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  • 1
    Call number: 9/M 07.0421(405)
    In: Geological Society special publication
    Type of Medium: Monograph available for loan
    Pages: 406 S. : farb. Ill., graph. Darst., Kt.
    ISBN: 9781862396586
    Series Statement: Geological Society special publication 405
    Classification: A.3.4.
    Location: Reading room
    Branch Library: GFZ Library
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  • 2
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    In:  Geological Society Special Publication 231: 315-324.
    Publication Date: 2007-10-08
    Description: The mechanism for structural damage during incipient slip on joints within the Melechov Granite, Czech Republic, changes with the misalignment of the joint's mesotopography, largely a plumose surface morphology. Prior to slip, the joint surfaces are well mated so that contact area is organized on a microscopic scale. During the first phase of slip, diffusion-mass transfer is the active deformation mechanism between the sliding surfaces of the joints, as indicated by the extensive growth of crystal-fibre lineations characteristic of slickenside surfaces. After slip of the order of 1 cm or more, the mesotopography becomes mismatched and the contact area is reorganized to form indentation pits aligned on the ridges of hackle plumes. Indentation pits, that are testimony to a brittle process, are generated by the excavation of Hertzian ring cracks that propagate under contact loading of a brittle substrate. The depth of the indentation pits increases with contact width, suggesting that indentation creep is active. Following indentation along Hertzian ring cracks the slip mechanism transforms to a frictional abrasion. The distribution of indentation track lengths is consistent with laboratory wear grooves generated during earthquake-like stick-slip sliding. The elliptical shape of the indentation pits indicates a gradual decrease in contact area, a process that is consistent with a slip-weakening mechanism during a stick-slip cycle.
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  • 3
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract The three deformation phases inferred from the detailed structural analysis of the Cesky Krumlov Varied Group record the Hercynian development of the Southern Moldanubian of the Bohemian Massif. The deformation is related to the NW-SE thrusting of the large crustal units including granulites. The formation of the NS and NW-SE trending shear zones is connected with the thrust movement. The structural development begins with F1 isoclinal fold formation, that could originate in unmetamorphosed sediments. In the final stage, they were strongly flattened and B1 boudinage developed in the rocks. Aplite dykes and migmatitization of paragneisses occurred at the same time the rocks were metamorphosed. The D2 deformational phase was produced by the simple shear deformation of the unit and folds of various styles around rigid inclusions and the strike-slip shear zone near the boundary of the granulite and the Varied Group were formed. The F1 and F2 folds are parallel with the stretching and mineral lineation indicating a NS to NW-SE direction of the thrusting. The youngest deformation is characterized by spectacular boudinage and by folding of the vertically oriented planes.
    Abstract: Résumé L'étude structurale détaillée de la Série Variée du Moldanubien méridional dans le Massif de Bohème a permis de distinguer trois phases de déformation dans le développement tectonique varisque. Cette déformation est liée au charriage, du Nord-Ouest vers le Sud-Est, de grandes unités crustales comportant des granulites. La genèse de zones de cisaillement plus jeunes, d'orientation N-S et NW-SE peut Être liée au mÊme processus de charriage. Le développement structural commence avec des plis isoclinaux F1 engendrés vraisemblablement dans les sédiments non métamorphisés. Au stade final de leur formation, ils ont été très aplatis et un boudinage B1 est apparu. L'intrusion de filons d'aplite et la migmatitisation des paragneisses sont contemporaines du métamorphisme. La deuxième déformation D2 a été le fait d'un cisaillement simple; à ce moment se sont formés des plis de style tectonique très variés, localisés fréquemment autour d'inclusions rigides. De cette étape date également le décrochement ductile entre les granulites et la Série Variée. Les plis F1 et F2 sont parallèles à la linéation d'étirement (linéation minérale) qui indique la direction N-S à NW-SE du charriage. La déformation la plus jeune comporte un boudinage spectaculaire et le plissement des plans d'attitude verticale.
