【作者】 李欢；

【导师】 魏俊浩；

【作者基本信息】 中国地质大学 ， 矿产普查与勘探， 2018， 博士

【摘要】 阿勒泰造山带南缘、准噶尔盆地东北缘的东准噶尔地区为新疆北部一个重要的金等多金属成矿区。大地构造位置位于西伯利亚板块和哈萨克斯坦-准噶尔板块的结合部位,伴随着相关古亚洲洋的俯冲消减和最终闭合,区内发育有大量古生代岩浆岩和金矿床（点）。本文以该区顿巴斯套及邻区金矿床及相关的岩浆岩为研究对象,在野外地质调查、岩浆岩及矿床地质特征分析基础上,对中酸性侵入岩开展岩相学、锆石U-Pb年代学、岩石地球化学和Sr-Nd同位素地球化学研究,同时对金矿床进行矿相学分析、黄铁矿Rb-Sr定年、流体包裹体研究和C-H-O-He-Ar-S-Pb同位素示踪,并结合区域上的研究成果探讨其岩石成因、成矿作用特征、构造背景及成矿模式,开展了区域成矿对比研究,进而建立东准噶尔地区古生代构造-岩浆演化模式和金矿找矿模型。主要认识和结论如下:1.石英闪长玢岩和闪长玢岩的锆石LA-ICP-MS U-Pb定年结果为378±2.Ma和381±2Ma,为中晚泥盆世岩浆活动的产物。岩石低SiO₂含量52.44%⁶8.64%,富Na₂O（平均5.14%）,Na₂O/K₂O为1.19².72,A/CNK为0.81¹.08,属准铝质钙碱性-高钾钙碱性系列,显示I型花岗岩的特点。岩石富集大离子亲石元素（LILE）和轻稀土元素（LREE）,亏损高场强元素（HFSE,Nb、Ta、P、Ti）,稀土元素配分曲线右倾,具有明显的轻重稀土分异,基本无Eu异常。岩石具有较低的(⁸⁷Sr/⁸⁶Sr)_i（0.703783⁰.703938）,正的ε_Nd（380 Ma）（+6.2⁺7.0）,年轻的Nd模式年龄T _DM（546⁶08 Ma）,显亏损地幔源区特征。岩石地球化学显示具有埃达克岩和弧岩浆岩特征,为西伯利亚板块与哈萨克斯坦-准噶尔板块之间的古亚洲洋俯冲作用的产物,主要为来自俯冲板片流体或熔体交代的地幔楔在局部拉张环境下产生减压熔融而形成;2.二长花岗岩的锆石LA-ICP-MS U-Pb定年结果为328±3Ma和329±3Ma,为早石炭世岩浆活动的产物。岩石相对富SiO₂（68.68⁷0.30%）、Al₂O₃（14.52%¹5.32%）和碱（K₂O+Na₂O）（8.76⁹.27%）,Na₂O>K₂O,A/CNK比值<1.1,属高钾钙碱性系列。岩石具相对较低的Fe₂O₃^T（2.13%².39%）、MgO（0.6%⁰.7%）、CaO（0.76%¹.69%）、TiO₂（0.38%⁰.43%）和P₂O₅（0.11%⁰.13%）,暗色矿物中主要为黑云母和角闪石,显示I型花岗岩的特点。岩石富集大离子亲石元素（LILE,如Rb、Ba、Th、K）,亏损高场强元素（HFSE,Nb、Ta、P、Ti）,但Zr和Hf亏损不太明显。稀土元素配分曲线右倾,具有明显的轻重稀土分异,基本无Eu异常。岩石具有较低的(⁸⁷Sr/⁸⁶Sr)_i（0.703556⁰.703888）、正的ε_Nd（t）值（+4.1⁺5.6）年轻的Nd模式年龄T _DM（566Ma⁶75Ma）,显示新生地壳来源特征。岩石地球化学显示其来自于新生地壳的部分熔融,由幔源玄武质岩浆底侵形成的新生地壳和先存的下地壳组成混合岩浆源区,主要形成于碰撞造山和后碰撞转换的构造背景,表明额尔齐斯洋盆在早石炭世之前已经闭合。3.LA-ICP-MS锆石U-Pb年代学结果显示2件晚期花岗岩的²⁰⁶Pb/²³⁸U加权平均年龄分别为265±1Ma和268±2Ma。岩体属高钾钙碱性岩系,具有高硅（SiO₂=70.81⁷5.60%）、富碱（K₂O+Na₂O=8.73¹0.22%）和铁（Fe₂O₃^T=1.30².25%）、贫钙（CaO=0.33².24%）和镁（MgO=0.11⁰.89%）特征。铝饱和指数A/CNK=0.92¹.07,为准铝-弱过铝质花岗岩。岩石整体富集K、Rb等大离子亲石元素（LILE）和U、Th等高场强元素（HFSE）,明显亏损Ba、Sr、P、Ti。LREE富集HREE相对亏损,且具强烈的Eu负异常（Eu/Eu^*=0.62⁰.85）。岩相学和地球化学显示其为A型花岗岩。岩石具有角低的(⁸⁷Sr/⁸⁶Sr)_i比值为0.703199⁰.703610,正的ε_Nd（t）（+3.1⁺4.0）,以及较为年亲的Nd模式年龄T_DM为671Ma⁸15Ma。这些地球化学特征共同表明其源区主要为由幔源玄武质岩浆底侵形成的新生地壳和先存的下地壳组成混合岩浆源区,来自新生下地壳的部分熔融,具有后碰撞花岗岩的典型特征,形成于伸展构造背景。4.顿巴斯套金矿床与东准噶尔地区典型金矿床具有相似的地质和矿化特征,均位于三条NW向区域性深大断裂旁侧,矿体严格赋存在这些大断裂附近NWW向韧脆性剪切构造变形带内次级脆性断裂、裂隙、破碎带中。主要矿体赋存于下石炭统姜巴斯套组第一岩性段浅变质含碳细碎屑岩中,受NWW向构造控制。矿化以赋矿围岩发育微裂隙浸染状硅化（石英）细网脉及金属硫化物细（网）脉为特征,具有典型热液脉状矿化特征。与金矿化密切相关的蚀变类型为毒砂-黄铁矿化、硅化和绢云母化。根据矿物共生组合及相互穿切关系,可将成矿期划分为四个成矿阶段:石英脉阶段、粗粒黄铁矿-石英脉阶段、细粒黄铁矿（毒砂）-石英脉阶段和石英-碳酸盐阶段,其中第三阶段为主成矿阶段,形成于张性环境。5.顿巴斯套金矿床9件主成矿期黄铁矿样品的Rb-Sr同位素等时线年龄为268.3±2.8Ma（MSWD=0.74）,与矿区深部及外围（265²68 Ma）的花岗岩年龄几乎同时,为早二叠世东准噶尔地区伸展构造背景下构造-岩浆-热液活动的产物。6.顿巴斯套金矿床流体包裹体均一温度范围为138℃³52℃,存在3个温度区间,140℃¹80℃、180℃²60℃、320℃³60℃。绝大多数包裹体分布在180℃²60℃温度区间内,总体显示出中低温成矿特征,与岩浆热液矿床的成矿流体类似。主成矿阶段流体δ¹⁸O和δD同位素组成分别为+1.1³.9‰和–115.5^–120.6‰,显示成矿流体以岩浆水为主,有少量大气降水的加入;主成矿期石英包裹体气相碳同位素δ¹³C的范围为-24.7‰^-25.4‰,显示可能主要为深源无机碳与地层有机碳不同程度的混合碳,深源流体对金的成矿具有重大影响,同时地层有机质也参与了金的运移和卸载;黄铁矿流体包裹体He-Ar同位³He/⁴He比值（0.52¹.58 Ra）介于壳源流体（0.01⁰.05Ra）和幔源流体（6⁹Ra）之间,He-Ar同位素组成的正相关关系与高³He/⁴He、⁴⁰Ar/³⁶Ar特征的幔源流体和低³He/⁴He、⁴⁰Ar/³⁶Ar特征的壳源流体混合趋势一致,成矿流体含有地壳He和地幔He,幔源比例占6.4¹9.6%,成矿流体的³He/⁴He比值低于饱和大气水,显示出改造型饱和大气水的特征。