Extension of Jiaonan Area in Shandong
胶南地区的伸展作用——以胶南—诸城一带为例

Jiaonan area experienced two period different direction extension. The early extension is characterized by subhorizontal E W stretching lineations and displays different deformation in different levels. The eclogite bearing lower crust gniesses, which cropout in the centre part of studies area, show LS constrictional strain fabrics with subhorizontal or gently W plunging lineations under eclogite facies metamorphism. These fabrics indicate that eclogite bearing lower crust experienced vertical flatting, subhorizontal stretching and S N compression. The detachment zone, which separated middle upper crust meta sedimentary rocks from lower crust eclogite bearing gniesses, suffered homogeneous simple shear from east to west under amphibolite facies condition with subhorizontal E W stretching lineations and hinges of shear folds and sheath folds. The late extension is characterized by S N extensional collapse. The subhorizontal detachment zone was rotated into E W striking, N dipping and S dipping ductile extensional shear zones with width of several hundred metres to several kilometres. The stretching lineations plunge separately toword NNW NNE and SSE SSW and overprinted on the early subhorizontal E W stretching lineations. Deformation structures and mineralogical petrological studies indicate that two ductile extensional shear zones underwent separately top to the north and top to the south penetrative homogenous simple shear under high greenschist facies condition.