摘要:
提要：边家大院银多金属矿床位于大兴安岭成矿带南段，是一个典型的热液脉型银多金属矿床。基于稳定同位素C、H、O、S和放射性Pb同位素的测试和分析，对边家大院银多金属矿床成矿流体及物质来源进行示踪。同位素测试结果表明：成矿流体中水的δD水?SMOW值为-138.5‰~-111.7‰，δ18О水?SMOW值为-8.85‰~9.38‰，表明成矿流体为岩浆水与大气降水的混合物。热液方解石δ13CPDB值为-7.7‰~-2.67‰，δ18OSMOW为-0.41‰~6.03‰，表明热液矿物方解石是2个阶段成矿作用的产物，成矿早阶段流体与岩浆水特征相似，碳主要来源于岩浆，成矿晚阶段流体具有大气降水的特征。边家大院银多金属矿床矿石硫化物δ34S值为0.7‰~4.4‰，显示银铅锌矿体的形成与岩浆作用密切相关，硫主要来自岩浆源。矿石样品208Pb/204Pb值介于38.1~38.634，207Pb/204Pb值介于15.518~15.681，206Pb/204Pb值介于18.155~18.284，表明成矿与岩浆作用关系密切，成矿流体中铅主要来自深源岩浆。成矿作用的发生是在一种总硫浓度比较低的平衡体系中进行的。边家大院银多金属矿床的成因类型属于火山-次火山热液脉状银多金属矿床。
Abstract:
Abstract: Located in the southern part of the Da Hinggan Mountains metallogenic belt, the Bianjiadayuan silver polymetallic deposit is a typical hydrothermal vein-type deposit. Stable (C, H, O and S) and radiogenic (Pb) isotopes of the Bianjiadayuan silver poly-metallic deposit were analyzed with the purpose of determining the source of the ore-forming fluids and materials. TheδDH2O-SMOW and δ18ОH2O-SMOW of the ore-forming fluids are -138.5‰- -111.7‰, and -8.85‰ -9.38‰, respectively, showing that they came from the mixing of magmatic water and meteoric water. The δ13CPDB and 18OSMOW of the hydrothermal calcite vary from -7.7‰ to -2.67‰ and from-0.41‰ to 6.03‰, respectively, indicating that the hydrothermal calcite was formed at two ore-forming stages. At the early stage, the ore-forming fluids were similar to magmatic water and the CO2 was related to the magma, whereas at the late stage, the ore-forming fluid was derived from meteoric water. The δ34S values of polymetallic ore in the Bianjiadayuan deposit range from 0.7‰ to 4.4‰, suggesting that the formation of the Ag-Pb-Zn orebody was closely related to magmatism and the sulfur probably came from the magma source. The ratios of lead isotopes in sulfides range from 38.1 to 38.634 for 208Pb/204Pb, 15.518 to15.681 for 207Pb/204Pb, and 18.155 to 18.284 for 206Pb/204Pb, respectively, indicating that the mineralization might have been induced by the magmatism, and the lead in the deposit was mainly derived from deep-seated magmatic source. The mineralization took place in a low δ34S∑S and equilibrium system. The Bianjiadayuan deposit can be genetically regarded as a volcanic-subvolcanic hydrothermal vein-type silver polymetallic deposit.
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