Structural Survey Of Linglong Gneissic-like Biotite Granite In Jiaodong Area

As the third largest gold concentration area in the world,Jiaodong gold deposit is an important gold producing area in China,and has great potential for prospecting in deep concealed areas.In view of the fact that most of the Jiaodong gold deposits occur in Mesozoic Linglong Gneissic-like biotite granite bodies,Strengthening the structural study of this type of granite is the basis and prerequisite for further understanding of metallogenesis and improving prospecting in concealed areas,which is of great significance to the theoretical study of gold mineralization.Through the mapping of tectonic deformation lithofacies,structural measurement and analysis,three-dimensional structural analysis,fractal characteristics and strain measurement of the area of about 2 km2 in the study area,the following understandings have been obtained about Linglong Gneissic-like biotite granite:(1)It is determined that the Linglong Gneissic-like biotite granite has the distribution characteristics of gneissic-like structuresLarge-scale mapping in the field shows that gneissic-like structures are generally developed,and gneissic-like structures are mainly characterized by C-facet and intermittent S-facet,which have the characteristics of S-C fabrics.C-plane tends to be 305 +10,NE and dip angle is between 15?50.The dip angle of S-plane and C-plane is between 5 and 25 degrees.The dip angle of gneiss-like facies in this rock mass has the characteristics of center higher than edge.Its sharp angle and other aspects reveal the distribution direction of the regional gneiss at about 315 degrees north-west.(2)The Left shear direction of Linglong Gneissic-like biotite granite is determinedFrom the study of three-dimensional block cutting and indoor measurement and analysis,it is found that the biotite orientation of the secondary shear band of C plane reason is composed of biotite enriched at the edge of the preferred orientation of mineral aggregates in S plane.Statistical analysis of gneissic-like data shows that the shear type is the direction of left-lateral shear according to the sharp angle of S-C fabric.(3)The type of tensile shear strain of Linglong Gneissic-like biotite granite is determined.The X/Z axis ratio of deformed quartz particles ranged from 1.440 to 1.918,with an average value of 1.677.Y/Z axis ratio ranged from 1.134 to 1.252,with an average value of1.172;X/Y axis ratio ranged from 1.150 to 1.677,with an average value of 1.435.Strain analysis shows that K value ranges from 1.577 to 4.111 with an average value of 2.561.Flinn diagram analysis shows that the strain type is general tensile type.It reflects the type of tensile shear strain in the process of uplift of magmatic core complex.(4)The temperature of shear deformation and the paleo stress are determinedThe fractal characteristics of quartz dynamic recrystallization were studied.The fractal dimension D was calculated by P-A method from 1.066 to 1.099,and the deformation temperature was 500 to 700 C by the relationship between thermometer and fractal dimension.Equivalent to the temperature of syntectonic deformed granite.Using the stress gauge formula,the paleo-differential stress is calculated between 4.39 MPa and 8.66 MPa,It reflects that the shear facies Linglong granite is in a medium-strength compressive stress environment.