显示成矿流体来源与岩浆活动,很可能为幔源、壳源有关的岩浆热液,以及改造型饱和大气水三者的混合流体;矿石中黄铁矿和毒砂的δ³⁴S分别为3.0-5.8‰和4.2-5.6‰,数值比较集中,指示成矿物质硫源具有岩浆硫特征,有深源参与,与区内早二叠世的花岗质岩浆活动有关;矿石中黄铁矿的Pb同位素组成基本一致,²⁰⁶Pb/²⁰⁴Pb、²⁰⁷Pb/²⁰⁴Pb、²⁰⁸Pb/²⁰⁴Pb分别为17.875¹8.102、15.483¹5.625和37.699³8.148,指示成矿物质铅源以地幔铅为主,并同化了壳源铅,应是一种分别来自地幔和上地壳的混合铅。结合矿床地质特征、成矿时代及多元同位素分析,认为顿巴斯套金矿床为岩浆热液型的构造破碎蚀变岩型金矿床,为早二叠世伸展构造背景下的构造-岩浆-流体活动综合作用的产物。7.通过对研究区内中酸性侵入岩进行系统的年代学和地球化学研究,结合前人的地质研究工作,综合最新获取的地质学证据,认为东准噶尔地区在古生代经历了如下的构造-岩浆演化过程:阿尔曼泰古洋盆在奥陶纪初期分别向南北两侧双向俯冲消减;早志留世初弧弧碰撞,实现早古生代早中期的洋陆转换;额尔齐斯洋在早泥盆世之前开始了一次新的俯冲消减过程,并于330Ma之前完成洋壳的关闭和弧陆或弧弧碰撞,实现晚古生代早中期的洋陆转换及构造体制转换;晚石炭世至早二叠世（265³30Ma）,东准噶尔地区进入后碰撞阶段,实现全面伸展。顿巴斯套及邻区早二叠世金矿床都是在陆-陆或弧-陆碰撞的地球动力学背景下,先经过早-中石炭世挤压构造背景下的推覆为主,兼具右行剪切变形阶段,形成不同级次的韧性剪切构造体系;后经晚石炭纪至早二叠世晚期伸展构造背景下的脆性构造变形阶段,沿早期形成的韧性剪切构造体系中的各种裂隙或薄弱带,在脆性变形过程中形成张性容矿空间。8.结合西伯利亚板块和哈萨克斯坦-准噶尔板块之间的古亚洲洋的演化特征及其对区内成岩成矿构造背景的指示,本文以顿巴斯套及邻区金矿床研究为基础,总结了顿巴斯套金矿床的成矿控制因素和矿化规律等,并开展了区域上同时代金矿成矿构造背景、成矿时代、成矿类型、成矿作用特征及构造控矿模式等方面的区域对比研究工作,认为它们在成矿构造背景和金的成矿作用特征等方面具有一定的相似性,均属中-低温的热液型金矿床,完全可以对比。结合东准噶尔地区相似地质背景下典型金矿床的研究分析,构建了东准噶尔顿巴斯套及邻区早二叠世金矿具有普适性的找矿模型。更多还原

【Abstract】 The eastern Junggar area,located in the southernmargin of the Altay orogenic belt and the northeastern margin of the Junggar basin,is animportantgold polymetallic metallogenic area in the northern Xinjiang.As far as the geotectonic position,the eastern Junggar area is situated at the joint region of the Siberia plate and the Kazakhstan-Junggar plate.With the relative subduction and closure of the Paleo Asian oceans,this region is abounded in the Paleozoic magmatic rocks and gold deposits.In this dissertation,taking the Dunbasitao and adjacent areas deposites and the relevant magmatic rocks as the research object,combined with the previous regional research acievements,through comprehensive studies of field geology,geological features of the magmatic rocks and the ore deposits,petrography,zircon U-Pb geochronology,whole-rock geochemistry,Sr-Nd isotopic geochemistry,pyrite Rb-Sr dating,fluid inclusions analysis and C-H-O-He-Ar-S-Pb isotopic tracing,I make clear the petrogenesis of intermediate-acid intrusions,the mineralization characteristics of gold deposites,and the metallogenic tectonic settings.Furthermore,through the comparative study of regional metallogenic characteristics,a new model for the Palaeozoic tectonic-magmatic evolution and regional metallogenic in the East Junggar area for the gold deposites were built.The main cognitions and conclusions are obtained as follows:1.The quartz diorite porphyrite and diorite porphyry,with the LA-ICP-MS zircon U-Pb dating results for 378±2Ma and 381±2Ma,respectively,were the products of the middle late Devonian magmatic activity.The intrusive rocks show relatively low SiO₂content（52.44%⁶8.64%）,rich Na₂O with an average（5.14%）,Na₂O/K₂O（1.19².72）,and A/CNK is from 0.81 to 1.08,which belong to metaluminous calc-alkaline and high-K calc-alkaline series.Both of them show the characteristics of the I-type granites.The rocks are enriched in large ion lithophile elements LILE（Rb,Ba,Th）and