    Notes: Zusammenfassung Drei Deformationsphasen der variszischen tektonischen Entwicklung sind in der Bunten Gruppe des südlichen Moldanubikums des Böhmischen Massivs enthalten. Die Deformation ist mit der von NW nach SE orientierten überschiebung von gro\en Krusteneinheiten mit Granuliten verbunden. Die Entstehung von jüngeren N-S und NW-SE verlaufenden Scherzonen kann auf die überschiebungsbewegung bezogen werden. Die Strukturentwicklung beginnt mit F1 isoklinalen Falten, die wahrscheinlich den nichtmetamorphisierten Sedimenten aufgeprägt wurden. Während der Abschlu\phase der Formung wurden sie stark geplättet und es entstand die B1 Boudinage. Die Aplitgänge, Migmatitisation der Paragneisse und Metamorphose der Gesteine sind gleichzeitig. Die D2 Deformationsphase wurde durch einfache Scherung der Einheit hervorgerufen und es entstanden Falten verschiedenen tektonischen Stils in der Umgebung starrer Einschlüsse und die Blattverschiebung an der Grenze von Granulit und Bunter Gruppe. Die F1 und F2 Falten liegen parallel zur Streckungslmeation und überschiebungsrichtung ab. Die jüngste Deformation ist charakterisiert durch eine spektakuläre Boudinage und Faltung der senkrecht stehenden Flächen.
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  • 4
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract Three tectonometamorphic events have been recognized in the crystalline rocks of the Catherine mantled gneiss Dome (CD) in the central Erzgebirge. The first tectonometamorphic event is characterized by the acquisition of a S1–S2 metamorphic foliation, development of F2 isoclinal partly syn-schistose folding and intrusion of early synkinematic granites. P-T conditions correspond to higher amphibolite facies metamorphism and culminate in anatexis. A diapiric intrusion of Cambro-Ordovician muscovite-biotite porphyritic granite has verticalized the S2 foliation and is responsible for the genesis of the classical mantled gneiss dome. Oblate strain and orthorhombic diffuse c-axis patterns are typical of the marginal parts of the dome. The whole rock sequence was subsequently affected by westward oriented heterogeneous Variscan ductile shearing under the conditions reaching amphibolite fades. A strongly non-coaxial deformation has partly overprinted the earlier fabrics in anatectic orthogneiss and produced augen-orthogneiss from porphyritic granite in the central part of the CD dome. Prolate to plane strain fabrics, oblique quartz c-axis patterns and a widespread occurrence of S-C fabrics are the most characteristic features of this phase.
    Abstract: Résumé Trois événements tectono-métamorphiques ont été reconnus dans les roches cristallines du dôme de gneiss coiffé de Catherine (Erzgebirge oriental). Le premier de ces événements est caractérisé par l'acquisition d'une foliation S1–2, le développement de plis isoclinaux F2 partiellement synschisteux et l'intrusion de granites syntectoniques précoces. Les conditions (P, T) correspondent au facies supérieur des amphibolites et atteignent l'anatexie. L'intrusion diapirique d'un granite à deux micas cambro-ordovicien a verticalisé la foliation S1–2 et est responsable de la genèse du dôme de gneiss coiffé. Une déformation par aplatissement et des fabriques orthorhombiques diffuses des axes c du quartz caractérisent les zones marginales du dôme. L'ensemble des terrains a été ensuite affecté par un cisaillement ductile varisque hétérogène à vergence ouest, dans les conditions du facies inférieur des amphibolites. Une déformation fortement noncoaxiale a transposé partiellement les structures précoces des orthogneiss anatectiques et a transformé les granites porphyriques de la partie centrale du dôme de Catherine en orthogneiss oeillés. Cette phase est caractérisée par des fabriques obliques pour les axes c du quartz et par de fréquentes structures s-c.
