甘肃李子园金矿床中金的赋存状态与成因意义OA

The Liziyuan Gold Deposit in Gansu Province is a large and very important orogenic gold deposit in the West Qinling Orogenic Belt of China.The occurrence state of gold in the Liziyuan Gold Deposit has been in-vestigated via field sampling of gold ores,hand specimen observation,microscopic observation and electron probe analysis.The results show that the main gold-bearing minerals in the ores are pyrite,chalcopyrite,gale-na,and quartz.There are four types of native gold dissemination:inclusion gold,intergranular gold,intergrown gold and fissure gold.The statistical results of 281 native gold particles observed under the microscope show that the number of inclusion gold particles(165)is the largest,accounting for 58.72％;the second is fissure gold particles(65),accounting for 23.13％;intergranular gold particles(27)and intergrown gold particles(24)are the least,accounting for 9.61％and 8.54％respectively.The micronative gold in the ore exhibits various morphologies and a wide range of particle size variations(0.003-0.41 mm),but it is dominated by micro-medium-grained gold(0.05-0.02 mm)and micro-fine-grained gold(0.02-0.01 mm),accounting for 36.65％and 25.26％,respectively.The number proportion of micro-coarse-grained gold and micro-macro-grained gold is low(17.44％),but their area proportion accounts for 74.60％;thus these two types of gold are crucial for the grade and reserves of ores.The results of electron probe analysis show that the contents of Au and Ag in the gold particles are 71.06-83.28 wt％and 14.27-26.40 wt％,respectively,and the gold particles also contain traces of mercury(1.32-1.77 wt％),indicating that the gold particles are mainly silver-bearing native gold The fineness of the native gold in Liziyuan Gold Deposit is low(849.50-853.73).The reasons for the low fineness of the native gold may be closely related to the relatively low temperature(generally moderate)of the Liziyuan Gold Deposit,the ore-forming hydrothermal fluids being mainly metamorphic fluids,and the co-precipitation of Ag and Pb with Au during mineralization.