light rare earth elements LREE,depleted in high field strength elements HFSE（Nb、Ta、P、Ti）.The rare earth element REE exhibit right-dipping patterns having significant LREE and HREE differentiation without Eu anomalies.All the samples have low(⁸⁷Sr/⁸⁶Sr)_i（0.703783⁰.703938）,positiveε_Nd（t）（+6.2⁺7.0）,as well as young Nd isotopic model ages(T_DM ranging from 546⁶08 Ma),indicating a deplete mantle source.These geochemical characteristics demonstrate that the rocks are arc magmatic rocks,with the characteristics of adakite.As the products of the subduction of the paleo-Asian ocean between the Siberia block and the Kazakhstan-Junggar,these rocks were mainly derived from decompression melting of the mantle wedge metasomatized by the the subducting fluid or melt in the local extensional environment.2.LA-ICP-MS zircon U-Pb dating shows the the monzogranite’s ²⁰⁶Pb/²³⁸Pb ages are 328±3Ma and 329±3Ma,which are the products of the early Carboniferous magmatic activity.The rocks show relatively rich inSiO₂（68.68%⁷0.30%）,Al₂O₃（14.52¹5.32%）and（K₂O+Na₂O）（8.76⁹.27%）,with Na₂O>K₂O and A/CNK<1.1,belonging to high-K calc alkaline series.Bue these rocks are characterized by low Fe₂O₃^T（2.13².39%）,MgO（0.6⁰.7%）,CaO（0.76¹.69%）,TiO₂（0.38⁰.43%）and P₂O₅（0.11⁰.13%）,the biotite and amphibole being main dark mineral,indicating characteristics of I-type granite.These intrusive rocks are enriched in LILE（Rb,Ba,Th,K）and depleted in HFSE（Nb,Ta,P,Ti）,but the depletion of Zr and Hf is not obvious.The REE exhibit right-dipping patterns having significant LREE and HREE differentiation without Eu anomalies.All the samples show a homogeneous low(⁸⁷Sr/⁸⁶Sr)_i（0.703556⁰.703888）,but high and positiveε_Nd（t）values（+4.1⁺5.6）,with young Nd mode age(T_DM ranging from 566⁶75 Ma),indicating the origin of the juvenile crust.Major and trace elements and Sr-Nd isotopic data suggest that they may be derived from the partial melting of a juvenile crust source,which is probably a mixed lithology formed by pre-existing lower crust intruded or underplated by mantle-derived basaltic magma.Both of them were mainly formed in the tectonic setting transform collision to post collision,which manifests that the ocean basin of Erqisi has been closed before the Early Carboniferous.3.LA-ICP-MS zircon U-Pb dating results show that two late stage granitesformed at 265±1Ma and 268±2Ma,which are the products of the early Permian magmatic activity.Petrography and chemical compositions show that they belong to high-K calc-alkaline series and are characterized by high silicon（SiO₂=70.81⁷5.60%）,enrichment in kalium（（K₂O+Na₂O）=8.73¹0.22%）and iron（Fe₂O₃^T=1.30².25%）but depletion in calcium（CaO=0.33².24%）,and magnesium（Mg O=0.11⁰.89%）.The A/CNK values vary from 0.92 to 1.07,show a metaluminous to weakly peraluminous affinity.The granitic rocks are enriched in high field strength elements（HFSE）（e.g.Zr and Hf）and large ion lithophile element（LILE）（e.g.Rb,U