熊耳山干树金矿流体包裹体及稳定同位素地球化学研究

Study of fluid inclusions and stable isotope geochemistry of the Ganshu gold deposit in the Xiong'ershan region

干树金矿是豫西熊耳山西段最重要的金矿之一。主成矿阶段包括黄铁绢英岩以及多金属铁白云石成矿阶段,黄铁绢英岩化蚀变与金矿的关系最密切。主成矿阶段石英中流体包裹体的均一温度为130~388℃,峰值为150~250℃;盐度为6.16%~12.51%,峰值为7%~11%;包裹体液相成分中阳离子主要为Na^+、Ca^(2+),阴离子主要为Cl~–;Na^+/K^+比值为0.17~1.28,平均0.73;F~–/Cl~–比值为0.04~0.06;根据含CO_2包裹体估算成矿压力为90~119 MPa,获得成矿深度为3.3~4.4 km,表明主成矿阶段成矿流体为浅成、中低温、低盐度、富钠钙的岩浆热液。主成矿阶段石英中H、O、C同位素研究显示,成矿流体的δ18O值为0.79‰~6.27‰,平均3.34‰;δD值为–104.1‰~–87.7‰,平均–95.6‰,表明主成矿阶段成矿流体中的水主要源于岩浆水,并混入大气降水,这与流体包裹体的研究结果相吻合。δ^(13)CPDB值为–4.1~–2.7‰,平均–3.4‰,与火成岩或岩浆系统相关,表明可能是在岩浆热液作用下,矿石发生蚀变而形成白云石、方解石等碳酸盐矿物,这与主成矿阶段铁白云石化的发育相吻合。综合研究认为干树金矿床属中低温岩浆热液型金矿床。

The Ganshu gold deposit is one of the most important gold deposits in the western part of the Xiong＇ershan region, western Henan Province. The main mineralization stages include the beresitization phase and polymetaIlic ankerite phase, with beresitization alteration being most closely associated with gold mineralization. Homogenisation temperatures of fluid inclusions, in quartz at the main mineralization stage, range from 130℃ to 388℃, mainly from 150℃ to 250℃; their salinities stand between 6.16% and 12.51%, mainly within the range of 7.0%-11.0%; the cations are mainly Na＋ and Ca2＋, but the anion is mainly Cl-; the ratios of Na＋/K＋ and F-/Cl- range from 0.17 to 1.28 （averaging 0.73） and 0.04 to 0.06, respectively; the mineralization pressure of CO2-rich inclusions is estimated to be 90-119 MPa, which indicates that the depth of mineralization ranges from 3.3km to 4.4 kin, showing that the ore-forming fluids at the main metallogenic stage were derived from magmatic- hydrothermal fluids characterized by hypabyssal origin, medium-low temperature, low salinity, and sodiumcalcium enrichment. Studies of H2O and C isotopes in the quartz at the main mineralization stage have shown that the δ180 values of ore-forming fluids range from 0.79‰ to 6.27‰（averaging 3.34‰）; the δD values range from -104.1‰ to -87.7‰ （averaging -95.6%0）. These research results indicate that water in the ore-forming fluids at the main metallogenic stage originated from magmatic water mixed with meteoric water, which is consistent with the research results of fluid inclusions. δ13CpDB is -4.1‰- -2.7‰ with an average of-3.4‰, which may be related to igneous rocks or magma rock system, indicating that ores may have experienced such magmatic-hydrothermal alterations under the action of magmatic-hydrothermalism as dolomitization, calcilization and others carbonate alterations, which is consistent with the development of ankeritization at the main metallogenic stage. Compre- hensive research results indicate that the Ganshu gold deposit belongs to the middlelow temperature magmatichydrothermal type of gold deposits.