Zusammenfassung
Eine Anzahl von Marmoren aus der Sierra Alhamilla (Spanien), intensiv deformiert unter natürlichen Bedingungen bei ca. 300° C, zeigt ausgeprägte Variationen in Mikrostruktur und Gefüge. Es kann gezeigt werden, daß die Entwicklung von bevorzugten Kristallorientierungen und Formanisotropien im Korngefüge erheblich von der rekristallisierten Korngröße abhängt. Dies wird als Ausdruck der relativen Aktivität verschiedener Deformationsmechanismen interpretiert. Superplastizität scheint eine relativ scharf definierte Obergrenze für Korngrößen von 10–15 /sm zu besitzen. Im Bereich des Potenzgesetz-Fließens wird die Verformung feinkörniger Aggregate wahrscheinlich von Diffusion, die von grobkörnigen von Dislokationsmechanismen bestimmt. Der Übergangsbereich zwischen beiden Mechanismen umfaßt einen Korngrößenunterschied von etwa 30 µ.
Abstract
A suite of marble specimens from the Sierra Alhamilla (Spain), deformed to large strains under natural conditions at about 300° C shows distinct variations in microstructure and fabrics. It can be demonstrated that the development of crystallographic preferred orientations and grain shape fabrics are strongly dependent on recrystallized grain size. This is interpreted to reflect the relative importance of various deformational mechanisms. Superplasticity seems to have a sharp upper grain size limit at 10–15 /smm. Within the power law creep regime, deformation in fine grained aggregates is probably dominated by diffusional, in coarser ones by dislocation mechanisms. The transition is a gradual one, and may span a grain size range of 30 /sm.
Résumé
Une série d'échantillons de marbres de la Sierra Alhamilla (Espagne), fortement déformés sous des conditions naturelles de 300° C, montre des variations distinctes de microstructure et de texture. On peut démontrer que la formation des orientations préférentielles cristallographiques et de l'aplatissement des grains dépend clairement des dimensions des grains recristallisés. Ceci est interpreté a comme le reflet de l'importance relative de plusieurs mécanismes de déformation. Il apparaît, que le domaine de superplasticité a une limite bien definie a 10–15 /smm. Dans le domaine du fluage en σn, la déformation des aggrégats fins semble être dominée par des mécanismes de diffusion, et des aggregats de grande taille par des mećanismes de dislocation. La transition est graduelle, et peut comprendre un intervalle dimensionel des grains de 30 /smm.
Краткое содержание
Были исследованы мра моры из района Сиерра Алгамилла (Испания). На основании изучения и х микроструктуры и ст роения считают, что их деформ ация происходила при прим ерно 300 °С. Установили, ч то образование и ориентация их криста ллов, а также анизотро пия форм в структуре зерен зависят в большей мер е от гранулометричес кого состава перекристал лизованного минерала. Это явление объясняют тем, что зде сь действовали различн ые механизмы деформаци и. Пластичность их, каж ется, ограничена гранулом етрическим составом и лежит в раз мерности зерен между 10 и 15 микрон (верхняя граница). В области дей ствительности закон а ползучести материал а преобразование мелкозернистых аггр егатов предопределя ется, вероятно, процессами диффузии, а грубозерн истых-механизмами ди слокации. Переходная зона между обоими механиз мами, вероятно, лежит в размерности 30 микрон.
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Behrmann, J.H. Microstructure and fabric transitions in calcite tectonites from the Sierra Alhamilla (Spain). Geol Rundsch 72, 605–618 (1983). https://doi.org/10.1007/BF01822084
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DOI: https://doi.org/10.1007/BF01822084