新疆东天山觉罗塔格韧性挤压带基本特征及动力学意义

新疆觉罗塔格韧性挤压带发育于吐哈地块和中天山地块之间石炭系东西向火山-沉积建造中,由一组走向东西、产状陡立的透入性片理组成。眼球状结构、平行带状结构和菱形网状结构是韧性挤压带不同构造区亚带的排布格式,它们相对变形带主界面而言具有很好的对称性。片理构造、拉伸线理构造、同生褶皱构造、布丁构造、压力影构造、碎斑构造、粒内面理构造、位错构造和矿物光轴优选定向等韧性构造形迹发育,这些不同尺度的韧性变形构造形迹的组构都具以片理面为对称面而呈现出对称的特征。韧性挤压带横分为3个亚带,3个亚带岩石形变相变和应力应变等方面都呈横向对称状分布。“奶油饼”结构是韧性挤压带的应变结构。该韧性挤压带成因于南北两侧吐哈地块和中天山地块的南北向水平共轴挤压作用,形成于255Ma至280Ma(早二叠世),压扁机制是该韧性变形带的变形机制,它的力学性质表明该韧性变形带不应属于南北两大板块之间的俯冲-剪切带,其成因可能与板块孤后盆地的对称开合有关。

CHARACTERISTICS AND DYNAMIC SIGNIFICANCE OF THE DUCTILE COMPRESSED ZONE IN EASTERN TIANSHAN Mt.IN JIAOLUOTAGE AREA IN XINJIANG PROVINCE

The ductile compressed zone in Jiaoluotage area in Xinjiang province is developed in Carboniferous volcanic and sedimentary formation striking EW between Tuha and zhongtianshan Landmass.It is comprised of a set of upright penetrative foliations striking EW.Eyeball shaped texture,parallel banding texture and rhombus net-shaped texture are configurations of subzones of the ductile compressed zone in various regions,which are symmetric relative to the main boundary plane of the deformational zone.Many kinds of ductile structural elements such as schistosity,stretching lineation,contemporary folds,boudinges,pressure shadows,deformed pebbles,mortar structures,intragranular foliations,dislocation structures and beltroporic fabrics of optic axis are well developed.All fabrics of these ductile structural elements in different orders and scales are symmetric while schistosity is considered as a symmetry plane.The ductile compressed zone can be transversely divided into three subzones,in which the distribution of deformation metamorphism and stress-strain patterns of rocks is in transversal symmetry.“Cream cake” texture is the characteristic strain texture of the ductile compressed zone.It was formed by NS trending horizontal syntaxial compression caused by the interaction of Tuha Landmass in northern side and middle Tianshan Landmass in southern side between 255Ma and 280Ma in early Permian.As a conclusion,the fabric of the ductile compressed zone in Jiaoluotage area is symmetric,and the flattening is due to deformation mechanism of the ductile deformational zone. The mechanical properties of the ductile compressed zone in Jiaoluotage area indicate that the ductile deformation zone should not be a subduction ductile shear zone between Tarim plate and Junggar plate,its origin may be related to the symmetrily pulling apart and closure of back-arc basin.