河南省皇城山高硫化型浅成低温热液型银矿床识别特征及其找矿意义

Identifying Characteristics of High-Sulfidation Epithermal Huangcheng Shan Silver Deposit in Henan Province and Their Ore-Search Implictaion

经过详细的野外勘查和热液蚀变、矿物标型特征研究,并结合稳定同位素研究资料综合分析,首次提出皇城山银矿床为浅成低温热液矿床中的高硫化型矿床。该矿床以发育多孔状石英岩的硅化带和高级泥化带为特征,组成矿石的金属硫化物以黄铁矿、铜蓝和辉铜矿等高硫金属硫化物组合为标志。矿石中闪锌矿的低Fe高Tl和强内反射显示低温闪锌矿标型特征。流体包裹体研究结果表明,成矿流体具有低温(150～200℃)、低盐度(低于5% NaClequiv)性质。多孔状石英岩和高级泥化蚀变反映酸性岩浆蒸气与围岩之间的相互作用,银及贱金属元素是由岩浆蒸气迁移并因岩浆蒸气随后的冷却冷凝作用而沉淀。金属硫化物较强的重硫亏损(δ34S:-11.7%～-22‰)特征反映成矿体系在近地表相对较开放的高氧逸度环境和较低温度条件下发生较强的硫同位素分馏作用。皇城山银矿床总体显示高硫化型浅成低温热液体系成矿特征。分析了成矿的地质制约因素以及重要找矿标志。

This work is based on detailed field geologic surveys, studies of hydrothermal alteration and mineralogical typomorphics, fluid inclusion and stable isotopes. The result shows that the Huangcheng Shan silver deposit in Henan Province belongs to the high-sulphidation epithermal type. Its major diagnostic characters as follows： occurrence of vuggy quartz formed by silicifieation, and advanced argillie alteration , high-sulphidation mineral assemblage of pyrite＋covelite＋ chalcocite. Extensive vuggy silica and advanced argillie alteration reflect interaction of the wall rocks with acidic magmatie vapors. Ag and base metal are interpreted to have been transported by these vapors and to have deposited as a result of their cooling and subsequent condensation. Sphalerite with low-Fe high T1 and strong internal reflection are typomorphism of low- temperature sphalefite. The ore-forming fluid show low temperature （ between 150 ~ 200 ~C ） and salinities （ 〈 5 %NaCl_equiv ）. The strong 34 S depletion of metal sulfides （ δ34 S ： - 11.7 % - -22 ‰） reflected the strong isotope fraetionation effect happened in near-surface ore-forming system under the relatively open environment of high oxygen fugacity and low temperature. Huang Chengshan silver deposit has typical characters of high-sulfidation epithermal system major geological constraints, and targeting criteria on regional and ore district are summarized.