Robert Anczkiewicz

The best approach for understanding the tectono-thermal evolution of a crustal level is through reconstructing its pressuretemperature-deformation-time ( P-T-D-t) evolution. Whereas P-T-D paths can be inferred from crystallization-deformation relationships, placing absolute time constraints on such paths remains challenging, especially because a link between major elementbearing index minerals and trace element-bearing geochronometers needs to be established. We present the example of medium-grade metasedimentary rocks (Orlica-Snieznik Dome, EuropeanVariscan Belt) for which results of Lu-Hf garnet and U-Th-Pb monazite dating are linked with prograde and retrograde stages of the P-T-D volution, respectively. On the macroscopic scale, a succession of three metamorphic foliations is recognized: initial subhorizontal S1, intermediate subvertical S2, and late subhorizontal S3. A garnet ±staurolite assemblage is ascribed to the S1 foliation, whereas the S2 fabric is associated with stauro...

The Dom Feliciano Belt in southern Brazil and Uruguay represents the western half of a Neoproterozoic orogenic belt located in the southern portion of the South Atlantic Neoproterozoic Orogenic System. Current interpretations are divided as to the nature of orogenesis in this belt, in part owing to lacking geochronological constraints. Metamorphosed and deformed supracrustal sequences of the Brusque Complex in the northern Dom Feliciano Belt, representing part of the orogenic foreland, record the onset and duration of crustal thickening. Structural analysis and pressure–temperature estimates indicate that the complex reached peak regional metamorphic conditions of 540–570°C and 5.5–6.7 kbar during thrusting and burial, consistent with orogenic metamorphism and early crustal thickening. Garnet–whole rock Lu–Hf and Sm–Nd isochron ages date this event to between circa 660–650 Ma. Ar–Ar dating of mica suggests thrust‐controlled exhumation and partial cooling by circa 635 Ma, and that localized deformation occurred into the late Ediacaran. Our results show that the orogenic foreland reached metamorphic conditions typical for crustal thickening 20–30 million years prior to the onset of massive magmatic activity in the hinterland. Such a delay is typical of hot, internal parts of orogens, which supports interpretations that hinterland magmatism in the northern Dom Feliciano Belt represents post‐collisional magmatism and not arc magmatism above a subduction zone. Instead, we suggest that orogenesis in the northern Dom Feliciano Belt was initiated by rift‐basin inversion driven by far‐field forces transmitted through the crust in an intracontinental rift or back‐arc rift setting.

This dataset was collected to investigate the tectono-metamorphic evolution of the Dom Feliciano Belt foreland. The dataset consists of whole-rock and mineral major element data, garnet-whole rock Lu-Hf and Sm-Nd isotope gechronology and garnet trace element data, monazite U-Pb geochronology and trace element data, and mica 40Ar/39Ar geochronology data. Whole-rock major element compositions were analysed at Bureau Veritas Mineral Laboratories in Vancouver, Canada, by inductively coupled plasma emission spectroscopy (ICP-ES), and the Czech Geological Survey, Prague, Czech Republic, by atomic absorption spectroscopy. Mineral major element compositions were analysed at the Faculty of Natural Sciences, Masaryk University, Czech Republic, and the Department of Geosciences, University of Oslo (UiO), Norway, by EMPA. Garnet─whole-rock Lu─Hf and Sm─Nd geochronology and trace element analysis was conducted at the Institute of Geological Sciences, Polish Academy of Sciences, Kraków Research C...

