长乐－南澳韧性剪切带中糜棱岩变形微构造研究

DEFORMATION MICROSTRUCTURES OF THE MYLONITES IN CHANGLE-NAN'AO DUCTILE SHEAR ZONE

长乐—南澳韧性剪切带糜棱岩的显微变形机制有粒间滑动、粒内滑动、位错及其滑移和蠕变、应变的局部恢复等。石英丰富的韧性变形和位错特征以及长石的脆一弹性变形说明糜棱岩形成于绿片岩相条件，变形时的温度约为３００—３５０℃。石英塑性变形处于重结晶一软化阶段和热加工一恢复阶段。由位错密度和动态重结晶颗粒粒径计算了差异应力和应变速率，分别为５６．８—９９．７ＭＰａ，（０．３５－１．６１）×１０－１３ｓ－１和１７５．８—４０６．９ＭＰａ，（０．７—７．２）×１０－１２ｓ－１，二者较大的差值表明糜棱岩是缓慢上升至地表的，这一结论与应变局部恢复现象一致。该韧性剪切带是闽粤沿海早白垩世末碰撞造山的产物。

liding within grains and between grains, dislocation structures and partial recovery are deformation micromechanisms of the mylonites in Changle-Nan'ao ductile shear zone. Our researches show that the mylonites formed in greenscliist factes (300-350℃, 15km) and occured during the processes of recovery and recrystallization. Differential palaeostress and strain rates calculated by dislocation density and dynamic recrystallized grain sizes are 56. 8-99. 7MPa, (0.35- 1.61 ) ×10-13s-1 and 1 75.8-406.9MPa, (0.7-7.2) ×10-12s-1, respectively. The large range of stresslevels irom two palaeostress indicators suggest that the mylonites lifted upto earth surface slowly. This conclusion is consistent with the development of partial recovery. The microstructures inform that Changle--Nan'ao ductile shear zone resulted from collision between min-Tat microcontinent and Fujian-Zhejiang Mesozoic volcanic arc in end of early Cretaceous.