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通过对西藏纳如松多铅锌矿床4套矿化型式的系统梳理,根据地质事实和相关同位素证据,初步建立了一个独立的和岩浆作用相关的热液铅锌成矿系统模式。纳如松多铅锌矿化和石英正长斑岩密切相关,目前已发现了产在斑岩外围的古新世典中组凝灰岩地层中的隐爆角砾岩型矿化、产在斑岩与二叠纪下拉组灰岩接触带上的矽卡岩型矿化、产在斑岩外围典中组凝灰岩与二叠纪昂杰组砂板岩岩性分界面上的矿层型矿化以及产在凝灰岩或砂板岩内部先存裂隙中的脉型矿化等4种铅锌矿化型式。它们均以绿帘石绿泥石化、硅化绢云母化和碳酸盐化为主要围岩蚀变类型,矿石矿物为方铅矿+闪锌矿,主要脉石矿物为黄铁矿+黄铜矿+石英+绢云母+方解石,蚀变和矿物组合特征指示它们发育在同一矿化系统中,但成矿热液温度逐渐降低。隐爆角砾岩型和矽卡岩型矿化成矿流体δDV-SMOW值分布范围较大(-177‰~-118‰和-164‰~-139‰),δ18OV-SMOW值分布范围较小(-2.76‰~3.29‰和-5.46‰~-4.58‰),反映其主要来自发生了去气作用的岩浆水,并混合了少量大气降水。4种矿化型式的S同位素值按照隐爆角砾岩型(4.15‰)、矽卡岩型(7.92‰)、矿层型(8.49‰)和脉型(8.80‰)的顺序逐渐增大,反映其主要来自发生了H2S去气作用的残余岩浆相。矿区成矿斑岩与冷水坑斑岩型铅锌矿床的成矿斑岩极为相似,推测矿区深部也有斑岩型铅锌矿化的可能。一个独立的和岩浆作用相关的铅锌成矿系统模式由此建立,它包括了发育在挤压环境中所有和岩浆作用相关的铅锌矿化类型,可简述如下:新特提斯洋壳俯冲回转,地幔楔及上覆地壳部分熔融,纳如松多独具特色的斑岩岩浆形成;岩浆上升侵位,H2O及H2S去气,流体初溶,岩浆内部和顶部分别汇集了富氧化性质S和金属物质及富还原性质S和金属物质的残余岩浆流体;岩浆进一步侵位,温度降低,矿物结晶,SO2水解,斑岩型铅锌矿化形成;岩浆侵位到凝灰岩地层中,凝灰岩高压致爆,硫化物沉淀,隐爆角砾岩型铅锌矿化形成;富成矿物质残余岩浆水向外运移,伴随H2S进一步去气,矽卡岩型、矿层型、脉型铅锌矿化在不同岩性地层和构造位置中形成。
Based on the systematic combing of four sets of mineralization patterns of the Nadusson-Songdo lead-zinc deposit in Tibet, an independent and magmatism-related hydrothermal Pb-Zn metallogenic system model was initially established based on geological facts and related isotopic evidence. Nashuduoduo lead-zinc mineralization is closely related to quartz-positive porphyry. At present, it has been discovered that the cryptoexplosive breccia-type mineralization in the tuffstone formation of the Paleocene-Paleo-Cenozoic group in the periphery of the porphyry has been found in the porphyry Skarn mineralization on the contact zone with the Lower Permian Limestone limestone is due to the mineralized mineralization at the interface between the Dianzhong formation tuff in Periplane and the Permian Yanjie formation at the lithologic interface and the tuff- Or within the pre-existing sand slate vein mineralization and other four types of lead-zinc mineralization. They are mainly chlorite chlorination, silicification sericification and carbonation as the main type of rock alteration, ore minerals galena + sphalerite, the main gangue minerals pyrite + chalcopyrite + Quartz + sericite + calcite, alteration and mineral assemblages indicate that they developed in the same mineralization system, but the temperature of ore-forming hydrothermal solution gradually decreased. The δDV-SMOW distribution values of the cryptoexplosive breccia and skarn mineralization fluids range from -177 ‰ to -118 ‰ and from -164 ‰ to -139 ‰, and the δ18OV-SMOW value range is small -2.76 ‰ ~ 3.29 ‰ and -5.46 ‰ ~ -4.58 ‰), reflecting that they are mainly from magmatic water with de-aeration and mixed with a small amount of precipitation. The S isotopic values of the four mineralization types gradually increase in the order of cryptoexplosive breccia type (4.15 ‰), skarn type (7.92 ‰), ore type (8.49 ‰) and pulse type (8.80 ‰) It mainly comes from the residual magmatic phase where H2S degassing occurred. The mineralized porphyry in the mining area is very similar to the mineralized porphyry in the cold pits porphyry Pb-Zn deposit, suggesting that there may be porphyry Pb-Zn mineralization in the deep part of the mining area. An independent and magmatism-related lead-zinc mineralization system model was established that includes all lead-zinc mineralization types associated with magmatism that develop in compression environments and can be summarized as follows: Neotetic oceanic crust Subduction and rotation, the mantle wedge and the overlying crust partially melted, and Nautonguo’s unique porphyry magma was formed. Ascending magmatic emplacement, H2O and H2S degassing, fluid initial dissolution, and magma enrichment S, and remnant magma of S and metal species; further magmatic emplacement, temperature reduction, mineral crystallization, SO2 hydrolysis and porphyry Pb-Zn mineralization; magmatic emplacement into tuff strata, tuff pressure Detonation, sulfide precipitation and cryptoexplosive breccia-type lead-zinc mineralization. The remnant magmatic water of rich ore-forming materials migrated to the outside accompanied by H2S further degassing, skarn type, ore type and vein type lead-zinc mineralization Formed in different lithology strata and tectonic positions.