Metamorphic minerals in the Brusque Complex of the northern Dom Feliciano Belt, Brazil, provide new insights into the timing and mode of regional convergence, challenging a long-lived subduction-collision model for orogenesis. The key evidence for subduction is an extensive linear belt of granitic rocks (the Granite Belt) that intruded the length of the hinterland of the Dom Feliciano Belt between ~630─580 Ma, and that is inferred to represent arc magmatism above the subducting Adamastor Ocean prior to continental collision. The study area comprises supracrustal units of a foreland fold-and-thrust belt outcropping along the western edge of the symmetric Kaoko─Dom Feliciano orogenic system. The integrated study of primary metamorphic mineral assemblages and associated deformation fabrics support the interpretation of a fold-and-thrust belt environment, with early tectonic movement top-to-NW away from the hinterland. P─T estimates constrained by garnet compositions indicate peak metam...

In the absence of other indicators, the link between the growth of a specific zircon crystal (or part of it) and the eclogite-facies part of the P–T evolution of a rock is commonly validated using the analysis of its REE signature (e.g. Rubatto, 2002). The absence of an Eu anomaly and a flat HREE pattern are considered to reflect a growth in a plagioclase-free garnet-bearing assemblage, typical for the eclogite facies. The ages obtained using this approach can reveal, however, to be in conflict with other geological evidence. Using two eclogite samples from the south of the French Massif Central, we argue that this approach should be used with caution. (1) Zircon grains from an eclogite embedded in massive amphibolite in the Najac-Carmaux Klippe yield a well-constrained U/Pb age of 386.0 ± 1.2 Ma (MSWD = 1.5) consistent with the Lu/Hf age of 382.8±1.0 Ma (MSWD = 0.61) and the Sm/Nd age of 377.8 ± 1.1 Ma (MSWD = 1.4) obtained on garnet. Yet, chrondrite-normalized REE spectra of the d...

Vertical transhumance is a subsistence strategy typical of many mountain ranges including the European Alps. It remains unclear, however, when this form of landscape use started to be practised in the Alps [1], which became relevant also in the context of the discovery and societal role of the Neolithic Alpine Iceman (Ötzi). It was early on suggested that Ötzi may have been involved in some form of early transhumance [2, 3], which however has more recently been questioned on the basis of pollen found in animal dung at the Iceman’s discovery site [4].

... Coward, MP, and Butler, RW, 1985, Thrust tec-tonics and the deep structure of the PakistanHimalaya ... and Molnar, P., 1993, Cause and effect among thrust and normal faulting, anatectic melting and exhumation in the ... troalpine nappes, Switzerland): Geology, v. 20, p. 923–926. ...

We studied the petrographical characteristics and bulk chemical composition along with the age of detrital zircon grains from quartzites exposed in the western part of the Orlica-Śnieżnik dome in the Saxothuringian zone. Age spectra of detrital zircons were obtained by U–Pb laser ablation inductively coupled plasma mass spectrometry dating. The zircon ages define a few clusters of which the most numerous are Cambro-Ordovician and Neoproterozoic, and less frequent are Paleoproterozoic and Archean. A distinctive feature of the investigated samples is the lack of Mesoproterozoic zircon grains. The youngest age cluster documented in the investigated quartzites points to a Late Cambrian maximum depositional age and detritus derivation from erosion of Cambro-Ordovician metagranitoids. Bulk chemical composition of the quartzites indicates that they originated owing to erosion of granite within sedimentary basins developed on a passive continental margin. Presented data prove the similarity...

The Teschenite Association Rocks (TAR) in the Outer Western Carpathian (OWC) flysch form a classic suite of alkaline intrusions where teschenite and picrite were first defined. They represent continental intraplate volcanism that produced a wide range of melano- to mesocratic rocks emplaced during the Early Cretaceous rifting within the southern margin of the European Plate. Geochemical modelling indicates that they may be a product of ~2–5 % partial melting of the metasomatised, asthenospheric mantle. The variations in REE (low / heavy REE content, LaN/YbN = 11–34) are consistent with deep melting of garnet peridotite. Initial ε(Nd)i = 5.0–6.3 and ε(Hf)i = 4.9–10.0 preclude the significant mature crust involvement. Instead, a linear array formed by the 143Nd/144Nd and 176Hf/177Hf isotopic ratios points to a genesis from the mixed, HIMU–OIB source with the more depleted, MORB-type component. Mantle metasomatism was most likely caused by the Variscan subduction–collision processes as...

