【作者】 杨帆；

【导师】 孙景贵；

【作者基本信息】 吉林大学 ， 矿物学、岩石学、矿床学， 2019， 博士

【摘要】 研究区位于内蒙赤峰和辽宁朝阳两个地级市接壤部位,地处华北地台北缘东段与兴蒙造山带接壤的复合构造区,复杂的构造、岩浆作用使得本区成为倍受关注的金成矿区。目前,已勘探出大中型金矿床20余座,包括撰山子、金厂沟梁、二道沟、奈林沟、小塔子沟等,是中国重要的金矿带之一。近些年,随着开发的推进,一些中小型矿床资源开采殆尽,亟待开展相关矿区深部和外围金矿的找矿工作,缓解研究区内资源枯竭的问题。如何解决这一现存的自然科学问题,迫在眉睫。因此,本文在综合前人研究的基础上并依托中国地质调查局项目,对研究区内具有代表性的金矿床（撰山子、金厂沟梁及二道沟矿床）开展了系统的矿床地质、流体包裹体、同位素年代学、同位素地球化学等方面的研究,以期为进一步找矿提供理论依据,所取得的成果与进展如下:1.研究区内典型矿床矿石类型以硫化物石英脉（石英大脉和细脉+网脉）型为主,少量为蚀变岩型;成矿作用大体经历四个阶段,依次为黄铁矿–石英阶段（成矿早阶段）、石英–黄铁矿阶段（成矿主阶段）、石英–多金属硫化物阶段（成矿主阶段）、碳酸盐阶段（成矿晚阶段）;围岩蚀变及分带现象较为明显,由矿体中心向两侧围岩依次呈现白色硅化、黄铁绢英岩化、青色硅化、青磐岩化、钾化等蚀变现象;矿石中的金属矿物以黄铁矿、黄铜矿、方铅矿、自然金等为主,含少量闪锌矿和黝铜矿等。2.矿床的矿物流体包裹体研究表明,金厂沟梁金矿成矿早阶段发育W型（水溶液）和C型（含CO₂水溶液）包裹体,其均一温度为356.4⁴16.8℃、盐度为3.33¹3.07wt.%、密度为0.54⁰.73g/cm³;成矿主阶段发育W型和C型包裹体,其均一温度为260.5⁴08.9℃、盐度为3.71¹1.48wt.%、密度为0.60⁰.84g/cm³;成矿晚阶段发育W型包裹体,其均一温度为202.8³34.2℃、盐度为8.94¹1.11wt.%、密度为0.76⁰.94g/cm³。二道沟金矿成矿早阶段发育W型包裹体,其包裹体的均一温度为334³95℃、盐度为7.72¹1.23wt.%、密度为0.67⁰.74g/cm³;成矿主阶段发育W型和C型包裹体,其均一温度为214³64℃、盐度为0.20²3.18wt.%、密度为0.59¹.00g/cm³;成矿晚阶段发育W型包裹体,其均一温度为172²72℃、盐度为0.35⁵.25wt.%、密度为0.76⁰.93g/cm³。撰山子金矿成矿早阶段发育W型包裹体,其均一温度为284⁴08℃、盐度为2.23⁶.58wt.%、密度为0.51⁰.79g/cm³;成矿主阶段发育W型包裹体,其均一温度为200³80℃、盐度为0.35³.23wt.%、密度为0.54⁰.89g/cm³;成矿晚阶段发育W型包裹体,其均一温度为145²45℃、盐度为0.35¹.05wt.%、密度为0.81⁰.93g/cm³。三个矿床其成矿早阶段含矿流体均属于中温、中低盐度的NaCl-H₂O-CO₂体系;成矿主阶段流体演化为中温为主、中低盐度共存的NaCl-H₂O-CO₂不混溶体系;成矿晚阶段,成矿流体已逐渐演化为以H₂O为主的低温、低盐度的NaCl-H₂O体系。3.矿物流体包裹体氢–氧同位素显示,初始含矿流体主要由深源岩浆提供,并且有幔源物质的加入,成矿过程伴随着大气降水的持续加入;氦–氩同位素显示金厂沟梁金矿的流体并非简单的地幔流体与大气降水的混合物,而可能是以洋壳俯冲为主的流体交代形成的EMⅡ型富集地幔的产物;硫–铅同位素揭示成矿物质具有以幔源为主的壳幔混合源属性,并且金厂沟梁和二道沟金矿可能来自下地壳具有Ⅰ型富集地幔属性,而撰山子金矿成矿物质呈现Ⅱ型富集地幔属性,成矿流体上升运移的过程中均萃取了少量围岩中的成矿物质。4.成岩成矿年代学示踪显示,撰山子金矿赋矿围岩的锆石U–Pb年龄介于252.0±1.5Ma²52.8±3.2Ma之间,金厂沟梁金矿开展的硫化物Rb–Sr同位素等时线年龄在127.6±5.5Ma¹27.5±2.0Ma之间。结合前人研究成果认为研究区内至少存在2期金成矿事件,依次为晚二叠世–早三叠世（252Ma²45Ma）和早白垩世（140Ma¹26Ma）。5.与成矿密切相关的岩浆热事件元素地球化学、Hf同位素特征揭示,撰山子花岗斑岩属高钾钙碱性岩石系列,富集大离子亲石元素、不相容元素和轻稀土元素,相对亏损重稀土元素和高场强元素,岩石表现为下地壳的部分熔融形成的岩浆经结晶分异作用生成的高分异I型花岗岩,其整体处于兴蒙造山带向华北板块碰撞造山后的拉张构造背景之下;西对面沟岩体（石英二长岩）属于钾玄岩岩石系列,富集大离子亲石元素、不相容元素和轻稀土元素,相对亏损重稀土元素和高场强元素,整体为C型埃达克质岩石,为加厚下地壳的部分熔融形成,其整体处于岩石圈强烈减薄的伸展时期。6.将岩浆作用、流体起源演化与区域构造演化背景相结合,认为撰山子金矿成矿与晚二叠世–早三叠世兴蒙造山带和华北板块碰撞造山后的伸展有关,其含矿流体库为俯冲板片脱水交代地幔楔形成的玄武质岩浆,该玄武质岩浆底侵至深部下地壳使其发生部分熔融形成酸性岩浆,两者混合形成初始岩浆房,伴随着岩浆的上升,释放出的初始含矿流体沿着撰山子金矿田内早期形成的不同方向的韧脆性断裂继续向上运移并萃取围岩中的成矿物质,大气降水的加入导致含矿流体发生强烈的不混溶作用,致使成矿流体的物理化学条件发生变化,由此导致撰山子金矿的形成;金厂沟梁及二道沟金矿的成矿处于早白垩世中国东部岩石圈大规模的减薄的背景下,俯冲板片脱离导致软流圈底侵下地壳使其发生部分熔融形成初始岩浆房,岩浆上移释放出的初始含矿流体沿早期形成的断裂继续向上运移并萃取围岩（变质岩系及火山岩）中的成矿物质,而后大气降水的加入导致含矿流体发生强烈的不混溶作用,致使流体的物理化学条件发生变化,并导致金和其他一些金属硫化物发生沉淀形成金厂沟梁、二道沟金矿。更多还原

