胶东主要金矿类型流体包裹体特征对比及其对成矿环境差异的指示——以纱岭、旧店和辽上金矿床为例

Comparisons of the fluid inclusions in the main types of gold deposits in Jiaodong area and the indication on their metallogenic conditional differences:a case study of Shaling,Jiudian and Liaoshang gold deposits

胶东是中国最重要的金矿集区,破碎带蚀变岩型、石英脉型和黄铁矿碳酸盐脉型金矿是区内的主要矿化类型,前人对不同矿化类型成矿条件的差异性尚缺乏深入研究。对胶东3种矿化类型的代表性金矿床流体包裹体研究发现:不同矿化类型金矿床主成矿期的流体包裹体具有相似的岩相学特征,均发育H_(2)O-CO_(2)(Ⅱ-g型)、富CO_(2)(Ⅲ_(CO_(2))型)和水溶液包裹体(Ⅰ-l型和Ⅱ-l型)4种流体包裹体,均属于CO_(2)-H_(2)O-NaCl±CH_(4)体系。不同矿化类型的流体特征也有差异,黄铁矿碳酸盐脉型金矿的流体包裹体以盐度和均一温度较高明显区别于其他矿化类型,石英脉型金矿流体包裹体以直径较大、三相包裹体占比略高,区别于破碎带蚀变岩型金矿。破碎带蚀变岩型和石英脉型金矿成矿流体整体属于中—低温、中—低盐度、低密度流体,黄铁矿碳酸盐脉型金矿成矿流体属于中—高温、中—低盐度、低密度流体。对纱岭金矿床-1000~-2000 m海拔高程范围矿体中的流体包裹体研究表明,在垂深2000 m深度范围内,成矿流体除盐度有不明显的降低趋势外,其他特征高度一致,说明不同深度成矿流体具有一致的性质和物理化学条件。不同矿化类型和不同深度金矿成矿流体特征的总体一致性和部分差异性指示,胶东金矿是在统一的成矿构造-流体背景下,不同的局部环境中短时间集中爆发成矿的。

Jiaodong area is the most important gold ore-concentrating area in China.The altered-rock-type in fractured zone,quartz-vein-type and pyrite-carbonate-vein-type gold deposits are the main mineralization types.Previous studies on the differences of mineralization conditions of different mineralization types are still lacking.Fluid inclusions of three typical gold deposits in Jiaodong are studied in this paper.The fluid inclusions of gold deposits of different mineralization types have similar petrographic characteristics in main mineralization stages.There are four types of fluid inclusions,including H_(2)O-CO_(2)(Ⅱ-g type),CO_(2)-rich(Ⅲ_(CO_(2)) type)and aqueous solution inclusions(Ⅰ-l type andⅡ-l type),which belong to CO_(2)-H_(2)O-NaCl±CH_(4) system.The fluid inclusions of pyrite-carbonate-vein-type gold deposit are obviously different from other types of mineralization due to higher salinity and homogenization temperature.The fluid inclusions of quartz-vein-type gold deposit are different from altered-rock-type gold deposit in fractured zone due to larger diameter and higher proportion of three-phase inclusions.The ore-forming fluid of altered-rock-type and quartz-vein-type gold deposits are belong to medium-low temperature,salinity and low density fluid as a whole,while the pyrite-carbonate-vein-type gold deposit belongs to medium-high temperature,medium-low salinity and low density fluid.The study of fluid inclusions in the ore-body at-1000~-2000 m depth in the Shaling gold deposit show that the ore-forming fluids have the same characteristics except the salinity decrease in the vertical depth of 2000 m,indicating that ore-forming fluids at different depths have the same properties and physicochemical conditions.The general consistency and partial difference of the fluid characteristics of different gold deposits indicate that the Jiaodong gold deposit was formed in a short time under a unified metallogenic structure-fluid background in different local environments.