Polycyclic Palaeozoic evolution of accretionary orogenic wedge in the southern Chinese Altai: Evidence from structural relationships and U-Pb geochronology.

Structural analysis and U-Pb geochronological study on zircons from the southern Chinese Altai (the Kalasu area, SE of the Altai city) show that the Cambro-Ordovician accretionary wedge (ca. 520-492 Ma) underwent four major geological events: 1) emplacement of Early Devonian magmas (ca. 410-400) associated with formation of a volcano-sedimentary cover, 2) major Middle Devonian (ca. 390-374 Ma) tectono-metamorphic event, 3) Late Devonian-Early Carboniferous folding without apparent metamorphism, and 4) a regional folding with localized Early Permian high- to ultrahigh-temperature reworking (ca. 300-280 Ma). The Early Devonian magmatism is characterized by emplacement of mafic rocks and granitoids in the centre of the NE-SW profile, coevally with granitoid magmatism and rhyolite volcanism in the southwest and northeast, respectively. The whole volcano-sedimentary and magmatic edifice was transposed by sub-horizontal metamorphic fabric associated with variable metamorphic degrees in different areas ranging from greenschist facies in the northeast (mu + bi±g) to amphibolite facies in the southwest (st + g ± sill) and granulite facies in the centre (g + sill+kfs). This metamorphic architecture, distribution of magmatism and character of metamorphic zircon populations allow to correlate these areas with upper, middle and lower orogenic crust that developed during important vertical shortening and horizontal flow in Middle Devonian. Subsequently, the whole edifice was affected by regional NE-SW trending upright (possibly Late Devonian-Early Carboniferous) folding. Finally, Early Permian shortening produced NW-SE trending regional upright folds in the southwest and northeast and a crustal-scale vertical, tabular deformation zone in the centre. The Permian deformation is accompanied by granulite facies (kfs + cd + sill+g) metamorphism and anatexis reworking the Devonian lower orogenic crust, with extensive resetting and growth of new zircons and with intrusions of Permian granites and gabbros. This study suggests that the Early Permian event was related to massive perturbation of thermal structure of the mantle lithosphere due to the collision of the Junggar arc with the Chinese Altai terrane

Pre-collisional crustal evolution of the European Variscan periphery: Constraints from detrital zircon U–Pb ages and Hf isotopic record in the Precambrian metasedimentary basement of the Brunovistulian Domain

In this study, U–Pb ages and Hf isotopic composition of detrital zircons from the Precambrian metasedimentary autochthon of the Brunovistulian Domain in the eastern Bohemian Massif were investigated to understand the pre-collisional evolution of the eastern periphery of the European Variscan belt. Detrital zircons of the Tonian sequences have mostly Paleoproterozoic to Neoproterozoic ages (c. 2.1–0.9 Ga) and are interpreted as detritus derived from the basement of either Baltica or Amazonia. The mostly positive εHf(t) values (–4 to + 16) indicate a juvenile nature of their magma sources with minor older crustal components. In contrast, the Ediacaran sequences contain dominantly Neoproterozoic zircons (c. 600 Ma) and only rare Paleo- and Mesoproterozoic ages indicate that they were sourced from the adjacent Neoproterozoic magmatic arc with very limited input of recycled cratonic detritus. The large spread of εHf(t) values (–15 to + 13) of the Neoproterozoic zircons suggests significant mixing of mantle-derived magmas with mature crustal material, typical of large continental magmatic arc systems. The zircon age patterns of the Ediacaran sequences, characterized by a dominance of the late Neoproterozoic zircons and limited Mesoproterozoic zircons, are nearly identical to those from the Teplá–Barrandian Unit and Moldanubian Zone, pointing to their similar sources. We consider such age populations as a record of sources actually exposed at the time of deposition, rather than the real provenance signature of the continental basement. The change in detrital zircon U–Pb age and Hf record of the Brunovistulian Domain took place between the early and late Neoproteorozoic, and probably reflects the plate-tectonic reconfiguration from the Rodinia formation/break-up to the evolution of the Gondwana or Baltica active margins. Our data challenge the main arguments for an existence of the Rheic oceanic suture between the Brunovistulian Domain and Moldanubian Zone and allow for an alternative pre-collisional model of the Bohemian Massif as a single Neoproterozoic crustal domai

Atmospheric deposition of beryllium in Central Europe: Comparison of soluble and insoluble fractions in rime and snow across a pollution gradient