【Abstract】 The research area is located at the border of Chifeng in Inner Mongolia and Chaoyang in Liaoning Province.It is located in the complex tectonic area bordering the Xingmeng orogenic belt in the eastern section of the north margin of the North China platform.The complex structure and magmatism make this area a gold forming area of great concern.At present,more than 20 large and medium–sized gold deposits have been explored,including Zhuanshanzi,Jinchanggouliang,Erdaogou,Nailingou and Xiaotazigou,which are one of the important gold belts in China.In recent years,with the advance of development,resources of some small and medium–sized mineral deposits have been exhausted,so it is urgent to carry out the prospecting work of relevant deep and peripheral gold mines to alleviate the problem of resource exhaustion in the research area.How to solve this existing problem of natural science is extremely urgent.Therefore,this article comprehensively on the basis of previous studies and relying on the China Geological Survey projects,in the typical gold deposit（Zhuanshanzi,Jinchanggouliang and Erdaogou deposit）to carry out the system of the ore deposit geology,fluid inclusions and isotopic geochronology and isotope geochemistry study,so as to provide theoretical basis for further prospecting.The results and progress achieved are as follows:1.The ore types of the typical deposits in the study area are mainly sulphide quartz veins（quartz large veins and veinlets+stockwork）,and a few are alteration rocks.Mineralization generally goes through four stages,namely,the pyrite–quartz stage（early stage of mineralization）,the quartz–pyrite stage（main stage of mineralization）,the quartz–polymetallic sulfide stage（main stage of mineralization）,and the carbonate stage（late stage of mineralization）.Surrounding rock alteration and zonal phenomena are obvious.From the center of ore body to the surrounding rocks on both sides,there are white silicification,pyritized phyllite,cyan silicification,propylitization,and potassic alteration.The metal minerals in the ore are mainly pyrite,chalcopyrite,galena,natural gold,and a small amount of sphalerite and tetrahedrite.2.Research on mineral fluid inclusions of the deposit shows that W–type（aqueous solution）and C–type（CO₂–containing aqueous solution）inclusions are developed in the early stage of metallogenic formation in Jinchanggou gold deposit.The average temperature is 356.4⁴16.8℃,the salinity is 3.33¹3.07wt.%,and the density is0.54⁰.73g/cm³.W–type inclusions and C–type inclusions were developed in the main stage of ore formation.The average temperature is 260.5⁴08.9℃,the salinity is3.71¹1.48wt.%,and the density is 0.60⁰.84g/cm³.In the late stage of mineralization,W–type inclusion developed,with the homogenization temperature of 202.8³34.2℃,salinity of 8.94¹1.11wt.%and density of 0.76⁰.94g/cm³.W–type inclusions were developed in the early stage of Erdaogou gold deposit.The inclusions had homogenization temperature of 334³95℃,salinity of 7.72¹1.23wt.%and density of 0.67⁰.74g/cm³.W–type and C–type inclusions were developed in the main stage of ore formation.The homogenization temperature is 214³64℃,the salinity is 0.20²3.18wt.