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Metamorphic Evolution of Chloritoid-Bearing Micaschist from the variscan Elstergebirge: Evidences for Stacking of High-Pressure Rocks in the Saxothuringian Zone of Central Europe

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Journal of Earth Science 2020年第3期31卷 425-446页

作者： Gelareh Rahimi Hans-Joachim Massonne Fakultat Chemie Universitat Stuttgart70569 StuttgartGermany School of Earth Sciences China University of GeosciencesWuhan 430074China

A chloritoid-garnet-bearing micaschist from the southern part of the Elstergebirge was studied to better understand the variscan orogenic evolution in the Saxothuringian zone of the northwestern Bohemian *** on the textural relations and compositions of minerals,especially of zoned garnet and potassic white mica,a P-T path was reconstructed using contoured P-T *** U-Th-Pb dating of monazite in the micaschist was undertaken with the electron *** micaschist experienced P-T conditions along a clockwise path between 16 kbar at 510℃and 5 kbar at 555℃followed by isobaric heating to about 600℃.Monazite ages range between 315 and 480 Ma with the most prominent maxima and side maxima at 346.0±1.1(2σ),357.3±2.3,and 368.3±1.7 *** older than 380 Ma were related to detrital monazite pointing to a Devonian sedimentary *** ages around 325 Ma were assigned to the isobaric heating by nearby post-tectonic *** high-pressure event,being the result of the collision of Laurussia and Gondwana after closure of the Rheic Ocean,occurred in the Late *** exhumation to 15-20 km(5 kbar)ended probably in the Early *** high-pressure micaschists from the Fichtelgebirge to the Erzgebirge crystalline complexes are suggested to represent a single nappe within a metamorphic nappe *** nappe is composed of metasedimentary slices,which experienced different peak pressures rather than representing a coherent crustal section.

关键词： Saxothuringian micaschist chloritoid garnet monazite dating variscan P-T path

Zircon SHRIMP U-Pb Dating and Geochemical Characteristics of Late variscan Granites of the Daitongshan Copper Deposit and Lamahanshan Polymetallic-Silver Deposit, Southern Daxing'anling, China

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Journal of Earth Science 2013年第5期24卷 772-795页

作者：周振华李泊洋王挨顺武新丽欧阳荷根冯佳睿 MRL Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral ResourcesChinese Academy of Geological Sciences No. 10 Institute of Geological Exploration Inner Mongolia Bureau of Geology & Mineral Resources Geological Survey Institute of Inner Mongolia School of Earth Science and Mineral Resources China University of Geosciences Research Institute of Petroleum Exploration and Development PetroChina

Daxing＇anling （大兴安岭） area is one of the regions that Phanerozoic granites are extremely developed in NW China. At present, the Hercynian granitoid research lags behind the Mesozoic granitoid research. In this article, we have taken systematic petrochemistry and geochronology researches on the Hercynian granitoids in Daitongshan （代铜山） copper deposit and Lamahanshan （喇嘛罕山） silver poly- metallic deposit, which were located at southern section of Daxing＇anling metallogenic belt. Zircon SHRIMP U-Pb dating results show that, the granite aplites in Daitongshan and the gneissic granites inLamahanshan were formed at （265±5）-（268±9） Ma and （252±2）-（252.6±3.4） Ma, respectively, which were both the products of late Herynian tectonic-magmatic events. Samples from Lama- hanshan are characterized by high SiO2 （69.72 wt.%-74.65 wt.%）, high potassium （3.53 wt.%-4.55 wt.%） and low P205 （0.03 wt.%0.12 wt.%）, aluminum saturation index （A/CNK） range from 0.95 to 0.98, Rb, Nd and K are en- riched, whereas the elements such as Nb, Ta, P and Ti are depleted, which belong to I-type grani- toids. Characteristics of samples from Daitong- shan are similar to H-type granitoids. The magmasource may be mostly originated from the lithospheric mantle component which were transformated or affected by the subduction components, and its formation may be closely related with the subduction and orogenesis of the Paleo-Asian Ocean.

关键词： SHRIMP U-Pb dating geochemistry variscan Daitongshan copper deposit Lamahan-shan silver polymetallic deposit Daxing'anling.

How many subductions in the variscan orogeny?Insights from numerical models

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Geoscience Frontiers 2020年第3期11卷 1025-1052页

作者： Alessandro Regorda Jean-Marc Lardeaux Manuel Roda Anna Maria Marotta Maria Iole Spalla Universita Degli Studi di Milano Dipartimento di Scienze Della Terra'A.Desio’Via Mangiagalli 34I-20133MilanoItaly Universite Nice Sophia-Antipolis UMR Geoazur250 Rue A.EinsteinSophia-Antipolis06560ValbonneFrance

We developed a 2 D numerical model to simulate the evolution of two superposed ocean-continent-ocean subduction cycles with opposite vergence,both followed by continental collision,aiming to better understand the evolution of the variscan *** models with different velocities of the first oceanic subduction have been *** differences in the thermo-mechanical evolution between the first subduction,which activates in an unperturbed system,and the second subduction,characterised by an opposite vergence,have been enlighten,in particular regarding the temperature in the mantle wedge and in the interior of the *** and temperature(P-T) conditions predicted by one cycle and two cycles models have been compared with natural P-T estimates of the variscan metamorphism from the Alps and from the French Massif Central(FMC).The comparative analysis supports that a slow and hot subduction well reproduces the P-T conditions compatible with data from the FMC,while P-T conditions compatible with data of variscan metamorphism from the Alps can be reproduced by either a cold or hot oceanic subduction *** the agreement of both double and single subduction models with natural P-T estimates,we observed that polycyclic models better describe the evolution of the variscan orogeny.

