河南省崤山地区典型金矿床的成矿流体特征及其对进一步找矿工作的启示

Characteristics of the ore-forming fluid of typical gold deposits in Xiaoshan area of Henan and their enlightenment to further prospecting works

崤山地区位于豫西小秦岭―崤山―熊耳山―外方山金银钼多金属成矿带的中西部,但其金矿探明储量远低于西部的小秦岭和东部的熊耳山地区。因此,崤山地区的进一步找矿潜力成为产业部门关注的重点。综合前人的研究资料,本文提出区内金矿主要以破碎带蚀变岩型和石英脉型为主。通过对典型矿床的分析,认为该区的金成矿作用从早到晚可划分为（1）石英-黄铁矿（毒砂）阶段,（2）黄铁矿-石英阶段,（3）石英-多金属硫化物阶段,（4）石英-碳酸盐阶段。其中（2）和（3）为主成矿阶段。对各成矿阶段石英晶体中流体包裹体的成分、均一化温度及硫、氢、氧、铅同位素组成进行分析,发现流体成分为富含CO2的水流体,且溶解了数量较多的Na＋和Ca2＋离子。流体包裹体均一温度为243℃~285℃,表明崤山地区的金矿床属以中温为主的热液矿床,缺少高温阶段的流体包裹体。金属硫化物δ34S值为-0.5‰~5.4‰,具深源硫特点;δ18 OH2O值变化为0.1‰~9.4‰,δ18 D值变化为-134.9‰~24.3‰,表明成矿流体以岩浆水为主,混有大气降水和变质水。结合崤山和小秦岭地区花岗质侵入岩出露面积对比,崤山地区找矿不理想的主要原因是剥蚀程度较低,因而深部仍有较大的找矿潜力。

Xiaoshan area is located inside the middle-west part of Xiaoqinling-Xiaoshan-Xiong＇ ershan-Waifang-shan Au-Ag-Mo polymetallic metallogenic belt in western Henan. However, the measured reserves of goldores is far less than that of Xiaoqinling area and eastern Xiong＇ ershan area. Therefore, the prospecting po-tential in Xiaoshan area attracts great attention of related industrial sectors. Combined with previous work,this paper put forth the theory that the gold ores in the area were predominated by fracture zone alterationrock type and quartz vein type. According to the analysis of typical deposits, the paper concluded that themineralization of gold ores could be divided into four stages from early to late： （1） quartz-pyrite （arsenopy-rite） stage, （2） pyrite-quartz stage, （3） quartz-polymetallic sulfide stage, and （4） quartz-carbonate stage.Among the four stages, stage （2） and （3） are the main stages of mineralization. The author conducted analy-sis on the content, homogenization temperature and S-H-O-Pb isotope composition of the fluid inclusions inthe quartz crystals in each ore-forming stage. It indicates that the fluid was CO2-rich aqueous fluid with nu-merous dissolved Na＋ and Ca^2＋ ions. The homogenization temperature of fluid inclusions ranges from 243℃to 285℃, and it suggests that the gold deposits in Xiaoshan area are mainly intermediate temperate hydro-thermal deposits being short of fluid inclusions of high temperature stage. The δ^34S value of metal sulfideranges from -0.5‰ to 5.4‰ and it shows the characteristics of deep source sulfur. And its ＇s OH2O valueranges from 0.1‰ to 9.4‰ and δ^18D value ranges from -134.9‰ to 24.3‰, and it shows that the ore-forming fluid occurs mainly as magmatic water with lesser atmospheric precipitation and metamorphic water.Based on the comparison between outcrop area of granitic intrusive rocks in Xiaoshan area and that in Xiao-qinling area, it appears that the unsatisfactory prospecting results in Xiaoshan area are due to low denudationdegree. Therefore the prospecting potential must be great in the deep part.