to the subduction of the Rheic Ocean beneath Gondwana, terminating with initial rifting and subsequent opening of the Paleotethys. This also marks the onset of the separation of a range of European terranes, including Adria and future Elba Island, from Gondwana. The Permo-Triassic Monticiano–Roccastrada Unit is the first to show a European provenance with the appearance of large amounts of Variscan and late to post-Variscan detritus. The presence of Variscan detrital zircons in the Permo-Triassic sediments is unexpected, since a Variscan age signature is so far not well recorded in the Adria Plate. This dataset is the most comprehensive detrital zircon dataset so far available for the Adria Plate and documents Adria's close affinity to Africa in the Lower Paleozoic, as well as its initial rifting within an active continental margin setting during the Ordovician and its final separation and independent evolution since late Palaeozoic times.

The LA-ICP-MS U-(Th-)Pb geochronology international community has defined new standards for the determination of U-(Th-)Pb ages. A new workflow defines the appropriate propagation of uncertainties for these data, identifying random and systematic components. Only data with uncertainties relating to random error should be used in weighted mean calculations of population ages; uncertainty components for systematic errors are propagated after this stage, preventing their erroneous reduction. Following this improved uncertainty propagation protocol, data can be compared at different uncertainty levels to better resolve age differences. New reference values for commonly used zircon, monazite and titanite reference materials are defined (based on ID-TIMS) after removing corrections for common lead and the effects of excess 230Th. These values more accurately reflect the material sampled during the determination of calibration factors by LA-ICP-MS analysis. Recommendations are made to graphically represent data only with uncertainty ellipses at 2s and to submit or cite validation data with sample data when submitting data for publication. New data-reporting standards are defined to help improve the peer-review process. With these improvements, LA-ICP-MS U-(Th-)Pb data can be considered more robust, accurate, better documented and quantified, directly contributing to their improved scientific interpretation. La communauté internationale de la géochronologie LA-ICP-MS U-(Th-)Pb a défini les nouvelles normes pour la détermination des âges U-(Th-)Pb. Un nouveau flux de travail définit la propagation adéquate des incertitudes pour ces données, en identifiant les composants aléatoires et systématiques. Seules les données avec des incertitudes relatives à l'erreur aléatoire devraient être utilisées dans les calculs des moyennes pondérées des âges de la population; les composantes de l'incertitude pour les erreurs systématiques sont propagées après cette étape, empêchant leur réduction erronée. En suivant ce protocole amélioré pour la propagation de l'incertitude, les données peuvent être comparées à différents niveaux d'incertitude pour mieux résoudre les différences d’âge. Les nouvelles valeurs pour les matériaux de référence zircon, monazite et titanite sont définies (basée sur ID-TIMS) après les corrections du plomb commun et les effets de l'excès en 230Th. Ces valeurs reflètent plus fidèlement le matériau échantillonné lors de la détermination des facteurs d’étalonnage par analyse LA-ICP-MS. Des recommandations sont faites pour représenter graphiquement des données avec seulement des ellipses d'incertitude à 2s et pour soumettre ou pour citer des données de validation avec les données de l’échantillon lors de la soumission des données pour publication. Les nouvelles normes de déclaration des données sont définies pour améliorer le processus d'évaluation par les pairs. Grâce à ces améliorations, les données LA-ICP-MS U-(Th)-Pb peuvent être considérés comme plus solides, exactes, mieux documentées et quantifiées, contribuant ainsi à une meilleure interprétation scientifique.

A petrological and metamorphic comparison of Mesoproterozoic metabasic rocks was conducted on the eastern margin of the Archaean Kaapvaal–Grunehogna Craton and the adjacent westernmost Maud Belt (western H.U. Sverdrupfjella), across a major structural discontinuity known as the Pencksokket–Jutulstraumen Discontinuity. Thermodynamic phase diagram modelling of the low- and high-grade metabasaltic assemblages on either side of the discontinuity revealed a difference in peak metamorphic conditions from T = 340 ± 25 to 700 ± 30°C and P = 0.29 ± 0.08 to 0.90 ± 0.10 GPa over an extrapolated orthogonal distance of 32 km across the strike of the discontinuity. Laser ablation inductively coupled plasma mass spectrometry U–Pb dating of titanite in a hornblende–plagioclase–quartz corona around garnet yielded a late Pan-African age of 491 ± 27 Ma for high-grade metamorphism in the western H.U. Sverdrupfjella of the Maud Belt. The new petrological and geochronological constraints indicate that peak upper amphibolite-facies conditions were achieved in the western H.U. Sverdrupfjella at c . 500 Ma; namely, c . 70–80 Ma after peak eclogite–high-pressure granulite-facies metamorphism in the eastern H.U. Sverdrupjella. The U–Pb age data argue against previous models that invoke only late Mesoproterozoic ( c . 1060–1030 Ma) granulite-facies metamorphism in the western H.U. Sverdrupfjella and Kaapvaal–Grunehogna Craton margin, and support the concept of a major diachronous Pan-African orogenic episode. A new geodynamic model is presented for western Dronning Maud Land, involving earliest Pan-African eclogite–high-pressure granulite- and upper amphibolite-facies metamorphism in a separate eastern H.U. Sverdrupjella terrane between c . 565 and 540 Ma, followed by later diachronous tectonic accretion of the eastern H.U. Sverdrupjella arc segment onto the western H.U. Sverdrupfjella crustal segment (including the easternmost Kaapvaal–Grunehogna Craton margin) that involved only upper amphibolite-facies metamorphism at c . 500 Ma. The new petrological data indicate that the inferred sub-glacial boundary (Pencksokket–Jutulstraumen Discontinuity) between the Kaapvaal–Grunehogna Craton and the western H.U. Sverdrupfjella region represents a major cratonic Pan-African thrust, which was subsequently reactivated by normal faulting during Gondwana break-up. Supplementary materials: Analytical details, representative mineral compositions, and geothermometry and geobarometry results are available at http://www.geolsoc.org.uk/SUP18832.

Zircon ages (U–Pb, LA-ICP-MS) obtained from skarns in the Kutna Hora and Svratka units and in the Moldanubian Zone (Bohemian Massif) show significant variations between the lithotectonic units as well as among samples from individual localities. The ages fall between 310 Ma and 3.1 Ga. We suggest that such large spread is a result of both different zircon clastic grain sources and subsequent metamorphic histories. The oldest Neoarchaean to Neoproterozoic ages are interpreted as detrital zircon grains from pre-Cadomian basement. Pronounced age maxima between 600 and 520 Ma (late Neoproterozoic to early Cambrian) were found in skarn samples from the Moldanubian Zone, Svratka and Kutna Hora units. We interpret these as maximum ages of skarn precursor deposition. Apparent Cambrian–Ordovician– Silurian to early Devonian zircon ages were obtained from non-mineralized samples of the Moldanubian Zone and also in the Kutna Hora Unit. This wide temporal interval could reflect maximum ages of skarn precursors related to disintegration of abundant early Palaeozoic magmatic rocks, provided the zircons were not modified by later metamorphism or fluid circulation. The early Carboniferous ages are interpreted to result from strong Variscan HT metamorphism and subsequent circulation of post-metamorphic fluids. Zircons of this age are dominant in skarns with massive magnetite mineralization, while the non-mineralized samples preserve the older ages.

Distinctly different crustal blocks converge in southern Tanzania which are thought to belong to the Paleoproterozoic Usagaran/Ubendian Belt, the Mesoproterozoic Irumide Belt and the Neoproterozoic East African Orogen. Zircons from thirteen samples were dated by LA-SC/MC-ICPMS in order to assign the different crystalline basement rocks to one of the above mentioned geological units based on the age of metamorphism and formation of the igneous precursor rocks. The mainly migmatic gneissic samples were taken along a traverse from Mbamba Bay, Lake Malawi to Masasi, S-Tanzania. Zircon cores and rims trace magmatic protoliths between 1000 ± 9 and 1055 ± 6 Ma and metamorphism between 563 ± 10 and 616 ± 12 Ma. Ages belonging to the Usagaran/Ubendian event as well as the 640 Ma EAO event were only found in the westernmost and easternmost part of the transsect, respectively. Magmatic ages of 724 ± 6 and 764 ± 4 Ma were determined in locally confined undeformed granitoid bodies. Mostly similar ages as well as lithological units can be found in the Unango and Marrupa Complexes in N-Mozambique which are considered as part of the Southern Irumide Belt. The exact location of terrane boundary between the Southern Irumide Belt and the Western/Eastern Granulites and the Usagaran/Ubendien Belts in southern Tanzania remains uncertain. With aid of digital elevation data, satellite images and airborne geophysical data we suggest that a combination of fault systems is responsible for the distribution of the different units. The northeastern limit of the Southern Irumide Belt (Unango and Marrupa Complexes) can be traced along a major tectonic boundary, the Mwembesi Fault system, that extends from Malawi to the south of the Mahenge Mountains in Tanzania.

