应用磁组构方法研究构造变形与成矿作用的时序关系

根据磁组构要素受热动力学影响特点，首次运用岩石磁组构结合变形分析确定岩石变形与成矿作用的时序关系。通过含矿与不含矿构造岩的磁组构特征的对比表明，北京崎峰茶蚀变糜棱岩型金矿，其糜棱岩的构造变形相对较早，矿化蚀变较晚。研究认为，湖南枞树板大型脉状铅锌矿的成矿作用是热液蚀变的成果，成矿后构造变形很弱，其铅锌蚀变矿化作用要早于花岗斑岩的侵位，这一结论与由地质，地球化学及同位素年代学资料分析结果相吻合。

STUDY ON THE CHRONOGENESIS RELATION OF MINERALIZATION AND DEFORMATION BY MAGNETIC FABRIC ANALYSIS

The magnetic fabric is a susceptibility anisotropy of the rocks. Magnetic fabric analysis, as a method of geological researches, is widely used to study structure deformation. According to its features of thermal demagnetization and thermal homogenization, the author determined the chronogenesis relation of the mineralization and the deformation by means of comparative analysis between the characteristics of the magnetic fabric and the deformation of the rocks.A negative correlation has been found between the gold abundance and susceptibility anisotropy ( P ) in the mineralized and unmineralized mylonite from Qifengcha altered mylonite type gold deposit, North Beijing,i.e., the higher the Au abundance is, the lower the susceptibility anisotropy ( P ) The results of this study suggest that the time of mineralization is later than that of deformation of the mylonite. This is important for the study of mineralizing mechanism of this type gold deposit. There is also a negative correlation between the content of Pb+Zn and the susceptibility anisotropy ( P value) of the samples from the section of the ore bearing structural zone in the Zongshuban vein Pb Zn mega deposit, south of Hunan, indicating that the deposit is formed by alteralization of ore bearing hydrothermal solution and that the deformation is weaker after the mineralization. Meanwhile, the P values of the altered rock and ore rock are higher(1.0441)than that of the granite porphyry(1.0146), and the orientation of the minimum susceptibility axis of the altered rock and ore rock (northeast) is different to that of the granite porphyry(southeast). These also suggest that the period of the emplacement of granite porphyry veins with weak deformation is later than that of mineralization, concordant to its genesis of magmatic hydrothermal deposit controlled by early Yanshanian granite and the fault or fractures drawn from the data of geology, geochemistry and isotopic geochronology.