    Notes: Zusammenfassung Im Kristallin des Katherinenberg ‘mantled gneiss dome’ im mittleren Erzgebirge wurde eine dreiphasige tektono-metamorphe Entwicklungsgeschichte nachgewiesen. Das alte Stadium stellt bereits eine polyphase Entwicklung dar. Es wird durch die Anlage eines penetrativen metamorphen Lagenbaus (syn D1 — syn D2), durch F2 früh Isoklinalfalten, sowie durch die Intrusion frühkinematischer z. T. anatektischer Granite charakterisiert. PT-Daten belegen amphibolitfazielle Bedingungen, die lokal zu Anatexis führen. Diapirartige Intrusionen kambro-ordovische, porphyrische Zweiglimmergranite bewirkten eine sehr unterschiedliche z. T. subvertikale Raumlage der regionalmetamorphen Einheiten. Diese Intrusionen des zweiten Stadiums sind verantwortlich für die Entstehung des eigentlichen ‘mantled gneiss dome’. Oblat Gefüge und diffuse Kreuzgürtel-Verteilungen der Quarz c-Achsen sind typisch für die Randbereiche dieses Gneisdomes. Während des jüngsten Stadiums prägen bzw. überprägen westvergente duktile Scherprozesse bei Bedingungen der niedriggradigen Amphibolitfazies die Gefüge. Schiefgürtel-Verteilungen der Quarz c-Achsen und S-C Gefüge charakterisieren diese jüngste, variszische Phase.
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  • 5
    Publication Date: 1992-06-01
    Description: Trois événements tectono-métamorphiques ont été reconnus dans les roches cristallines du dôme de gneiss coiffé de Catherine (Erzgebirge oriental). Le premier de ces événements est caractérisé par l'acquisition d'une foliation S1–2, le développement de plis isoclinaux F2 partiellement synschisteux et l'intrusion de granites syntectoniques précoces. Les conditions (P, T) correspondent au facies supérieur des amphibolites et atteignent l'anatexie. L'intrusion diapirique d'un granite à deux micas cambro-ordovicien a verticalisé la foliation S1–2 et est responsable de la genèse du dôme de gneiss coiffé. Une déformation par aplatissement et des fabriques orthorhombiques diffuses des axes c du quartz caractérisent les zones marginales du dôme. L'ensemble des terrains a été ensuite affecté par un cisaillement ductile varisque hétérogène à vergence ouest, dans les conditions du facies inférieur des amphibolites. Une déformation fortement noncoaxiale a transposé partiellement les structures précoces des orthogneiss anatectiques et a transformé les granites porphyriques de la partie centrale du dôme de Catherine en orthogneiss oeillés. Cette phase est caractérisée par des fabriques obliques pour les axes c du quartz et par de fréquentes structures s-c.Three tectonometamorphic events have been recognized in the crystalline rocks of the Catherine mantled gneiss Dome (CD) in the central Erzgebirge. The first tectonometamorphic event is characterized by the acquisition of a S1–S2 metamorphic foliation, development of F2 isoclinal partly syn-schistose folding and intrusion of early synkinematic granites. P-T conditions correspond to higher amphibolite facies metamorphism and culminate in anatexis. A diapiric intrusion of Cambro-Ordovician muscovite-biotite porphyritic granite has verticalized the S2 foliation and is responsible for the