Geochemical Characteristics Of Ore-forming Fluid From Hatu Gold Metalogeny

The Hatu gold metalogeny is located in West Junggar, one of the most significant gold metalogenies in northern Xinjiang. Q?(Hatu), Q?, Q?, Q ?and Q ?gold deposits with similar geologic features are distributed from the southwest to northeast, and controlled by Anqi fault and its second fractures. Based on field surveys and study on minerology, lithology, fluid inclusions and isotope geochemistry, the ore-forming fluid geochemistry of Hatu, Q ?and Q?gold deposits are mainly investigated. The oreforming fluid geophysical-chemical characteristics, composition characters, source of fluid, fluid evolution and so on are studied for setting deposit genetic types.Hatu, Q and Q? ?gold deposits are divided into three ore-forming stages. The fluid inclusions of Hatu deposit are classified as three types: liquid-rich phases, vapor-rich phases and CO2-H2 O phases, while fluid inclusions of Q?, Q?deposits are mainly the first two types. The uniform temperature of the main ore-forming stage is 213~285?, 240~306?, 225~319?; the sality of the three deposits is 0.530~4.14%Na Cleqv, 1.91~7.99%Na Cleqv, 0.88~3.23%Na Cleqv; the density of the three deposits is 0.574~0.948g/cm3, 0.730~0.934g/cm3, 0.536~0.918g/cm3; the mineralization pressure is 52.1 ~ 69.5MPa, 62.9 ~ 68.8MPa, 49.9 ~ 80.7MPa, respectively. The fluid is characterized by middle-low temperature, low sality and low density. Fluid inclution composition analysis shows that they have the similar composition belonging to Na ClH2O±CH4±CO2±N2, Na Cl-H2O±CH4, Na Cl-H2O±CH4±CO2 system, respectively. The water-rock interaction and fluid immiscibility are the main factors for gold deposition. Hydrogen and oxygen isotope analysis show that ore-forming fluid derive from metamorphic water with minor magmatic water. Sulfur isotope analysis shows that ?34S is?2.0‰~3.7‰, indicating the same source of sulfur may be magma genesis or the orehosted rocks-basalt. In a word, the ore-forming fluid geochemistry characteristics of Hatu metalogeny are similar, with geological features such as ore-controlling structure, ore type and hydrothermal alteration, confirming that they belong to orogenic gold deposit.