【作者】 张万益；

【导师】 聂凤军；

【作者基本信息】 中国地质科学院 ， 矿物学、岩石学、矿床学， 2008， 博士

【摘要】 内蒙古东乌旗北部一带构造位置位于西伯利亚板块南缘的查干敖包—奥尤特—朝不楞早古生代构造岩浆带、大兴安岭成矿带西侧。受华北地台、古蒙古洋壳和西伯利亚板块多期次俯冲、碰撞和对接作用影响,研究区内古生代火山—沉积岩分布较广,深大断裂带（层）纵横交错,各类侵入岩十分发育和金属矿床（点）星罗棋布,具有特殊的地质构造背景和有利的成矿环境。研究区内已发现和圈定的各类金属矿床（点）共23处,其中大型矿床1处,中型矿床5处和小型矿床5处,包含的矿种主要有钨、铁、铜、铅、锌、银、金、铋等。矿床类型主要有矽卡岩型金属矿床（点）、与花岗岩类侵入岩有关的金属矿床（点）和中低温热液矿床（点）。为了探讨研究区内岩浆活动与金属矿床的成矿关系、了解金属矿床的成矿规律、指导找矿勘查,论文选取吉林宝力格等5个代表性花岗岩类岩体和吉林宝力格、查干敖包、阿尔哈达3个典型金属矿床,通过野外地质调查、岩石学、地球化学、同位素以及SHRIMP U—Pb年代学研究等工作,对各代表性岩体和典型矿床进行系统研究和解剖。研究结果表明研究区内侵入岩普遍富碱,大部分属钾质、碱性—钙碱性花岗岩类,且铝含量较高,部分岩体中成矿元素Pb、Zn、Au和Ag等含量较高。花岗岩类的铅同位素比值都非常接近,在铅同位素构造模式图上显示地幔铅的特征;具有较低的(⁸⁷Sr/⁸⁶Sr)_i初始比值、正的εNd（t）值和较低的模式年龄,与兴蒙造山带火成岩具有相似的Sr、Nd同位素特征。SHRIMP U—Pb测年结果表明吉林宝力格岩体、阿钦楚鲁早期岩体、阿钦楚鲁晚期岩体、查干敖包岩体和阿尔哈达岩体的形成年龄分别为314±8.8Ma、299±5Ma、284.3±9.7Ma、234±6Ma和218±5Ma。通过判别分析认为,吉林宝力格、阿钦楚鲁早期和晚期二长花岗岩属岛弧花岗岩,查干敖包石英闪长岩具有埃达克岩特征,而阿尔哈达岩体则属A型花岗岩,后两者形成于碰撞后拉张环境。吉林宝力格银—金矿床的成矿物质主要来源深部岩浆,围岩中的矿质组分也参与了成矿。同位素资料显示矿床的硫来自沉积岩与岩浆硫的混合,但以岩浆硫源为主,铅主要来源于二长花岗岩。成矿热液经构造运移、通过充填交代等方式沉淀富集,经过次生富集作用形成工业矿体。查干敖包铁—锌矿床的石英闪长岩和部分矽卡岩的微量元素和稀土的配分曲线形状接近:硫同位素闪锌矿的δ³⁴S值为10.39‰,而石英闪长岩中的黄铁矿则为0.8‰,二者有所差别,推测矿床的硫同位素可能是来自沉积岩与岩浆的混合。锶—钕—铅同位素示踪结果显示查干敖包成矿物质来源岩浆并受到壳源物质的混染。综合认为查干敖包铁—锌矿床是一与石英闪长岩有关的矽卡岩型矿床。矿床形成于板块碰撞后的拉张环境下,含矿的古老残留洋壳部分熔融,受到富钾基性地幔的交代后侵入到浅部,岩浆交代大理岩、自身发生钠长石化析出成矿物质。相比之下,吉林宝力格铅—锌—银矿床的容矿围岩之一的凝灰岩属富钾和铝、拉班玄武岩系列的中性火山岩。矿床硫化物中δ³⁴S值显示矿床硫源具有混合来源特征。共生硫化物对计算矿床形成温度为399℃—407℃和194℃—287℃两组。铅同位素组成显示成矿物质来源于岩浆和围岩,是一与印支期中酸性岩浆活动有关的热液矿床。东乌旗北部一带金属矿床形成时代为海西期至燕山期,在时空分布和成因上与花岗岩类侵入岩体关系密切。一般来说,侵入岩岩浆提供主要的成矿物质、提供热源和动力促使流体对流循环,在碳酸盐岩地段交代围岩形成矽卡岩型矿床,在泥质板岩、砂岩等地段活化围岩中的有益组分,与来源于岩浆中的矿质组分一起在合适的构造部位沉淀、充填形成工业矿体。针对上述规律,文章最后提出了有效的找矿标志和有利的找矿方向。更多还原