genesis of the classical mantled gneiss dome. Oblate strain and orthorhombic diffuse c-axis patterns are typical of the marginal parts of the dome. The whole rock sequence was subsequently affected by westward oriented heterogeneous Variscan ductile shearing under the conditions reaching amphibolite fades. A strongly non-coaxial deformation has partly overprinted the earlier fabrics in anatectic orthogneiss and produced augen-orthogneiss from porphyritic granite in the central part of the CD dome. Prolate to plane strain fabrics, oblique quartz c-axis patterns and a widespread occurrence of S-C fabrics are the most characteristic features of this phase.Краткое содержаниеВ кристаллиновых пор одах гнейсового купо ла с оболочкой на восток е Рудных гор установи ли три стадии тектоно-мо рфологического развития. На первой стадии под в лиянием процессов метаморфизма развив ается листоватость п ород (S1), одновременно образ уются плоские складк и типа f1 и происходит вн едрение ранних синкинематических г ранитов. Термобароме трические условия способствов али появлению амфиболитной фации, л окально завершившей ся анатексисом. На второй стадии, в кем брии/ордовике, имело место внедрени е мусковит-биотитово го гранита, в следствие ч его листоватость S1 приподнялась и образ овала классический г нейсовый купол с оболочкой, при чем на окраинах этого купола происхо дит образование сплю щенных структурных элемент ов и возникает орторомбическая ори ентировка С-осей квар ца. В период варисского г орообразовательног о процесса вся горная т олща подверглась нео днородному пластическому сдвиг у на запад. При этом в ортогнейсах, из мененных под воздейс твием анатексиса, явная деф ормация вращения наложилась на более д ревние структуры, а в центральной части ку пола из порфировых гр анитов образовались очковы е ортогнейсы. На этой стадии отмечают плоский сдвиг с косой ориентировкой С-осей кварца и развитие структур типа S — С.ZusammenfassungIm Kristallin des Katherinenberg ‘mantled gneiss dome’ im mittleren Erzgebirge wurde eine dreiphasige tektono-metamorphe Entwicklungsgeschichte nachgewiesen. Das alte Stadium stellt bereits eine polyphase Entwicklung dar. Es wird durch die Anlage eines penetrativen metamorphen Lagenbaus (syn D1 — syn D2), durch F2 früh Isoklinalfalten, sowie durch die Intrusion frühkinematischer z. T. anatektischer Granite charakterisiert. PT-Daten belegen amphibolitfazielle Bedingungen, die lokal zu Anatexis führen. Diapirartige Intrusionen kambro-ordovische, porphyrische Zweiglimmergranite bewirkten eine sehr unterschiedliche z. T. subvertikale Raumlage der regionalmetamorphen Einheiten. Diese Intrusionen des zweiten Stadiums sind verantwortlich für die Entstehung des eigentlichen ‘mantled gneiss dome’. Oblat Gefüge und diffuse Kreuzgürtel-Verteilungen der Quarz c-Achsen sind typisch für die Randbereiche dieses Gneisdomes. Während des jüngsten Stadiums prägen bzw. überprägen westvergente duktile Scherprozesse bei Bedingungen der niedriggradigen Amphibolitfazies die Gefüge. Schiefgürtel-Verteilungen der Quarz c-Achsen und S-C Gefüge charakterisieren diese jüngste, variszische Phase. ©1992 Ferdinand Enke Verlag Stuttgart