The Eger Complex in the northwestern Bohemian Massif consists mainly of amphibolite facies granitic gneisses containing a subordinate volume of felsic granulites. Microstructural changes and modelling of metamorphic conditions for both rock types suggest a short-lived static heating from ~760 to ~850 °C at a constant pressure of ~16 kbar, which led to the partial granulitization of the granitoid rocks. Detailed study of the protolith zircon modifications and modelling of the Zr re-distribution during the transition from amphibolite to granulite facies suggests that the development of c. 340 Ma old zircon rims in the granulite facies sample is the result of recrystallization of older (c. 475 Ma) protolith zircon. This study suggests that the partial granulitization is a result of a short exposure of the Eger Complex metagranitoids to a temperature of ~850 °C at the base of an arc/fore-arc domain and their subsequent rapid exhumation during the Lower Carboniferous collision along the western margin of the Bohemian Massif.

Isotopic dating of detrital zircon populations from metasediments and of magmatic zircon from intercalated metavolcanic layers in the medium- to high-grade part of the Kaoko Belt in Namibia provides first robust constraints on the age of Neoproterozoic sedimentation along the southwestern margin of the Congo Craton. Dating of detrital zircons from metasediments directly overlying the cratonic basement shows maximum sedimentary ages of c. 1.00 and c. 1.45 Ga, and age populations comparable with known protolith ages from the gneisses of the Congo/Kalahari cratons. Dating of zircon from associated metavolcanics constrains the age of the earliest preserved sediments at c. 740–710 Ma. Detrital zircon populations from the samples collected from the upper parts of the metasedimentary succession contain only small proportion of grains with ages similar to those from the Congo Craton. These samples show dominance of c. 1.00 Ga, c. 750 Ma and c. 650 Ma old zircon grains that are probably derived from the Punta del Este – Coastal Terrane (Dom Feliciano and Kaoko belts) that acted as an arc/back-arc domain at c. 650–630 Ma. Neodymium model ages for the samples of metasedimentary cover of the cratonic basement provide another evidence that the youngest preserved sediments could not have been derived from the Congo Craton. Recognition of the Punta del Este – Coastal Terrane crust as a source region for the youngest pre-collisional sediments of the Kaoko Belt suggests that this terrane must have been in close proximity to the Congo Craton passive margin already some time prior to their mutual collision at c. 570–550 Ma. This is in accord with an interpretation that the c. 650–630 Ma arc/back-arc Punta del Este – Coastal Terrane has developed directly on top of, or very close to, the attenuated Congo Craton passive margin.

High-pressure kyanite–K-feldspar granulites in the Běstvina granulite body, which belongs to the Variscan orogenic root in the Bohemian Massif, preserve muscovite, rutile and kyanite inclusions in garnet. High-Ti muscovite (Ti = 0.09–0.20 p.f.u., Si = 0.21–3.24 p.f.u.) included in garnet is associated with quartz and is in crystallographic continuity with biotite, interpreted in terms of exsolution from an original less-dioctahedral higher-Ti muscovite. The assemblage garnet–kyanite–antiperthite–perthite–quartz–rutile and the mineral compositions indicate a peak of metamorphism at about 900 °C and 17–21 kbar, based on P–T pseudosection modeling, ternary-feldspar and Zr-in-rutile thermometry. The matrix assemblage garnet–kyanite–plagioclase-K-feldspar–quartz–rutile–ilmenite and garnet rim compositions at contact with feldspars and quartz indicate the end of overall equilibration in the presence of melt at 12–14 kbar and 820–840 °C. Embayments of biotite and plagioclase locally replacing garnet, and connected with modification of garnet composition, may indicate sites of last isolated melt or diffusion of H2O from that melt down to 10 kbar and 800 °C. Zircon with uniform cathodoluminescence (CL) pattern is present as rims around cores with faint oscillatory zoning, or as entire rounded grains. These zircons gave a cluster of ages at 359 ± 4 Ma, interpreted as the age of metamorphism. Zircon ages from the cores with common faint oscillatory zoning range from 500 to 398 Ma, and are interpreted as magmatic grains variably reset during metamorphism. Two older ages obtained on cores of 620 ± 18 Ma probably represent an inherited zircon component. Molar isopleths of zircon along the P–T path in pseudosections suggest that crystallization of metamorphic zircon occurred during decompression and cooling from 17 to 21 kbar and 900 °C to 12–14 kbar and 820–840 °C. The inferred P–T path and the age of metamorphism are discussed in the framework of a geodynamic model that considers the granulites to be a part of a subducted plate that failed to continue to subduct and was spread below the upper plate.

Detrital zircon U–Pb age data from the Moldanubian part of the Bohemian Massif obtained by laser ablation inductively coupled plasma mass spectrometry show variations between the lithotectonic units and point to their formation in spatially close but separated basins that were supplied by detritus from somewhat different source areas, possibly over different periods of time. The youngest detrital zircon component in metasediments of the Monotonous and Varied Units is Early Ordovician and Mid- to Late Devonian in age, respectively, suggesting their deposition in Palaeozoic times. Reliable interpretation of the Mid- to Late Devonian zircons recovered from metasediments of the Gfohl Unit is precluded by their high metamorphic grade and presence of anatectic melt. The Early Carboniferous zircons from the Gfohl Unit are interpreted as being of metamorphic origin. Comparison of detrital zircon age spectra from the Moldanubian, Tepla–Barrandian and Moravo-Silesian metasediments suggests that these were deposited in separate basins but the overall similarity of the Neoproterozoic and Palaeoproterozoic age maxima and sparse Neo- and Mesoarchaean ages suggest that the three crustal segments must have been spatially related prior to the Variscan orogeny. Future tectonic models of the Variscan assembly of the Bohemian Massif must account for nearly synchronous evolution of the Moldanubian, Tepla–Barrandian and Moravo-Silesian Palaeozoic sedimentary basins that shared a common crust and most of their sedimentary sources, as well as for a rapid burial of the Moldanubian sediments to mid- and lower crustal levels that was followed by their rapid exhumation to the upper crust in Mid-Devonian to Early Carboniferous times. Supplementary material: Results of LA-ICP-MS U–Pb analyses of zircons extracted from the Moldanubian and Moravo-Silesian metasediments are available at www.geolsoc.org.uk/SUP18676.

Inter-laboratory comparison of laser ablation ICP-MS and SIMS U-Pb dating of synthetic detrital zircon samples provides an insight into the state-of-the art of sedimentary provenance studies. Here, we report results obtained from ten laboratories that routinely perform this type of work. The achieved level of bias was mostly within ± 2% relative to the ID-TIMS U-Pb ages of zircons in the detrital sample, and the variation is likely to be attributed to variable Pb/U elemental fractionation due to zircon matrix differences between the samples and the reference materials used for standardisation. It has been determined that ~ 5% age difference between adjacent age peaks is currently at the limit of what can be routinely resolved by the in situ dating of detrital zircon samples. Precision of individual zircon age determination mostly reflects the data reduction and procedures of measurement uncertainty propagation, and it is largely independent of the instrumentation, analytical technique and reference samples used for standardisation. All laboratories showed a bias towards selection of larger zircon grains for analysis. The experiment confirms the previously published estimates of the minimum number of grains that have to be analysed in order to detect minor zircon age populations in detrital samples. Une comparaison inter-laboratoires de datation U-Pb d'echantillons de zircons detritiques de synthese par les methodes d'ablation laser ICP-MS et SIMS donne un apercu de l'etat de l'art des etudes de provenance sedimentaire. Nous presentons ici les resultats obtenus par dix laboratoires qui effectuent regulierement ce type de travail. Le niveau de biais atteint etait compris dans l'intervalle ± 2% par rapport aux âges U-Pb ID-TIMS des zircons de l'echantillon detritique et la variation peut certainement etre attribue a un fractionnement elementaire Pb/U variable relie a des differences de matrices entre les zircons des echantillons et les zircons de reference utilises pour la normalisation. Il a ete determine qu'environ 5% de difference d'âge entre les pics d'âge adjacents est actuellement a la limite de ce qui peut etre resolu en mode routine par la datation in situ d'echantillons de zircons detritiques. La precision de la determination de l'âge de zircon individuel reflete principalement la reduction des donnees et les procedures de mesure de la propagation de l'incertitude, et elle est largement independante de l'instrumentation, de la technique d'analyse et des echantillons de reference utilises pour la standardisation. Tous les laboratoires ont montre un biais vers la selection des plus gros grains de zircon pour l'analyse. L'experience confirme les estimations precedemment publiees sur le nombre minimum de grains qui doivent etre analyses afin de detecter les populations mineures d'âge de zircons dans les echantillons detritiques.