and Th）but depleted in Ba,Sr,P,and Ti.REEs are characterized by negative Eu anomalies（Eu/Eu^*=0.62⁰.85）and exhibit right-inclined patterns with LREE enrichment but HREE depletion.Mineralogy and geochemistry show an affinity to A-type granite.The rock show a homogeneous low(⁸⁷Sr/⁸⁶Sr)_i（0.703199⁰.703610）,positiveε_Nd（t）values（+3.1⁺4.0）,with young Nd mode age(T_DM ranging from671⁸15Ma).Major and trace elements and Sr-Nd isotopic data suggest that they may be derived from the partial melting of a juvenile crust source,which is probably a mixed lithology formed by pre-existing lower crust intruded or underplated by mantle-derived basaltic magma.These granites generated in a post-collisional extensional tectonic setting.4.Gold deposits in the Dunbasitaoand the East Junggar area have similar metallogenic geological characteristics.Three NW trending regional fault structure is closely related to ore-forming.Ore-controlling structure is the NWW trending ductile-brittle shear zone.Regional ductile shear zone controls gold deposits distribution.Brittle structure controls the gold deposits.The main orebodies are hosted in the first member of the Lower Carboniferous Jiangbasitao group,which comprises low-grade metamorphic clastic rocks.The deposit is well controlled by the NWW trending structures.The dominant alterations related to gold mineralization are arsenopyrite-pyritization,silicification and sericitization.The hydrothermal ore-forming processes can be divided into four stages accoding to the mineral assemblages and the crosscutting relationships of the mineral as follow:quartz vein;coarse-grained pyrite-quartz vein;fine-grained pyrite-arsenopyrite-quartz vein;and quartz-carbonate vein.The third stage is the chief ore-forming stage,which was formed in the extensional environment.5.Rb-Sr isotopic dating of 9 pyrites separated from the Dunbasitao gold deposit yielded an isochron age of 268.3±2.8Ma（MSWD=0.7）,this result is in good agreement with the early Permian（265 Ma²68Ma）granite in the periphery of ore district,indicating that Gold mineralization was related to granite crystallization.Meanwhile,combining with the high-precision studies about metallogenic chronology of diagenetic and mineralization in eastern Junggar in recent years,we point out that Early Permian from 270Ma to 260Ma may be an important time range of gold mineralization in eastern Junggar,Xinjiang.According to the precise Rb-Sr ages we have reported and previous studies,we interpret the Dunbasitao gold deposit formed in an extensional setting related to activity of tectonic,magma and fluid during the Early Permian in eastern Junggar.6.The fluid inclusions from Dunbasitao gold deposit have final homogenization temperatures of 140¹80℃,180²60℃and 320³60℃,respectively.Most of the inclusions are distributed in the temperature range from 180℃to 260℃,showing the characteristics of middle to low temperature