Late Paleozoic Deformation In Huangshan Area,Xinjiang Province

In Huangshan area,the east segment of the Kangguertage--Huangshan ductile shear zone in Eastern Tianshan,Carboniferous volcanic,volcanoclastic and varies sedimentary rocks outcrop.Foliations are seen everywhere in these rocks which the original sedimentary beds are difficult to recognize.The ductile shear zone is controversial about its deformation mechanics and tectonic setting in which simple shear and pure shear are put forward as the opposite point of views.A field survey is launched on Huangshan area,Xinjiang,and regional geological study was carried out before based on reading of published documents and research papers.Varies deformation appearances are observed such as folds,foliations,lineations,and deformed pebbles during the field survey.After the field trip,the rock samples collected are sent to cut and make rock slices.Deformations expressed in microstructures are observed and analyzed under polarized microscopes.Finally,such conclusions are deduced from our field and indoor research:1.Two stages of deformations are observed in Huangshan area.The first stage is manifested by the north-south direction co-axial compress deformation which composes the main body of regional structural deformation;the second stage is represented by dextral strike-slip deformation which only express along regional faults.2.the north-south direction compress deformation results the east-west direction steep slope foliations which appeared broadly,and also other deformation phenomenon such as lineation,squashed deformation of pebbles and folds with horizontal axis.In microscope,stress shadows of pyrite grains,rotations of phenocryst and mechanic twinning of feldspar are belong to this stage.Both deformation in outcrop scale and micro scale indicate co-axial deformation in general.3.Dextral strike-slip deformation appears only in part area.The extraordinary asymmetric spindle-shape of Huangshan Eastern pluton is an indication of the dextral strike-slip deformation which is contemporary with the emplacement of the pluton.It is also indicated by folds shapes on the north of the pluton and distribution of Cu-Ni ore bearing ultramafic rocks of late stage of emplacement.4.Two stages of deformations are corresponding to the collision of plates and after-collision adjustment.The Aqishan-Yamansu collided with the Middle Tianshan block in Late Carboniferous--Early Permian,as a result,Kangguertage in-arc basin which include Huangshan area deformed strongly as a weak zone.The east-west strike-slip movements are adjustment of the inhomogeneous continental deformation after collision.