Lu–Hf geochronology and trace element distribution in garnet: Implications for uplift and exhumation of ultra-high pressure granulites in the Sudetes, SW Poland     

Robert Anczkiewicz  Jacek Szczepa&#x;ski  Stanis&#x;aw Mazur  Craig Storey  Quentin Crowley  Igor M. Villa  Matthew F. Thirlwall  Teresa E. Jeffries 《Lithos》2007,95(3-4):363-380

Combining Lu–Hf garnet geochronology with in situ trace element analyses in garnet allowed us to gain new insight into the metamorphic evolution of UHP–UHT rocks in the Stary Gierałtów region, in the Polish Sudetes. Prograde garnet growth recorded by Rayleigh-type heavy REE (HREE) zoning in the felsic granulites indicates that the obtained 386.6 ± 4.9 Ma Lu–Hf age represents the time of garnet crystallization on a prograde UHP metamorphic path. The surrounding rocks were metamorphosed at the same time as indicated by 381.2 ± 6.7 Ma Sm–Nd garnet age obtained for the mid-crustal metapelites. The second metamorphic episode, which affected most of the lower crust in the Orlica–Śnieżnik Massif (OSM) occurred at ca. 340 Ma as determined by U–Pb zircon and Sm–Nd garnet dating of granulites in this and previous studies is interpreted as a high temperature event, which took place on a retrograde path.

Trace element distribution in garnets from the layered granulites showed significant differences in distribution of medium and HREE in garnets from mafic and felsic protoliths over the course of the metamorphic evolution. This had strong impact on the isotopic dating results and led to “decoupling” of the Sm–Nd and Lu–Hf clocks, which recorded timing of the two different metamorphic episodes separated by as much as 40 Ma. Moreover, the preservation of the HREE growth zonation profile in garnets from the felsic granulites whose minimum metamorphic temperature was established at 900 °C implies that the Lu–Hf system under relatively dry conditions does not undergo significant diffusional re-equilibration even at such extreme temperatures and therefore it sill provides the age of prograde garnet growth. Under hydrous conditions, at least some resetting will take place, as documented by the partially relaxed HREE zonation profile in the amphibolitised mafic granulite, which yielded a 10 Ma younger age. The HREE distribution study appeared to be a particularly valuable and essential tool, which allowed us to distinguish garnet growth from post-growth complexities and hence, provide improved age interpretation. Medium REE, on the other hand, did not show any obvious correlation with the isotopic signature of garnet.

Two distinct metamorphic episodes recorded in the Stary Gierałtów region show that buoyancy-driven uplift of UHP rocks can be arrested at the base of a continental crust if not supported by any additional force. In our case study, the UHP rocks would have never reached the surface if their uplift had not been resumed after a long pause under a different tectonic regime. The multistage, discontinuous uplift revealed by the UHP rocks of the OSM provides a new scenario for the exhumation of continental crust from mantle depths distinct from the fast-track exhumation histories recognized in UHP terranes elsewhere.  相似文献   

Mantle heat flow and geotherms for major tectonic units in central Europe     

Jacek Majorowicz 《Pure and Applied Geophysics》1978,117(1-2):109-123

The results of seismic measurements along the deep seismic sounding profile VII and terrestrial heat flow measurements used for construction of heat generation models for the crust in the Paleozoic Platform region, the Sudetic Mountains (Variscan Internides) and the European Precambrian Platform show considerable differences in mantle heat flow and temperatures. At the base of the crust variations from 440–510°C in the models of Precambrian Platform to 700–820°C for the Paleozoic Platform and the Variscan Internides (Sudets) are found. These differences are associated with considerable mantle heat flow variations.The calculated models show mantle heat flow of about 8.4–12.6 mW m^–2 for the Precambrian Platform and 31 mW m^–2 to 40.2 mW m^–2 for Paleozoic orogenic areas. The heat flow contribution originating from crustal radioactivity is almost the same for the different tectonic units (from 33.5 mW m^–2 to 37.6 mW m^–2). Considerable physical differences in the lower crust and upper mantle between the Precambrian Platform and the adjacent areas, produced by lateral temperature variations, could be expected. On the basis of carbon ratio data it can be concluded that the Carboniferous paleogeothermal gradient was much lower in the Precambrian Platform area than in the Paleozoic Platform region.  相似文献   

5-alkylsalicylaldoximes as collectors in flotation of sphalerite,smithsonite and dolomite in a Hallimond tube     

Tadeusz Kiersznicki  Jacek Majewski  Jan Mzyk 《International Journal of Mineral Processing》1981,7(4):311-318

Flotation tests for sphalerite, smithsonite and dolomite were carried out in a Hallimond tube at various pH values and two concentrations of collector.Adsorption of 5-alkylsalicylaldoximes on the surface of minerals was examined and isotherms for 5-butylsalicylaldoxime plotted.It was shown that sorption intensity of 5-alkylsalicylaldoximes on the surface of minerals decreased in the order: smithsonite, sphalerite and dolomite.Relationship between length of aliphatic chain and collecting activity of 5-alkylsalicylaldoximes was investigated in microflotation tests in a Hallimond tube.5-Propylsalicylaldoxime proved to have the best selectivity in flotation for the range of parameters studied, taking the difference in flotation rates of smithsonite and dolomite as a criterion.It was found that modifications of pH value resulted in changes in both adsorption and flotation.  相似文献   

Protoplanetary dynamics – I. Dynamical modes of isothermal protoplanets     

B. Pe&#;nik †  G. Wuchterl ‡ 《Monthly notices of the Royal Astronomical Society》2007,381(2):640-646

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From Cadomian arc to Ordovician passive margin: geochemical records preserved in metasedimentary successions of the Orlica-Śnieżnik Dome in SW Poland     