mineralization,which is similar to the magmatic hydrothermal deposits derived from the magmatic activities of the study area.Theδ¹⁸O andδD values range from+1.1 to+3.9‰and from–115.5 to–120.6‰,respectively.The H-O isotopes signature indicates that the ore-forming fluid was dominated by magmatic water with the participation of some meteoric.Theδ¹³C values of the ore-forming fluid range from-24.7‰to-25.4‰,indicating that carbon of ore-forming fluid is a mixture of inorganic carbon from deep source and organic carbon from strata at varing proportions.It is obviously that gold mineralization has been related to deep-source fluid and the organic carbon derived from sedimentsry strata in this area plays an important role on transportation and unloading of deep-source gold.Fluid inclusions in pyrite He-Ar isotopic ratio of ³He/⁴He（0.52¹.58Ra）is between the crust-derived fluid（0.01⁰.05Ra）and mantle-derived fluid（6⁹Ra）.Metallogenic fluid contain crust-derived He and mantle-derived He,with mantle-derived He proportion accounted for 6.4 to 19.6%.The ³He/⁴He ratio of ore-forming fluid was lower than that of saturated meteoric water,which showed the characteristics of modified saturated meteoric water.The He and Ar isotopes also display a magma origion,which indicate that the ore fluids origion of the Dunbasitao deposit characterized by mantle,crust and modified air-saturated water.These data suggests that the ore-forming fluids are mainly from a magmatic water,and the mineralization of hydrothermal superimposition disply a more possibility.Theδ³⁴S values of the pyrite and arsenopyrite form the Dunbasitao ores range from 3.0‰to5.8‰and from 4.2 to 5.6‰,respectively,which displays that the derivation of ore-forming materials sulfur mainly comes from the magmatic sulfur with the participation of deep-source sulfur.The ²⁰⁶Pb/²⁰⁴Pb,²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb values of the pyrite form the Dunbasitao ores range from 17.875 to 18.102,from 15.483 to15.625,and from 37.699 to 38.148.Pb isotope is coincident and reveals that lead mainly comes from the mantle,which is a mixture of mantle-source and upper crust-source lead.Based on the H,O,C,He,Ar,S and Pb isotope geochemistry signatures of the mineral systems,combined with the comprehensive studies on geological characteristics and metallogenic tectonic setting of ore deposit,we argue that Dunbasitao gold deposit is a structure-controlled magmatic hydrothermal type and altered rock type deposit,and formed in an extensional setting related to activity of tectonic,magma and fluid during the Early Permian in eastern Junggar.7.Based on our results from geochronology and geochemistry studies of theintermediate-acid intrusive rocks,combinedwith the systematic summaries of the previous geological research,published data and newly comprehensive geological evidence,we proposed that the East Junggar area could have experienced a complex