Little is known about atmospheric input of beryllium (Be) into ecosystems, despite its highly toxic behavior. For 35 three consecutive winters (2009–2011), we measured Be concentrations in horizontal deposition (rime) and 36 vertical deposition (snow) at 10 remotemountain-top locations in the Czech Republic, Central Europe. Beryllium 37 was determined both in filtered waters, and in HF digests of insoluble particles. Across the sites, soluble Be 38 concentrations in rime were 7 times higher, compared to snow (6.1 vs. 0.9 ng·L 39 −1). Rime scavenged the pollution-rich lower segments of clouds. The lowest Be concentrations were detected in the soluble fraction of 40 snow. Across the sites, 34% of total Be deposition occurred in the form of soluble (bioavailable) Be, the rest 41 were insoluble particles. Beryllium fluxes decreased in the order: vertical dry deposition insoluble>vertical 42 dry deposition soluble>horizontal deposition soluble>vertical wet deposition insoluble>vertical wet deposi- 43 tion soluble>horizontal deposition insoluble. The average contributions of these Be forms to total deposition 44 were 56, 21, 8, 7, 5 and 3%, respectively. Sites in the northeastweremore Be-polluted than the rest of the country 45 with sources of pollution in industrial Silesia.JRC.E.5-Nuclear chemistr

Paleozoic Geodynamics and Architecture of the Southern Part of the Mongolian Altai Zone

The Mongolian Altai Zone of the Central Asian Orogenic Belt has been traditionally interpreted as a mosaic of Paleozoic magmatic arcs, back-arcs, and Precambrian continental terranes. In order to define its architecture and its tectonic evolution, three domains previously interpreted as terranes were investigated. The findings show that the Northern and Central domains are formed by a metamorphic sequence characterized by Barrovian S1 fabric transposed by recumbent folds and dominant sub-horizontal amphibolite facies S2 schistosity. The latter is associated with the intrusions of late Devonian syntectonic granite sheets and anatexis in the south. The Southern domain is formed by early Permian migmatites and anatectic granites separated from the metamorphic envelope by amphibolite to green-schist facies D3 shear zone cross-cutting S2 fabrics. All domains have been reworked by E-W upright folds associated with axial-planar greenschist facies cleavage, reflecting the final mid-Permian to Triassic D4 shortening. Lithological, geochemical, and U-Pb zircon analyses of metasediments of all domains indicate that they are formed by Ordovician mature quartzite derived from Precambrian basement intruded by Cambrian-Ordovician continental arc and Silurian immature graywacke which originated through erosion of an oceanic arc. Altogether, the whole sequence represents a fore-arc basin in front of a migrating arc affected by thickening and late Devonian extension. The Southern domain is interpreted as an early Permian core complex amplified by mid-Permian to Triassic compression. The apparent 'terrane' architecture of the Mongol Altai Zone originated due to Devonian and Permian heterogeneous reworking of a giant Ordovician to Silurian fore-arc basin

Correlation between the Trans-Altai Zone and Mongolian Altai: Evidence from detrital zircon U-Pb and Hf isotopic data