关键词： Alps Double subduction French Massif Central Numerical modelling variscan orogeny

Garnet Sm-Nd and U-Pb systems: A case study of a granulite from the European variscan belt

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Chinese Science Bulletin 2002年第15期47卷 1284-1288页

作者： CHEN FukunInstitut fur Mineralogie, Petrologie und Geochemie, Universitat Tubingen, 72074 Tubingen, Germany Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China Institut für Mineralogie Petrologie und Geochemie Universität Tübingen Tübingen Germany Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China

This study presents zircon and garnet ages of a mafic granulite from the high-grade variscan basement of the Black Forest, Germany and discuss isotope closure temperature of garnet Sm-Nd and U-Pb systems. Zircon grains yield 207Pb/206Pb ages between -340 and -414 Ma by the U-Pb and evaporation methods. In contract, garnet dating gives Sm-Nd and Pb-Pb isochron ages of (398±3) Ma and (411±14) Ma, respectively, which are older than most of zircon ages. These data imply that most of zircons lost radiogenic Pb, probably due to metamictization or recrystallisa-tion during the granulite-facies metamorphism (-800°C) at -340 Ma. Garnet Sm-Nd and U-Pb systems preserve chronological information of pro-grade metamorphism, probably profiting from a fluid-absence metamorphic environment. These results demonstrate that garnet mineral can be a better candidate than zircon mineral to date high-grade metamorphism by the U-Pb and Sm-Nd methods in some cases.

关键词： variscan granulite garnet Sm-Nd U-Pb.

Garnet Sm-Nd and U-Pb systems:A case study of a granulite from the European variscan belt

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Garnet Sm-Nd and U-Pb systems:A case study of a granulite fr...

中国科学院地质与地球物理研究所2002学术年会

作者： CHEN Fukun Institut f(?)r Mineralogie,Petrologie und Geochemie,Universit(a|¨)t T(u|¨)bingen,72074 T(u|¨)bingen,Germany Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China

This study presents zircon and garnet ages of a mafic granulite from the high-grade variscan basement of the Black Forest,Germany and discuss isotope closure temperature of garnet Sm-Nd and U-Pb *** grains yield Pb/ Pb ages between～340 Ma and～414 Ma by the U-Pb and evaporation *** contract,garnet dating gives Sm-Nd and Pb-Pb isochron ages of 398±3 Ma and 411±14 Ma,respectively,which are older than most of zircon *** data imply that most of zircons lost radiogenic Pb,probably due to metamictization or recrystallisation during the granulite-facies metamorphism(～800℃) at～340 *** Sm-Nd and U-Pb systems preserve chronological information of pro-grade metamorphism,probably profiting from a fluid-absence metamorphic *** results demonstrate that garnet mineral can be a better candidate than zircon mineral to date high-grade metamorphism by the U-Pb and Sm-Nd methods in some cases.

关键词： variscan granulite garnet Sm-Nd U-Pb

Polymetamorphism of the variscan basement of the Moldanubian Black Forest(Germany)documented in zircon and garnet minerals from gneisses

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Polymetamorphism of the Variscan basement of the Moldanubian...

中国科学院地质与地球物理研究所2002学术年会

作者： CHEN Fukun Institut f(u|¨)r Mineralogie,Petrologie und Geochemie,Universit(a|¨)t T(u|¨)bingen,72074 T(u|¨)bingen,Germany Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China

High-grade metamorphic variscan basement is exposed in the Moldanubian zone of the Black Forest(BF),being the internal zone of the European variscan *** grains from K-rich felsic orthogneisses and an anatectic paragneiss in the Moldanubian Black Forest demonstrate a multi-stage crystallization at～600 Ma,～480 Ma,～400-380 Ma,and～350 *** last three stages of crystallization probably represent metamorphic overprint during pre-variscan and variscan metamorphism. Using stepwise leaching procedures,garnet minerals from felsic orthogneisses as well as paragneisses in the Moldanubian Black Forest yielded Early Carboniferous Sm-Nd ages(～330 Ma - 340 Ma),which are consistent with the well-constrained variscan HT metamorphic event,and Early Palaeozoic(～480 Ma) to Devonian(～400-370 Ma) Pb-Pb *** of growth time for zircon and garnet minerals at Early Palaeozoic is interpreted as dating a metamorphic *** garnet data demonstrate that the Moldanubian BF basement underwent at least two metamorphic events during the Early Palaeozoic and Early *** the variscan HT metamorphism, the Sm-Nd system of garnet was disturbed,but not the U-Pb system,implying the peak metamorphic temperature was lower than～800℃.