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  • 6
    Publication Date: 1986-10-01
    Description: The three deformation phases inferred from the detailed structural analysis of the Cesky Krumlov Varied Group record the Hercynian development of the Southern Moldanubian of the Bohemian Massif. The deformation is related to the NW-SE thrusting of the large crustal units including granulites. The formation of the NS and NW-SE trending shear zones is connected with the thrust movement. The structural development begins with F1 isoclinal fold formation, that could originate in unmetamorphosed sediments. In the final stage, they were strongly flattened and B1 boudinage developed in the rocks. Aplite dykes and migmatitization of paragneisses occurred at the same time the rocks were metamorphosed. The D2 deformational phase was produced by the simple shear deformation of the unit and folds of various styles around rigid inclusions and the strike-slip shear zone near the boundary of the granulite and the Varied Group were formed. The F1 and F2 folds are parallel with the stretching and mineral lineation indicating a NS to NW-SE direction of the thrusting. The youngest deformation is characterized by spectacular boudinage and by folding of the vertically oriented planes.кРАткОЕ сОДЕРжАНИЕМАссИВ МЕНДЕРЕс НА жА пАДЕ тУРцИИ ьВльЕтсь гОРАМИ АльпИИскОгО тИпА И сО стОИт Иж тРЕх тЕктОНИкО-лИтОлОгИЧ ЕскИх ЕДИНИц, пОДРАжДЕльЕМ ых НА: “гНЕИсОВОЕ ьДРО”, “слАНцЕВУУ ОБО лОЧкУ” И “МРАМОРНУУ О БОлОЧкУ”. В ДАННОМ ОпУБлИкОВАН ИИ пРИВОДьтсь РЕжУль тАты ИжОтОпНОгО АНАлИжА, п РОВЕДЕННОгО НА МЕтАс ЕДИМЕНтНых И МИгМАтИЧЕскИх сВИт Ах пОРОД УжНОгО кРАь МАссИВА (т Ип А) И НА МЕтАтОНАлИЧЕ скОИ И МЕтАгРАНИтНОИ сЕРИ ьх пОРОД ЕгО сЕВЕРНОг О кРАь (тИп В). ИжОхРОНА цЕльНОИ пОР ОДы тИпА А пО МЕтОДУ РУБИДИь-стРОНцИь ДАлА ВОжРАст В 502±10 МА, И ж НАЧЕНИЕ ИсхОДНОгО сООтНОшЕН Иь ИжОтОпОВ стРОНцИь 0,71174±73. сЧИтАЕтсь, ЧтО ЁтИ ДАН НыЕ ОтРАжАУт пЕРИОД МИгМАтИжАцИИ ЁтИх пО РОД. ОДНАкО Дль тИпА В пОлУЧИлИ ВОжРАст 471±9 М АпРИ ИсхОДНОМ жНАЧЕН ИИ сООтНОшЕНИь ИжОтОпО В стРОНцИь В 0,70684±25, пРИЧЕМ ЁтОт ВОжРАст, к Ак сЧИтАУт, ДОлжЕН ОтР АжАть ВОжРАст ИНтРУжИИ. пЕРИОД кРИстАллИжАц ИИ АльпИИскИх пАРАгЕ НЕжОВ МИНЕРАлОВ ВыВЕлИ Иж с РЕДНЕгО жНАЧЕНИь ВОж РАстА БЕлых слУД МЕтОДОМ РУ БИДИь-стРОНцИь В 56±1 МА. БЕлыЕ слУДы Иж пОРОД т ИпА В ДАлИ сООтВЕтсВЕ ННО ВОжРАст В 120–230 МА, кОтОРы И пОДпАДАЕт пОД ИНтЕР ВАл МЕжДУ сРЕДНЕАльпИИс кИМ И кАлЕДОНскИМ МЕт АМОРФИжМОМ. БИОтИты ОБОИх тИпОВ п ОРОД ДАлИ сРЕДНИИ ВОжРАст 37±1 МА, кОтОРыИ ИНтЕРпРЕтИРОВАлИ, кАк ВОжРАст АльпИИск ОгО ОхлАжДЕНИь. жНАЧЕНИь ИжОтОпОВ кИ слОРОДА В пОРОДАх тИп А А кОлЕБлУтсь От 10,4 ДО 14,6‰, А У тИпА В От 8,9 ДО 11,8‰. РАжлИЧИь В сООтНОшЕН ИИ ИжОтОпОВ кИслОРОД А И стРОНцИь У ЁтИх тИпОВ пОРОД УкАжыВАУт НА тО, ЧтО тИп А, пО ВсЕИ ВЕРОьтНО стИ, ИМЕЕт МАтЕРИкОВО Е пРОИсхОжДЕНИЕ, А тИп В — ОкАжыВАЕтсь сМЕшАН НыМ тИпОМ Иж МАтЕРИкОВОИ кОРы И МАНтИИ.RésuméL'étude structurale détaillée de la Série Variée du Moldanubien méridional dans le Massif de Bohème a permis de distinguer trois phases de déformation dans le développement tectonique varisque. Cette déformation est liée au charriage, du Nord-Ouest vers le Sud-Est, de