【Abstract】 Located in the Chaganobo—Aououte—Chaobuleng along the southern edge of the Siberian plate, the study area of northern Dong Ujimqin Banner of Inner Mongolia lies in western of Greater Xing’an Mountains metallogenic belt. Controlled by the multiple subduction, collision and connection of North China platform, the ancient Mongolia section of oceanic crust and Siberia platform, the region is characterized by widely exposed Paleozoic volcanic-sedimentary rock, complex structures, all kinds of intensive magmatic activities, and widespread ore deposits and occurrences. The study area was of special geological structure and context of a favourable environment mineralization.At present, more than 23 deposits and occurrences have been found in northern Dong Ujimqin Banner of Inner Mongolia, including one large deposit, five medium-sized deposits and five small deposit. There were many kinds of ore deposits such as tungsten, iron, copper, lead, zinc, silver, gold, bismuth, and so on. Deposits were the main types of skarn deposits, plutonic intrusions-related deposits and medium-low temperature hydrothermal deposits. In order to study the region of magmatic activity and polymetallic deposits of mineralization, to find out the mineralization and to guide mineral exploration, the paper studied five representative granitoid intrusions and three typical deposits. The research on geological survey, petrology, geochemistry, isotope and SHRIMP U-Pb chronology of the granitoid intrusions and deposits in the study area was the first conducted systematically, and the emplacement setting and age of the major intrusions as well as their relations to deposits were discussed in detail.Most intrusions of the study area were alkali-rich, potassic and alkaline-calc- alkaline granitoids. And there were high content of Al₂O₃ as well as Pb, Zn, Au, Ag etc.. Lead isotope ratios of granitoid intrusions were similar. In plumbotectonic model diagram, the lead isotopic compositions of granitoid intrusions were mainly located around mantle. According to Sr-Nd isotopic analytical results, granitoid intrusions had similar Sr, Nd isotopic characteristics to those of Xing’an-Mongolia orogenic belt such as low (⁸⁷Sr/⁸⁶Sr)_i initial ratios, positiveεNd（t） and lower model ages. SHRIMP U-Pb isotopic ages of Jilinbaolige intrusion is 314±8.8Ma, early stage Aqinchulu intrusion is 299±5Ma, late stage Aqinchulu intrusion is 284.3±9.7Ma, Chagan Obo intrusion is 237±6Ma and Aerhada intrusion is 218±5Ma, respectively. It has been suggested that Jilinbaolige intrusion and Aqinchulu early and late stage intrusions belong to island-arc granite, Chagan Obo quartz diorite is Adakitic rock, Aerhada intrusion belong to A type granite. The later two intrusions formed in an extensional environment of post collision. Metallogenic material of Jilinbaolige silver-gold deposit mainly derived from magma and only a few derived from derived from strata. Isotope analytical results showed that sulfur mainly derived from magma, but a few from sedimentary rock, lead mainly derived from magma. It is considered that hydrothermal ore forming solution mainly moves upward along the fracture and deposits by the process of filling and replacement. Quartz diorite and partial skarn of Chagan Obo iron-zinc deposit showed nearly uniform rare earth element and trace element distribution patterns. Theδ³⁴S value of sphalerite was 10.3‰, and pyrite of quartz diorite compared with 0.8‰. Not only S-Pb but also Sr-Nd isotope analysis results imply that metallogenic material of Chagan Obo deposit derived from magma but was contaminated by crust. Chagan Obo iron-zinc deposit belong to skarn deposit which related to quartz diorite. The article considered that Chagan Obo iron-zinc deposit formed in an extensional environment. During ore-forming process, ore bearing ancient residual oceanic crust melted partly at first, and then intruded shallow depths in the crust after mixed by potassium rich basic mantle, and separated out iron at last most likely to be the result of metasomatism by sodium when magma contacted with marble. By contrast, the Jilinbaolige lead - zinc - silver ore deposit was hydrothermal deposit which related to Indosinian intermediate-acidic magmatism. Tuff which was one of host rock of the deposit was intermediate volcanic rocks belong to potassium and aluminium rich tholeiite series. The values ofδ³⁴S of sulfide from deposit showed sulfur derived from magma and sedimentary rock.. Temperature calculated from sulfide pairs showed two groups values of 399℃—407℃and 194℃—287℃. Lead isotope analysis results imply that metallogenic material of deposit derived from magma and sedimentary rock.The regional ore deposits in the study area formed in three periods, i.e. Hercynian, Indosinian and Yanshanian. They were closely related to granite intrusions in the temporal and spatial distribution. Generally speaking, the intrusions not only provided heat source, part ore-forming fluids and elements, but also caused the long convective circulation of heat water which leached ore-forming elements of into the appropriate spaces to form ore-bodies. Finally, this paper concludes effective prospecting criterias and puts forward favorable prospecting directions in the study area.更多还原