Geologische Rundschau

, Volume 75, Issue 3, pp 665–683 | Cite as

Hercynian-thrust related shear zones and deformation of the Varied Group on the contact of granulites/Southern Moldanubian, Bohemian Massif/

  • Petr Rajlich
  • Jaroslav Synek
  • Michal Sarbach
  • Karel Schulmann
Article

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.

Keywords

Shear Zone Bohemian Massif Rigid Inclusion Detailed Structural Analysis Simple Shear Deformation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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.

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.

кРАткОЕ сОДЕРжАНИЕ

МАссИВ 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.

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Copyright information

© Ferdinand Enke Verlag Stuttgart 1986

Authors and Affiliations

  • Petr Rajlich
    • 1
  • Jaroslav Synek
    • 1
  • Michal Sarbach
    • 1
  • Karel Schulmann
    • 1
  1. 1.Institute of Geology and GeotechnicsCzechoslovac Academy of SciencesPraha 8Czechoslovakia

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