Application Of Multivariate Statistic Analysis In Research Into Geochemical Characteristics Of Pulang Porphyry Copper Deposit

The porphyry copper deposit is an important type of copper deposit since it was discovered. Zhongdian Island Arc Belt, being rich in mineral resources, is proved to be an important district of prospecting copper-polymetallic deposits. Pulang porphyry copper deposit is a large porphyry copper deposit discovered in this belt so far. It possesses copper intrinsic economic resource amount of 9.2×10⁵t, and its perspective resource will be more than 3×10⁶t, in addition to that, it includes 300t of gold and silver. The potential economic value of this deposit is about 40 billion Yuan.On the basis of geochemical data, this paper analyses the ore-bearing potentiality of the intrusive rocks, ore-forming characteristics and zonation of primary halos. The studied results are as follows: (1) Compared with compositions of granodiorite in China, the porphyry rocks in this area are richer in W , Mo (K≥5), rich in Cu, Au, As, Sb, F, V, Na₂O (1.2≤K<5), poorer in Pb, Zn, Co (K≤0.8), and equal in Ag, Cr, Ni, K₂O, CaO, SiO₂(0.82O (1.2≤K<5), poorer in V, Cr, Ni, Na₂O,CaO (K ≤0.8), and equal in F, Co, SiO₂(0.81: (Cu-Au-Ag-Zn-Pb-As).It reveals Cu mineralization and the special enrichment of Au, Ag, Zn, Pb and As. F₂: [Na₂O-Cr-CaO]—-[K₂O]. K₂O is in distinctly negative correlations with Na₂O and CaO. According to the results of sample analysis, K replaced Na and Ca. Therefore, F₂ indicates that albites and plagioclases were altered into potassium feldspars and sericites. F₃: [Ni-Co-V] — -[SiO₂]. It demonstrates the negative correlations between Ni-Co-V and SiO₂. According to the results of sample analysis, the content of SiO₂ increased with the decreases of Ni-Co-V during the hydrothermal processes of mineralization and alteration. So we can infer that F₃ indicates silication. F₄: (W-F-Mo). It may reflect thehigh temperature hydrothermal mineralization of W, Mo and F (fluorite alteration). (3) C·B·Gregorian's zoning index method is used to determine the axial zonation sequence of primary halos in exploration profile of No.0 line. The result is: Zn—Ag —Cu—Au—W—Mo. The ratio of (Ag·Zn)_D/(Mo·W)_D decreases rapidly from the head to tail of the ore body, so it can be regarded as an index of predicting potential resources in the depth.