云南兰坪白秧坪银多金属矿集区成矿流体研究

ORE-FORMING FLUID IN BAIYANGPING SILVER-POLYMETALLIC MINERALIZATION CONCENTRATION FIELD IN LANPING, YUNNAN PROVINCE

对云南兰坪白秧坪银多金属矿集区流体包裹体的岩相学、均一温度、盐度、密度及其关系和流体包裹体氢、氧同位素特征的研究表明 ,该矿集区主成矿期温度均低于 2 0 0°C,属中低温流体作用范畴。其中三山 -河西矿带 (东矿带 )的成矿流体为中低温( 110～ 180°C)、低盐度 [w( Na Cl)为 7%～ 17%]、低密度 ( 0 .717～ 0 .967g/ cm3 )流体 ,以 Na Cl-H2 O二元体系为主 ;富窿厂 -白秧坪矿带 (西矿带 )成矿流体为中低温 ( 12 0～ 15 0°C)、较高盐度 [w ( Na Cl)为 17%～ 2 5 %]、中低密度 ( 1.0 10～ 1.15 6g/ cm3 )流体 ,主要为 Mg Cl2 -Na Cl-H2 O和 Ca Cl2 -Na Cl-H2 O三元体系。流体包裹体氢、氧同位素组成表明成矿流体主要为大气降水补给的地下水 ,主成矿期有效水岩比值较小 ( 0 .0 1～ 0 .10 ) ,岩石与成矿流体间存在较强烈的同位素交换。结合矿石矿物组合及矿床的硫、铅、碳同位素组成 。

The Baiyangping silver-polymetallic ore-concentration field is located in Lanping,Yunan Province.The research of the fluid inclusions expounds that the temperature of the mineralization stage is generally lower than 200°C, and thus should belong to low-middle temperature fluid flow field. While the Sanshan-Hexi ore zone shows the ore-forming fluid has a low temperature(110-180°C),low salinity ([w(NaCl)) is 7%-17%],and low density (0.717-0.967 g/cm^3) with Nacl-H_2O-rich compositions.The Baiyangping-Fulongchang ore zone,on the other hand,displays low temperature (120-150°C),higher-salinity [w(NaCl) is 17%-25%] and medium low density (1.010-1.156 g/cm^3) with MgCl_2-NaCl-H_2O-rich and CaCl_2-NaCl-H_2O-rich compositions. The characteristics of hydrogen-oxygen isotope composition expresses the water of ore-forming fluid was mainly derived from the circulating meteoric water, with a relatively small water-rock ratio of the main mineralization epoch(0.01-0.10), and strong water-rock interaction.The compositions of ore and stable isotope (sulfur,lead,carbon etc.),indicate the ore-forming fluid of the Baiyangping ore-concentrated field comes from deep-circulated hot brine.