| Earth's lithosphere is made of inhomogeneous rocks in different region and depth,as well as featured by different structural geometries.It is needed to build the bridge between the deformations in different scales.One such approach,called the multi-order power-law approach(MOPLA),has been developed in recent years which would be used to investigate the deformation of L tectonites by simulating the partitioning deformations within the heterogeneous inclusions.The deformation models for Qinling and Danfeng complex have been built by MOPLA,the simulating results and the geometries,geochronology features of Qinling and Danfeng complex along Shangnan-Danfeng region show that:(1)The local strain filed cannot be simpily related to the regional strain filed,strain partitioning is involved when there is scale variation of strain field.The investigation shows that,L-tectonites develop only in rheological heterogeneities that are moderately stronger than the bulk material as a whole,the bulk field must be simple shearing,simple-shearing dominated plane-strain general shearing,or simple-shearing-dominated Sanderson and Marchini transpression.The lineations of the L-tectonites are always nearly parallel to the lineations in the bulk material.Where the lineations are nearly 90° degree from the vorticity axis,the macroscale flow is close to a plane-strain general shearing.Where the lineations are oblique to the vorticity axis and more variable,a simple-shearing-dominated triclinic thinning zone with mainly uniaxial boundary stretching is likely.Obliquely divergent boundary conditions are accommodated by folding and fracturing structures in the upper lithosphere and development strain-localized simple-shearing-dominated detachment shear zones in the ductile lithosphere.The concept of a homogeneous transtensional zone with vertical vorticity axis is unrealistic and unsupported by fabric evidence.(2)Three deformation generation have been recognized from Qinling Complex in ShangnanDanfeng region.The first deformation generaltion probabily represents the geological events in Jingning Period,the second deformation generation is caused by the subduction of Shangdan Ocean and collision between North and South Qinling block,the third deformation generation may be caused by the subduction Mianlue Ocean which also cause the folding of South Qinling sedimentary layers during the Indosinian period,While the Qinling Complex is unsensetive to the evolution of Mianlue Ocean,the third deformation generation is characterized by the occasionally magma vein or weak fold in a few local areas which probabliy caused by the subduction of Mianlue Ocean.Qinling Complex in Shangnan-Danfeng area is characterized by the penetrative transposition foliation which strike along SEE-NWW,the lineations from the transposition foliation form a great circle on the sterenet diagram which means the lineations is varying from horizontal to vertical.The geometries and geochronology data show that Qinling Complex was fomed in sinistral-simple-shearingdominated(convergence angel is 10°)Sanderson and Marchini transpression,that is to say the Shangdan Ocean subducted under North Qinling block featured by the convergence angel ?=10°,the geomertry pattern for Qinling Complex was formed during the process of subduction and collision of Shangdan Ocean in Caledonian Period,there is no strong structural activities in Indosinian and Yanshan period.(3)Danfeng complex and Qinling complex have experienced different geological process.The geometry patterns show that Danfeng complex were mainly deformed by the sinistral simple shear(or simple shear dominated shear zone),and this shear zone will have an extension along the strike direction(plane strain)to blance the volum decreasing if there is pure shear component.Danfeng complex is activated till in indosinian period or even Yanshan period which may relate to the subduction towarding the north of Mianlue Ocean. |
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