Discontinuous and kinematically unrelated C-S fabrics have been recognized along the contact between the Gemeric and Veporic Units in the Western Carpathians. The formation of S and C fabrics within orthogneiss, quartzite and chloritoid-kyanite schist of the Veporic Unit is associated with Cretaceous syn-burial orogen-parallel flow and subsequent exhumational unroofing. The formation of the two fabrics characterized by distinct quartz deformation microstructure and metamorphic assemblage is separated by an inter-tectonic growth of transversal chloritoid-, kyanite-, ± monazite-bearing assemblage. The monazite U-Th-Pb concordia age of 97 ± 4 Ma was obtained by the laser ablation ICP-MS dating method. The age of this inter-tectonic metamorphic stage together with existing 40Ar/39Ar ages on exhumation of the Veporic Unit indicate that despite the similar appearance to shear bands or C-S mylonites there is a time span of at least 10 Myr between the formation of homogeneous S fabrics and superposed discrete C fabrics in the studied rocks

The postcollisional tectonic development of northeast Mozambique and subsequent cooling from high-temperature metamorphism is delineated with an extensive new set of U-Pb titanite, 40Ar/39Ar hornblende, and 40Ar/39Ar mica analyses. The complex data suggest a polyphase metamorphic history from the late Neoproterozoic to the Ordovician within the East African–Antarctic Orogen (EAAO), with marked differences between the major constituent blocks. In all the data sets, samples from the basement south of the Lu´ rio Belt show generally younger ages than those from the north, resulting from a late metamorphic event and slow cooling between ca. 520 and 440 Ma. The ages north and south of the Lu´ rio Belt are consistently offset by ca. 30–70 Ma, a difference that is maintained and even appears to increase during cooling from very high temperatures to ca. 350C. Based on the first-order assumption that all the ages are cooling ages, cooling rates in the south are estimated at ca. 7–8C/Ma, while those north of the Lu´ rio Belt are faster at ca. 16C/Ma. The data are consistent with previous geochronological, petrographic, and field data and suggest a late high-temperature/low-pressure metamorphic event that affected only the basement rocks south of the Lu´ rio Belt and portions of the latter. This late metamorphism and subsequent delayed, slower cooling agree well with a model of elevated heat flow following lithosphere delamination in the southern part of the orogen, which also explains the observed widespread granitoid magmatism, migmatization, and renewed deformation in the southern basement.

*Corresponding author The Guacimal Pluton is situated in the Cordillera de Tilaran in the northwestern Costa Rica. It forms an oval-shaped body strongly elongated in the NW–SE direction. Its dimensions are ~15 × 4–6 km with an exposed surface of 60–70 km 2 . The pluton intruded basic volcanic rocks of the Aguacate Group (Miocene–Pliocene) and is surrounded by a wide thermal aureole of calc-silicate metasomatic rocks. The pluton is mainly formed of monzogranites to granodiorites, which strongly prevail over more basic types occuring scarce and relatively thin dykes and enclaves. The dominant magmatic minerals of this felsic suite are quartz, plagioclase, and K-feldspar with subordinate Mg-rich biotite, amphibole I, and magnetite. Orthopyroxene, Mn-rich ilmenite, Al-poor titanite, rutile, apatite, zircon, thorite, and chalcopyrite are accessories. Secondary minerals, which occur as fillings of miarolitic cavities and interstices, are quartz II, K-feldspar II, epidote, chlorite, actinolite, ilmenite II and Al-rich titanite II. The much less frequent mafic suite (mainly quartz diorite to quartz monzodiorite/monzogabbro) is composed of plagioclase, pargasite, actinolite, K-feldspar, quartz and magnetite, with accessory amounts of opaque minerals, epidote, chlorite, and titanite. The pluton was emplaced at a depth of c. 3 km, crystallized at temperature of c. 760–800 °C under a relatively high oxygen fugacity (1.6–2.1 log units above the NNO buffer). Increased activities of volatiles (H 2 O, F) upon cooling are indicated by the presence of highly aluminous, F-rich titanite and other hydrous silicates in miarolitic cavities. The prevailing, felsic rocks of the Guacimal Pluton are high-K calc-alkaline, whereas the mafic suite is nearly exclusively medi um-K calc-alkaline in nature. Laser ablation ICP-MS dating of zircons from two granite samples yielded statistically identical U–Pb ages of 6.3 ± 0.5 and 6.0 ± 0.4 Ma, respectively. The Sr–Nd isotopic compositions are rather primitive ( 87 Sr/ 86 Sr 6 = 0.70380–0.70413, e 6 Nd ~ +7.3 to +7.9). Narrow range of these values rules out open-system processes such as magma mixing or assimilation of isotopically contrasting upper continental crust. Instead, the felsic suite is interpreted as either having crystallized from a highly fractionated melt extracted from a plagioclase–amphibole-dominated crystal mush in a putative deep crustal reservoir or a product of partial melting of older arc-related rocks, such as intermediate lavas or volcaniclastics or immature psammitic sediments rich in volcanic material. The observed variation in the felsic suite was most likely produced by low degrees of closed-system fractional crystallization of an assemblage dominated by feldspars. At least some of the rocks of the volumetrically subordinate mafic suite may represent litholo gies rich in the complementary cumulates.

*Corresponding author Skarns in the Svratka Unit, in the neighbouring part of the Moldanubian Zone and in the Kutna Hora Complex were studied with respect to their metamorphic evolution, major- and trace-element geochemistry, oxygen isotopic composition and zircon ages. Skarns form competent lenses and layers in metamorphosed siliciclastic rocks and preserve some early deformation structures and several equilibrium assemblages representing the products of successive metamorphic reactions. The main rock-forming minerals, garnet and clinopyroxene, are accompanied by less abundant magnetite, amphibole, plagioclase, epidote ± quartz. In the Svratka Unit the early prograde M 1 , prograde/peak M 2 , and retrograde M 3 metamorphic stages have been distinguished. Metamorphic conditions in skarns of the Moldanubian Zone are limited to a relatively narrow interval of amphibolite facies. The prograde and retrograde events in the Kutna Hora Complex skarns probably took place under amphibolite-facies conditions. The presence of magnetite and the increasing proportion of the andradite component in the garnet indicate locally increased oxygen fugacity. Skarn geochemistry does not show systematic differences in the skarn composition among the three units. The regional variations are exceeded by differences among samples from individual localities. The Al 2 O 3 /TiO 2 , Al 2 O 3 /Zr, TiO 2 /Nb ratios point to the variable proportion of the detrital material, combined in skarn protoliths with CaO and FeO, the major non-detrital components. The skarns exhibit elevated abundances of Cu, Zn, Sn and As. The Eu/Eu* ratio varies in the range of 0.5–8.6, the total REE contents vary from 8 to 345 ppm. The lowest ΣREE values (< 100 ppm) occur in skarns with magnetite mineralization. The wide intervals of ΣREE and Eu/Eu* values are interpreted to indicate variations in the temperature and redox conditions among layers of the same locality and at various localities. The oxygen isotope compositions of garnets, pyroxenes and amphiboles from skarns of the Svratka Unit exhibit a range of δ 18 O = 0.1 to 4.1 ‰. In situ (laser-ablation ICP-MS) U-Pb dating of zircon from one of the Svratka Unit skarn bodies yielded a wide range of ages (0.5–2.6 Ga), supporting the detrital origin of this zircon population. The skarn protoliths were probably rocks of mixed detrital-exhalative origin deposited on the sea floor . The geological position of skarns, with their structural and metamorphic record, probably reflect tectono-metamorphic evolution shared with that of their host rocks. The geochemical characteristics, including oxygen isotopic compositions and the presence of detrital zircons with a wide range of ages exclude metasomatic, and point to a sedimentary-exhalative mode of origin for the studied skarns.

The Pinjarra Orogen, stretching along the western coast of Western Australia, is one of the least understood orogens on the continent. Exposure is limited to fault-bound basement blocks within the Phanerozoic Perth Basin, which have been interpreted as either remnants of a Mesoproterozoic orogen or as allochthonous blocks within a Neoproterozoic orogen. Thus even the timing of orogenesis is controversial. However, since the orogen is in a critical position for reconstructions of both Rodinia and Gondwana, a better understanding is highly desirable. New U–Pb ages of detrital zircon cores, metamorphic zircon rims and metamorphic monazites from the Northampton Complex, the northernmost and largest of the exposed basement blocks, provide better insights into the sedimentary provenance and metamorphic history of the metasediments exposed in this part of the orogen. Both the monazite ages and the youngest metamorphic zircon rims constrain metamorphism in the Northampton Complex to 1090–1020 Ma. Additionally, a large number of older metamorphic zircon rims pre-date this event and were inherited from the Albany-Fraser Orogen in southwestern Australia, which is also identified as the main source region for the detrital zircon cores. Additional sources of detrital zircons are the Mawson Continent (the South Australian Craton and parts of East Antarctica) and possibly the North Australian Craton, as well as synsedimentary volcanic rocks. However, the combination of ages from the cores and inherited metamorphic rims shows that zircons from the Mawson Continent/North Australian Craton were not directly transported to the Northampton Complex but arrived there after being incorporated into the Albany-Fraser Orogen and then eroded from there. The dataset records therefore two orogenic cycles: (1) erosion of the Mawson Continent/North Australian Craton, deposition along the craton margins, collision between the Mawson Continent and North-West Australian Craton and metamorphism in the Albany-Fraser Orogen and (2) erosion of the Albany-Fraser Orogen, deposition along Australia's western margin and metamorphism during the Pinjarra Orogeny. This highlights the care that must be taken in detrital zircon studies, since many of the detrital cores record a second-order provenance. It also explains how zircons from the Mawson Continent could be transported across the Albany-Fraser Orogen that should normally have been a barrier to northwest-directed sediment transport. Finally, in light of these new and previously published data, we support the interpretation that the Pinjarra Orogen is a Mesoproterozoic orogen formed along Australia's western margin.

