THEORETICAL BASIS, METHOD AND CALCULATION ON TECTONO-CORRECTED DEPTH OF PETROGENESIS AND METALLOGENESIS
L? Guxian1, Liu Ruixun2, Wang Fangzheng3, Guo Tao1, Shu Bin1, Xia Lin1, Liu Dujuan1
1. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081; 2. School of Earth and Space Science, Peking University, Beijing 100871; 3. China University of Geosciences, Wuhan 430074
According to the tectonic correcting method of measurement and calculation of formation depth of rocks and ore deposits, we should subtract additional tectono-induced hydrostatic pressure from the total pressure and then measure overlying rock’s thickness. This method on basis of the knowledge of the crust rock in solid stress state, taking the elastic pattern rather than the state-fluid pattern, was more accorded with the actual situation in the crust than the method weight/special weight. This paper, with the examples of Linglong-Jiaojia-type gold deposits in the Jiaodong area and the Dabie ultrahigh pressure metamorphic belt in central China, introduced the theoretical basis about this method of measurement with tectonic correction, and field research method-mapping of tectonic deformed petrofacies, the setting up system of strain-stress equations to get 3 D principal stresses, the choosing the conversion coefficient of stress value being 0～0.1 in transtension zone, the value 0.1～0.5 in shear zone and the value 0.5～0.75 in transcompression zone, respectively, so as to get the stress values of model. Finally, we could do the calculation and correction method of formation depth of gold deposits with additional tectono-induced hydrostatic pressure (1PS=1/3(R1+R2+R3)) 2,i. e. to subtract PS firstly from measured P and then use PG supposed by Terzaghi and Peck (1948). New data about 2.5～3.5 km of metallogenic depth of gold deposits in the Jiaojia area and over 32 km of formational depth of coesite-bearing eclogite in the Dabie ultrahigh pressure metamorphic belt were calculated by the tectono-corrected method.