Deformation mechanisms in second-phase affected microstructures and their energy balance

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• 作者：Marco Herwegh ; Alfons Berger
• 关键词：Polyphase-rocks ; Zener drag ; Deformation mechanisms ; Steady state ; Microstructures ; Energies ; Calcite
• 刊名：Journal of Structural Geology
• 出版年：2004
• 出版时间：August 2004
• 年：2004
• 卷：26
• 期：8
• 页码：1483-1498
• 全文大小：682 K

文摘

Based on the relationship Zener parameter (Z=second-phase size/second-phase volume fraction) vs. calcite grain size (d_g), second-phase controlled aggregates and microstructures that are weakly affected by second-phases are discriminated. The latter are characterized by large but constant grain sizes, high calcite grain boundary fractions and crystallographic preferred orientations (CPO), while calcite grain size and calcite grain boundary fraction decrease continuously and CPO weakens with decreasing Z in second-phase controlled microstructures. These observations suggest that second-phase controlled microstructures predominantly deform via granular flow because pinning of calcite grain boundaries reduces the efficiency of dynamic recrystallization favoring mass transfer processes and grain boundary sliding. In contrast, the balance of grain size reduction and growth by dynamic recrystallization maintains a steady state grain size in microstructures that are only weakly affected by second-phases promoting a predominance of dislocation creep. With increasing temperature, the relationship between Z and d_g persists but the calcite grain size increases continuously. Based on microstructures, the energy of each modifying process is calculated and its relative contribution is compared with energies of the competing processes (surface energy, dragging energy, dynamic recrystallization energy). The steady state microstructures result from a temperature-dependent energy minimization procedure of the system.