grandes unités crustales comportant des granulites. La genèse de zones de cisaillement plus jeunes, d'orientation N-S et NW-SE peut Être liée au mÊme processus de charriage. Le développement structural commence avec des plis isoclinaux F1 engendrés vraisemblablement dans les sédiments non métamorphisés. Au stade final de leur formation, ils ont été très aplatis et un boudinage B1 est apparu. L'intrusion de filons d'aplite et la migmatitisation des paragneisses sont contemporaines du métamorphisme. La deuxième déformation D2 a été le fait d'un cisaillement simple; à ce moment se sont formés des plis de style tectonique très variés, localisés fréquemment autour d'inclusions rigides. De cette étape date également le décrochement ductile entre les granulites et la Série Variée. Les plis F1 et F2 sont parallèles à la linéation d'étirement (linéation minérale) qui indique la direction N-S à NW-SE du charriage. La déformation la plus jeune comporte un boudinage spectaculaire et le plissement des plans d'attitude verticale.ZusammenfassungDrei Deformationsphasen der variszischen tektonischen Entwicklung sind in der Bunten Gruppe des südlichen Moldanubikums des Böhmischen Massivs enthalten. Die Deformation ist mit der von NW nach SE orientierten überschiebung von groen Krusteneinheiten mit Granuliten verbunden. Die Entstehung von jüngeren N-S und NW-SE verlaufenden Scherzonen kann auf die überschiebungsbewegung bezogen werden. Die Strukturentwicklung beginnt mit F1 isoklinalen Falten, die wahrscheinlich den nichtmetamorphisierten Sedimenten aufgeprägt wurden. Während der Abschluphase der Formung wurden sie stark geplättet und es entstand die B1 Boudinage. Die Aplitgänge, Migmatitisation der Paragneisse und Metamorphose der Gesteine sind gleichzeitig. Die D2 Deformationsphase wurde durch einfache Scherung der Einheit hervorgerufen und es entstanden Falten verschiedenen tektonischen Stils in der Umgebung starrer Einschlüsse und die Blattverschiebung an der Grenze von Granulit und Bunter Gruppe. Die F1 und F2 Falten liegen parallel zur Streckungslmeation und überschiebungsrichtung ab. Die jüngste Deformation ist charakterisiert durch eine spektakuläre Boudinage und Faltung der senkrecht stehenden Flächen. ©1986 Ferdinand Enke Verlag Stuttgart
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  • 7
    Publication Date: 2011-08-01
    Description: As the continental crust thickens during mountain building, it can become hot enough to start melting, leading to a profound reduction in its strength. Melt-weakened crust can flow outward or upward in response to the pressure gradients associated with mountain building, and may be transported hundreds of kilometres laterally as mid-crustal channels. In the Himalayan-Tibetan system, melting began about 30 million years ago, and widespread granite intrusion began at 20-23 Ma. Geophysical data indicate that melt is present beneath the Tibetan plateau today, and deeply eroded mountain belts preserve evidence for melt-enhanced ductile flow in the past. Flow of partially molten crust may limit the thickness and elevation of mountain belts and has influenced the deep structure of continents.
