甘肃岷县寨上金矿地质地球化学特征及成因

GEOLOGICAL AND GEOCHEMICAL FEATURES AND ORIGIN OF ZHAISHANG GOLD DEPOSIT IN THE MINXIAN COUNTY,GANSU

寨上金矿位于西秦岭造山带北亚带。矿脉体的产出受控于NWW向断裂和褶皱构造,走向NWW。矿石主要为蚀变岩型,成矿可分为4个阶段。矿石微量元素分析发现,Au为一独立元素组。流体包裹体中气相成分以H2O为主,其次为CO2、CH4、C2H6,离子以Na+、K+、SO2-4、F-、C l-为主,Na+/K+为1.2~5.4,且富F-。流体包裹体氢同位素δDH2O介于-65‰^-92‰之间,氧同位素δ18OH2O-SMOW值介于4.71‰~11.01‰之间。硫化物的δ34S为3.0‰~9.2‰。矿石稀土元素含量特征与围岩明显不同。金矿是在深部和浅部流体相互作用下,形成于中低温、低盐度环境中。

Zhaishang gold deposit is located in the west Li - Min mineralizing area and Beiya belt of western Qinling orogen. Ore bodies are controlled by NWW - trending faults and fold structures, and strike of the bodies is NWW direction. Ores in the area are mainly altered - rock type, and mineralization can be divided into 4 stages. Rare element analysis of ores shows that Au is an independent element group. Gas composition of fluid inclusion is mainly composed of H2O, and then CO2 , CH4, C2H6. The majority of ion content in fluid inclusion are Na^＋ , K^＋ , SO4^2- , F^- , and Cl^-. Na^＋/K^＋ is at 1.2 - 5.4, and F^- is richer. Hydrogen isotope of water is fluid inclusion is at range of 65‰～~ 92‰, and oxygen isotope is between 4. 21‰～11.1‰. Sulfur isotope of sulfide is at 3.0‰～9.2‰. Rare - earth elements of ores are obviously different from wallrocks. Gold ores were formed at low temperature and low salinity during interaction of deep and shallow fluids.