%,and the density is 0.59¹.00g/cm³.In the late stage of mineralization,W–type inclusions developed,with average temperature of 172²72℃,salinity of 0.35⁵.25wt.%and density of 0.76⁰.93g/cm³.W–type inclusions developed in the early stage of Zhuanshanzi gold deposit,with a homogenization temperature of 284⁴08℃,salinity of2.23⁶.58wt.%and density of 0.51⁰.79g/cm³.W–type inclusions developed in the main stage of ore formation,with a homogenization temperature of 200³80℃,salinity of0.35³.23wt.%and density of 0.54⁰.89g/cm³.In the late stage of mineralization,W–type inclusions were developed,with homogenization temperature of 145²45℃,salinity of 0.35¹.05wt.%and density of 0.81⁰.93g/cm³.The ore–bearing fluids in the early stage of mineralization in the three deposits all belong to the NaCl–H₂O–CO₂ system with medium temperature and intermediate–low salinity.The fluid in the main stage of ore formation evolved into an inmiscible NaCl-H₂O-CO₂ system with moderate temperature and coexistence of medium and low salinity.In the late stage of mineralization,the ore–forming fluid has gradually evolved into a low–temperature and low–salinity NaCl–H₂O system dominated by H₂O.3.The hydrogen–oxygen isotopes of mineral fluid inclusions show that the initial ore–bearing fluids are mainly provided by deep source magma,and mantle source materials are added.The mineralization process is accompanied by the continuous addition of meteoric precipitation.The helium–argon isotope shows that the fluid in the Jinchanggouliang gold deposit is not simply a mixture of mantle fluid and meteoric water,and may the product of formation fluid metasomatism of oceanic crust subduction type EMⅡenrichment mantle;The sulfur–lead isotopes reveal that the metallogenic materials have the property of crust–mantle mixed source,which is dominated by mantle source.Jinchanggouliang and erdaogou deposits may be derived from the lower crust withⅠ–type enriched mantle.Zhuanshanzi gold deposit ore–forming materials presentⅡ–type enrichment mantle.In the process of upward migration of ore–forming fluid,a small amount of ore–forming materials in surrounding rocks were extracted.4.Diagenetic and metallogenic chronology shows that the U–Pb ages of zircons in the surrounding rocks of Zhuanshizi gold deposit range from 252.0±1.5Ma to252.8±3.2Ma,and the isochronic age of sulfide Rb–Sr isotopic in Jinchanggouliang gold deposit range from 127.6±5.5Ma to 127.5±2.0Ma.Based on previous research results,it is concluded that there are at least two gold metallogenic events in the study area,which are late Permian to early Triassic（252Ma²45Ma）and early Cretaceous（140Ma¹26Ma）.5.Geochemical and Hf isotope characteristics of magmatic thermal event elements closely related to mineralization reveal that Zhuanshanzi granite porphyry