International audienceThe Trans-Altai Zone (TAZ) represents a narrow linear segment of the Silurian–Devonian oceanic realmin southern Mongolia (Helo et al.,2006; Rippington et al.,2013). It records the mid to late Paleozoicgeodynamic evolution of the Paleo-Pacific Ocean. In general, the TAZ is composed of several terranesinterpreted as island arcs, back-arc basins/forearcs and accretionary wedges (Badarch et al.,2002; Lamb& Badarch,1997). Here, we present new structural, whole-rock geochemical and zircon U-Pb ages andHf isotopic data from the Carboniferous rocks of the TAZ to decipher the tectonic-sedimentary evolutionof this tectonic zone. The sedimentary rocks studied were collected from key units of the TAZ called theKhuvinkhar and Zoolon subzones. The Khuvinkhar subzone marks the northernmost extremity of the TAZseparated from the northerly Mongolian Altai by the Trans-Altai Fault (Kozakov,2002; Lamb & Badarch,1997). The Zoolon subzone represents the southernmost part of the TAZ limited by the Gobi-TianshanFault (Cunningham et al.,1996) in the south. The rocks of the Khuvinkhar subzone preserve a low-grade(D2) cleavage (potentially of Permian–Triassic age) that affected the bedding of Devonian–Carboniferousstrata. Ontheotherhand, therocksintheZoolonsubzonerecordedtheearlierdeformationevent(D1)as-sociatedwithgreenschist-toamphibolite-faciesmetamorphismthatwasreworkedbyS2verticalcleavage.However, the age of the D1deformation remains unconstrained. The sediments studied from both sub-zones are poorly sorted greywackes which indicates proximal sources (CIA = 45–55). The sediments fromboth subzones show subduction-influenced geochemical characteristics such as low HFSE (Ta, Nb, Ti) con-tents. In detail, the greywackes in the Zoolon subzone reveal the oceanic arc-derived sources, whereasthose in the Khuvinkhar subzone are characterized by active continental margin tectonic affinity. Newresults of U-Pb isotopic dating of detrital zircons collected from TAZ sediments suggest Mississippian–Permian depositional ages (ca. 297–348 Ma). The depositional ages of the sediments in the Khuvinkharsubzone (ca. 297–325 Ma) are younger than those in the Zoolon subzone (ca. 322–348 Ma). Interest-ingly, the Cambrian–Ordovician and Silurian–Devonian age populations in all dated samples may imply adirect correlation between the TAZ and Mongolian Altai. However, the youngest detrital zircon age popu-lations indicate a source from the proximal Carboniferous volcanic arc (Nguyen et al.,2018). In addition,a litharenite collected from the northernmost part of the Khuvinkhar subzone yields an Ordovician depo-sitional age (ca. 475 Ma) similar to the sediments typical of the Gobi-Altai Zone in the Mongolian Altai tothe north (Gibson et al.,2013; Kröner et al.,2010). This Ordovician litharenite is unconformably overlainby Carboniferous sequences of the TAZ. Therefore, the boundary between the TAZ and Mongolian Altaican be interpreted as having a stratigraphic and not tectonic significance. The greywackes and tuffaceoussandstoneintheZoolonsubzoneshowmainlypositiveinitialepsilonHfvalues(+15.2to-1.7; TDM.2stg=0.4–1.1 Ga) that support a juvenile source. However, several zircons with CHUR-like initial Hf values indicate acontribution of a crustal source. Comparison with East Junggar sedimentary sequences allows the stud-25ied greywacke-type sediments of the Khuvinkhar and Zoolon subzones to be attributed to CarboniferousDulateback-arcsequences (Jiang etal.,2024; Sukhbaataretal.,2024). It canbeconcludedthatboth Khu-vinkharandZoolonCarboniferoussequencesrepresentacontinuationoftheEastJunggarDulateback-arcsystem sourced in a nearby Carboniferous arc

Correlation between the Trans-Altai Zone and Mongolian Altai: Evidence from detrital zircon U-Pb and Hf isotopic data

