江西金山金矿成矿过程流体作用地球化学特征  

Geochemical Features of Ore-forming Fluid in the Jinshan Gold Deposit, Jiangxi Province

作　　者：华仁民[1] 李晓峰[1] 张开平[2] 邱德同[1] 杨风根[1] 

机构地区：[1]南京大学地球科学系,内生金属矿床成矿作用国家重点实验室,南京210093 [2]江西金山金矿,江西德兴334200

出　　处：《南京大学学报（自然科学版）》2002年第3期408-417,共10页Journal of Nanjing University（Natural Science）

基　　金：国家自然科学基金重点项目 (4 973312 0 )

摘　　要：金山金矿位于赣东北矿集区内 ,是与韧性剪切带有关的大型金矿床 .该矿床不同类型蚀变变形岩石与围岩千枚岩在微量元素、稀土元素等方面具有相同的地球化学特点 ,Co/Ni,U/Th ,Th/Sc ,Th/Co比值较为一致 .超糜棱岩和含金石英脉中Au/Ag比值较高 ,反映了金矿化的特征 .千枚岩、糜棱岩、超糜棱岩和含金石英脉的稀土元素分配模式十分相似 ,具有明显向右缓倾的特点 ,铕亏损较明显 (δEu =0 .6 2～ 0 .71) ,而铈基本没有明显的富集或亏损 (δCe =0 .97～1.0 1) .这些都说明它们具有相同的来源 .金山金矿成矿流体以富H2 O、CO2 ,富Na+、K+为特征 ,并具有较高含量的N2 、Ar组分 ,反映了成矿流体的来源较深 .硅同位素研究表明 ,超糜棱岩和含金石英脉中的石英为变质成因 ;钻孔全岩氧同位素测试结果则显示成矿流体作用过程中有大气降水的加入 .金山金矿流体作用过程中 ,SiO2 、CaO为带入组分 ,Al2 O3、TiO2 、TFe、MgO、K2 O为带出组分 .研究表明金山金矿成矿流体为深部来源的变质水 ,后期有大气降水的加入 ,成矿流体具有中低温、中等盐度、弱酸性。The Jinshan gold deposit is located in the northeastern part of Jiangxi province, and is one of the important large deposits in the northeast Jiangxi ore-concentrating district. The ore forming process is closely related to a NE_trending ductile shear zone. Gold ore bodies occur in mylonite and ultramylonite of the shearing strain center. Different rock types, i.e., mylonite, ultramylonite and gold-bearing quartz vein, which are caused by different degrees of alteration-deformation procedure, have similar geochemical features in respect to trace elements and REE compositions, which also resemble regional phyllitic wall rocks. For example, ratios of Co/Ni, U/Th, Th/Sc and Th/Co in all rock types are less than 1, whereas the Au/Ag ratio is high in ore-bearing rocks. Different rock types have similar REE patterns of slight right slope, with δEu=0.62～0.71 and δCe= 0.97～1.01. The ore-forming fluid is rich in H 2O, CO 2, Na +, K + and has higher contents of N 2 and Ar, indicating that the ore-forming fluid originated from deeper sources. Silicon-oxygen isotope compositions indicate that the quartz in ultramylonite and gold-bearing quartz vein was the product of alteration_deformation process, which differed from the quartz in nearby Dexing porphyry copper-gold deposit. Oxygen_hydrogen isotope feature shows that the ore fluid is generally of metamorphic origin; however, the downward decreasing of oxygen isotope compositions from drill hole rocks indicates that circulated meteoric water played certain roles in the later mineralization stage. Variation of major element concentrations indicate that only SiO 2 and CaO were added, while Al 2O 3, TiO 2, TFe, MgO, and K 2O were drained away by fluid flow in the ore_forming system. The variation of K +/ Na + and Ca 2+/ K + reveals a pressure reduction evolution process of the ore-forming fluid.It is concluded that the ore_forming fluid in the Jinshan gold deposit originated from deep metamorphic water, which was characterized by mid_low temperature, medi

关 键 词：金矿 成矿过程 流体作用 地球化学特征 微量元素 稀土元素 

分 类 号：P618.51[天文地球—矿床学]