Discussion For Petrology And Mineralogy Character Of JinChang Gold Deposit And Genesis Of Ore Bodies In Heilongjiang Province

Jinchang Gold Deposit of Dongning County, Heilongjiang is located in the eastern end of Songnen terrain in the North China Orogenic belt. It is an important part of Jihei magmatic metallogenic province. The determination on the alteration features of the wall rock and the mineralization type for this typical porphyry gold deposit has theoretical and practical significance to contrast on regional metallogenic and deep prospecting. This paper has studied the gold deposit on the characteristics of igneous rocks, alteration petrology and mineralogy of 18 ore body, geological features, geochemistry of ore-forming fluid, ore genesis and the direction of prospecting, and has mainly achieved the following results:①Petromineralogy, petrochemistry and geochemistry studies on mineralized granite of No. 18 ore body show that granitic rocks in Indo-late are rich in Fe, Na2O/K2O, DI <90, lack of Eu. Fm is 0.65-0.85.δEu> 0.3, La / Yb> 10. The result indicates a sign of gold mineralization. Trace elements and isotopes studies on granitoid rocks show that granitoid rocks originated from granite magma of the lower crust, mixing with mantle material.②The results of complete chemical analysis, REE and trace elements analysis on granitic rocks alteration of this area show that the activity of ore-forming fluid is relatively strong during the process of water-rock reaction. Comprehensive study on all the results and calculations on elements transfer during the process of water-rock reaction confirmed that silicification, potash-alteration has close relationship with mineralization. SiO2, K2O, H2O + is the major media of gold transfer and deposition.③The results of Infrared Spectroscopy and X-ray diffraction show that the degree of order of potassium feldspar in hydrothermal stages rises as the alteration intensity of rocks improved. And the degree of order is positively correlated to fluid. The final structure temperature of the potassium feldspar in Jinchang is 400-420℃, which indicates that they might be the products of hydrothermal alternation..④The trace elements and REE of different mineralization stages indicate that the ore-forming fluid came from granite porphyry. The ore-forming fluid contains high Cl, but low F, and has undergone the superposition of multi-stages ore-forming fluids.⑤Isotope geochemistry study on He of inclusions and Pb, S in pyrite of different mineralization stages shows that the ore-forming fluids originated from crust. The crustal component came from granite porphyry of the under part of No. 18 ore body. Little atmospheric water might interfuse into ore-forming thermal fluid. The geochemistry studies of trace elements and REE on mineralized granitic rocks, ore and sulfides further proved that the ore-forming fluids originated from crust and related to granite porphyry. During magmatic hydrothermal stages of granite porphyry, multi-stages hypothermal fluids were involved in the mineralization of this area.