Detrital zircon grains in coarse-grained sedimentary rocks of the Noisy formation, (traditionally considered as the H6 unit of the uppermost Hooggenoeg Formation) in the Paleoarchean Barberton Greenstone Belt (BGB) South Africa, are investigated by laser ablation (LA)-ICP-MS to constrain their U–Pb and 207Pb/206Pb ages for depositional age and provenance determination. Drill core and field observations indicate that these rocks are clastic polymictitic diamictites and sandstones. A wide range in 207Pb/206Pb ages between ca. 3600 and 3430 Ma is reported. The youngest detrital zircon grain identified has an age of 3432 ± 10 Ma, constraining the maximum depositional age of the sedimentary sequence and the formation of a major underlying erosional unconformity. The youngest grains correspond in age to the ca. 3460–3430 Ma tonalite–trondjemite–granodiorite (TTG) gneisses of the Stoltzburg terrane and felsic intrusions of the uppermost Hooggenoeg Formation that constitute most of the Songimvelo Block of the BGB on the Kaapvaal craton. The 207Pb/206Pb ages of the oldest grains identified corresponds to plutonic sources identified in older proto-continental blocks of the Kaapvaal craton, namely the ca. 3509 Ma Steynsdorp Block and ca. 3667–3223 Ma Ancient Gneiss Complex (AGC). This new data indicates provenancial linkage between the Songimvelo Block and older proto-continental blocks exposed on the Kaapvaal craton at ca. 3432 Ma. It is argued here, that the Noisy formation is a remnant of the earliest tectonic basin in the BGB, that developed during major tectonic accretion and uplift at ca. 3432 Ma that lead to formation of the erosional unconformity. In conjunction with new drill core and field observations, the geochronological constraints presented here support plate-tectonic processes operating in the proto-Kaapvaal craton that resulted in its formation as a stable continental landmass as early as ca. 3432 Ma.

Age spectra of detrital zircons from metamorphosed quartzites of the Krkonoše–Jizera Massif in the northeastern part of the Saxothuringian Domain were obtained by U–Pb laser ablation inductively coupled plasma mass spectrometry dating. The zircon ages cluster in the intervals of 450–530 Ma and 550–670 Ma, and show individual data between 1.6 and 3.1 Ga. Zircons in the analysed samples are predominantly of Cambrian–Ordovician and Neoproterozoic age, and the marked peak atc. 525–500 Ma suggests a late Cambrian maximum age for the sedimentary protolith. Detritus of the quartzites probably originated from the erosion of Cambrian–Ordovician granitoids and their Neoproterozoic (meta)sedimentary or magmatic country rocks. The lack of Neoproterozoic (meta)sedimentary rocks in the central and eastern part of the Krkonoše–Jizera Massif suggests that the country rocks to voluminous Cambrian–Ordovician magmatic bodies were largely eroded during the formation of early Palaeozoic rift basins along the southeast passive margin of the Saxothuringian Domain. The detrital zircon age spectra confirm the previous interpretation that the exposed basement, dominated by Neoproterozoic to Cambrian–Ordovician granitoids, was overthrust during Devonian–Carboniferous subduction–collision processes by nappes composed of metamorphosed equivalents of the uppermost Cambrian–Devonian passive margin sedimentary formations. Only a negligible number of Mesoproterozoic ages, typically from the Grenvillian event, supports the interpretation that the Saxothuringian Neoproterozoic basement has an affinity to the West African Craton of the northwestern margin of Gondwana.

Detrital zircon U–Pb and Lu–Hf isotope data from Neoproterozoic to Cretaceous sandstones exposed in eastern Greenland, 70°30′–74°N, are reported to characterize and evaluate the provenance from Greenland during pre-breakup and post-breakup sedimentation in the Norwegian–Greenland Sea. Middle Devonian to Lower Cretaceous samples all show similar detrital zircon age distributions characterized by variable Archean populations, abundant Proterozoic populations ranging from ca. 2000 to 900 Ma and a Caledonian population peaking at ca. 440 Ma. Neoproterozoic sediments of the Eleonore Bay Supergroup give a more narrow age distribution with a dominant age peak at 1100 to 1000 Ma, a secondary peak at 1700–1400 Ma, and rare Archean to Paleoproterozoic ages. We suggest that the Neoproterozoic metasediments of the Krummedal and Smallefjord sequences and the Eleonore Bay Supergroup together with Caledonian rocks of age ca. 440 Ma and variable amounts of Paleoproterozoic basement were the main sources for the analyzed Middle Devonian to Lower Cretaceous sandstones. The scarcity of Archean zircons could indicate a rather limited role of the Archean basement rocks of the eastern Greenland Caledonian orogenic belt as a source for some of the analyzed younger sedimentary rocks. The composite age distribution of the zircons from the Phanerozoic eastern Greenland samples, i.e., a minor Archean to Paleoproterozoic (Siderian and Rhyacian) component, abundant Paleoproterozoic (Orosian) to Neoproterozoic (Tonian) ages, and a significant Lower Silurian (Caledonian) signal, is very similar to zircon age distributions reported for Upper Cretaceous turbidite sandstones from large parts of the Norwegian Sea, and to the age distributions determined in this study for three Oligocene sandstone samples from east of Jan Mayen Island. Upper Cretaceous to Paleocene Norwegian Sea sandstones, known to be derived from Norway, differ from this eastern Greenland-derived pattern by a near total lack of Archean zircon ages and a less pronounced Caledonian component. Wide detrital zircon age spectra with a distinct Silurian group and a population of Neoarchean zircons is thus suggested as indicative of sediments sourced from the studied area of eastern Greenland. The Hf isotopic compositions of detrital zircons suggest that Eoarchean crust derived from a source with chondritic Lu/Hf ratios at ca. 3900–3700 Ma contributed to zircon-forming processes in the source area for the eastern Greenland sandstones until ca. 2300 Ma. The Caledonian orogeny in this area was probably a crust reworking event with a limited contribution from depleted mantle.

International audience; LA-ICP-MS U-Pb analyses performed on zircon grains from the Lizio granite yielded an emplacement age of 316 6 Ma. Typical S-C structures show that the Lizio granite was emplaced contemporaneously with dextral shearing along the northern branch of the South Armorican Shear Zone and that it was therefore active at that time. 40Ar/39Ar analyses performed on muscovite grains yielded plateau dates ranging between 311.5 and 308.2 Ma. Muscovite chemistry is typical of primary magmatic muscovite, which precludes a late fluidsinduced resetting of the K-Ar isotopic system. 40Ar/39Ar dates thus likely correspond to the cooling ages below the argon closure temperature. Considering the uncertainties on the measured ages, we can propose that either the Lizio granite cooled down quickly in less than a million of years or that it remained in a hot environment for several millions of years after its emplacement. This latter scenario could have been sustained by shear heating during dextral shearing along the northern branch of the South Armorican Shear Zone.

A detailed description of the newly defined Mendel Formation is presented. This Late Miocene (5.9–5.4 Ma) sedimentary sequence with an overall thickness of more than 80 m comprises cyclic deposition in terrestrial glacigenic, glaciomarine and marine environments. Subglacial till was deposited by a thick grounded Antarctic Peninsula ice stream advancing eastwards through the Prince Gustav Channel, crossing the northernmost part of present-day James Ross Island, with most of the material carried actively at the base of the warm-based glacier. The form of the Prince Gustav Channel originated before the late Miocene and its present glacial over-deepening resulted in multiple grounded glacier advances during the Neogene and Quaternary. The sea prograded from the east and the glacier margin became buoyant, building a small ice shelf, below and in front of which glaciomarine and marine sediments were deposited. These sedimentary deposits are composed of material that was transported mostly by small glaciers and subsequently by the floating ice shelf and by calving icebergs towards the open sea. These environmental and glaciological conditions differ strongly from the present cold-based local glaciers of James Ross Island and the Antarctic Peninsula. These changes were triggered by the global sea level fluctuation connected with climatic changes due to Antarctic ice sheet build up and decay. This reveals Late Miocene obliquity-driven cyclicity with a ~ 41 ka period. The Mendel Formation sedimentary sequence is comprised of at least two glacial periods and one interglacial period. Sea level rise at the northern tip of the Antarctic Peninsula between glacial lowstand and interglacial highstand was more than 50 m during the late Miocene and was followed by a subsequent sea level fall of at least the same magnitude. The presence of well-preserved, articulated pectinid bivalves support “interglacial” open sea conditions. The re-deposition of palaeontological material was shown to be important for the Mendel Formation. Reworked pectinid shells revealed an open marine “interglacial” condition in this part of the Antarctic Peninsula during the Early to Mid Miocene (20.5–17.5 Ma). Unfortunately, relevant sedimentary deposits have not been found on land.