International audienceThe Trans-Altai Zone (TAZ) represents a narrow linear segment of the Silurian–Devonian oceanic realmin southern Mongolia (Helo et al.,2006; Rippington et al.,2013). It records the mid to late Paleozoicgeodynamic evolution of the Paleo-Pacific Ocean. In general, the TAZ is composed of several terranesinterpreted as island arcs, back-arc basins/forearcs and accretionary wedges (Badarch et al.,2002; Lamb& Badarch,1997). Here, we present new structural, whole-rock geochemical and zircon U-Pb ages andHf isotopic data from the Carboniferous rocks of the TAZ to decipher the tectonic-sedimentary evolutionof this tectonic zone. The sedimentary rocks studied were collected from key units of the TAZ called theKhuvinkhar and Zoolon subzones. The Khuvinkhar subzone marks the northernmost extremity of the TAZseparated from the northerly Mongolian Altai by the Trans-Altai Fault (Kozakov,2002; Lamb & Badarch,1997). The Zoolon subzone represents the southernmost part of the TAZ limited by the Gobi-TianshanFault (Cunningham et al.,1996) in the south. The rocks of the Khuvinkhar subzone preserve a low-grade(D2) cleavage (potentially of Permian–Triassic age) that affected the bedding of Devonian–Carboniferousstrata. Ontheotherhand, therocksintheZoolonsubzonerecordedtheearlierdeformationevent(D1)as-sociatedwithgreenschist-toamphibolite-faciesmetamorphismthatwasreworkedbyS2verticalcleavage.However, the age of the D1deformation remains unconstrained. The sediments studied from both sub-zones are poorly sorted greywackes which indicates proximal sources (CIA = 45–55). The sediments fromboth subzones show subduction-influenced geochemical characteristics such as low HFSE (Ta, Nb, Ti) con-tents. In detail, the greywackes in the Zoolon subzone reveal the oceanic arc-derived sources, whereasthose in the Khuvinkhar subzone are characterized by active continental margin tectonic affinity. Newresults of U-Pb isotopic dating of detrital zircons collected from TAZ sediments suggest Mississippian–Permian depositional ages (ca. 297–348 Ma). The depositional ages of the sediments in the Khuvinkharsubzone (ca. 297–325 Ma) are younger than those in the Zoolon subzone (ca. 322–348 Ma). Interest-ingly, the Cambrian–Ordovician and Silurian–Devonian age populations in all dated samples may imply adirect correlation between the TAZ and Mongolian Altai. However, the youngest detrital zircon age popu-lations indicate a source from the proximal Carboniferous volcanic arc (Nguyen et al.,2018). In addition,a litharenite collected from the northernmost part of the Khuvinkhar subzone yields an Ordovician depo-sitional age (ca. 475 Ma) similar to the sediments typical of the Gobi-Altai Zone in the Mongolian Altai tothe north (Gibson et al.,2013; Kröner et al.,2010). This Ordovician litharenite is unconformably overlainby Carboniferous sequences of the TAZ. Therefore, the boundary between the TAZ and Mongolian Altaican be interpreted as having a stratigraphic and not tectonic significance. The greywackes and tuffaceoussandstoneintheZoolonsubzoneshowmainlypositiveinitialepsilonHfvalues(+15.2to-1.7; TDM.2stg=0.4–1.1 Ga) that support a juvenile source. However, several zircons with CHUR-like initial Hf values indicate acontribution of a crustal source. Comparison with East Junggar sedimentary sequences allows the stud-25ied greywacke-type sediments of the Khuvinkhar and Zoolon subzones to be attributed to CarboniferousDulateback-arcsequences (Jiang etal.,2024; Sukhbaataretal.,2024). It canbeconcludedthatboth Khu-vinkharandZoolonCarboniferoussequencesrepresentacontinuationoftheEastJunggarDulateback-arcsystem sourced in a nearby Carboniferous arc

Cadmium contents of vertically and horizontally deposited winter precipitation in Central Europe: Spatial distribution and long-term trends

Cadmium (Cd) and its forms has recently been a focus of attention due to its toxic effects on human health and the environment. We evaluated the atmospheric deposition of Cd during three consecutive winter seasons (2009-2011) at 10 mountain-top locations in the Czech Republic along the borders with Poland, Germany, Austria and Slovakia. Cadmium concentrations of soluble and insoluble forms in both horizontal (rime) and vertical (snow) deposition were determined using sector-field ICP-MS. Across the sites, 94% of the total winter Cd deposition occurred in the soluble (bioavailable/environmental available) Cd form. Mean concentrations of soluble Cd in rime were six times higher than in snow (398 vs. 66 ng L-1). Vertical deposition contributed as much as 41% to the total winter Cd input. Significant among-site variability in winter Cd deposition ranged between 13 and 108 g m-2 winter-1. Overall, Cd concentrations in winter deposition did not reach legislated drinking water limits and did not pose a direct threat for human health. Long-term trends (1996-2017) in winter Cd deposition were evaluated using six GEOMON sites (a monitoring network of small forested catchments). Since 1996, Cd input in winter atmospheric deposition was reduced by 73-93%. Simultaneously, we found declines in among-site variability in winter Cd inputs. The highest recent winter Cd inputs were found at sites in the northeast of the country. A north-south pollution gradient, which has frequently been mentioned in the literature, was not observed, with both northwest sites and southern sites among those with the lowest Cd pollution. Backward trajectories of the HYSPLIT model for fresh snow samples identified Poland and Germany as major transboundary Cd pollution sources for the Czech Republic.JRC.G.II.6-Nuclear Safeguards and Forensic

