江西省德兴市渔塘金矿的流体包裹体研究

The fluid inclusion study on the Yutang gold deposit in Dexing,Jiangxi province

渔塘金矿位于扬子地块和华夏地块之间的新元古代江南造山带,属于德兴大型铜金矿集区.渔塘金矿成矿阶段石英脉中的流体包裹体可分为三类:H_2O-CO_2包裹体(Ⅰ型)、富CO_2包裹体(Ⅱ型)和水溶液包裹体(Ⅲ型).成矿前石英-黄铁矿脉主要含有Ⅰ型包裹体,CO_2含量较为一致,均一温度为345℃~383℃,盐度为2.0wt.%~6.5wt.%NaCl eq..在金成矿期脉体中,有三种类型的包裹体,并且气相比和CO_2含量变化较大,Ⅱ型包裹体的均一温度为275℃~314℃,盐度为1.8wt.%~4.8wt.%NaCl eq.;Ⅲ型包裹体的均一温度为278℃~354℃,盐度为4.2wt.%~9.6wt.%NaCl eq.;Ⅰ型包裹体的均一温度为290℃~363℃,盐度为1.0wt.%~5.5wt.%NaCl eq..成矿后石英-黄铁矿脉只包含Ⅲ型包裹体,以较低的温度和盐度为特征.因此成矿前为高温、富CO_2的富矿流体;在成矿期发生了不混溶作用,形成不同盐度的两种流体,导致流体具有较为一致的温度和不同的盐度,金主要在此阶段富集;成矿后流体具低温和贫CO_2的特征.渔塘金矿的成矿流体具有典型的不混溶特征,是典型的造山型金矿.

The Yutang gold deposit is located in the Neoproterozoic Jiangnan orogenic belt between the Yangtze and Cathaysia blocks,which belongs to the large copper-gold ore deposit cluster in Dexing area. These fluid inclusions can be divided into three categories： H2O-CO2 inclusions（type Ⅰ ）, COd-enriched inclusions（typeⅡ）, and aqueous solution inclusions（type Ⅲ）. Before the mineralization,the pre-ore stage of barren quartz veins mainly contain type Ⅰ inclusions, and the proportion of CO2 bubble ratio is relatively constant, with homogenization temperatures（Th）of 345 ℃ ~383 ℃ and salinities of 2.0 wt.%~6.5 wt.% NaCl equivalent;There are three types of inclusions in the ore stage of quartz veins with variable gas ratios and CO2 contents, type Ⅱ inclusions show homogenization temperatures （Th）of 275 ℃ ~314 ℃ and a salinity of 1.8 wt.% ~4.8 wt.% NaCl equivalent,type Ⅲ inclusions show homogenization temperatures（Th）of 278 ℃~354℃ and a salinity of 4.2 wt.%-9.6 wt.% NaCl equivalent,the type Ⅱ and type Ⅲ inclusions show similar homogenization temperatures,but different from the salinities,while type Ⅰ inclusions display homogeneous temperatures （Th） of 290℃ ~ 363 ℃ and a salinity of 1.0 wt. % ~ 5.5 wt. % NaCl equivalent. In the post-mineralization stage,quartz-pyrite veins contain only type llI inclusions with lower tempera- tures and a lower salinity. The results of petrological observation and microscopic temperature measurement show that the fluid immiscibility mainly occurrs in the ore-forming stage of gold, resulting in uniform temperatures and different salinities,and gold is mainly enriched at this stage. The Yutang gold deposit shows similar metallogenic characteristics with the Jinshan gold deposit, as the ore-forming fluid has typical characteristics of fluid immiscibility. The Yutang gold deposit is a typical orogenic gold deposit.