belongs to a series of rocks with high potassium,calcium and alkali content.And enrichment of large ion lithophile elements,incompatible elements and light rare earth elements,relative loss of heavy rare earth elements and high field strength elements.The rocks are highly differentiated I type granites formed by the magma formed by partial melting of the lower crust through crystallization differentiation.It is under the background of extensional tectonics after the Xingmeng orogenic belt colliding with the North China Plate.Xiduimiangou rock mass（quartz monzonite）belongs to the series of potassium basaltic rocks.And enrichment of large ion lithophile elements,incompatible elements and light rare earth elements,relative loss of heavy rare earth elements and high field strength elements.It shows C type adakitic–like rocks and formed by partial melting of thickened lower crust.As a whole,it was in the extensional period of intense thinning of lithosphere.6.Combining magmatism,fluid origin and evolution with regional tectonic evolution background,it is believed that the mineralization of Zhuanshanzi gold deposit is related to the extension of Xingmeng orogenic belt and North China Plate after collision orogen from late Permian to early Triassic.The ore–bearing fluid reservoir is basaltic magma formed by subduction plate dehydrated metasomatism mantle wedge.The basaltic magma floor penetrated into the deep lower crust and caused partial melting to form acidic magma,and the two mixed to form an initial magma chamber.With the rise of magma,the initial ore–bearing fluid released continued to migrate upward along the ductile brittle faults in different directions formed in the early stage of Zhuanshanzi gold field and extracted the ore–forming materials in the surrounding rocks.The addition of meteoric precipitation led to the strong immiscibility of ore–bearing fluid,which led to the change of physical and chemical conditions of ore–bearing fluid,which led to the formation of Zhuanshanzi gold deposit.The mineralization of Jinchanggouliang and Erdaogou gold deposits is under the background of massive thinning of lithosphere in eastern China during the early Cretaceous.The subduction plates break off,causing the asthenosphere to submerge into the crust and cause partial melting to form the initial magma chamber.The initial ore–bearing fluid released by magma migration continues to migrate upward along the faults formed in the early stage and extracted metallogenic materials from surrounding rocks（metamorphic series and volcanic rocks）.The addition of meteoric water results in strong immiscibility of ore–bearing fluids,resulting in changes in the physical and chemical conditions of the fluids.Gold and other metallic sulfides precipitate to form Jinchanggouliang and Erdaogou gold deposits.更多还原