关键词： variscan Moldanubian Black Forest zircon and garnet ages metamorphism

Zircon and titanite geochronology of the F(u|¨)rstenstein granite massif,Bavarian Forest,NW Bohemian Massif:Pulses of the late variscan magmatic activity

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Zircon and titanite geochronology of the F(u|¨)rstenstein g...

中国科学院地质与地球物理研究所2004学术年会

作者： WOLFGANG SIEBEL Institut fr Geowissenschaften

The F(u|¨)rstenstein granite massif is the largest late variscan granitoid body exposed in the Moldanubian basement of the Bavarian *** granite massif comprises different rock types,ranging from diorite to granite in *** study provides precise zircon and titanite ages,obtained by the U-Pb isotopic dilution and Pb-Pb evaporation methods,and Nd-Sr isotopic data on this *** dating constrains an intrusive sequence as following:Dioritic rocks crystallised about 334 to 332 Ma ago, earlier than the high-temperature peak stage of the variscan metamorphism of the Moldanubian basement(325 to 320 Ma) in the Bavarian *** medium- to coarse-grained Tittling granite was emplaced about 10 Ma later,between 324 and 321 Ma,while the medium-grained Eberhardsreuth granite crystallised between 316 and 312 Ma,contemporaneously with the coarse-grained porphyritic Saldenburg *** from the dioritic rocks give U-Pb ages of about 321±4 Ma,indicating thermal resetting or crystallisation due to the intrusion of the Tittling *** diorites have initialε values of -1.3 to -2.9 and relatively low initial Sr/Sr ratios of 0.7056 to 0.7067,which suggest mantle contribution to melts or melting of young mafic lower *** granites have similar initialε values of -3.6 to -4.1 but show some variation in their Sr isotopic composition(initial Sr/Sr ratios of 0.7063 to 0.7074),probably indicating the involvement of crustal material in their genesis.

关键词： Bavarian Forest Fiirstenstein variscan granite zircon age

Geochemical and isotopic composition and inherited zircon ages as evidence for lower crustal origin of two variscan S-type granites in the NW Bohemian massif

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Geochemical and isotopic composition and inherited zircon ag...

中国科学院地质与地球物理研究所2003学术年会

作者： W.Siebel M.Satir Institut für Geowissenschaften Universitt TübingenWilhelmstraβe 5672074 TübingenGermany

Geochemical and Nd-Sr isotopic compositions and U-Pb zircon ages of two variscan granites(Neunburg and Oberviechtach) from southern Oberpfalz,NW Bohemian massif,have been investigated in order to place constraints on their formation and on the crustal reworking. Both granites exhibit similar mineralogical,chemical and isotopic *** have peraluminous compositions(A/CNK ratios 1.2-1.3) and display high K

关键词： Moldanubian Nd-Sr isotopes S-type granite variscan Zircon age

Lead isotope evolution of the Central European upper mantle:Constraints from the Bohemian Massif

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Geoscience Frontiers 2020年第3期11卷 925-942页

作者： Simona Krmíckova Lukas Krmícek Rolf L.Romer Jaromír Ulrych Department of Geological Sciences Faculty of ScienceMasaryk UniversityKotlarska 2CZ-61137BrnoCzech Republic Institute of Geology of the Czech Academy of Sciences Rozvojova 269CZ-16502Prague 6Czech Republic Brno University of Technology Faculty of Civil EngineeringAdMaS CentreVeverí95CZ-60200BrnoCzech Republic Deutsches GeoForschungsZentrum GFZ TelegrafenbergD-14473PotsdamGermany

The Pb isotope composition of the upper mantle beneath Central Europe is heterogeneous due to the subduction of regionally contrasting material during the variscan and Alpine *** variscan to Cenozoic mantlederived melts allow mapping this heterogeneity on a regional scale for the last ca.340 *** Cretaceous and Cenozoic anorogenic magmatic rocks of the Bohemian Massif(lamprophyres,volcanic rocks of basanite/tephrite and trachyte/phonolite series) concentrate mostly in the Eger *** ultramafic lamprophyres yielded the most radiogenic Pb isotope signatures reflecting a maximum contribution from metasomatised lithospheric mantle,whereas Tertiary alkaline lamprophyres originated from mantle with less radiogenic ^(206)Pb/^(204)b ratios suggesting a more substantial modification of lithospheric source by interaction with asthenosphericderived *** volcanic rocks of the basanite/tephrite and trachyte/phonolite series define a linear mixing trend between these components,indicating dilution of the initial lithospheric mantle signature by upwelling asthenosphere during *** Pb isotope composition of Late Cretaceous and Cenozoic magmatic rocks of the Bohemian Massif follows the same Pb growth curve as variscan orogenic lamprophyres and lamproites that formed during the collision between Laurussia,Gondwana,and associated *** implies that the crustal Pb signature in the post-variscan mantle is repeatedly sampled by younger anorogenic *** Cenozoic mantle-derived rocks of Central Europe show similar Pb isotope ranges as the Bohemian Massif.

关键词： Lead isotopes Lamprophyres Volcanic rocks Mantle components Bohemian massif variscan orogeny