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  • 8
    Publication Date: 2012-04-01
    Description: During the ascent, emplacement and post-emplacement deformation of igneous rocks, two or more phases of deformation that overprint each other are often depicted. These overprints, when magnetic minerals are present, are recorded in magnetic fabric. In this contribution, overprints are studied by means of numerical modeling, following several basic scenarios common to igneous rocks. Biotite and amphibole that occur often together in igneous rocks are considered as carriers of the anisotropy of magnetic susceptibility. Modeling shows that (1) a constrictional fabric with a low degree of anisotropy as commonly recorded in magmatic rocks may result from a deformation overprint and not necessarily from an extensional/transtensional regime, and (2) that the constrictional AMS fabrics originates from orthogonal superimposition of a deformation event on an AMS fabric inherited from earlier magma emplacement history. Therefore, the interpretation of a constrictional fabric must be performed with caution. Numerical modeling may provide a suitable help in strengthening the interpretation of real magnetic fabric data. ©2011 Springer-Verlag
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  • 9
    Publication Date: 2012-04-01
    Description: Orogenic compression-related fabrics (~340–335 Ma) were reworked during regional extensional deformation (~328–325 Ma) in a large anatectic crustal domain of the Central Vosges (NE France). The extension was first accommodated by brittle dilation affecting vertically anisotropic high-grade rocks associated with emplacement of subvertical granitic sheets. The AMS fabric of granitoids is consistent with highly partitioned transtensional deformation marked by alternations of flat and steep foliations and development of orthogonal lineations. This deformation passes to top-to-the-southwest ductile shearing expressed in southerly migmatitic middle crust. The AMS fabric revealed moderately west-dipping foliations bearing subhorizontal NNW–SSE-trending lineations and predominantly plane strain to prolate shapes. This fabric pattern is interpreted as a viscous response of stretched partially molten crust during continuous ductile extension. Vertical ascent of voluminous granites and stoping of the upper crust occurs further south. This gravity ascent triggered by extension leads to development of south-dipping AMS foliations, south-plunging lineations and oblate fabrics in various crustal granites. Vertical shortening related to ascent of these (~325 Ma) granitoids and persistent N–S stretching is responsible for reworking and remelting of originally vertical compression-related fabric in roof supracrustal granites (~340 Ma) and development of highly prolate fabrics in these rocks. This work shows that the finite shape of AMS fabric ellipsoid is highly sensitive to both strain regime and superpositions of orthogonal deformation events. ©2011 Springer-Verlag
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  • 10
    Publication Date: 2015-03-01
    Description: During orogenic processes continental crust experiences significant partial melting. Repeated thermal pulses or fluctuation in fluid content can even cause multiple anatectic events that result in complex intrusion suits. In the Vosges mountains, France, two main generations of magmatic rocks are recorded. The first magmatic event occurred at ca. 340 Ma, and is represented by extensive K-Mg granitoids magmatism. The second magmatic event occurred at ca. 325 Ma and produced large quantity of felsic anatectic melts which further pervasively intruded and compositionally and texturally reworked previously formed granitoids. Detailed field and microstructural observations revealed continuous transitions from porphyritic granite with large euhedral Kfs and Pl phenocrysts (Type I granite) via intermediate granite (Type II) to fine-grained apparently isotropic granite (Type III) dominated by the neo-crystallized melt. The Type I granite preserves the original magmatic assemblage and has only incipient amount of the newly crystallized melt. The new melt-crystallized material forms narrow, fine-grained pathways along grain boundaries or cuts across pre-existing magmatic grains and forms an interlinked network. With increasing amount of the newly crystallized material the original magmatic grains are resorbed and show highly corroded shapes. The early formed feldspars grains have strong compositional zoning, with oscillatory zoned cores reflecting range of original magmatic compositions and rims showing later melt overgrowths. Original magmatic feldspars have different composition from the new phases crystallizing in the partially molten granite. We interpret the fine-grained microscopic corridors as melt pathways that were exploited by the new magma. We suggest that this melt pervasively migrated through the older granitoids resulting in mixture of inherited “xenocrysts” and of new melt-derived crystals. The interaction between the new melt and previously crystallized granitoids results in variety of granite textures and fabrics. These reflect different degrees of equilibration between the bulk rock and the passing melt. Finally, Type III granite carries mixed isotopic signature intermediate between the type I granite and the surrounding metasediments and granulites, suggesting mixing of the original granite with new later magma with source in these rocks.
    Print ISSN: 0037-9409
    Electronic ISSN: 1777-5817
    Topics: Geosciences
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