Late La Tène bronze rivets from selected sites in Bohemia: material research

Abstract The study presented focuses on material research of La Tène rivets and represents the very first study conducted into this class of archaeological finds from the Bohemian region. The rivets examined come from two significant archaeological sites situated in this geographical area—a hillfort Kolo near Týnec nad Labem and an oppidum in Stradonice. The sets of the rivets selected for the study were dated to the Late La Tène period (second–first century BC)—in the context of Western Europe, the term Celtic period can also be found. Thorough material research of the objects utilised a range of methods such as scanning electron microscopy with energy dispersive analyser, atomic absorption spectrometry, X-ray micro-tomography scanning, laser ablation-inductively coupled plasma-mass spectrometry, and Raman spectrometry. As a result, the research has identified and described three different technologies used to produce the rivets. The rivets uncovered there were mostly produced by casting from a bronze alloy or by putting wrought iron pins into the bronze melt of rivet heads. In addition, a minority of the rivets were produced using forged wrought iron with their heads plated with a very thin bronze plate. The results of the elemental analysis showed that several of the rivets and most of the rivet heads were made of bronze alloys with a tin content of 2–10 wt.%. The lead content of bronze alloy rivets from both sites varies from 0.2 to 10.1 wt.%. It can be assumed, that lead was intentionally added to the bronze melt used to produce the majority of the artefacts examined. Also, several bronze rivet heads were found to be decorated with enamel, which is a type of soda-lime-silica high lead glass coloured with crystals of Cu2O (the Colour of the enamel was predominantly red). In conclusion, two different groups of enamels were distinguished: (a) enamels with PbO up to 20% and (b) enamels with a higher content of PbO reaching up to 40%

The Fate of Atmospherically Derived Pb in Central European Catchments: Insights from Spatial and Temporal Pollution Gradients and Pb Isotope Ratios

Soils in polluted regions are generally regarded as a delayed, long-lasting source for Pb contamination of aquatic systems. Lead deposited on topsoil is slowly transported downward with particulate and colloidal organic matter, driven by infiltrating precipitation. Then, Pb is tightly retained in mineral soil. Lead export from catchments is extremely low and decoupled from the atmospheric input. We tested this hypothesis in 11 small catchments, differing in pollution levels. Input/ouput Pb fluxes were monitored for 14–15 years in an era of decreasing industrial Pb emission rates. Between 1996/1997 and 2010, Pb deposition fluxes decreased significantly, on average by 80%. At the beginning of the monitoring, Pb export constituted 2 to 58% of Pb input. At the end of the monitoring, Pb export constituted 2 to 95% of Pb input. Highly polluted sites in the northeast exported significantly more Pb than less polluted sites further south. The ²⁰⁶Pb/²⁰⁷Pb isotope ratios of runoff (1.16) were identical to those of topsoil and present-day deposition, and different from mineral soil and bedrock. Lead isotope systematics and between-site flux comparisons indicated that a portion of the incoming Pb had a relatively short residence time in the catchments, on the order of decades

Lead fluxes and 206Pb/207Pb isotope ratios in rime and snow collected at remote mountain-top locations (Czech Republic, Central Europe): Patterns and sources

During three winter seasons (2009-2011), Pb concentrations were measured in precipitation at 10 high-elevation sites in the Czech Republic, close to the borders with Austria, Germany, Poland, and Slovakia. Soluble and insoluble Pb forms were quantified in snow (vertical deposition), and rime (horizontal deposition). The objective was to compare Pb input fluxes into ecosystems via vertical and horizontal deposition, and to identify the residual Pb polution sources in an era of rapidly decreasing industrial pollution. Lead soluble in diluted HNO3 made up 96 % of total Pb deposition, with the remaining 4 % Pb bound mainly in silicates. Four times higher concentrations of soluble Pb in rime than in snow, and 1.6 times higher concentrations of insoluble Pb in rime than in snow were associated with slightly different Pb isotope ratios. On average, the 206Pb/207Pb ratios in rime were higher than those in snow. Higher 206Pb/207Pb ratios of insoluble Pb than in insoluble Pb may indicate an increasing role of geogenic Pb in recent atmospheric deposition. A distinct reversal to more radiogenic 206Pb/207Pb ratios in snow and rime in 2010, compared to literature data from rain-fed Shagnum peatlands (1800-2000 A.D.), documented a recent decrease in anthropogenic Pb in the atmosphere of Central Europe. Since the early 1980s, Pb concentrations in snow decreased 18 times in the rural south of the Czech Republic, but only twice in the industrial north of the Czech Republic. Isotope signatures indicated that Pb in today’s atmospheric deposition is mainly derived from Mesozoic ores mined/processed in southern Poland and coal combustion in the Czech Republic and Poland.JRC.G.II.6-Nuclear Safeguards and Forensic