In order to facilitate the understanding of the geological evolution of the Kalahari Craton and its relation to South America, the provenance of the first large-scale cratonic cover sequence of the craton, namely the Ordovician to Carboniferous Cape Supergroup was studied through geochemical analyses of the siliciclastics, and age determinations of detrital zircon. The Cape Supergroup comprises mainly quartz-arenites and a Hirnantian tillite in the basal Table Mountain Group, subgreywackes and mudrocks in the overlying Bokkeveld Group, while siltstones, interbedded shales and quartz-arenites are typical for the Witteberg Group at the top of the Cape Supergroup. Palaeocurrent analyses indicate transport of sediment mainly from northerly directions, off the interior of the Kalahari Craton with subordinate transport from a westerly source in the southwestern part of the basin near Cape Town. Geochemical provenance data suggest mainly sources from passive to active continental margin settings. The reconnaissance study of detrital zircons reveals a major contribution of Mesoproterozoic sources throughout the basin, reflecting the dominance of the Namaqua-Natal Metamorphic Belt, situated immediately north of the preserved strata of Cape Supergroup, as a source with Archaean-aged zircons being extremely rare. We interpret the Namaqua-Natal Metamorphic Belt to have been a large morphological divide at the time of deposition of the Cape Supergroup that prevented input of detrital zircons from the interior early Archaean Kaapvaal cratonic block of the Kalahari Craton. Neoproterozoic and Cambrian zircons are abundant and reflect the basement geology of the outcrops of Cape strata. Exposures close to Cape Town must have received sediment from a cratonic fragment that was situated off the Kalahari Craton to the west and that has subsequently drifted away. This cratonic fragment predominantly supplied Meso- to Neoproterozoic, and Cambrian-aged zircon grains in addition to minor Silurian to Lower Devonian zircons and very rare Archaean (2.5 Ga) and late Palaeoproterozoic (1.8-2.0 Ga) ones. No Siluro-Devonian source has yet been identified on the Kalahari Craton, but there are indications for such a source in southern Patagonia. Palaeozoic successions in eastern Argentina carry a similar detrital zircon population to that found here, including evidence of a Silurian to Lower Devonian magmatic event. The Kalahari and Rio de la Plata Cratons were thus in all likelihood in close proximity until at least the Carboniferous.

Geochemical and petrologic studies on Paleogene basanites from the Carpatho-Pannonian region (Poiana Rusca, Romania) and associated peridotite xenoliths provide information about the composition of the underlying lithosphere, the petrogenetic evolution of the magma and its mantle source, as well as the geodynamic significance of the igneous activity in a regional context. Major and trace elements as well as Sr–Nd isotopic ratios reveal an ocean–island basalt signature, interpreted as the derivation from an upper mantle source chemically similar to the European Asthenospheric Reservoir after low fraction partial melting. Due to estimated average mantle source temperatures and the absence of any subduction-related geochemical features, the igneous activity in Poiana Rusca was apparently triggered by adiabatic decompression melting, as postulated for similar and nearly coeval alkaline rocks in eastern Serbia. Differentiation processes within the Poiana Rusca magmatic suite initially resulted from removal of mainly olivine, followed by olivine + clinopyroxene fractional crystallization. The spinel-lherzolitic to harzburgitic composition of the mantle fragments point to 2–30% fractional melting at a depth of approx. 70 km. Petrographic and geochemical investigations indicate both cryptic and modal metasomatism related to the influence of both alkaline-rich silicate and alkaline-rich hydrous silicate melts rather than subduction-related fluids/melts.

The Letovice Complex, composed of metamorphosed enriched mid-ocean ridge basalts with trondhjemitic sheets, as well as gabbroic and ultrabasic bodies, is exposed within an important Variscan suture separating the Moldanubian Domain (to the west) from the Brunovistulicum (to the east) in the eastern part of the Bohemian Massif, Czech Republic. A polyphase tectonic evolution of the study area was connected with underthrusting and subsequent exhumation of the former oceanic realm, which resulted in three deformation phases (D 1 –D 3 ). New U–Pb laser ablation inductively coupled plasma mass spectrometry dating of magmatic zircons from amphibolite and trondhjemite yielded statistically identical concordia ages of 530 ± 6 Ma and 529 ± 7 Ma (2σ), respectively. These are interpreted as dating intrusions of the Early Cambrian protoliths of the studied rocks. Based on this age as well as whole-rock geochemical and Nd isotopic data, the Letovice Complex is interpreted as a vestige of an incipient oceanic basin developing on attenuated crust. The most likely geotectonic setting was a post-Cadomian extensional regime at the northern margin of Gondwana that marked the onset of its break-up. Supplementary material: Photomicrographs of microstructures, sample locations, descriptions of analytical techniques, and selected electron microprobe analyses of the main rock-forming minerals are available at http://www.geolsoc.org.uk/SUP18424.

Annual growth rings of a common hardwood species, Picea abies L., were investigated as a potential archive of past atmospheric Pb pollution. Wide distribution of trees in terrestrial settings and straightforward chronology are two advantages of this potential geochemical archive, but several processes described in the literature may obscure the trends in past Pb deposition. These confounding factors include, e.g., radial post-depositional mobility of Pb in xylem, and ecosystem acidification leading to higher bioavailability of Pb. One- to five-year annual wood increments were analyzed for Pb concentrations and 206Pb/207Pb ratios at Jezeri (JEZ), Uhlirska (UHL) and Na Lizu (LIZ), three sites in the Czech Republic, differing in atmospheric Pb loads. Three to four trees per site were included in the study. Distinct Pb concentration maxima between 1960 and 1990 at the two heavily polluted sites (JEZ and UHL) coincided with historical Pb emissions known from inventories of industrial production. No Pb concentration maxima were found at one site, LIZ, situated in a national park 150 km from major pollution sources. Spruce tree rings from JEZ, located just 5 km from coal-burning power stations, contained a large proportion of coal-derived Pb (a high-206Pb/207Pb ratio of 1.19). A coal-related maximum in 206Pb/207Pb in JEZ tree rings was found using two different analytical techniques, laser-ablation multi-collector ICP MS, and single-collector sector-field ICP MS. In a three-isotope graph (206Pb/207Pb vs. 208Pb/207Pb), tree-ring data plotted into the field of ombrotrophic (i.e., rain-fed) peat bogs, suggesting negligible contribution of bedrock-derived Pb in the xylem. We concluded that none of the potential confounding factors played a major role at our sites. Annual growth rings of P. abies in Central Europe faithfully recorded historical changes in atmospheric Pb depositions.

Albitization is a common metasomatic process active in various geodynamic contexts. In the northern Pyrenees, there are several occurrences of albitites but, until now, only one occurrence has been dated (117 Ma, Ar–Ar dating). This paper presents new U–Th–Pb ages for several albitite occurrences throughout the Pyrenees to test whether they are contemporaneous and, if so, to specify the regional extent of the albitization event. Ages obtained from large euhedral titanite and monazite grains from distinct albitites are 110 ± 8 and 98 ± 2 Ma, respectively. The zircon U–Th–Pb isotopic system did not record this Cretaceous metasomatic event, even when grains were selected in metasomatically Zr-enriched rocks or in hydrothermal structures (millimetre-sized veins cross-cutting granitoids). We argue that the total time span of 20 Ma recorded by albitites corresponds to a long-lived hydrothermal system that was active during the rotation of Iberia around Europe, along the North Pyrenean Fault. Because albitization and talc mineralization have the same spatial and temporal distribution in the Pyrenees, we argue that these two metasomatic phenomena are two independent records of this single, regional-scale, long-lived hydrothermal system.

We studied primary ore samples from Kalmakyr, a giant Cu–Au–Mo porphyry deposit in eastern Uzbekistan. Disseminated and stockwork-type high-grade Cu–Au–Mo mineralization showed average concentrations of 55 ppb Pd, 5.5 ppb Pt, 0.95 ppb Rh, 0.49 ppb Ir, and 4.1 ppm Au (n = 8). This type of mineralization is characterized by the presence of pyrite, chalcopyrite, molybdenite, and gold. A peak Pd content of 292 ppb was determined in a base-metal-rich quartz vein in granodiorite porphyry, which contains galena, sphalerite, chalcopyrite, tetrahedrite, and gold. Palladium correlates with Cu, Ag, Se, and S. Mineralogical and laser ablation ICP-MS study confirmed that Pd is homogeneously distributed in chalcopyrite, which contains up to 110 ppm Pd, and tetrahedrite, containing up to 20 ppm Pd. An assessment of the Pd and Pt budget at Kalmakyr showed the potential of approximately 17 t of Pd and 1.7 t of Pt.

The metamorphic evolution of micaschists in the north-eastern part of the Saxothuringian Domain in the Central European Variscides is characterized by the early high-pressure M1 assemblage with chloritoid in cores of large garnet porphyroblasts and a Grt–Chl–Phe–Qtz ± Pg M2 assemblage in the matrix. Minerals of the M1–M2 stage were overprinted by the low-pressure M3 assemblage Ab–Chl–Ms–Qtz ± Ep. Samples with the best-preserved M1–M2 mineralogy mostly appear in domains dominated by the earlier D1 deformation phase and are only weakly affected by subsequent D2 overprint. Thermodynamic modelling suggests that mineral assemblages record peak-pressure conditions of ≥18–19 kbar at 460–520 °C (M1) followed by isothermal decompression 10.5–13.5 kbar (M2) and final decompression to

Changes in phase and chemical composition of the mineral titanite (monoclinic CaTiSiO(5)) during laser ablation and plasma-aerosol interaction were investigated using electron diffraction and electron microbeam X-ray analysis with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Laser ablation of titanite with a solid state 213 nm nanosecond laser generates a bimodal aerosol consisting of condensed nanoparticles and spherical micrometer-sized particles. The two types of particles produced by laser ablation are amorphous on the scale resolvable by the electron diffraction. The ratio of Ca-Si-Ti does not change significantly during laser ablation. Aerosol of titanite particles introduced into the ICP and collected after interaction with the plasma contains nanometer-sized particles of a condensate and spherical micrometer-sized particles with a molten surface. The condensed particles are enriched in silicon whereas the spherical micrometer-sized particles show a deficiency in Si relative to the titanite composition. During laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) analysis of titanite, Si and Ti showed positive and negative fractionation trends relative to Ca, respectively. This is consistent with the observed chemical composition changes of the titanite aerosol within the ICP. This study links for the first time the chemical and phase changes of a sample within the ICP to the elemental fractionation during LA-ICPMS.

