【摘要】 锡-银多金属成矿系统主要产于主动大陆边缘、板内伸展和造山后伸展等构造背景中。全球典型成矿带包括玻利维亚南部带、俄罗斯远东Sikhote-Alin带、我国大兴安岭南段、南岭和欧洲Erzgebirge地区。成矿相关岩浆岩主要为浅成中酸性侵入体或次火山岩体,包括流纹英安-流纹质火山/次火山岩、石英斑岩、花岗斑岩、花岗闪长斑岩等,并与同期火山岩和碱性基性岩脉密切共生。岩浆源区不仅有大量地壳物质的参与,还普遍存在不同比例地幔物质成分的加入。围岩蚀变由早到晚、由成矿中心向外依次发育电气石化/云英岩化、绢云母化、伊利石化和高级泥化,金属矿化组合相应的依次为Sn(-W)→Zn-CuPb-Sn→Ag-Pb-Zn-Sb-Sn→Ag-Sb-Pb,锡矿化产于电气石和云英岩化带内,银矿化产于伊利石化和高级泥化带内。以银为主矿体多在浅部呈多条陡立脉状产出,以锡为主的矿体在深部呈大脉状和热液角砾岩体产出,也可呈浸染状或细网脉状产出(此时称为斑岩型锡矿)。此类矿床还常伴生In、Cd、Ga等矿化,主要产于闪锌矿、黄铜矿和方铅矿为主的硫化物成矿阶段。对成矿金属起源的研究显示锡可能主要来自中上地壳富锡的变质沉积岩,但银的来源尚无明确解释,沉积岩、地幔、围岩地层可能都有贡献。岩浆较低的氧逸度条件和富Cl的成分有利于形成富锡和其它金属的成矿流体,成矿早期流体常具有较高的盐度,伴随温度的降低和天水流体的稀释过程,流体由早期的高温高盐度逐渐演化到晚期的低温低盐度,并伴随不同金属的依次沉淀,这一过程中,可能多期次流体的叠加作用对大型矿床的形成起重要作用。在前人研究基础上,提出了本类型矿床研究中存在的一些关键问题:(1)普遍存在的壳幔相互作用在成矿过程中的作用尚不明确,地幔物质可能是重要的热源、硫和金属的来源;(2)火山作用与成矿之间的关系及其所起的作用;(3)在同一锡-银多金属成矿带中,富锡贫银、富银贫锡、富锡又富银这三类矿床之间的成因联系如何?造成它们金属组合差异的原因如何?可能需要从岩体侵位深度、矿床剥蚀程度、成矿流体性质等方面进行研究探讨;(4)不同金属元素的起源与耦合成矿作用,Sn-Ag-In等重要的成矿元素可能不是相同的起源,其进入流体的时间及沉淀的物理化学条件也是有差异的,它们在同一矿床中耦合成矿的详细过程与机制尚不清楚,原位微区流体包裹体成分分析、硫化物微量元素和同位素原位分析和面扫描技术可能是解决这一难题的重要手段。上述问题的解决不仅有助于提高对锡-银多金属矿床成矿过程的认识,还可为相关矿床的勘查找矿工作提供理论支持。更多还原

【Abstract】 Sn-Ag-base metal deposits are dominantly generated in active continental margins,intracontinental and post-orogenic extensional settings,including southern Bolivia tin belt,Sikhote-Alin belt in the Far East,Russia,southern Great Xing’an Range and Erzgebirge district in Europe. Ore-forming magma mainly comprises shallow felsic volcanic-intrusive rocks,such as rhyodacite-rhyolite,quartz porphyry,granite porphyry,granodiorite porphyry,and shows close spatial and temporal relationships with volcanic rocks and alkali mafic dykes. These ore-related magmas are mainly derived from meta-sedimentary in middle to upper crust,with variable proportions of mantle derived materials. From early to late and from center to periphery, the wallrock alteration include tourmalinization/greisenization,sericitization,illitization and advanced argillization,accompanying the metal assemblages of Sn(-W)→Zn-Cu-Pb-Sn→Ag-Pb-Zn-Sb-Sn→Ag-Sb-Pb. Most tin concentrates in tourmalinization and greisenization zones,while the silver mineralization correlate with the illitization and advanced argillization. The silver-base metal orebodies commonly occur as sheeted steep lodes or veins in shallow level,whereas the tin orebodies not only occur as lodes and breccias,but also as stockwork veinlets or disseminated in wallrocks in deep level. The Sn-Ag-base metal deposits usually contain significant In,Cd and Ga,which are formed during the stage of sulfide mineralization such as sphalerite,chalcopyrite and galena. Study results on the metal sources show that the meta-sedimentary rocks from middle to upper crust are the dominant tin sources,while the silver sources are still unclear,and sedimentary rocks,mantle and wallrock are the probable candidates. The key factors controlling the formation of ore-forming fluid rich in tin and other metals are low oxygen fugacity and rich-chlorine magma. The earliest fluids often have high saline. Subsequently,the fluids undergo cooling and mixing with meteoric water,and changed from early high saline fluid to late low saline fluid,accompanying the deposition of different metals. The superposition of multiple pulses of metal-rich fluids may play an important role in the formation of large-scale ore deposits. The future research needed to solve several key problems as below:( 1) The role of mantle-derived materials in the mineralizing process which may be important sources of heat,sulfur and metals.( 2) The relationship between volcanism and mineralization.( 3) What is the connection between tin-rich and silver-poor deposits,silver-rich and tin-poor deposits and tin-rich and silver-rich deposits in the same Sn-Ag metallogenic belts? What is the reason of different metal assemblages? The possible answers may need future researches on depth of emplacement,denudation level of the deposit and properties of ore-forming fluids.( 4) The origin and coupling mineralization of different metal elements are still unclear. Sn,Ag,In and S may have different sources,and differences also exist on the time of metal entered into fluid and the physical-chemical conditions of metal precipitation. Some improved analysis methods may provide important technical support to solve these problems,such as in-situ compositional analysis of fluid inclusions,in-situ trace elements and isotopic analysis of sulfide minerals and element mapping of minerals. The solving of these problems may help to improve the understand on the Sn-Ag-base metal mineralization process,and provide supports for the exploration of the same type of deposits.更多还原