Jacek Szczepański  Sławomir Ilnicki 《International Journal of Earth Sciences》2014,103(3):627-647

The chemical composition of metamorphosed siliciclastic rocks in the Orlica-?nie?nik Dome (Bohemian Massif) identifies the main sources for the Neoproterozoic [the M?ynowiec Formation (MF)], Early Cambrian [the Stronie Formation (SF)] and Late Cambrian/Early Ordovician [the Goszów quartzites (GQ)] sediments. The MF developed from erosion of a Cadomian magmatic arc along the northern Gondwana margin. The variegated SF, with supra-subduction affinities, shows chemical characteristics pointing to erosion of the freshly exhumed Cadomian orogen and detritus deposition in the back-arc basin. The very different chemical features of the GQ indicate deposition in a basin sited on a passive continental margin. The explanation proposed for the observed changes in chemical composition involves three main stages: (1) The pre ~540 Ma evolution of an active continental margin and related back-arc basin ceased with the collision and accretion of the magmatic arc to the Gondwana margin; (2) Early Cambrian rift to drift transition (540–500 Ma) and development of a depositional basin filled with detritus derived from remnants of the magmatic arc; (3) Peri-Gondwana break-up leading to the formation of shallow-water passive margin depositional basins filled with quartz-rich detritus resembling Early Ordovician Armorican quartzites known from other parts of the Variscan Belt.  相似文献   

Reply to a comment in G. Meinhold “Geochemical discrimination of rutile from the Belomorian Mobil Belt”     

S. G. Skublov  T. Zack  A. V. Berezin  A. E. Mel’nik  N. G. Rizvanova 《Geochemistry International》2014,52(4):335-335

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Multistage Svecofennian metamorphism: Evidence from the composition and U-Pb age of titanite from eclogites of the Belomorian Mobile Belt     

S. G. Skublov  A. V. Berezin  N. G. Rizvanova  A. E. Mel’nik  T. A. Myskova 《Petrology》2014,22(4):381-388

The first geochemical study of titanite from eclogites and associated rocks of the Belomorian Mobile Belt (BMB) by secondary ion mass spectrometry made it possible to establish the compositional features of this mineral in the garnet-bearing and garnet-free assemblages. Titanite from garnet-bearing assemblages is characterized by upward convex REE pattern and lowered HREE content relative to LREE, as well as the average Gd_N/Yb_N ratio around 16.5. Titanite from metaultrabasic rock inherits the specific features of the host rock, which should be taken into account when comparing with titanite from metagabbro. Results of U-Pb (TIMS) dating of titanite confirms the identification of the early and late stages of the Svecofennian metamorphism in the studied areas of BMB: early metamorphism with the peak eclogite facies conditions at around 1900 Ma, retrograde amphibolite facies metamorphism at 1870–1880 Ma, and late allochemical metamorphism accompanied by the pegmatite formation with an age of 1840 Ma.  相似文献   

Galaxy–galaxy weak lensing in the Sloan Digital Sky Survey: intrinsic alignments and shear calibration errors     

Christopher M. Hirata  Rachel Mandelbaum  Uro&#; Seljak  Jacek Guzik  Nikhil Padmanabhan  Cullen Blake  Jonathan Brinkmann  Tamas Budávari  rew Connolly  Istvan Csabai  Ryan Scranton  Alexander S. Szalay 《Monthly notices of the Royal Astronomical Society》2004,353(2):529-549

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Tracing exhumation record in high-pressure micaschists: A new tectonometamorphic model of the evolution of the eastern part of the Fore Sudetic Block,Kamieniec Metamorphic Belt,NE Bohemian Massif,SW Poland     

Jacek Szczepański  Marcin Goleń 《Chemie der Erde / Geochemistry》2022,82(1):125859

The Kamieniec Metamorphic Belt comprises a volcano-sedimentary succession exposed within a collision zone between the Saxothuringian and Brunovistulian crustal domains of the European Variscides. The studied rocks recorded two metamorphic episodes. The first episode, M₁, occurred at conditions of c. 485 ± 25 °C and 18 ± 1.8 kbar related to burial within a subduction zone. The subsequent episode, M₂, was linked to the final phases of exhumation to mid-crustal level, associated with pressure and temperature (P–T) conditions ranging from c. 520 ± 26 °C and 6 ± 0.6 kbar through 555 ± 28 °C and 7 kbar ± 0.7 to ~590 ± 30 °C and 3–4 ± 0.4 kbar. The documented deformation record is ascribed to three events, D₁ to D₃, interpreted as related to the burial and subsequent exhumation of the Kamieniec Metamorphic Belt. The D₁ event must have witnessed the subduction of the Kamieniec Metamorphic Belt rock succession whereas the D₂ event was associated with the exhumation and folding of the Kamieniec Metamorphic Belt in an E-W-directed shortening regime. A subsequent folding related to the D₂ event was initiated at HP conditions, however, the planar fabric produced during a late stage of the D₂ event, defined by a low-pressure mineral assemblage M₂, indicates that the D₂ final stage was synchronous with the onset of the M₂ episode. Consequently, the entire D₂ event seems to have been associated with the exhumation of the Kamieniec Metamorphic Belt to mid crustal level. The third deformation event D₃, synchronous with the M₂ episode, marked the last stage of the exhumation, and was linked to emplacement of granitoid veins and lenses. The latter resulted in heating and rheological weakening of the entire rock succession and in the formation of non-coaxial shear zones.  相似文献   

Accounting for Galileo–GPS inter-system biases in precise satellite positioning     

Jacek Paziewski  Pawel Wielgosz 《Journal of Geodesy》2015,89(1):81-93

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