Linking mineral growth and time is required to unravel the evolution of metamorphic rocks. However, dating early metamorphic stages is a challenge due to subsequent retrograde overprinting. A fresh eclogite and a former eclogite retrogressed under amphibolite facies from the southern French Massif Central (Lévézou massif, Variscan belt) were investigated with a large panel of geochronometers (U–Pb in zircon, rutile and apatite, Lu–Hf and Sm–Nd in garnet) in a petrological context tightly constrained by petrographic observations, trace element analyses and phase equilibrium modelling. Both samples recorded similar HP conditions at 18–23 kbar and 680–800°C, whereas the retrogressed eclogite later equilibrated at 8–9·5 kbar and c.600°C. In the retrogressed sample, most of the zircon grains are characterized by negative Eu anomalies and HREE enrichment, and yield an Ordovician U–Pb date of 472·3 ± 1·7 Ma, interpreted as the emplacement age of the mafic protolith. In agreement with other...

Mobility of people and goods during the Upper Paleolithic has proven difficult to reconstruct given the relative rareness of remains. Nevertheless, archaeological contexts like the Late Pleistocene horizon of Borsuka Cave (Southern Poland) represent a unique opportunity to explore patterns of objects’ transportation across Central Europe. We investigated the origin of four ornaments made of European elk (Alces alces L.) incisors recovered at Borsuka Cave – the oldest known burial site in Poland, possibly a child grave. Laser-ablation plasma source mass spectrometric analyses of trace elements and Sr isotopic compositions revealed that one elk was roaming within a geologically uniform area while the others changed their pastures during their lifetimes. The non-local origin of the elk teeth is inferred from their exotic Sr isotopic compositions and the lack of evidence for the presence of elk in this territory during the Pleistocene. Instead, the elks’ Sr isotopic composition show goo...

<p>Ultra-high temperature (UHT) metamorphism is a thermal regime that can be attained by the lower continental crust in exceptional contexts and that is usually accompanied by fluid-absent dehydration melting. Such conditions are observed in the Gruf Complex, a 12 x 10 km migmatitic body located in the Central Alps, which is characterized by the presence of UHT granulitic schlieren and enclaves within migmatitic orthogneisses and charnockites. Two types of granulites, both with a massive and melanocratic texture, were investigated. The first granulite contains sapphirine, garnet, orthopyroxene, K-feldspar and biotite in the peak mineral assemblage, whereas the second type displays garnet, orthopyroxene, sillimanite and biotite. In both granulites, garnets are porphyroblastic and can reach up to 2 cm in size. These garnets are almost pure almandine-pyrope solid solutions and are zoned, showing pyrope-richer rims (Alm<sub>43-54</sub>Prp<sub>43-55</sub>Sps<sub>0-2</sub>Grs<sub>1-6</sub>) compared to cores (Alm<sub>47-62</sub>Prp<sub>32-48</sub>Sps<sub>0-3</sub>Grs<sub>2-9</sub>). A clear zoning is also observed in the rare earth elements (REE), with garnet cores showing the highest REE concentrations. Moreover, the porphyroblastic garnets are characterized by the presence of numerous melt inclusions (MI), which can be noticed both in garnet cores and rims. The MI occur as polycrystalline (nanogranitoids) and glassy inclusions, and dominantly display a peraluminous, rhyolitic composition, suggesting that they were originated, along with the host garnet, by incongruent, fluid-absent melting reactions during crustal anatexis. Lu-Hf ages obtained for the MI-bearing garnet cores of both granulites indicate that they formed at about 41 ± 4 Ma, which therefore can be interpreted as the time that crustal anatexis generated the UHT granulites. Considering the granulites in the context of the alpine framework, it is also inferred that UHT conditions in the lower crust were achieved as a consequence of asthenospheric upwelling, probably related to slab steepening or slab breakoff.</p>

