闽—粤东南沿海大陆边缘韧性剪切带的基本特征

东南沿海大陆边缘剪切带是西太平洋活动大陆边缘构造带的组成部分,它是一条具有多次活动的左旋韧性平移剪切带。在本剪切带中可以观察到3种类型的构造:（1）规模巨大的呈北北东—北东向展布的糜棱岩带以及山拉伸线理组成的线状构造带。它们在平面上有明显的从断目两侧向中心递进变形特征;（2）呈北东走向陡倾角的糜棱叶理（Sa）、应变滑劈理或破劈理（Sb）、小型剪切带（Sc）;（3）由西到东断层作用样式和断层岩具有明显的递进变化特点。西部（浅部）断层作用以脆性剪切滑动为主,其断层岩则由假玄武玻璃及镜面糜棱岩组成;中部断层作用以跪—韧性剪切为主,为断层泥—碎裂岩—超碎裂岩;东部(深部,以韧性剪切作用为主,其断层岩为暖棱岩—花岗糜桂片麻岩—眼球状糜棱岩系列。以上特点表明在本剪切带内透入性和非透入性变形之间有着密切的关系,反映出在变形过程中具有由韧性变形逐渐向脆性变形的发展趋势。

THE CHARACTERISTIC OF DUCTJLE SHEAR ZONE ALONG SOUTHEASTERN COAST CONTINENTAL MARGIN OF CHINA IN FUJIAN-GUANGDONG

The shear zone along continental margin in southeastern coastof China is a transcurrent- ductile shear zone with a sinistral displacement of more than 100km, which developed under low am-phibolite to greenschist facies conditions in the western Peri Pacific active tectonic belt. The age of the structure is considered to be 177.7?.1 Ma. The belt traverses more than 500km along the Fujian-Guangdong coastal region with a width of 20-40km, trending 2530. Three distinct structures can be observed within the shear zone: (l)There exists a large scale mylonite belt orientating NNE-NE and linear structural zone consists of penetrative mylonitic foliation etc. In which the strain intensity increases gradually within the fault zone from margin to center. (2,>There well developed NE trending deeply inclined mylonitic foliation (Si), cleavage (S2) and minor shear zone (S3). They are distributed in S pattern from the borders of the shear zone inward. (3) The models of faulting and types of fault rocks in the fault zone change progressively from east to west. The faults in the western part(shal-lower part) of the belt are characterised by pseudotachylyte and mirror plane mylonite, the faults in middle part of the belts are characterised by brittle-ductile shears and gouge-breccia-catadasite series, while the faults in eastern part (deeper parti of the belt are characterised by ductile shears and mylonite series. Minor structure analysis presented above imply the intimate interaction between penetrative and nonpenetrative deformation processes within the shear zone of the southeastern continental margin, which changes gradually with time from ductile to brittle deformation.