Study On Geological Characteristics And Genesis Of Hadamengou Gold Deposit In Inner Mongolia

Hadamengou super-large gold deposit is located in Wulashan-Daqingshan metallog enic belt of the west section of northern uplift in the North China Craton, characterizi ng by widespread K-feldspathization. This paper based on the regional geological back ground, systematically summarized the geological characteristics, geochemical characteri stics and genesis of Hadamengou gold deposit by means of the knowledge of Petrolog ist, Mineral Deposits, Geochemistry of Mineral Deposits, Fluid Inclusions Geology and Stable Isotope Geochemistry.Hadamengou gold deposit are hosted by metamorphic rocks of Wulashan Subgrou p, and the gneiss is the main ore bearing lithology. The ore bodies occurred as nearly east-west, parallel and equidistant, and the distribution of the ore bodies is controlled by piedmont fault and its secondary faults. The ore types are quartz vein type, quart z-K-feldspar vein type and potassic-silicified altered rock type. The main gold bearing minerals are pyrite, followed by quartz, potassium feldspar and chalcopyrite. The wall rock alteration includes potassic, silicification, chloritization, epidotization, sericitization and carbonation. The mineralization stage can be divided into potash feldspar-quartz s tage, quartz-pyrite stage, quartz-polymetallic sulfide stage and carbonate stage. The oreforming fluid is H2O-CO2-NaCl system. The mineralization process is a process of dec reasing the temperature(397℃â†'269℃â†'169℃), reducing the salinity(15.1â†'11.46â†'4.6wt%NaCl.eq), and the smaller density(0.77 g/cm3â†'0.96g/cm3). The metallogenic pressu re ranges from 17.5 to 42.5MPa, and the metallogenic depth ranges from 1.75 to 5.16 km. The study of hydrogen and oxygen isotope shows that the ore-forming fluid is m ainly magmatic water, and then mixed with meteoric water. Sulfur and lead isotope co mpositions indicate that the ore-forming material source is complex.The distribution around mining area of Dahuabei rock mass, Shadegai rock mass and the pegmatite veins are the granite of high silicon, alkali(potassium) rich and hig h differentiation. The diagenetic age of Dahuabei rock mass is 328~365Ma and the S hadegai rock mass is 219.7Ma. The formation of pegmatite vein is more period of time. The mineralization age are mainly concentrated in the three ages of 132 Ma,217~240Ma and 351~386Ma, and the metallogenetic age is consistent with the age of regi onal magmatic thermal event. So we think that the Hadamengou gold deposit belongs to the deposit of magmatic hydrothermal(medium to high temperature) and intrusive r elated.The study of potassic alteration and gold mineralization is belived that the Hadam engou gold deposit’s mineralization system is enclosed, it is one of the reasons of pot assium-containing ore of the deposit. The occurrence of blasting pressure relief in alka li metasomatite is the cause of gold mineralization.