南秦岭寒武系黑色岩系中夏家店金矿床地质地球化学特征

Geology and geochemistry of the Xiajiadian gold deposit in the Cambrian black rock series in the South Qinling

研究取得如下成果和认识:确定了微细浸染型金矿床赋存于含矿性好的重晶石-硅质岩热水沉积岩系之中:矿床形成经历同生沉积成矿预富集,韧-脆性剪切构造叠加和后生热液改造金的工业富集过程,与本区古大陆俯冲-碰撞造山大地构造演化密切耦合。成矿作用共划分为3期8阶段,矿石由3类11亚类型组成,体现出复杂改造的成矿过程。矿化矿物流体包裹体均—温度集中在199～300℃,成矿压力为370×10~5～820×10~5 Pa,具中-低温热液成矿特征:成矿早期流体包裹体盐度3.27(NaCl)%,中晚期5.25(NaCl)%;6件矿化矿物氢氧同位素组成δ^(18)O_(H_2O)为-7.86‰～0.37‰,δD_(H_2O)为-80.70‰～66.30‰,具有由大气降水向右横向漂移的以天水为主的成矿流体受到较强烈的改造:金矿床属于热水沉积-韧脆性构造叠加-大气降水为主含矿热液改造的微细粒浸染型(类卡林型)金矿床。

Study of the Xiajiadian gold deposit, South Qinling, has led to the following understanding： microdisseminated gold deposits are hosted in gold-rich barite-chert hydrothennal sedimentary rock series, and the formation of the ore deposits has gone through synsedimentary preconcentration and a process of industrial concentration from brittle-ductile shear structural overprinting to post-hydrothennal reworking. The gold mineralization has close coupling relations to the tectonic evolution of continental subduction-coUisional orogeny in the area. The ore-forming processes of this gold deposit may fall into three epochs and eight stages. The ores are composed of three types and eleven subtypes, showing complex ore-forming processes. The homogenization temperatures of fluid inclusions in ore minerals cluster at the range of 199-300℃ and the mineralization pressures range from 370×10^5 to 820×10^5 Pa, showing the features of meso- and epithermal mineralization. The salinities of the fluid inclusions were 3.27 wt.% NaClequiv. in the early mineralizing stage and 5.25 wt.% NaClequiv. in the middle and late stages. The hydrogen and oxygen isotopic compositions of the ore minerals form six samples are δ^18OH2O=-7.86‰ to ＋0.37‰ and δ DH2O=-80.70‰ to -66.30‰. The data points in the plot shift laterally from meteoric water to the right, suggesting that the ore fluids consisting predominantly of meteoric water have been subjected to intense reworking. The Xiajiadian gold deposit is a microdisseminated （Carlin-like type） gold deposit. The mineralization has the features of hydrothermal deposition-brittle-ductile structural overprinting- reworking of hydrothermal ore fluids dominated by meteoric water.