At the northeastern edge of the Moldanubian Zone, a large body of felsic to intermediate granulite with relics of high-pressure mineral assemblage is exposed within medium-grade paragneisses, micaschists and metagranites. A polyphase tectonic evolution in the study area resulted in three deformation phases (D 1 –D 3 ). Peak metamorphic conditions (860–1000 °C and 16 kbar) in granulites are interpreted as reflecting an early stage of the high-grade evolution of the orogenic lower crust. These conditions were followed by exhumation of the orogenic lower crustal block to mid-crustal levels (6–8 kbar). In contrast to this, the study of metamorphic conditions in the surrounding micaschists (660 °C and 8 kbar) shows that these rocks never experienced pressures and temperatures of the orogenic lower crust. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb dating of zircon from the granulite yielded a concordia age of 354 ± 7 Ma, whereas the conventional isotope dilution thermal ionization mass spectrometry (ID-TIMS) and LA-ICP-MS dating of xenotime gave identical concordia ages of 336.2 ± 1.2 and 339 ± 3 Ma, respectively. Combination of new structural and petrological results with LA-ICP-MS zircon and xenotime dating leads to development of a well-constrained exhumation model and brings new insights into the behaviour of lower crustal rocks during orogenesis.

Metamorphic basement rocks, that are exposed beneath the very low-grade to unmetamorphosed Upper Jurassic-Eocene formations north of the Torud fault zone within the Great Kavir Block, were investigated to elucidate the origin of their protoliths and the pressure and temperature conditions of metamorphism. The basement, previously assumed as a pre-Cambrian metamorphic complex, is mostly formed by amphibolite-facies orthogneisses (tonalite, granodiorite, and granite) with amphibolites and small amounts of metasediment-micaschists. Major- and trace-element geochemistry in combination with U–Pb age dating of zircon showed that the protoliths formed during Late Neoproterozoic continental arc magmatism that has also been identified in other tectonic blocks of Central Iran. In addition to quartz, feldspar(s), micas in orthogneisses, and amphibole + plagioclase in amphibolite, all rocks may contain garnet that shows prograde zoning. Kyanite was found only in some Al-rich amphibolite together with gedrite. The PT conditions of the rocks, based on conventional geothermobarometry and the pseudosection method, show a medium-pressure amphibolite-facies metamorphism. Ar–Ar age dating of muscovite reveals that this metamorphism occurred in the Middle Jurassic (166 Ma) and related to the closure of the Neotethyan basin.

Northeast Africa 003 (NEA 003) is a lunar meteorite found as a two paired stones (6 and 118 g) in Libya, 2000 and 2001. The main portion (∼75 vol%) of the 118 g meteorite, used for this study, (NEA 003-A) consists of mare-basalt and a smaller adjacent portion (∼25 vol%) is a basaltic breccia (NEA 003-B). NEA 003-A has a coarse-grained magmatic texture consisting mainly of olivine, pyroxene and plagioclase. The late-stage mineral association is composed mainly of elongated plagioclase, ilmenite, troilite, fayalite, Si–K-rich glass, apatite, and a rare SiO2 phase. Other accessory minerals include ulvospinel, chromite, and trace Fe–Ni metal. Olivine and pyroxene contain shock-induced fractures, and plagioclase is completely converted into maskelynite. The Fe/Mn values of the whole rock, olivines and pyroxenes, and the bulk-rock oxygen isotopic composition provide evidence for the lunar origin of NEA 003-A meteorite. This is further supported by the presence of Fe–Ni metal and the anhydrous mineral association. NEA 003-A is geochemically and petrographically distinct from previously described mare-basalt meteorites and is not paired with any of them. The petrography and major element composition of NEA 003-A is similar to the composition of low-Ti olivine mare basalts from Apollo 12 and olivine-normative basalts from Apollo 15. The NEA 003-A meteorite shows obvious geochemical similarities in trace elements contents with Apollo 15 olivine-normative basalts and could represent a yet unknown geochemically primitive member of the olivine-normative basalt series. The meteorite is depleted in rare earth elements (REE) and incompatible trace elements indicating a primitive character of the parental magma. The bulk-rock chemical composition demonstrates that the parent melt of NEA 003-A was not contaminated with KREEP components as a result of magma mixing or assimilation processes. Results of crystallization modelling and low minimum cooling rate estimates (∼0.07 °C/h) suggest that the parent melt of NEA 003-A crystallized in the lower part of a lava flow containing cumulate olivine (∼10%) and was probably derived from more primitive picritic magma by fractional crystallization processes. Sm–Nd dating yields an age of 3.09 ± 0.06 Ga which corresponds to the period of lower Eratosthenian lunar volcanic activity, and the near-chondritic eNd value of −0.4 ± 0.3 indicates that the meteorite could be derived from a slightly enriched mantle source similar to the Apollo 15 green glasses. Ar–Ar step release results are inconsistent with Sm–Nd ages suggesting that NEA 003-A was exposed to one or more impact events. The most extensive event took place at 1.8 Ga and the shock intensity was likely between 28 and 45 GPa. The absence of solar Ar suggests that NEA 003-A has not been directly exposed at the lunar surface but the cosmic ray exposure age of 209 ± 6 Ma suggests that NEA 003-A resided in the upper regolith for part of its history.

(Fe–Zn–Mg)-spinel-bearing assemblages in the high-grade rocks from three localities in the Moldanubian domain of the Bohemian Massif (Variscan belt of Central Europe) have been studied to monitor the partition behaviour of zinc along the pressure–temperature path followed by the host rock and to discuss the role of Zn in spinel stabilization. Spinels in two studied samples are characterized by low gahnite content (max. 0.09 Zn p.f.u), they crystallized only under silica-undersaturated conditions and the presence of zinc is thus assumed to be insignificant for their stabilization. One sample contains spinels that are gahnite-rich (up to 0.58 Zn p.f.u) leading to their stabilization within a quartz-bearing matrix. All spinel-bearing domains reflect late re-equilibration corresponding to decompression. However, in samples with preserved relics of a high-pressure mineral assemblage, changes in the zinc content attributed to prograde garnet growth were observed in the garnet cores. In order to monitor the distribution of zinc along the pressure-temperature path, textural observations have been combined with electron-microprobe and laser ablation ICP-MS data. The results point to preferential partitioning of zinc into biotite during the spinel-absent early stages of decompression and suggest that biotite was the main source of zinc for spinel crystallizing at low pressures.

Using a state-of-the-art 193 nm-LA-MC-ICP-MS system and with careful control of analytical procedures, the long term external reproducibility and accuracy of the ages Phanerozoic zircons measured over a period of months using calibrator bracketing for the 206Pb/238U and 207Pb/206Pb ages were ca. 1% (2 RSD) if a single reference zircon was used for the matrix-matched calibration. When different reference zircons were used for the calibration, suspicious systematic shifts in the obtained ages were observed and thus a reduction in the overall accuracy of the dating method became obvious. Such shifts were within a few percent range of the U-Pb and Pb/Pb ages and seemed to vary independently of zircon age and composition. A “test of accuracy” experiment was conducted reducing instrumental effects as far as possible by analysing five different reference zircons mounted on a single mount eight times during the same session. An identical protocol was used for all analyses, with unchanged instrument parameters and with ion beam intensities kept as identical as possible. For data reduction, every zircon served consecutively as the reference zircon for calibration, with the others in the batch treated as unknowns. The known reference age and the four calculated ages obtained using the four other RMs for calibration were then compared. Even using such a strict analytical protocol, shifts in 206Pb/238U, 207Pb/235U and 207Pb/206Pb ratios were still present. They varied non-systematically and ranged from −4.35% to 3.08% for the investigated age range (1065 Ma to 226 Ma). Assuming the absence of instrumental effects (i.e., memory, dead-time correction, non-linearity of ion counters and interdetector calibration, crystallographic orientation, ablation cell geometry and setup, gas flows), the observed shifts were attributed to matrix and/or ablation related effects. It is proposed that non-spectral matrix effects in the Ar plasma torch resulted in non-uniform signal enhancement (or depression?) leading to shifts both in elemental and Pb isotopic ratios. Additionally, the ablated particle size distribution could be an important factor controlling plasma conditions and thus mass bias and fractionation. Until such effects are well understood and controlled, it would seem that any LA-ICP-MS zircon U-Pb and 207Pb/206Pb age determination cannot be meaningfully interpreted at below a ca. 3% to 4% (2 RSD) confidence level. Ce travail repose sur l'utilisation d'un systeme de 193 nm-LA-MC-ICP-MS de derniere generation, avec un controle minutieux des procedures analytiques. La reproductibilite externe et la justesse des mesures d'âges 206Pb/238U et 207Pb/206Pb effectuees par la methode de l'encadrement par des calibrateurs sur des zircons d'âge phanerozoique, ont ete testees sur plusieurs mois et sont de l'ordre de 1% (2 RSD) si un seul zircon de reference etait utilise pour effectuer la calibration de matrice identique. Quand differents zircons etaient utilises pour la calibration, des biais systematiques suspects etaient obtenus sur les âges mesures entrainant une moins bonne justesse globale de cette methode de datation. Ces biais etaient de l'ordre de quelques pourcents sur les âges U-Pb et Pb/Pb et semblaient varier independamment de l'âge du zircon ou de sa composition. Un test de justesse a ete realise, afin de reduire au maximum les effets instrumentaux, en analysant 8 fois durant une meme session, 5 zircons de reference differents, montes dans la meme pastille. Le meme protocole analytique a ete utilise pour toutes ces analyses, sans modification des parametres instrumentaux et avec des intensites des signaux emis conserves aussi proches que possible. Lors du traitement des donnees, chaque zircon a servi de zircon de reference pour la calibration, les autres etant traites comme des inconnus. Les âges recommandes et les âges mesures des 4 zircons ainsi traites en inconnus ont ete compares. Les biais sur les rapports 206Pb/238U, 207Pb/235U et 207Pb/206Pb etaient encore presents, malgre l'application d'un tel protocole. Ils montraient des variations aleatoires, de l'ordre de −4.35%a 3.08% pour la gamme d'âge consideree (1065 Ma a 226 Ma). Nous avons suppose l'absence d'effets instrumentaux tels que: effet de memoire, correction du temps mort, non linearite des compteurs d'ions, probleme d'inter calibration des detecteurs, orientation cristallographique, geometrie de la cellule d'ablation, flux des gaz. En consequence, les biais observes ont ete attribues a des effets de matrice ou des effets lies au processus d'ablation. Des effets de matrice, non spectraux, au niveau de la torche a plasma d'argon pourraient entrainer des amplifications (ou attenuations) du signal, conduisant a des biais, a la fois entre elements et entre isotopes du Pb. De plus la distribution de la taille des particules ablatees pourrait etre un facteur important dans le controle des conditions du plasma, donc des biais de masse et des fractionnements. Tant que de tels effets ne sont pas compris et controles, il semble que l'intervalle de confiance de toute determination d'âge U-Pb ou 207Pb/206Pb par LA-ICP-MS ne peut pas etre inferieur a 3 ou 4% (2 RSD).