<p>The Coastal Terrane of the Kaoko Belt in Namibia was originally defined as a Neoproterozoic arc terrane that originated outboard of the attenuated Congo Craton margin. Early (~650–630 Ma) igneous activity and high-grade metamorphism were interpreted as connected with subduction of the Adamastor Ocean and related arc magmatism. Protoliths of metasedimentary lithologies were interpreted as juvenile clastic sediments originating from the arc erosion. Later deformation (~580 Ma) was associated with lower amphibolite-facies conditions during thrusting over the Congo Craton margin.</p> <p>Our research, however, suggests different evolutionary scenario.  The structurally lowermost part of the metasedimentary complex contains amphibolites and orthogneisses with U–Pb zircon ages between ~820–785 Ma, interpreted as metamorphosed syn-sedimentary bimodal volcanics. Detrital zircon ages from associated metamorphosed clastic sediments show identical patterns as observed in the metasedimentary cover of the underlying Congo Craton. Towards the structural hanging wall, the metasediments are devoid of metavolcanic rocks, and their detrital zircon age spectra are comparable with those from flysch sediments in the eastern, less metamorphosed parts of the Kaoko Belt.</p> <p>The structurally lowermost part of the Coastal Terrane shows signs of partial melting broadly coeval with intrusion of ~650 Ma (U–Pb zircon) granitic–dioritic/gabbroic rocks. The temperature and depth of this migmatization event remains unconstrained, because the original mineral assemblages were overprinted during thrusting over the Congo Craton margin.</p> <p>The thrusting period is characterized by solid-state reworking and partial retrogression of the migmatites in the lower part, and by pervasive metamorphism in the upper part, of the metasedimentary complex. Lu–Hf age (583 ± 2 Ma) of garnet from reworked migmatite shows that the garnet-bearing mineral assemblage represents conditions of thrusting, which were determined at ~660–670°C and 5.5–6 kbar. The ~580 Ma (and beyond) period of deformation started with development of flat-lying metamorphic fabric, later overprinted by folds with step axial planes, steep cleavage and isolated shear zones with general N–S to NNW–SSE trend. The associated intrusions show steep magmatic fabric, which transits into solid-state deformation in bodies close to the base of the Coastal Terrane.</p> <p>Rather than an arc, the Coastal Terrane probably represents the inner part of an early Neoproterozoic rift. This interpretation is supported by the zircon provenance data and the presence and age of the bimodal volcanic rocks. The early, ~650–630 Ma magmatic activity and migmatitization coincides with the early period of rift inversion that took place along the western edge of the rift system in the Dom Feliciano Belt (Brazil and Uruguay). At this period, the former rift centre was established as the high-grade hinterland system of the developing Kaoko–Dom Feliciano–Gariep orogen. Inversion of the eastern rift edge started at ~580 Ma, as recorded in the Coastal Terrane, and continued up to ~550 Ma, which is the…

This paper reports evidence of Pu isotopes in the lower part of the troposphere of Central Europe. The data were obtained based on atmospheric aerosol fraction samples collected from four places in three countries (participating in the informal European network known as the Ring of Five (Ro5)) forming a cell with a surface area of about 200,000km(2). We compared our original data sets from Krakow (Poland, 1990-2007) and Bialystok (Poland, 1991-2007) with the results from two other locations, Prague (Czech Republic; 1997-2004) and Braunschweig (Germany; 1990-2003) to find time evolution of the Pu isotopes. The levels of the activity concentration for (238)Pu and for ((239+240))Pu were estimated to be a few and some tens of nBqm(-3), respectively. However, we also noted some results were much higher (even about 70 times higher) than the average concentration of (238)Pu in the atmosphere. The achieved complex data sets were used to test a new approach to the problem of solving mixing i...