山西省支家地银铅锌矿床包裹体特征及热液来源探讨

Characters of the inclusions in Zhijiadi Ag-Pb-Zn deposit,and the origin of their hydrothermal solution

山西省支家地银铅锌矿床是华北地块北缘与燕山期火山岩有关的大型银铅锌矿床．流体包裹体以串珠状次生、假次生包裹体居多，显微镜下见到三类包裹体：富液相包裹体（Ⅰ）、富气相包裹体（Ⅱ）、纯液相包裹体（Ⅲ）．Ⅰ类包裹体气液比15％～25％，均一温度142—170℃；Ⅱ类包裹体气液比〉80％，均一温度160—235℃；Ⅲ类包裹体气液比为0，均一温度120～140℃．包裹体盐度（0．2％～1．8％）、均一温度（120～235℃），演化趋势属于盐度、均一温度逐渐降低的类型，为含矿热液稀释过程．此外包裹体液相成分Na^＋／k^＋值≥1，pH值为中性、弱碱性，气相成分复杂，8^18OH20、8D值分别为5．47、-83均表明成矿热液是岩浆水及大气降水混合来源．

The Ag-Pb-Zn deposit in Zhijiadi, Shanxi province, a large Yanshanian stage volcanic rock-related deposit, is located on the North margin of Huabei Plate. Most fluid inclusions are secondary bead-like, or pseudo-secondary ones. Three types of fluid inclusions, namely gas-liquid inclusion （Ⅰ）, liquid-gas inclusion （Ⅱ）, and liquid inclusion （ Ⅲ ）, can be discriminated with microscope. Type I inclusions have homogenization temperatures of 142 - 170 ℃and liquid/gas ratios of 15-25 %; type I1 inclusions have homogenization temperatures of 160-235 ℃ and liquid gas/ratios of more than 80%; and type 111 inclusions have homogenization temperatures of 120 - 140℃and liquid gas/ratios of 0%. With a salini- ty of 0. 2 - 1.8%and homogenization temperatures of 120-235℃, the fluid inclusions show a falling tendency of the salin- lty-homogenization temperature, and hence a dilution process of the ore-bearing hydrothermal solution. Moreover, lots of other traits of Zhijiadi inclusions demonstrate that the ore-bearing hydrothermal solution has even been mixed with meteoric water. These traits contained a Na ＋/k ＋ ratio ≥ 1, a pH ≥7, a 818 OH2O = 5.47, and a 8D = -83, as well as complex gas components.