We present a comprehensive geochemical data set for a suite of back-arc alkaline volcanic rocks from James Ross Island Volcanic Group (JRIVG), Antarctic Peninsula. The elemental and isotopic (Sr, Nd, Pb and Li) composition of these Cenozoic basalts emplaced east of the Antarctic Peninsula is different from the compositions of the fore-arc alkaline volcanic rocks in Southern Shetlands and nearby Bransfield Strait. The variability in elemental and isotopic composition is not consistent with the JRIVG derivation from a single mantle source but rather it suggests that the magma was mainly derived from a depleted mantle with subordinate OIB-like enriched mantle component (EM II). The isotopic data are consistent with mantle melting during extension and possible roll-back of the subducted lithosphere of the Antarctic plate. Magma contamination by Triassic–Early Tertiary clastic sediments deposited in the back-arc basin was only localized and affected Li isotopic composition in two of the samples, while most of the basalts show very little variation in δ 7 Li values, as anticipated for “mantle-driven” Li isotopic composition. These variations are difficult to resolve with radiogenic isotope systematics but Li isotopes may prove sensitive in tracking complex geochemical processes acting through the oceanic crust pile, including hydrothermal leaching and seawater equilibration.

Mantle xenolith bearing olivine melanephelinites from the Okhotsk sector of the Okhotsk–Chukotka Volcanic Belt (OCVB), northeastern Russia, occur as small isolated volcanoes emplaced within massive late Early to Late Cretaceous subduction-related calc-alkaline rocks. The xenoliths are typical mediumto fine-grained anhydrous mainly spinel lherzolites that are strongly to weakly foliated with intensive to minor recrystallization to equigranular texture. The primitive mantle normalized whole-rock REE have flat patterns or patterns with slightly elevated light REE (LREE) ((La/Yb)N 1⁄4 0.48–1.38). The REE in clinopyroxenes have systematically decreasing normalized abundances from Sm to La, implying that the LREE enrichments in the whole-rock REE patterns are attributed to circulation of minor intergranular fluids or melts. Equilibration temperatures and pressures calculated for the Viliga samples are in the range of 1050–1160 8C and 15–21 kbar, respectively. Ca diffusion rates in olivine reveal a rapid transport to the surface (2–6 days) of these peridotites. Model calculations have shown that the fertile lherzolites can be produced by 2–9% batch melting, whereas the depleted peridotites require 15% batch melting of a primitive source. The cessation of the interaction between the palaeo-Pacific plate and the NE Russian margin at c. 87 Ma apparently caused a ‘piecemeal’ collapse of the former followed by intrusion and ascent of olivine melanephelinitic magma, which entrained xenoliths from the asthenospheric mantle of the subducted plate during the Pliocene through the generated window(s). Moreover, clinopyroxenes that have low Sr/Sr and high Nd/Nd and plot in and above the mid-ocean ridge basalt (MORB) field are consistent with an upwelling asthenospheric mantle through the window(s) created by the ‘piecemeal’ collapse of the palaeo-Pacific plate. Mantle xenoliths in alkali basalts emplaced in massive subduction-related calc-alkaline rocks are important rocks, as they could provide information about the nature of the lithospheric mantle wedge and the geochemical and metasomatic processes that occur in such tectonic settings. Fluids released from sediments of a downgoing subduction slab could cause modal metasomatism in the lithospheric mantle wedge, forming hydrous phases such as amphibole and phlogopite (Peacock 1993). Migration of melts produced by melting of a downgoing subduction slab can also affect the lithospheric mantle wedge, causing crypticmetasomatism, as has been demonstrated by Kilian & Stern (2002) for the Cerro Fraile mantle xenoliths in southernmost Patagonia and by Kepezhinskas et al. (1996) for the Valovayam Volcanic Field in the northern segment of Kamchatka arc xenoliths. The mantle xenoliths from the Viliga River volcanic field in the northern Okhotsk region, NE Siberia (Fig. 1), are hosted by olivinemelanephelinites and basanites and occur at two localities (Kananyga River and Aliki River areas) on top of calc-alkaline rocks up to 1550 m above sea level, which are related to the subduction of the palaeo-Pacific slab (Zonenshain et al. 1990). The age of the undersaturated lavas ranges from 10.7 to 7 Ma (Akinin 1997, 2005; Apt et al. 1998). A limited number of mantle xenoliths from the region have been studied by Akinin et al. (1997) and Apt et al. (1998). Here we present a summary of the petrology, mineralogy and geochemistry of the ultramafic xenoliths from both localities and discuss the implications of these data with respect to the subduction slab and mantle wedge processes.

Granitoid intrusions of the Boundary Igneous Complex separate segments with different ages of high-grade metamorphism in the Kaoko Belt, NW Namibia. Two granitoids of this complex were dated at 575 ± 10 Ma (secondary ionization mass spectrometry; SIMS) or 571 ± 9 Ma (laser ablation inductively coupled plasma mass spectrometry; LA-ICP-MS) and 562 ± 11 Ma (SIMS) or 572 ± 4 Ma (LA-ICP-MS), respectively. The age of granulite-facies metamorphism in the eastern part of the Western Kaoko Zone was established at 549 ± 5 Ma (SIMS) by analysing metamorphic overgrowths of older ( c . 1850–1000 Ma) zircons from melt segregations in amphibolites. The coastal part of the Western Kaoko Zone consists of horizons of migmatitic metasedimentary rocks that are intercalated with fine-grained orthogneisses and amphibolites resembling metamorphosed sequences of bimodal volcanic rocks. Zircons from felsic members of two bimodal suites have SIMS ages of 805 ± 4 Ma and 810–840 Ma, respectively, that are interpreted as dating their respective igneous protoliths. Melt segregations in the mafic member of the lower bimodal suite contain two populations of zircon dated at 650 ± 5 Ma (SIMS) or 645 ± 5 Ma (LA-ICP-MS) and 629 ± 6 Ma (SIMS) or 630 ± 5 Ma (LA-ICP-MS), respectively. The later age is indistinguishable from the age of 630 ± 4 Ma (SIMS) or 625 ± 10 Ma (LA-ICP-MS) obtained from melt patches present in overlying metagreywackes. The available age data suggest that the Boundary Igneous Complex masks the suture between the Coastal Terrane and the rest of the Kaoko Belt. Ages of granitoid intrusions in this igneous complex are indicative of magmatic activity between 580 and 550 Ma.