tectonic-magmatic evolution history as follows:Armantai oceanic exist idirectional subduction（north and south）in the early stage of Ordovician.The tectonic setting transformation from ocean to continentinthe early Paleozoic through arc-arc collision in the early stage of Early Silurian.The Erqisi ocean start a new subduction process before the early Devonian.Before the late stage of the EarlyCarbonifeous（330Ma）,the ocean basin could finally closed and the tectonic setting begin to transformation from arc-arc collision or arc-continent collision to post-collision.The East Junggar terrane witnessed a tectonic transition from compression to post-collisional extension between the Early Carboniferous and the Late Carboniferous.The East Junggar terrane begin into a post-collisional extension stage from the Late Carboniferous to the Early Permian（265³30Ma）.In the geodynamic setting of arc-arc or arc-continent collision,the Early Permian gold deposits in the Dunbasitao and adjacent areas first form the ductile shear tectonic system in the extruded tectonic setting in the Early-Middle Carboniferous,and then form all kinds of brittle cracks along the ductile shear belt of the early stage in the post-collisional extension tectonic setting in the Late Carboniferous-Early Permian.The tectonic deformation control on gold mineralization is expressed by geological discontinuity between the ductile-brittle andbrittle deformation.The gold mineralization kept up with the brittle deformationand had a significant superposition relationship with the ductile deformation.Brittle structure controlled ore body unified in theright-lateral strike-slip shear and extensional system,with different deformation levels,deformation characteristics and mineralization characteristics.8.Considering to the evolution history of the Paleo-Asian ocean between the Siberia plate and Kazakhstan-Junggar plate,and its geodynamic implications for the perogenesis,mineralization,and metallogenic tectonic setting.Based on the relevant research on Dunbasitao and adjacent area of gold deposit,this dissertation summed up the metallogenic controlling factors and mineralization regularityof the Dunbasitao golddeposit,and carried out a comparative study of gold metallogenic tectonic background,metallogenic epoch,mineralization types,mineralization and ore-controlling tectonic mode ofregional contemporaneous gold deposits.This dissertationargue that these gold deposits have some similaritiesin metallogenic tectonic background,gold mineralization characteristics and other aspects,belonging to the middle-low temperature hydrothermal gold deposit.These gold deposits can be compared completely.Combined with the research of the typical gold deposits with similar geological setting in the East Junggar area,this dissertation construct a gold prospecting model of the East Junggar and adjacent areas in the Early Permian,which is universal.更多还原