摘要
蓬莱地区金矿床以石英脉型为主,其次是蚀变岩型;成矿条件与著名的玲珑金矿床相似。金主要产于黄铁矿和多金属硫化物石英脉中。流体包裹体研究表明,金矿床中主要存在两种类型的流体包裹体:CO_2-H_2O 包裹体和中低盐度的NaCl-H_2O 溶液包裹体。CO_2-H_2O 包裹体气相以 CO_2为主,可含少量 CH_4、H_4S、CO。其中,黄铁绢英岩的石英中含有丰富的CO_2-H_2O 包裹体,而黄铁矿石英脉和多金属硫化物石英脉中富 CO_2与富 H_2O 的 CO_2-H_2O 包裹体共存。显微测温结果显示,黄铁绢英岩中的 CO_2-H_2O 包裹体的均一温度范围为230℃～300℃;而黄铁矿和多金属硫化物石英包裹体的均一温度为220℃～390℃,鉴于这些包裹体是从不混溶的 CO_2-H_2O 流体中捕获的,因此它们的温度下限220℃～250℃左右,应该看作是它们的形成温度。成矿早期流体为富含挥发份(流体密度0.92～0.985g/cm^3)、中低盐度(4.15%～5.23%NaCl eqv)的流体;到主成矿期逐渐演化为温度升高,盐度变化范围大(1.02%～15.5%NaCl eqv),水溶液以 NaCl 为主,气体仍以 CO_2为主,但可含少量的 CH_2、H_2S、CO 及有机质等的流体(流体密度0.32～0.99g/cm^3);成矿期后的流体盐度、温度及 CO_2含量降至最低。本区矿床中石英的δ^(18)O 值变化在13.8‰～18.3‰,成矿流体的δ^(18)O 值在4.9‰～10.9‰之间,流体包裹体中δD变化范围很小,从-78‰变化到-101‰,主要集中在-78‰～-88‰之间。由此表明成矿流体以岩浆水为主,伴有大气降水的参与。在主成矿期成矿流体表现出明显的多期、多来源特征。温度降低和流体不混溶是导致金等成矿元素沉淀和富集的重要机制。
Gold deposits in the Penglai gold field, Shandong peninsula are mainly auriferous quartz-veins with subordinate disseminations in altered granites （e.g. pyrite-sericite-quartz rock）. The mineralization conditions are similar to those of the famous Linglong gold deposits. Gold occurs mainly in pyrite and in polymetallic sulphide quartz veins. Fluid inclusion study indicates that there are two major types of fluid inclusions in the gold deposits： CO2-H2O inclusions and NaCl-H2O inclusions of medium-low salinity. CO2 is the dominant component of the vapour phase of CO2-H2O inclusions which sometimes contains minor CH4, HES and CO. Abundant CO2-H2O inclusions are present in pyrite-sericite-quartz rock whereas CO2-rich and HEO-rich CO2-H2O inclusions with variable phase ratios coexist with each other in pyrite-quartz veins and polymetallic sulphide - quartz veins. Microthermometric results have shown that the homogenization temperatures of CO2-H2O inclusions in pyrite-sericite-quartz rock range between 230℃ - 300℃ whereas those for fluid inclusions in pyrite-quartz veins and polymetallic sulphide - quartz veins vary from 220 to 390℃. As the CO2- H2O inclusions with variable phase ratios were trapped from the immiscible CO2-H2O fluids the lower temperature range of ca. 220 - 250℃ is considered to be their formation temperature. The fluids in the early mineralization stage were volatile-rich and medium-low salinity （4.15% -5.23% NaC1 eqv） ones with densities from 0.92g/cm^3 to 0. 985g/cm^3. During the main mineralization stage the fluids evolved to higher-temperature CO2-H2O fluids containing a NaCl-dominated aqueous liquid （1.02% -15.5% NaCl eqv） and a CO2 vapour with minor CH4, HES, CO and even organic substance; its density vary from 0. 32 to 0. 99g/cm^3. In the post mineralization stage the temperature, salinity and CO2 content of the fluids decreased to the minimum. The δ^18O values of quartz in the deposits vary between 13.8‰ and 18.3‰ while the δ^18O values of the mineralizing fluids between 4.9‰ and 10.9‰.The 6D values of fluid inclusions show a narrow range between - 78‰ and - 101‰ with a mode of - 78‰ - - 88‰, suggesting that the mineralizing fluids originated mainly from magmatic water and accompanied with participation of meteoric water. The mineralizing fluids of the main mineralization stage exhibit feature of multiple sources. Temperature decrease and fluid immiscibility are the important mechanisms for deposition and enrichment of gold and other mineralizing elements.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2007年第9期2241-2256,共16页
Acta Petrologica Sinica
基金
国家重点基础发展规划项目(2006CB403506)
基金委优秀创新群体基金项目(40221301)
关键词
胶东
蓬莱金矿区
流体包裹体
氢氧同位素
Jiaodong （Eeastem Shandong）, Gold deposits in the Penglai area, Fluid inclusions, Hydrogen and oxygen isotopes
作者简介
侯明兰，女，1966年生，博士研究生，矿床地球化学专业。
通讯作者：蒋少涌，E—mail：shyjiang@nju．edu．cn
