变质岩中变斑晶成核生长及旋转问题的述评

发生递进变形的变质岩中,斑晶成核生长于变形分解作用的递进缩短带内,斑晶的大小受两侧递进剪切变形带的限制。除少数螺旋状石榴石外,产于共轴或非共轴递进不均匀缩短变形过程中的斑晶不发生旋转,斑晶内部包体形迹(Si)反映外部面理(Se)的再活化。利用未旋转斑晶中的包体形迹可以确定早期面理的取向,寻找构造演化的时间标志,确定褶皱轴迹等,本文给出了斑晶中包体形迹弯曲的成因模式图。

NUCLEATION, GROWTH AND ROTATION OF POR-PHYROBLASTS IN METAMORPHIC ROCKS

Porphyroblasts in the progressively deformed metamorphic rocks nucleate and grow within the zone of progressive shortening by deformation partitioning. The size of por-phyroblasts is controlled by the progressive shearing zone on the two sides. Except for the spiralled garnets, most of the porphyroblasts do not rotate during the coaxial or noncoaxial progressive bulk inhomogeneous shortening. The inclusion trails of porphyroblasts reflect a re-activation of external foliation. The inclusion trails in nonrotated porplyroblasts can help determine the orientation of the old foliation, fold axes, and the time criteria of deformation history. A genetic model of curved inclusion trails in porpphyroblasts is given in the paper.