The Huqf Supergroup in Oman contains an exceptionally well-preserved and complete sedimentary record of the Middle to Late Neoproterozoic Era. Outcrops of the Huqf Supergroup in northern and central Oman are now well documented, but their correlation with a key succession in the Mirbat area of southern Oman, containing a sedimentary record of two Neoproterozoic glaciations, is poorly understood. Integration of lithostratigraphic, chemostratigraphic and new U–Pb detrital zircon data suggests that the Mirbat Group is best placed within the Cryogenian ( c . 850–635 Ma) part of the Huqf Supergroup. The c . 1 km thick marine deposits of the Arkahawl and Marsham Formations of the Mirbat Group are thought to represent a stratigraphic interval between older Cryogenian and younger Cryogenian glaciations that is not preserved elsewhere in Oman. The bulk of detrital zircons in the Huqf Supergroup originate from Neoproterozoic parent rocks. However, older Mesoproterozoic, Palaeoproterozoic and even Archaean zircons can be recognized in the detrital population from the upper Mahara Group (Fiq Formation) and Nafun Group, suggesting the tapping of exotic sources, probably from the Arabian–Nubian Shield.

Hf isotopic data of minerals in a mafic pyroxene granulite from the southern Bohemian Massif, together with their major and trace element composition and petrological observations were used to decipher the metamorphic history and behaviour of zircon in the granulite. The Hf isotopic composition in the minerals was used to estimate whether the decompression reaction, namely the consumption of garnet and rutile, could have provided Zr for the formation of newly grown metamorphic zircon. The age of the decompression reaction indicated by the evolution of Hf isotopes in garnet and orthopyroxene is between 333 and 331 Ma, i.e. ca. 7 Ma younger than the available U–Pb zircon ages from the Moldanubian granulites and than the newly obtained 343 ± 2 Ma laser ablation ICP-MS U–Pb age of zircons. The combination of bulk and in-situ Hf isotopic data, major and trace element composition and petrological modeling of P–T evolution revealed that the formation of zircons can not be related to the decompression phase of the evolution of the mafic granulites.

Laser ablation inductively coupled plasma mass spectrometry (LA ICP—MS) is a newly established technique that is capable of in-situ U(Th)—Pb dating of accessory minerals in a wide range of rock types and geological environments. Recent developments in laser technology and mass spectrometry have led to substantial improvements in precision and accuracy of isotopic ages obtained by LA ICP-MS. Despite the advancements in technology, the precision and accuracy of U(Th)—Pb laser ablation ICP-MS dating are still limited by laser-induced elemental fractionation of Pb and U. This paper reviews the technique's history and summarizes recent achievements and possible future developments of this novel dating method.

Zircon fission-track (FT) and U–Pb analyses were performed on zircon extracted from a pseudotachylyte zone and surrounding rocks of the Asuke Shear Zone (ASZ), Aichi Prefecture, Japan. The U–Pb ages of all four samples are ∼ 67–76 Ma, which is interpreted as the formation age of Ryoke granitic rocks along the ASZ. The mean zircon FT age of host rock is 73 ± 7 (2 σ ) Ma, suggesting a time of initial cooling through the zircon closure temperature. The pseudotachylyte zone however, yielded a zircon FT age of 53 ± 9 (2 σ ) Ma, statistically different from the age of the host rock. Zircon FTs showed reduced mean lengths and intermediate ages for samples adjacent to the pseudotachylyte zone. Coupled with the new zircon U–Pb ages and previous heat conduction modeling, the present FT data are best interpreted as reflecting paleothermal effects of the frictional heating of the fault. The age for the pseudotachylyte coincides with the change in direction of rotation of the Pacific plate from NW to N which can be considered to initialize the NNE–SSW trending sinistral–extensional ASZ before the Miocene clockwise rotation of SW Japan. The present study demonstrates that a history of fault motions in seismically active regions can be reconstructed by dating pseudotachylytes using zircon FT thermochronology.

The rocks of the crystalline basement of the East European Craton in southern Estonia show effects of partial melting under granulite facies conditions. Zircons extracted from partial melting products (tonalite from the Tapa Zone – 1824 ± 26, tonalite from the South Estonian Zone – 1788 ± 16 Ma and charnockite from the Tapa Zone – 1761 ± 11 Ma) yield U–Pb crystallisation ages that span over approximately 80 Ma, suggesting a prolonged high-grade metamorphism or several separate events. U–Pb zircon age of one sample of charnockite is concordant with the Nd model age of partial melting of its host mafic granulite facies gneiss (intercept at 1.76 Ga). Linear geochemical trends and similar initial Nd isotopic compositions of mafic granulites and charnockites suggest their possible genetic relationship. From our new and previously published data it follows that the peak granulite metamorphic conditions and formation of tonalites and charnockites (850 °C and 6 kbar) in the Estonian basement occurred at 1788–1778 Ma. Then, the rocks cooled down, passing through the garnet closure temperature of approximately 650–700 °C at 1728 ± 24 Ma. The age of metamorphism of the Estonian granulites is lower than the metamorphic ages known from southern Finland, but it is similar to the age of metamorphism reported from the Belarus-Baltic Granulite Belt in Latvia.

A new method has been developed for the accurate and precise measurement of sulfur isotopes (32S, 33S, 34S) in solids on a scale down to 80–100 μm by laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). The method was developed independently on two different sets of instrumentation, both of which give equivalent results with comparable accuracy and precision. The first instrumental set-up utilizes Xe gas in a hexapole collision and reaction cell for interference attenuation coupled with a mass discrimination correction by external normalization using a nebulised vapour of 37Cl/35Cl standard solution. The second employs high mass resolution by sector field mass spectrometry to avoid the interfering O2+ isobars with a 30Si/29Si standard aerosol for external normalization. The external isotope mass discrimination correction was applied using the exponential law and was further calibrated for both sets of instrumentation by linear interpolation in a sample–standard bracketing method. Mean δ34SV-CDT and δ33SV-CDT show excellent agreement (within analytical error, typically 0.6 and 1.5‰, respectively) with compiled data for IAEA-S series AgS standard reference materials. Results for NIST SRM 127 (sulfate) were less accurate when calibrated against the IAEA-S series sulfides, whilst significant and consistent deviations in accuracy of up to 3‰ were observed in both sets of instrumentation for Soufre de Lacq SRM sulfur. Such generic matrix effects may be widespread in LA-ICP-MS due to differential ablation rates, particle formation, particle transport efficiency and ionization efficiency in an argon plasma.

New single-grain and within-grain U-Pb zircon ages from the central Tauern Window help sorting out the time dimension among the various Variscan and pre-Variscan basement components that were strongly overprinted by Alpine orogeny. Single-grain isotope dilution (ID-TIMS) U-Pb zircon geochronology of three Basisamphibolit samples yield protolith formation ages of 351±2, 349±1 and 343±1 Ma. Laser ablation ICP-MS and ID-TIMS U-Pb detrital zircon dating of the Biotitporphyroblastenschiefer constrained the maximum time of sedimentation to between 362±6 Ma and 368±17 Ma. Paragneisses from the Zwolferzug yield maximum sedimentation ages from 345±5 Ma (ion microprobe data) to 358±10 Ma. Zircons from gabbroic clasts and detrital zircons from a meta-agglomerate from the Habach Phyllite give an upper intercept age of 536±8 Ma and a near-concordant age of 506±9 Ma, respectively. Hence, apart from the Habach Phyllite, the maximum sedimentation ages of the metasediments investigated range from Upper Devonian to Lower Carboniferous. Consequently, the Basisamphibolit, the Biotitporphyroblastenschiefer, and the paragneisses of the Zwolferzug form parts of the Variscan basement series. The Basisamphibolit (351-343 Ma) is distinct both in space and time of formation from the Zwolferzug garnet amphibolite (c. 486 Ma), which forms part of the pre-Variscan basement.

The chemical and phase compositions of particles produced by laser ablation (266 nm Nd:YAG) of silicate NIST glasses and zircon were studied by SIMS and HR-TEM techniques. The data suggest that the formation of phases of different mineralogy and/or chemical composition from the original sample at the ablation site can result in elemental fractionation (non-stoichiometric sampling) in material delivered to the ICP-MS for quantitative analysis. Evidence of the element fractionation is preserved in chemically zoned ejecta deposited around the ablation pit. The chemical composition and mineralogy of particles varies with particle size so that the efficiency of transport of particles also plays a role in elemental fractionation. During the first 250 pulses in a typical ablation experiment using a 266 nm laser, particle sizes are mainly

The isotopic composition of Fe in iron meteorites and iron sulfides was studied with a UV laser (213 nm wavelength) and a high-mass resolution multicollector-ICP-MS. The long term reproducibility of Fe isotopic measurements was 0.16 and 0.21‰ (2 standard deviations) for δ56Fe and δ57Fe, respectively, i.e., a factor of ∼2 worse than conventional solution analysis. At present the major limitations of precision and accuracy in the laser ablation technique are instrumental mass discrimination (2.0–4.9% per amu) and laser-induced fractionation (up to 4‰ during a single analysis) of Fe isotopes. Laser ablation of iron metal and iron sulfides produces two types of particles: (1) coarse (50–600 nm) spherical and crystalline particles that are isotopically heavier than (2) fine (2–7 nm) amorphous particles. Differential transport of the two types of particles to the ICP can compromise the accuracy of Fe isotope measurements by laser ablation MC-ICP-MS. Despite lower precision compared with solution MC-ICP-MS analysis, the laser ablation technique is capable of resolving Fe isotopic variations between seafloor and sub-seafloor hydrothermal sulfides, and between kamacite and taenite alloys that are commonly present as thin lamellae in iron meteorites. The most important applications of the technique will be for the analysis of small samples where the textural context of the analysed objects is important for the interpretation of Fe isotopic data.